TR 245

Technical Report 245

AN INVESTIGATION OF CORE DRJLLING tN PERENNIALLY FROZEN GRAVELS AND ROCK

G. Robert Lange

Dec-ember 1973

CORPS OF ENGiNEERS, U.S. ARMY

COLD REGIONS RESEARCH AND ENGINEERING LABORATORY . . HANOVER, NEW HAMPSHI.RE

APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED.

AN INVESTIGATION OF CORE DRILLI.NG IN PERENNIALLY FROZEN GRAVELS AN.~D,'. RQCJ{~

G. Robert Lange

December 1973

CORPS OF ENGINEERS, U.S. ARMY

COLD REGIONS RESEARCH AND ENGINEERING LABORATORY HANOVER, NEW HAMPSHIRE

APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED.

ii

PREFACE

This report was prepared by G. Robert Lange, Geologist, Northern Engineering Research Branch, Experimental Engineering Divis ion, U.S. Army Cold Regions Re­search and Engineering Laboratory (USA CRREL).

The core drilling reported here was carried out by the U.S~ Army Snow, Ice and Permafrost Research Establishment (USA SIPRE) near Fairbanks, Alaska, during the summer and fall of 1959. The work was supported by the U.S. Army Gorps of Engineers {Office, Chief of Engineers) under project Drilling and Coring in Frozen

Ground.

The preparation of the report was supported ·by the Atlantic Richfield Company and the Exxon Company. The author is grateful for the assistance ·of Jack Tedrow of USA CRREL and Robert Patenaude, during the field work, and for the assistance of Specialist Elwood F. Wells of USA CRREL in the compilation of tables and photo­graphs. Technical review of the manuscript by B. Lyle Hansen and Paul V. Sellmann of USA CRREL is gratefully acknowledged.

An abbreviated version of this report was published in the Proceedings of the Second International Conference on Permafrost.

The contents of this report are not. to be used for advertising, publication or pro­motional purposes. Citation of trade names does not constitute an official endorse­ment or approval of the use of such commercial products.

Manuscript received 17 August 1973

CONTENTS

Preface •••••••••••••••.•..•••••.•••••••...•••••••. • • · · • · • • • • • • • · · • • • • • o •

Metric conversion· table ••.•••.••.•.•••••.••••.••••.••.•..•..••. • • • • • • • • • • ·

Introduction .•••••••••••••••.• o ••••••••••••••••••••••••••••• • • • • • • • • • • • •

The problem •••..••• · ••.••.•••••••••..••.•• • • • · • • · • • • • • • • • • • • • • · · • • • • Background •••••••••••••••••••••••..••.• .- ••.••• o o •••••••• o ••.••••••••

Scope •••••••••••••••.•••. ; ••••.•..••...••••••.•••••••.••••••.•••••• Equipment, tools and observations .•••••••••••••••••••••••••••.••••.•••..•••

Drill rig •••••••••••••••••••••••••..•.•••..•• • ....•• • • · • • · • • • • • • • • • · • Pump and compressor •••••••.••••. · •••.••••••.•.••••••••..•.•••.••••• ,~ ••

Refrigeration ••••••••••••••••••.••••.•.••..•••.•• · •• • • • • • • • • • • · · • • · • • Core bits ••••. ; •••••••.••••..•• ~ ••••••.• • • • • • · • • • • • • • • • · • • • · • • • • • • • • Core barrels ••••••••••••..•• ~ ••••••••••. · •••••••.•••• • ••••• • • • • • • • • • • • Drilling fluids •••..•.•••.••.••••••.•••••• ~ •.•••••.••••••••••••• • • • • • Other tools and equipment •••.••.•..•••.•••..••••••••••••••••••••••••• Measurements and calculations~ •.••••..•••••.•••••••..••••••••••••••.•

Drilling· operations •••• o ................................................. .

Hole GP-1 ••••••.•.••••••••••••••.•••••••.•••••..•.•••••••••••••••••• I-I ole GP-2 ••••••••••.••.••••••.••.•••••••••.••• ·· ••••••••••••••••••••••

Core drilling in frozen, fractured rock •••••.••••••..•••••••••.•••.•.••••••••• Results and conclusions •...•.••.••••••. ; •••••••.•...•••••••••••••.•••••• Literature cited ••.•••.•••••••.••••••.•••••••••••••••.••.••••••.•••.•.•••• Appendix· A. Core photographs ....................................... • ••••• Appendix B. Suggestions for deep continuous coring in permafrost •••.••••••• o.

Abstract •.•••••••••.••••••.•••••••••••••• ~ •••••••.••••••••.••.• • •• • • . • ·

ILLUSTRATIONS

Figure

Page ii iv

1 1 2 2 3 3 4 4 5 5 5 8 8

9 9

14_ 15 17 18 19 25 27

1. Location map of holes GP-1 and GP-2 at Ft. Wainwright, Alaska......... 3 2. Rig in place over hole GP-2 ·•••• . • • • • • • • . • • • • • • . • • . • • • • • • • • • • . • • • . . . 4 3. Diamond core bits • • • . . • • • . • • • • • • • • • . • • . • • • • • • • • . . • . • • • • • • • • • • • • • . . 6

· 4. Cutaway views of 2% x 37/s -in. and 4 x 5~ -in . .J;>CD~A large series core barrels • • • • • • • • • • • . • • • • • . • • • • • • • . • . • • • • • • • • • • • • • • • • • • • . • • • • . • • • 8

5. Log of materials, hole GP-2 • • • • • • • • • • • . • . • • • • • • • • • • • • .• • • • • • • • • • • • . . 12

TABLES

I. Summary of core drilling operations • • • • • . • ..• • • • • • • . • . . • • • • • • . • • . • • • • • 10 II. Operational data for core drilling of frozen, fractured rock during Project

Chariot., 1960 ~ • • • • • . • • • • • • • • • • . • • • . • . • . . • • • . • • • . • . • • • . • • • • . • . • • • 16

i~i

The problem

AN llNVESTlllGATfiOlN Olf COl!RE lill!RlllLlLllNG llN JPEIRENNllAlLlL'f FIROlZEN GIR.AVElLS ANlill IR.OlCK

by

' G. Robert Lange

KNIJflRODlUC'ltKON .

The foundation design of a large and important structure in any area requires good subsurface samples; however, for structures to. be founded on or in permafrost the requirements for quality a~d quantity of subsurface data may be even greater. Because thermal influences as well as mechamcal stresses must be considered, both thermally and mechanically "undisturbed" samples may be reo

quired.

Good samples of frozen fineagrained soils may be ·taken by either core drilling or driv~ sampling (Davis and Kitze 1967) although use of the latter method raises .some questions of mechanical diso turbance. Even coreadrilled samples may be disturbed by rebound or slight thermal alterations (Smith et al. 1973). Where possible, however, sites underlain by fineograined material (which may be icearich) are not usually considered· if an alternate site can be used which is underlain by gravel or bedrock. Sometimes these latter materials are <considered ·safe since it is assumed that they would suffer little or no consolidation upon thawing. This assumption, especially in the case of fractured and weathered rock, has led to serious problems where ice-filled cracks were thawed, re­sulting in intolerable foundation deflection (Linell 1973, McAnerney 196'8). On the other hand the recovery of samples of gravel and fractured rock, even when cemented by ice, has always been con­siderably more difficult.

The recent and rapid development of the North has raised problems where large thermally and mechanically .. undisturbed" samples, suitable for a variety of mechanical and thermal test.~. may be required for proper design of warm structures.

For example, the extraction of hot oil up through thick permafrost presents a novel design problem. In the Prudhoe Bay oilfield, the hot oil (180° F) will flow up the production casing and pass through approximately 1800 ft of permafrost. The surrounding permafrost will thaw .. The magnitude and· distribution of thaw will depend on both permafrost properties (thermal) and the well configuration in the permafrost. Upon thaw there will be some soil movement. The magnitude· and distribution of this :movement again will depend on permafrost properties (mechanical). This move"' ment will strain the well casing. The design problem is to predict thaw, soil movement and casing strain for various well configurations and then to select the· best configuration on an economic risk basis. Obviously, some knowledge of the ·permafrost is required. ;·

In the Prudhoe Bay oilfield, the upper 400 ft of permafrost is ~ostly frozen, wellograded gravel. Below 400ft the permafrost soils are silts, sandy silts and poorly graded sands. One attempt was · made to continuously core the ·permafrost with an oil well drilling rig. This rig was considerably

2 CORE DRILLING IN PERENNIALLY FROZEN GRAVELS AND ROCK

.larger than traditional coring rigs used for engineering investigations. • Only a meager amount of ·gravel core was obtained for the upper 400 ft. Highly fractured gravel cores have been obtained in other attempts. All the gravels recovered were of low ice content. High quality cores were ob~. tained of the silts -and sands.

The Alyeska Pipeline is another important example. • Over 2000 ·shallow holes have been drilled to establish alignment and foundation conditions .. Much of the line ·passes through ·perennially frozen gravel and bedrook where prediction of thaw subsidence could be important in anticipating pipe deflection. Some of the pumping stations may be located on perennially frozen gravel and bed­rock. ·Available boring records suggest that the bedrock is likely to be weathered or fractured. Thaw subsiqence prediction for both types of foundat.ions· could be critical if thawing is allowed.

Other potential problems associated with permafrost include: thaw beneath other surface struc­tures, drainage difficulties, failure of the ·slopes of open pit mines, caving of all sorts of drill holes. and the failure of tunnel walls in mining and civil works.

In short, there has been a substantial increase in the requirements for subsurface samples of frozen gravel and rock.

Background -

In the slimmer of 1958. the U.S. Army Snow, Ice and Permafrost Research Establishment began a detailed investigation of the problems of core drilling in frozen silts near Fairbanks, Alaska · (Fig. 1). In 1959 the problems of core drilling frozen gravel, the subject of this report, were inves­tigated. These investigations were important to the core drilling for Project Chariot, a study of a proposed nuclear excavation in northwestern Alaska in 1960 .•. The drilling for Project Chariot was reported by Lange and Smith (1972~

The recently increased need for good s'amples of all perennially frozen earth materials suggests that the details of our investigation of the more difficult problem, coring frozen gravels, be reported at this time. ·The only other known work which has specific reference to· coring frozen gravel is 'by Hvorslev and Goode (1963). They reported successfully coring frozen gravel near Thule, Greenland, where the ~round temperature at a depth of 30ft was +109 F (-12°C). :In colder ground the stronger ice bond reduces some of the problems of coring, whereas coring in materials near the freezing point -presents increased difficulties.

The work was carried out solely for the purpose of i~vestigating the problem of core drilling in permafrost. • The samples and hole were used for no other purpose and for this reason afforded a rare opportunity for experimentation. The chief objective of the investigation was to see if close control of the drilling fluid temperature and good core drilling practices would produce uniformly good quality core samples. ·Other objectives included an investigation of certain special bit designs and a com­parison· between chilled compressed air and diesel fuel as drilling fluids. • At that time it was_ also felt desirable to find the minimum core size ·that might be. taken from frozen·gravel at ground tempera­tures just below freezing. The concept of using the chilled fluid to stabilize the frozen borehole wall as opposed to the use of casing to prevent the gravel from running into the hole was also tested.

Scope

Two holes were cored continuously below the thawed active layer, one to a depth of 57 ft and the other to 78 ft. Both chilled compressed air and diesel fuel with some viscosity additives were used as drilling fluids. Two sizes of coring bits were used, 2% x 37/s in. and 3% x 5% in. The investigation ·Was in general limited to the problems Of COre drilling to investigate foundations for engineering s~ructures. Non-'coring bits were used only to penetrate the upper thawed material to .set casing and for cleanout purposes ·between coring runs.

0

Drill rig

CORE DRILLING IN PERENNIALLY FROZEN GRAVELS AND ROCK

Loop

2 3 miles

2 3 4 5 km.

Birch Hi II 6

E lev. (ft}: I 0 50+

Chena Hot Springs

Runways

Fort Wainwright

Hwy.

Figure 1. Location map of holes GP-1 and GP-2 at Ft. Wainwright, Alaska.

EQUIPMENT, 'fOOLS AND OBSERVATIONS

3

A versatile rig and standard "off the shelf" tools were used, along with some ·other special features and equipment designed for use in permafrost. A Failing Model 1500SS, rated for 1500-ft depth and a s .. in. hole, was mounted on a trailer with its own power unit (Fig. :2). · An 80-hp gaso­line engine drove the drill head with a 2"% -in. :x 28-ft splined kelly; the double drum draw works was capable of a ·15,000-lb pull and had a sand reel with a capacity of 1600 ft of 3is -in. wire line. The 38-ft folding mast had a gross capacity of 40,000 lb, and a racking capacity for about 2000 ft of NW drill rod. It was also equipped with a power breakout table. Special features included two constant rate of feed devices, useful for coring in homogeneous materials. For precision feeding of weight on the bit from the drill string only,· the normal running end of the main hoist lirie was stored on a truck winch which was driven by a small electric motor through a hydraulic transmission which furnished ratios of 1:1 to 100:1. For use with hydraulic feed an adjustable constant flow valve

4 CORE DRlLLlNG lN PERENNlALLY FROZEN GRAVELS AND ROCK

Figure 2. Rig in place over hole GP-2. Liquid chiller for drilling fluid and part of refrigeration at right. Mud pit~ in center.

was incorporated ~into the hydraulic feed system. :The entire rig was mounted on a semi-trailer 8 ft wide by 24 ft long, equipped with triple axles and dual tires. Removable tracks fitted over the tires and wrapped around all three axles, and a dolly with tandem axles, similarly .equipped with tracks, allowed mobility for tundra and beach.

Pump and compressor

The skid-mounted pumping unit consisted of a 4 ~ x 5-in. duplex piston pump, with a rated capacity of 100 gal./min at 400 psi, driven by an 80-hp engine similar to the rig power unit. A four­speed transmission provided pump speed control. ~ portable construction type rotary compressor rated at 600 scfm at 125 psi supplied the compressed air.

Refrigeration

The refrigeration unit, a Freon compressor driven by a 30-hp gasoline engine, furnished 5 tons of refrigeration at +15°F. The Freon was used to chill a flow of ethylene glycol, which was cir­culated through the outer shell of the heat exchanger while the drilling fluid was pumped through the tube ·bundle. ·When used to chill liquid drilling· fluids, this system was capable of imposing a tem­perature drop of 3°F· at -+15°F upon a flow of 100 gal./min of clean diesel fuel in an ambient tem­perature of +65°F (i.e. 5 tons at +15°F). Cuttings were ·removed .from the diesel fuel returning from the hole by settlement in first one and later two baffled steel tanks approximately 3~ ft wide and

CORE DRILLING TN PERENNiALLY- FROZEN GRAVELS AND ROCK 5

totaling 18 ft long. After returning from the hole annulus. the recirculated diesel fuel entered the heat exchanger at +18°F. under design c-onditions. Calculations for sizing,the pump and refrigerator are given by Lange (1963). The two mud pits and part of the -refrigeration system may be seen in Figure 2.

The compressed air cooling system consisted first of a fan-driven ambient air cooler which chilled the compressed air from the receiver temperature of about +250°F to the ambient temperature plus 5 to 7° F. The compressed air then entered a pressure vessel containing a commercial tube and fin heat exchanger which carried ethylene glycol circulated from the refrigeration system described above. The pressure vessel was fitted with a drain for defrosting. At the design ambient tempera­ture of +65° F. the system was capable of cooling 600 scfm of air compressed at 125 psi from +250° F to +15°F ..

Core bits

Some Impregnated and surface set diamond core bits of special design were used. These and the standard bits used, except for bits 19 and 20, are shown in Figure 3. Bits 19 and 20 were also of standard ·design. Bit 19 fitted the 4 x 5% -in. core barrel. It was the impregnated type, with bottom disc.harge. eight equally spaced 5

/,6 -in.-diam water holes and a full round crown. Bit 20 fitted the 23~ x 37/s -in. core barrel. It was also the impregnated type, with bottom discharge, six equally spaced water holes % in. in diameter and a full round crown. Both bits 'had waterways at 25° to the radius, matching the water holes.

Bit 14 was modified in the field by plugging the water holes. converting it from bottom discharge to internal discharge. This was done during earlier trials with compressed air in frozen silt to in­crease the amount of air flow and improve the distribution of air across the bit face. A "cracker­jack" metal coring bit, also not illustrated, was tried during runs 4, 5 and 6 in hole GP-1. It was similarto a full crown bottom discharge diamond bit except that broken, sharp-edged lumps of tung­sten carbide, 2-3 mm in diameter, were embedded in a random manner in the bit matrix.

The kerf area of all the larger (odd numbered) bits for the 4 x 5% -in. barrels ·had been opened to cut 37/s -in. core and 5% -in; hole for improved annular uphole air flow during the earlier trials in frozen silt. It was not feasible to modify the 23~ x 37/s -in. (even numbered) bits in a similar way since they were run through 4-in.-ID casing. It is felt that for use with low viscosity liquid drilling

, fluids this modification is of no value and may be deleterious to core quality and recovery.

Core barrels

Standard Diamond Core Drill Manufacturers Association (DCDMA) large series core barrels. were used in the ·2% x 37/s -in. and 4 x 5% -in. sizes (Fig. 4). The 4 x 5% -in. core barrel was used with an API to NW sub and sludge barrel while the 2% x 37/s -in. core barrel had no sludge barrel and was fitted with NW box threads. Blank reaming shells were used, with the outside q.iameter reduced slightly to improve air 'circulation.

Drilling n uids

Chilled compres~ed air was supplied by a mobile rotary compressor rated ·at 600 scfm at 110 psi, and the refrigerator -described above. Arctic grade diesel fuel was used along with small amounts of Baragel for viscosity control. Gilsonite and methanol were required to mix the Baragel with the diesel fuel.

6 CORE DRILLING IN PERENNIALLY FROZEN GRAVELS AND ROCK

6-10° Mod. Sq. Thds.

Impregnated Type, Approx.48 cts Fragmented Sort

4-875

Water holes plugged after Run GP -1-1

Impregnated Type, Approx.ll8 cts Fragmented Sort

14~778

Surface Set Type, Approx. 33 cts 6-10 per ct Cl Congo

12-796

Surface Set Type, Approx.46 cts 6-10 per ct Cl Congo, Full Crown

18-850

Figure 3. ·Diamond core bit~. First part pf bit .number corresponds to number used in tables and text.

CORE £?RILLING IN PERENNIALLY FROZEN GRAVELS AND ~OCK

-10° Mod. Sq. Thds:

Waterways ~"xl"x..L" 8 2 4

Impregnated Type, Approx.l53 cts Fragmented Sort

1-709

· Impregnated Type, Approx. 80 cts Fragmented Sort

. 5-849

Impregnated Type; Approx. 108 cts Fragmented Sort

3-845

Impregnated Type, Approx. 260 cts Fragmented Sort .

13-803

b. Bits 31/s x 53~ in . .

Figure 3 ( cont' d).

7

8 CORE DRILLING IN PERENNIALLY FROZEN GRAVELS AND ROCK

Surface Set Type, Approx. 80 cts 6-10 per ct. Cl Congo, Full Crown

17-851

b. Bit~ 3% x 5% in.

Figure 3 (cont'd) • . Diamond core bits. First part of bit number corresponds

tq number used in tables and text.

Other tools and equipment

OUTER TUBE CAP WITH SUB AND SLUDGE BARRELS STANDARD ON 4" • 5%" AND 6" • 7%" CORE BARRELS

FACE BOITOM

DISCHARGE BIT

PLUG

INTERNAL DISCHARGE

BIT (STANDARD)

Figure 4. Cutaway views of 2% x 37/s -in. and ·4 x 5%-in. DCDMA .large series core barrels.

NW diamond drill type rods were used for drill pipe. These are 25/s in. OD, flush outside with inside upset couplings. Twenty-foot lengths along with a few shorter lengths were available. No drill collar was used. Four- and six-in.-ID casing with threaded joints which were flush inside and out was used to case off the thawed active layer. ·

Measurements and calculations

The measurements and calculations given in Table I were obtained in the following manner. Percent recovery was obtained by dividing the length of eore ·recovered by the length of core cut in that run. ·Core cut and dropped during the previous run was assigned to the run from which it was recovered. RPM was usually measured with a hand-held tachometer; otherwise it was estimated. The penetration -·rate was measured with chalk marks on the kelly and a stopwatch. The feed rate (rev/in.) was obtained by dividing the RPM by the penetration rate~ The weight on the bit was calculated from the ·known weight of the tools, including kelly and swivel, when weight alone was used .. When the chuck was tightened for hydraulic feed the force resulting from the hydraulic pres-

. sure was added. The force per point is the total weight on the bit divided by the· approximate total number of diamonds in the surface set bits, regardless of their position in the bit. The pressure on

. . . CORE DRILLING IN PERENNIALLY FROZEN GRAVELS AND ROCK

the ,bit is the total<weight of the bit divided by the projected or kerf area of the impregnated bit, tegardless of the ·shape of the bit .. · The outside and "inside edge -velocities were calculated from

9

the bit dimensions and the RPM to· see if there was any relationship between this variable and the plucking or tearing of gravel particles from the core; no correlation was obvious. The drilling liquid f1ow rate was .measured from time to.time with ·a calibrated bucket and a stopwatch; other­wise it. was estimated. ,The compressed air flow rate was measured with a simple piston type air flow-meter normally used to monitor air consumption of small percussive rock drills. Fluid tempera­tures were measured with alcohol and mercury type thermometers set in wells incorporated into the piping Cor that purpose. The a·mbient air temperature was measured in the shade at waist to eye level. The -uphole velocity around the pipe was calculated from the volumetric flow rate and the crossa~ectional area of the rods and the ·hole~ The absolute viscosity of the inud -was measured with a Baroid rotary viscometer. ·Photographs were taken of all the core recovered from both holes (Appendix A). This core photography provides a valuable record and is therefore a routine· proce• · dure in this type of investigation.

DRILLING OPERATIONS

Most of the Fort Wainwright (then Ladd Field) reservation is situated near Fairbanks, Alaska, on the Tanana gravels. These materials consist of well-rounded alluvial gravels and sands generally derived from hard metamorphic and igneous rocks. Permafrost is discontinuous and minimum ground temperatures are only about 30°F. The permafrost bodies are generally less than 100ft thick. While most of the frozen sands and gravels appear to be ice-saturated and subsequently well-bonded this is not always the case.

A search for a suitable site was conducted during August 1959; at this time of year the ground may be thawed to depths of nearly 10 fL The search was limited to the military re~ervatiol) in order to facilitate use of the land. Several shallow holes were drilled with the Failing 1500 using com­pressed air along the toe of the south slope of Birch Hill (Fig. 1). • A suitable site was finally chosen north of the east end of the runway, in a clearing, more or less adjacent to an unused gravel pit .. A detailed log of the materials encountered in one of the ·core drilling trial holes (GP-2) is ·given ·in Figure 5. Because of the proximity of the two holes it also represents the general subsurface con­ditions encountered iii GP-1.

Table i summarizes the operational data collected during the ·drilling of both holes, and Appen­dix A (Fig. A1, A2) shows all the core that was recovered. Reference to the table and the core photographs will assist the reader in the narrative that follows.

Hole GP-1

Thawed silt, sand and a little gravel were drilled with rock and drag bits using .chilled com·. pressed. air, and 6-in.-ID casing was set into the top of permafrost at a depth of 9.0 ft. The thawed material continuously caved into the hole and the last foot of casing advance was accomplished by alternately drilling through the casing with a 5% -in. drag bit and driving the casing.

The first attempts to core were made in hole GP-1 (Gravel Pit No. 1) on 20 August using the 2% x 37/s -in. bits and core barrel and chilled compressed air. (Table I, Fig. A1). Diamond core bit 14 was used without modification in the first coring run, and although a foot of core of frozen sand and gravel < 1 in. was recovered, the run was stopped due to repeated interruptions of the circulating ~ir. This problem had been partially resolved with another bit ·during the earlier coring attempts in silt by plugging the bottom discharge holes and modifying the bit to effect internal discharge. This

.·

'l'dlle I. SaiiiD•Y of core drUliq operatloDB.

Bit edge -·

- Depth, ft . . Recovery, tt .; velocity Drilling fluid Temperature, °F Q>

l! ' = .a ... ~ ! "" :.. i 0 Ill ... i ·u cu ~ = c:: ~ ... ~ ... "' Q> Q> ·o; Q> o<>. Q> c:: ' "' eo .s c:: :s .e- -·- t,) ... :.. Q> e -~ ~ ~ = Q> ~ .5 .::: ' ~

0 Q>Q,Q>

= ~ ~ 0 = t 0 ~ .::: ... e = ... :....,"'

~ s ... ~ e- l! ~s ......

"'' ilt'-.., .., Q> "" ~-§~ vt· ., Q> ~ .5 ~~~- ~:e "" ~ ~i ·:; :c; § a:: Q., "" toe ~ 'Pi "' ii:· ~ e cit ,g 0 .

Q> 'iii £ ~ ~

Ill Q> 0 "C ... ~ Q., c.. ~ c.. <5 Q., ::;:, Remarks

HOLE NO. GP-1 1 14/778 9.0 10.6 1.0 L6. 61 250 1.0 250 400 85 4.2 2.9 470 93 air 27 63 178 Frozen sand, occasional gravel - 2'1. x 371. in. bottom dis-

charge coring bit in 6 in. casing-uphole air now plugged bv thawed r.uttimz.

2 14-778 10.5 11.2 0.5 0.7 71 250 400 85 4.2 2.9 460 93 air 26 60.8 174 Bit modified to internal discharge. ,_ 100

3 14-778 11.2 12.0 0.8 0.8 100 250 400 85 4.2 2.9 400 90 air ·26 62.6 152 Frozen sand trace of gravel.

4 cracker 12.0 15.1 2.6 3.1 84 300 4.0 750 400 5.1 3.5 520 85 air 27 62.6 197 Loose gravel on top of core-tungsten carbide "cracker-jack jack" bit.

5 cracker 15.1 16.6 1.4 1.5 93 350 5.0 70.0 400 5.9 4.1 85 air 27 66.2 Ciroulation plugged as above -dropped core. jack 6.0 58.3

6 cracker 16.6 18.1 0 1.5 0 350 2.0 175.0 400 5.9 4.1 500 80 air 30 64 189 Tried to pick up core-bit worn - no recovery. jack 6.0 58.3 550 208

7 2Q-890 18.0 19.4 0 1.4 0 350 2.0 175.0 400 75 5.9 4.1 500 85 air 28 65 189 No recovery - rock bit to 18 rt to clean hole, standard _ 30 bit.

8 2Q-890 22.7 24.2 0 1.5 0 350 3.0 116.7 400 75 5.9 4.1 550 75 air 30 68 208 Reamed to 23.1 ft -no recovery.

9 5-849 23.9 26.1 0 2.2 0 350 1.5 223.3 650 600 70 air 28 62 227 Reamed with 5'1. i~ rock bit to 23.9 ft using 371. x 5';. in semi-ribbed bit and large barrel-fragment of frozen wood.

10 1-709 diesel fuel Changed to chilled diesel fuel - loose gravel - no core -- increased viscosity gravel plugged pump.

11 1-709 26.1 29.4 1.5 3.3 350 4.0 87.5 650 55.6 8.8 5.9 30 27 68 Flat crowned bit - frozen sand and loose gravel.

12 1-709 26.1 29.2 0 0 0 - 350 0.0 00 700 62.8 8.8 5.9 29 27 52 Core catcher jammed with coarse cuttings and brok_e 2.0 175 blocking core early.

13 1-709 350 700 62.8 8.8 5.9 24 24 57 Core blocked as above.

14 1-709 28.9 33.4 3.4 4.5 100 375 2:0 187.5 700 62.8 9.4 6.3 150 31 29 55 Frozen sand and loose gravel - dropped some core., 2.5 150

15 1-709 33.4 33.5 0.5 0.1 100 350 700 62.8 8.8 5.9 150 24 23 55 Previous core recovered with loose gravel.

16 1-709 33.3 35.7 0.8 2.4 33 350 0.5 700 700 62.8 8.8 5.9 30 50 30 23 572 24 0.5 Frozen sand and loose gravel - core barrel head 1.5 233;3 100 plugged.

17 1-709 35.9 38.0 2.0 2.1 95 350 1.0 350 2060 1W 8.8 5.9 60 20 23 18 608 0.9 Frozen sand - sludge barrel full of loose gravel. 2.0 175 100 23 20

18 1-709 37.9 40.5 2.1 2.6 81 350 1.0 350 8.8 5.9 80 50 20 19 446 1.3 Some frozen gravel and sand - better core - blocked 2.0 175 125 25 22 early.

19 19-859 40.6 42.0 0.8 1.4 56 350 0.5 700 1750 157 8.8 5.9 60 50 22 46.4 18 0.9 Core blocked early, standard impregnated bottom dis-2.0 175 100 charge bit.

20 19-859 42.0 43.5 1.5 1.5 100 350 0.5 700 - 1750 157 8.8 5.9 40 26 48.2 22 Frozen gravel, modified lifter - splined inside - smoot_h 2.0 175 120 outside.

21 19-859 43.5 47.4 2.8 3;9 71 350± 1.0 2150 192 8.8 . 5.9 40 24 48.2 19 Frozen sand and gravel - good core. 2.0 100

'l'a.ae 1. (Cca&'t).

Bit edse Depth, ft Recovery,: ft velocity Drillins fluid Temperature, °F ---·

.; ~ ' .. ~ !-· . -'1::1 ~ > :a ~ Ill 2! ·c; fl} ·;;

~-~-~ t ~ c:: c:: :q Q. c:: ~ ~ Q.

§ N Q, > § Q ·- i =· t QN

~ -5 -5

::s "ii Ill

iS ~ Q E! ·- E! ~~ :::

~ Q Q.

~ Cl) ... ~ ~ .e- ~': I! c..,. ....... eli :; :s c:: ·a >"a .. Ill Ill i- ~ eli '-. E! ~g~ -

~ a.. ~ .s '1::1 Ill- fll.a '1::1 ilt'-Ill "a

~ fll- fl} ~ :a fi c:: Ill

~ Ill ·;;

;;:-=. ~ Ill r:: ~ tt 2! E! ,;; gil a.. 0 .s a.. ~ Remarks

22 1~859 47.4 48.0 0.6 0.6 100 350 slow 2150 192 8.8 5.9 60+ 60 25 46.4 21 0.95 Core blocked early. 120

23 19-859 48.3 52.0 3.2 3.7 87 350+ 1.0 350 2000 179 8.8 5.9 60 60 23 50.0 18 0.95 Frozen sandy gravel -good pore. 2.0 175 120 ..

24 19-859 51.9 55.7 3.4 3.8 90 350 1.0 350 2100 188 8.8 5.9 100 100 26 51.8 22 1.61 Frozen sandy gravel -: good core. 2.0 175 180

25 19-859 55.7 59.6 4.2 3.9 100+ 425 0.5 425 2150 193 10.7 7.2 80 80 26 24 51.8 22 1.31 Frozen sandy gravel - good core. .-1.3 850 100 160 1.61

26 17-851 59.6 63.7 3.9 4.1 95 350 1.0 350 2150 3.36 8.8 5.9 60 100 25 26 55.4 26 0.95 Excellent core frozen sandy gravel - standard surface 2.0 175 1500 2.35 150 25 set bottom discharge bit. •

27 17-851 63.6 67.6 3.7 4.0 92 350 0.5 700 2000 3.13 8.8 5.9 60 50 22 22 55.4 22 0.95 Excellent core frozen sand gravel. 1.0 350 40 100 0.66

28 17-851 67.4 70.0 2.0 2.8 71 300+ 0.5 700 2000 3.13 7.5 5.1 40 20 27 26 59.0 24 0.66 Chattering - some bit wear on gage_ stones - hole 4.0 75 "sticky".

29 3-845 69.9 73.2 3.0 3.3 91 325 3.0 108 1950 bearing 8.2 5.5 60 50 22 21 53.6 21 0.95 Good core frozen sandy gravel ~ ribbed bit ~l()W in 4.0 81 area? 100 gravel.

ribbed

30 13-803 73.2 74.6 1:2 1.4 86 350 1~0 350 2300 206 8.8 5.9 80 100 25 25 44.6 26 1.25 Poor core - "v" contour bit -blocked early. 200

31 13-803 74.6 78.4 3.8 3.8 100 350 1.0 350 2300 206 8:8 5.9 100 200 26 25 44.6 26 1.61 Thickened mud - full core - p~tially·· thawed - not th.e .. 2.0 175 300 30 saturated (bottom or permafrost?)

HOLE NO. GP·2 1 2Q-890 11.4 15.4 3.5 4.0 88 200 2.o- 100- 1700 338 3.4 2.3 60 100 25 27. 17 28 3.1 Diesel fuel and 2'1. x 3'1, in barrels - standard im-

4.0 50 27 pregnated bottom discharge core bit - 4 in. casing to 11.1 rt -lifter modified as before -refrigerator ne~ded onlv intermittently_ -Jtood core frozen sand.

2 2Q-890 .15.4 19.0 4.0 3.~. 100+ 200 l.o- 2Do- 1800 358 3.4 2.3 50 50 25 23 25 26 2.6 Excellent core frozen sand -frozen sandy gravel-14.1 2.0 100 21 . 19 t6 26 to 31ft.

3 Mod. 19.3 23.3 4.0 4.0 100 200 2.0 100 1700 365 3.4 2.3 50 50 20 16 28 16 2.6 "V" coot()ur surface set modified bit - good core. 14-778 80

4 12-796 23.3 27.4 4.0 4.1 98 . 200 . 4.0 50 2050 8.1 3.4 2.3 50 50 18 19 18 18 2.6 "V" contour bottom discharge bit - good core - not ice 21 22 20 saturated.

5 4-875 27.4 31.0 4.4 4.6 96 200 2.0 . 100 1750 (ribbed, 3.4 2.3 50 100 27 28 21 27 2.6 Good core-ribbed bit flattened. line· 27 24 24 contact)?

6 18-850 31.4 36.0 4.5 4.6 98 200 8.0 25 1650 4.5 3.4 2.3 53 50 22 20 22 20 2.7 Frozen silt with organic material with some sand and 100 20 17 18 gravel - standard bit.

7 18-850 36.1 44.8 . 8.4 8.7 97 200 l.o- 2oo- 1600 4.3 3.4 2.3 43.6 50 18 17 21 18 2.2 10 ft barrel - excellent core - 8.4 rt frozen coarse 4.0 50 sand and sand gravel.

8 14-778 44.8 47.3 0.0 2:5 0 200 2.0 100 1750 375 3.4 2.3 60 50 27 28 20 22(?) 3.1 Core blocked early -core barrel stuck -dropped core. 100

9 12-796 46.5 53.0 1.3 6.5 20 200 2.0 100 1900 7.5 3.4 2.3 60 40 20 22 20 22 3.1 Ran rock bit but hole not cleaned - ground part or core 100 60 29' 5.1 rest good.

10 12-796 54.0 56.6 0.5 2.6 19 2i.- 2.0 100 1850 7.3 3.4 2.3 60 100 23 25 17 20 3.1 Increased viscosity and ran rock bit to 45 rt thawed sand and gravel from bottom or hole plugged system (bottom or permafrost?)

12 CORE DRILLING IN PERENNIALLY FROZEN GRAVELS AND ROCK

LOCATION: Ft. Wainwright, % mile N of E run- ;I DRILLER:

way, North. Bank Chen a River Tedrow

HOLE NO.: INSPECTOR: GP-2 Lange

ELEV.: RIG': 45.0-475 ft (approx.)

'• Failing 1500 SS

DEPTH: 56.6 ft RECOVERY: 34.6 ft DATE:

Depth Cored 45.2 ft 76.5% START: 15 oct ·59 FINISH: :20 Oct •59

CLASSIFICATION REMARKS SYMBOL

LEGEND ;o-.---. ... ~----------------------~---------------------------------

10ft of 4 in. casing thru thawed material -cemented by freezing water.

GM Thawed silt, sand and gravel Chilled diesel fuel, some Baragel. 2% x 37/s DCDMA barrel and diamond bits. Refrigerator used intermittently due to low

11.4 -------+-f-L-l--'--'-4----------------------+air temperature. b::(j. s 3

1 2 GW ~:.o. ··: andy gravel < Is in. Nb

3. ~-._-__ -+o~o~or---------------------SW- o ~-. Med. coarse gray sand. Nb.

· · · · · Some gravel < 3 in. GW Q:Q:· Ice coating. Vc

. 17.6 -------r:--:-.~. -w----------------; GW :o.~·. ell frozen sandy gravel.

< 3 in. Nb DEPTH

(ft)'

.()··· ···a·· Ice coating, thickness vari­.'0 ··· able, on pebbles. Vc

. ·.a· Gravel becomes more uniform .... ·o·.

31.6 ----M--L~,..,~,;-.,11 1-1-l'l -S-i-lt_w __ / s_o_m_e __ o-rg_a_n-ic __ m_a_t ,-1-. --I Drilling rapidly

''I Nbn 32.4~--~~i~~~~~-----------------------1

SP­GP

C ·• Well frozen coarse sand-• • gravel < 1 in. ~ •. Layers 3 in. thick. Nbe

36 '5 _._ __ G_W~~;~~~(>~ .. :~ .. -S-a_n_d_y_g_r-av_e_l_< __ 2_i_n_._N_lie~~ 39.0~---+~~---------------------1

GP # • Sandy gravel< 2 in. Nbe 40.4~~-+-.--+-------------------~1

SP­GP

• • Coarse gray sand to sandy • ;, gravel.. Nbn to Nbe with •. • depth. Many quartz pebbles.

44.8------4---+----------.,.----1 No core.

47.3-----~--~-----------------------1

OW o: ·. ·. Well frozen sandy gravel < p~ 3 in., quartz pebbles. Nbe

48.0------~~:....j------------l Dropped core.

Core blocked, core barrel stuck.

Ran rock bit to clean hole. Thickened mud to 20-30 cp.

53.0~--4-~ .. ~.~------------1 GW :o · Sandy gravel< 3 in. Nbe Plugged core barrel head -thinned mud-

.·:·.·.· thawed gravel in hole after thinning mud. ::.:a·. Bottom of permafrost (?)--'f Bottom of hole .. t

56.6~---L~~~--~-----~~-L~~----~-L-----------------

?

Figure 5. Log of materials, hole GP-2. Soils are classified in accordance with U.S. Army TM5-852-2 and AFM88-19, Chap. 2.

CORE DRILLING IN PERENNIALLY FROZEN GRAVELS AND ROCK 13

was accomplished with bit 14 with silver solder and nail heads and the bit was used during the second coring run with ~orne succt:ss, considering the fact that the drop ball had not been inserted in the core barrel (Fig. 4). The high air pressure shown during run 2, while air was circulating through the core barrel (unobstructed by the ball), probably indicates damp cuttings obstructing the air during its uphole flow past the cor~ barrel. Althougp Table I shows an even better percentage recovery for run 3 the run was again stopped after less. than a foot because of plugging of uphole circulation. The next attempt, run 4, using the "crackerjack" (tungsten carbide) bit and a rather rapid rate of penetration, produced over 21h ft of good core before the uphole circulation was again plugged. During runs 4 and 5 some loose gravel was noted on top ·of the core, probably from the hole wall; ·however, the carbide bit cut several quartz pebbles without tearing them from the core.

Run 5 was stopped when the circulation was ·plugged after only a little more -than a foot of coring. Some of the core slipped through the ~ifter and was dropped down the hole during this run (Table I). Run 6 was an attempt to pick up the core dropped on the previous run, but this was un­successful and the "crackerj~ck" bit was completely worn, probably from running on loose gravel from the previous core or from the hole wall. The hole was cleaned out with a drag bit to 18 ft and another attempt to core was made with an impregnated diamond bit (no. 20). Run 7 also resulted in no recovery. The hole was reamed to 23.1 ft with a rock bit in preparation for run 8, which was also unsuccessful. The cuttings seemed too dry to furnishtherice bond necessary for core drilling.

Preparations were made to attempt to core with the larger core barrel and bits in hope that the larger diameter core might be stronger. The hole was rea!Ped with a 5% -in: rock bit to a depth of 23.9 ft. Run 9 was attempted ·with a bottom discharge ribbed style 37/s x 5% -in. diamond core bit (no. 5). The bit was badly worn during this run and only a fragment of frozen wood and. some loose gravel was recovered.

Attempts to core with compressed air were abandoned at this poirit. In general, it was felt that the chief reasons for the lack of success were 1) the inability of the chilled compressed air to cool the tools, which had oeen warmed in the ambient air, and 2) the poor distribution of air flow across the face of the bits. ·Defrosting difficulties also slowed operations.

Diesel fuel with no additives was circulated at +23° F for run 10, but no core was recovered. Loose gravel particles jammed between the core barrel and hole wall and scored the barrel. When a loss of drilling fluid was noted the vis.cos~ty of the diesel fuel was increased by adding some Baragel (1.5 lb/gal.}, and the casing was advanced to 14.5 ft .. With the increased viscosity, sand and gravel < 3/s in. plugged the pump intake and the mud was thinned to 1.2 lb/gal. .

Several inches of well-bonded frozen sarid ·and loose gravel < 2 in. (Fig. Ala) was recovered on run 11 using a flat crown, impregnated bottom discharge coring bit (no. 1). The core lifter jammed and broke during run 12, preventing the entry of core into the core barrel. During .run 13 the core was again prematurely blocked when sand and cuttings lodged behind the lifter. A 3.5-ft-long co~e of frozen sand with loose gravel on top was recovered on run 14. Some fluid loss was noted, perhaps to the gravel layer, and a little Baragel was added. Part of the core was dropped during this run. The balance of the core was recovered during the next run (no. 15) along with some loose gravel. Frag­ments of core of frozen sand were recovered from run 16 but the· gravel layers were again recovered in a loose or washed condition (Fig. Ala). The fluid passages of the core barrel were found to be plugged with scraps. of rubber, possibly from the pump pistons or the hoses, and the ·sludge barrel was full of < ~ in. gravel. Small gravel particles were flushed from the hole during washing prior to cutting and -recovering 2 ft of hard frozen sand in run 17. The ·sludge barrel was full of < ~ in. gravel. Apparently the gravel layers were ·too weakly bo~ded by ice to be cleanly cut by the core bit; on the other hand, occasio~al single gravel particles in sand layers were cleanly cut.

14 CORE DRILLING IN PERENNIALLY FROZEN GRAVELS .AND ROCK

Better quality core was recovered during run 18. · It included a partly thawed or eroded layer of frozen gravel which can be seen in Figure Ala. All or most of a sand layer was recovered,- but the core was prematurely blocked by sand and gravel around the lifter after. 2% ft had been cut. The drilling fluid became less viscous (< 9.0 centipoise) as diesel fuel was added to .take up spillage. An impregnated bottom discharge ·bit (no.- 19) with a full round crown was used for the next few runs. The core blocked prematurely again in run 19, apparently for the same reason, after 1.3 ft had been drilled and only a fragment of core ·recovered.·

·The outer splines of the core lifter were filled with brazing metal, leaving splines on the in~ side (next to the core) in an attempt to prevent fouling of the lifter by sand and cuttings. This appeared to work quite well as a core of frozen gravel was cut in fair condition in run 20. ·In spite of some washing or tearing of gravel partiCles core quality_ was improved in run 21 and a good many gravel ,Particles were cut cleanly. The core was prematurely blpcked after 0~6 ft during run 22, probably for the same reason as before. During run 23, 3.2 ft of frozen sandy gravel was recovered in good condition with only very little tearing or plucking of gravel partiCles from the core. Runs 24 and 25 were of equally good qualitywith. only occa~ional evidence of plucking or tearing.(Fig. Alb).

A surface set bottom discharge bit (no-. 17) was tried starting with run 26 in order to compare performance with the impregnated bits. ·Some wear on the gage stones was noted. ·Excellent core was recovered with very little plucking of gravel (Fig. Alb). ·Following this run, the rubber pump pistons were found to be badly worn from chemiGal attack by diesel fuel, or abrasion by sand and cuttings, or both. ·The pistons were replaced following run 27. • Equally good quality core of frozen sandy gravel was obtained during run 27 with only a little ·evidence of tearing or plucking. Core was of good quality in run 28 and in spite of some chattering the bit was in fair condition except for wear on the gage stones. • The hole was "sticky," with loose particles of small gravel in it, probably because of the thin mud, which was straight diesel fuel with a viscosity of 5 centipoise.

A ribbed bottom discharge impregnated bit (no. 3) was used during run 29, and while the bit was slow when cutting the larger gravel particles, 'reasonably good core was recovered.

A "V contour" bottom discharge bit (no. 13) was used for run 30 but the lifter jammed, blocking the core prematurely .. What little core was recovered was in poor condition. After the mud was thickened a little, a full core was taken during run 31. It appeared to be partially thawed, but un­damaged by coring. This may have been evidence of the proximity to the bottom of the permafrost body at a depth of about 75ft.

Hole GP-2

It was felt desirable to see if good quality core could be consistently taken in frozen sand and gravel using diesel fuel and the smaller .(2% X 37/s-in.) bit.s_ and core ~arrel. Good core had been re­covered using diesel fuel and the smaller bits and core barrels during the coring trials in frozen silt which included some soft, weathered gravel.

The rig was moved several .feet to the south of hole GP-1 and 4-in. casing was set through thawed sand, silt and ,gravel to a depth of 11 ft. The casing was cemented and sealed simply by pouring water around it and allowing it to freeze overnight.

Diesel fuel with a very small amount of Baragel was prepared. Core lifters were again modified by removing the fingers from a finger type lifter. · Thus tl:tey presented a smo_oth inside surface to the core and a splined outside surface to the inner tube extension. The refrigerator was run only inter-; mittently as needed during the coring of this entire hole due to the 1ow .ambient temperatures.

.. ;· .. -..... ,,.,

CORE DRILLING IN PERENNIALLY FROZEN GRAVELS AND ROCK 15

A full round impregnated bottom discharge bit (no. 20) was used to take a good core of well-. frozen sand and sandy gravel on run no. t·in spite of the fact that the ·insertion of the drop ball was neglected during coring. Excellent core was taken on run 2 (Fig. A2a). The transition from altere. nating layers of frozen sand· and sandy gravel .to frozen· sandy gravel occurred at 14 ft ·and all of the cores were classified as frozen ·sandy gravel until about 31ft where considerable frozen sand with

·some layers of gravel was encountered (Fig. 5). The impregnated V contour bit. mOdified from bottom discharge to internal discharge, was used in run 3. Good core was obtamed except that a couple of cobbles nearly 4 in. ~n diameter appeared to be tom from the· core.; A surface set V con­tour bottom discharge bit was tried in·run 4 and some gravel particles were torn from the core, re­sulting in core of only poor to fair quality. The gr~vel was not entirely ice-saturated, and ice­coated pebbles and cobbles were ob~erved.

At this point a new secondary mud pit was added that was designed to allow the ·settlement of particles as fine as silt size from diesel 'fuel containing no additives at normal pump discharge rates (Fig. 2). This appeared to eliminate the ·damage to the pump pistons caused by sand and cuttings. Due to the low ambient temperature the refrig~ra:tor had not been used during run 4. How­ever, the sun appeared dilring run 5 and the refrigerator was started. The ribbed internal discharge impregnated bit (no. 4) was used and evidence of some plucking or tearing of gravel particles from the core was noted. The crown of this bit, which had shown soine wear previously. became visibly flattened during this run (Fig._ A2a).

A full round surface set bottom discharge bit was used during run 6 to cut an excellent core which consisted of frozen silt with organic material and ·sand with some layers of frozen sandy gravel < 1 in. This bit cut very fast in the frozen sand, but appeared to dull or "polish''' rapidly. A 10-ft-long core barrel and the same bit were used during run 7 to cut an excellent core 8.4 ft long which consisted of layers of frozen coarse sand and sandy gravel (Fig. A2b). ·There was little if any evidence of plucking or tearing even though some of the cobbles consisted of quartz and quartzite. Apparently during run 8 the core prematurely blocked and the core barrel stuck in the hole during withdrawal. ·The core was dropped during attempts to free the barrel. _A rock bit was run in an attempt to clean the hole- but an error was apparently made in measuring the drill rods and the bit may never have reached the bottom, leaving loose gravel in the hole. This condition may account for the poor results of the final two runs in this ·hole. During run 9, advance of the tools during coring was difficult due to loose gravel in the hole and while the core that was recovered was in good condition, the rest was lost and ground.

Mud was mixed to a viscosity of 20-30 centipoises and a rock bit was run to 54.1 ft to .clean out the hole. Cuttings < 1 in. were lifted and the hole seemed clean in preparation for run 10. After 2.6 ft of codng the pump pressure suddenly rose and the ·pressure relief valve was sheared. The thick mud apparently carried cuttings and/or thawed sandand gravel into the head of the core barrel where the flow of fluid was completely blocked. The tools stuck in the hole during witbdrawai. Thinner mud was mixed and th~ tools were run in_ the hole for another coring attempt but they could not be lowered to the bottom because of the loose material. ·It was assumed that thawed material had entered the hole because the bottom of the permafrost body had been penetrated.

COIIU! IDI!Ul.l..ING IN Jli'IROZEN, Jli'RAC'.lrlUIRED ROCK

Some of the exploration drilling carried out in connection with Project Chariot, approximately 100 miles north of Kotzebue, Alaska, during the summer of 1960 demonstrated that virtually undis­turbed samples of frozen, badly fractured bedrock can be taken with techniques and equipment similar to those used in the frozen gravel. On· this project; two holes were drilled and cored to depths of

16 CORE DRILLING IN PERENNIALLY FROZEN GRAVELS AND ROCK

. . . . . . '

1000 and 1200 ft in perennially frozen fine-grained sedimentaryrock (chiefly thinly bedde(}-mudstone) (Lange and Smith 1972). Approximately 10ft of each 100-ft interval was cored. _ Lachenbruch et al. (1966) report near-surface ground temperatures- at this time of year ranging from 32°F at a depth of -1 ft to 23°F at about 10ft. At depth, temperatures unaffected by seasonal fluctuations showed a linear gradation from 23°F at 50 ft to 32°F at the bottom of permafrost at 1000 and i200 ft (Lange and Smith 1972).

The -rig, refrigerator and ·other equipment were essentially -the same as described earlier.-- The 2% x 37/s -in. DCDMA large series core barrels (Fig .. '4)_~Q standard surface set bottom discharge diamond core bits were used.

Two conditions pertinent to this report were encountered during this project. _ On hole D, coring was initiated 1.2 ft from the surface, where the top of permafrost was encountered. The material consisted of frozen silt and ice with rock fragments and graded to frozen shattered bedrock with ice­filled cracks at about 5 ft. Crack width and frequency decreased rapidly with depth. All this core is illustrated in Figure A3a. Pertinent operational details of these two coring runs are given in Table II.

. . . .

Several zones of faulted crushed rock were encountered at depth in both holes. , The core from one of these fracture zones is illustrated in Figure A3b. The measured total water content of the material illustrated was only 2.1% by weight, but when this material was thawed all cohesion between the .small chips was lost and the sample became a completely incompetent pile of chips and powder.

Depth

Bit

Core barrel

Weight on bit

Table U. Operational data for core drilling of frozen, fractured rock during Project Chariot, 1960.

Hole D

1.2-10.4 ft

EG 561, 234 x 37/s-in. surface set, 10-14/ct (bottom discharge full round crown?)

234 x 37/s -in. DCDMA Large Series, 5 ft

2000 lb

Hole C

194.6:203.6 ft

AM 850, 234 x 37/s -in. surface set, 6-10i ct (bottom discharge full round crown)

Same, ·10ft

2200 lb

Rate of penetration 1-5 in.lmin 1-2 in./min

RPM

Fluid Fluid pressure Fluid flow Fluid temp in Fluid temp out

Fluid viscosity

Coring time

Remarks

225

Diesel fuel 50 psi 45 gaL/min 24°F 24°F

5-7 centipoise

2 runs, 4.6 Ct each, 30 min each

Excellent core, soil to rock transition

200

Diesel fuel 200 psi 60 gal./min 20°F 2,1°F

13 centipoise

1 run, 8_. 7 ft, 1 hr 15 min

Good core, fractured zone

CORE DRILLING IN PERENNIALLY FROZEN GRAVELS AND ROCK 17

IRESIUlLIJrS 'AND CONClLlUSllONS

Th~ detailed results are illustrated in the core photogniphs (Fig. A1, A2). All the core that was recovered is shown in these photographs with the exception of- one or two short intervals . where negativ~s wer~ lost. The quality of the core can be judged 'from these photographs and the

quantity is given in the ·"recovered" column in Table I.

In general, poor results were obtained when attempting to core with air during warm ambient air temperatures. This is in part due to the fact that core drilling in shallow holes exposes the tools to the refrigerated air for a short time relative to the time they spend being warmed at the sur­face. Further, and more·.-importartt, air is a much less effective he'at transfer medium (Lange 1963). 'At the mass flow rate required for each ~f the two different fluid streams to remove the cuttings from the hole, the diesei fuel has several orders of magnitude. greater capacity for heat removal than the compressed air. When the ambient air is at +25°F or lower, compre~sed air can be chilled suffi­ciently, with a properly designed, fanodrivenambient-air;.to-compressed-air heat exchanger, to be used as a drilling fluid to take consistently good cores of .frozen rocks and soils~ At temperatures substantially below freezing, expedient air coolers of all sorts using ambient air as the coolant have been successfully used~ Although Fairbanks normally has a dry summer climate, defrosting problems made the chilling of compressed air by direct mechanical refrigeration (i.e. compression and expan­sion of a refrigerant gas) almost an impossibility.

The mechanical refrigeration system used in this work included two stages due to the original requirement for cooling both compressed air and. a liquid; Greater efficiency and convenience would be afforded by a single stage liquid chiller system in which the refrigerant directly cools the drilling liquid without the use ·of an intermediate brine.

The use of diesel fuel brought substantially better results in terms of quality and amount of core. Difficulties were experienced when loose sand and gravel or cuttings jammed the core.'lifter and caused the premature blocking of the core upon entering the barrel. Some of this loose material may have been cuttings, especially from core tha:t had .been dropped and ground .. However, some of it · probably was eroded from the hole walls. It is difficult to conceive df tq!s material being thawed by the drilling liquid during the use of chilled diesel fuel with or wHhout additives since· drilling fluid was never introduced into the hole at temperatures above freezing. It is more likely that this material was eroded Jrom "dry frozen" zones, i.e. where complete ice saturation was lacking. Two such zones were noted in the core (runs GP-l-31 and GP-2-4). ·Modification of the core lifters ameliorated this problem considerably, suggesting that a different choice of lifter or a new design may be necessary. ·

Control of the density and viscosity of the mud were crude at best and it is likely that modern mud technology, such as the use of foams, might also reduce the magnitude of this problem if not eliminate it. The ·deleterious solids might also be removed by the use of desanders or other mechan­ical means of separation at the ·surface. Control of the permeable, "dry frozen" zones might be accomplished ;directly by use of a mud additive to obtain the appropriate filtration properties. Perhaps more attention should have been given to the proper preparation of the hole before coring runs by careful and more frequent use of a non-coring full hole bit, especially one that produced finer cuttings.

The impregnated ribbed bits cut rapidly in frozen sand and finer grained material but were slow and dulled quickly in gravels containing hard rock types. The V contour bits worked well and are to be .re?ommended. Standard bit types also were ·satisfactory, especially those with a full round crown. Surface set bits were fast ~ut were prone to damage and excessive wear when run on loose gravel

18 ·CORE DRILLING IN PERENNIALLY FROZEN GRAVELS AND ROCK

particles of hard rock types. Impregnated bits ·were not damaged or worn so easily but tended to cut more slowly. Surface set bits with the V contour probably are a promising design, but this style. was bnly used on one occasion (runs 9 and 10 in GP-2) and under otherwise difficUlt con­ditions. ·There is very little evidence for a choice between i!lternal discharge or bottom discharge, except to speculate that bottom discharge seems to afford no advantage .. There ·is probably no advantage tO expanding the kerf dimenSiOnS Of the bitS aS WaS done With the 37fe X 5% -in. bitS, at least for diesel fuel or thin oil-based muds. Hvorslev and Goode (1963) found the-clearances of the standard 4· x 51~-in. bits satisfactory with this size core barrel.

When die~el fuel is to be use.d as the basic drilling fluid, consideration should be given to the possibility .o( contaminating the core. During core drilling trials in frozen silt the diesel fuel was observed to soak into the sample as much as % in. However this was easily removed by scraping, exposing.a completely uilqontaminated sample. Diesel fuel was removed from core samples ob­tained at Project Chariot. by the use of the Soxhlet extraction process in the laboratory in order to obtain accurate total water content values (Lange and. Smith 1972). Th~ pos-sibility that the presence of diesel fuel may adversely affect the accuracy of certain other physical (and certainly chemical) tests should be examined. Additives with appropriate filtration qualities might be used to inhibit the migration of diesel fuel into the core -in order to reduce the contaminated volume of the core.

It is concluded -that satisfactory cores of well-frozen gravel and frozen, fraQtured and weathered rock at near-freezing ground. temperatures may be taken· even in 'sumrrier weather by circulating a liquid drilling fluid chilled to temp~ratures just below the ground temperature. Cooling compressed air is not feasible for core drilling until the ambient air temperature reaches +25° F or cooler~ ~Cores of excellent quality as -small as 23~ ln. were consistently taken. Hvorslev and Goode (1963) were successful withNX size core in colder permafrost. Borehole·wall stabilization was satisfactorily achieved with tpe chilled liquids, except possibly where complete ice saturation was not present ...

LITERATURE CITED

Davis, R.M. and F.F. Kitze (1967) Soil sampling and drilling near Fairbanks, Alaska: Equipment and .procedures. U.S. Army Cold Regions Research and Engineering Laboratory (USA CRREL) Technical Report 191.

Hvorslev, M. Juul and T.B. Goode (1963) Core drilling in frozen soils. Proceedings, First Permafrost Inte.rnational Conference, Purdue University, NAS-NRC Publica­tion 1287.

Lachenbruch, A.H., O.W. Green and B.V. Marshall (1966) Permafrost and geothermal regimes. In Environment of the Cape Thompson Region, Alaska (Wilimovsky and Wolfe, Editors). U.S~ Atomic Energy Commission.

Lange, G.R. (1963) Refrigerated fluids for drilling and coring in permafrost. Proceedings, Fin~t Permafrost International Conference, Purdue University, NAS-NRC. Publica~ tion 1287.

Lange, G. and T .K. Smith (1972) Rotary drilling and coring in permafrost, Deep core drilling, core analysis and borehole thermometry at:;:Cape Thompson Alaska. US:A CRREL Technical Report 95, Part III.

Linell, K.A. and G.H. J<:>hnson (1973) Engineering design and construction in permafrost re­gions: A review. Proceedings, Second International Permafrost Conference, Yakutsk, U.S.S.R. .

McAnerney, J.M. (196S) An investigation of subsurface drainage at BMEWS Facility, Thule, Greenland. USA CRREL Special Report 111.

Smith, W.S., R.E. Smith and K. Nair (1973) Sample disturbance and thaw-consolidation of a deep sand permafrost. Proceedings, Second International Permafrost Conference, Yakutsk, U.S.S.R.

·---------------------------~---

Run 1 (9.0-10.6 It)

Run 5 (15.1--16.6 It).

Run 2 (10.5-11.21t)

Run 6-10 No core

Run 14 (28.9- 33.4 ft)

Run 16 (33.3·35.7 ft)

Rur;J 18 (37.9-40.5 tt)

Run 3 (11.2-12.0 ft)

Run 11 (26.1- 29.4 ft)

Run 4 (12.0-15.1- ft)

Run 12 and 13 No core

Run 15 (33.4-33.5 ft)

- . . •. ... >·~,. ~ • .._ I~ .. t .. ~ ~t ~ « I! ~.. ''<• • #, :( ' '• W f X , ~ . .

~fill;, '!!i"\ >< ~•:t f .. ~~ ;~~"'~to~·.

Run 17 (35.6· 38.0 ft)

:/Jl/!i6] 8'1

Run 19 (40.6-42.0 ft) Rur;J 20 (42.0·43.5 ft)

a. Runs 1-20.

Figure A1. Photographs of core from hole GP-1.

1 2 . J l 4 • :_ <'

Run 21 (43.5-47.4 ft) Run 22 (47.4-48.0 ft)

Run 23 ( 48.3 • 5~.u ct)

Run 24 ( 51.9- 55.7 ft)

Run 25 (55. 7- 59.6 ft)

Run 26 ( 59.6-63.7 tt)

b. Runs 21-26.

Figure A1 (cont'd). Photographs of core from hole GP-1.

Run 27 (63.6·67.6 tt) Run 28 (67.4-70.0 ft)

RuQ 29 (69.9 -73.2 It) Run 30 (73.2· 74.6 It)

Run 31 (74.6-78.4 It)

c. Runs 27-31.

Figure Al ( cont' d).

Run 1 (11.4-15.4 lt)

Run 2 (15.4 -19.0 ft)

.. - - ~- _, .._ ..

- - - -····· Run 3 (19.3 • 23.3 ft).

Run 4 (23.3·27.4 lt)

,~-,.··· . '· .. ·-·. ,. . . . . ' "':' ' .• . -~ "' ,: . . -.'·' . . • • ,. .., ., • ' *' • • ~ -. • ' ' . . . . •' • .. . ~ & .. • . ., ; ~ •

~ - • t. -

Run 5 pa .4- ;J~.u ctJ

a. Runs 1·5.

Figure A2. · PhotQgraphs of core from hole .GP-2.

•- 9, 3, ~ 1 2 3 • 5 • (> 7 8 'I ~ft I 2 J 1 I 2 3

Run 6 (31.4·36.0 tt)

Run 7 (36.1,. 44.8 ft)

Run 9 ( 46.5· 53.0 tt)

b. Runs 6-10.

Figute .A2 (cont'~).

.9

Run 8

Photo .missing, core continuous

No core recovered

---- .-.... ._ I l I

Run 10 (54.0·56.6 ft)

a. Hole D, 1.3-10.4 ft. These photos show tl~e character of the surface of the bedrock at Hole Dog. The interspaces between rock fragments are filled with frozen silt and ice. The run begins at 1.5 ft and the quality of the core is continuously good; the upper loot of core contains only silt and ice and the frequency of rock fragments increases with increasing depth. Strong vertical orientation of

the rock fragments commences at about 4 ft.

b. Hole C, 196.7-202.3 ft . . Typically good quality core obtained from the highly crushed zones. The darker streaks and shading are caused by diesel fuel which soaked into the core during drilling. A great d~al of the diesel fuel was removed from the surface before these photographs were taken.

Figure A3. Frozen rock core, Project Char.iot.

25

APPENDIX. B. SUGGESTIONS FOR DEEP OON.THNUOUS·.coRnNG HN PERMAFROST

Using the equipment and techniques with the. improvements suggested above, deeper (500-2000 ft) holes could be (or perhaps have been) continuously cored in competent permafrost. Deep holes have been cored .in unfrozen "hard rock" with the conventional equipment as a routine matter for many years. However, even when using longer (up to 60 ft) core barrels the time involved for the large number of round trips required for continuous core has made these operations time-con­suming and expensive. Often this was onlyfeasible when labor was cheap or the informationto be gained from the hole was indispensable.

It is suggested that the wireline coring equipment presei,J.tly in use by the "hard rock" diamond drilling industry be considered when_ planning deep continuous coring in permafrost .. Table BI gives some of the critical dimensions and weights of the tools currently available. The advantage in re­ducing rig hoisting .capacity is ·obvious, eslfecially if the "composite" rods are used. The rig mentioned earlier in this .report (Failing 1500) is rated to handle 2000 ft of the "PQ" steel rod using a multiple sheave traveling block, yet the rig, exclusive of vehicle, weighs on the order of 12,000 · lb. In this case the rig is at full rated capac.ity. However, this example is given only to demonstrate the several advantages that might be realized by using this lighter equipment. While pump pressure requirements have not yet been carefully determined preliminary data show that they could be quite reasonable. The pump volumetric discharge requirements would be very modest because of the narrow rod to wall annulus.

Table BI. Dimensions and weights of wireline coring tools. Data furnished by E.J. Longyear Co., Minneapolis, Minn.

NQ HQ

Core size (in.) 17/s 2~

Hole size (in.) 26%4 32%2

Core barrel OD (in.) 2'% 3% Rod OD (in.) 2% 3~

Rod ID (in.) 2% 3l;i6

Wt/10-ft length,- standard (lb) 51 77

. Wt/.10-ft length, composite (lb) 44 57.3

PQ

311/32

45%4

4% 41~*

41;i6

103

t *All standard weight rods and couplings are fiush inside and out except that

PQ couplings are slightly upse.t to 4% in. tPQ rod is not presently available in the composite weight.

Although core-to-hole diameter ratios are not as favorable (i.e. narrow kerf) as the dimensions of the conventional diamond drilling sizes, the use of the V contour bits mentioned earlier might minimize this problem. Stepped contour bits are often used with wireline equipment; they should also offer an advantage in this regard.

26 APPENDIX 8

The narrow annulus between the drill string (core barrels and drill rod) and the hole wall sug­gests that special attention should be given to desanding so that the downhole fluid stream is as free of particulate matter as possible. This will also be important to prevent clogging of the narrow down-hole fluid passages in the core barrel.

If caving or other problems occur that require casing the hole, the drill string in use at the time might be used as casing without removing it from the hole.· Examination of the hole and core

· dimensions in Table BI would suggest that smaller size tools cannot be run through the next larger size core bit and barrel with the ·inner tube removed. However, if this operation is anticipated, it is understood that "drillable" bits are available which, for example, would permit HQ tools to be worked through the PQ bit, barrel (less inner tube) and rods. A small ring in the outer tube of the

. larger core barrel may also have to be drilled out. Thus the larger PQ string may be left in place as casing while coring continues with the smaller HQ tools.

The drilling plant selected for this sort of operation should be fully equipped with the best available instrumentation and· drilling controls. ·If and when the retractable wire line coring bit be­comes available, this should certainly be considered. The advances in bit design made during the

·development of the second generation lunar drilling equipment should also be investigated. ·

Unclassified Security Classification

DOCUMENT CONTROL DATA· R & D (Security classification ol title, body ol •'-tract and lnde1tln1l annotation must be entered when the overatl report Is classllledl_

~.ORIGINATING ACTIVITY (Corporate author) Ut. REPORT SECURITY CLASSIFICATION

U.S. Army Cold Regions Research and Engineering Laboratory

H~nover. _New Hamn~hi..re 0171)1) 3. REPORT TITLE

Unclassified 2b. GROUP

CORE DRILLING IN PERENNIALLY FROZEN GRAVELS AND ROCK

4. OESCRIPl'IVE NOTES (Type ot report and Inclusive dates)

2L

~~--A~U~T~H~O~R~(S~I~(F~I~rs~t-~-m-e-,~m~id~d~le~in~/t~/a~l,~l~aa~t~n~am~e~)------------------------------------------------------..--·---

G. Robert Lange

b. 1-"F:;:')JEC T NO.

c.

ci.

Technical Report 245 ab. oTHER 'REPORT NO lSI (Any other numbers that may bo assi~Zned ..

this report)

________________________________ __.. ___________________________ ,. __ _ 10. O!S"TRII:liJTIOI'' STATEMENT

Approved." for public release; distribution unlimited. J-o.-~------------------------r:I~2.-:S~P~O-NS:":O~R~IN-::G:-:M~I~L~IT:-:'A-=-R7:"Y-:"A"7"C:-=-TI:-:":V-::IT:7Y:---------'-····­

I!. suPPLEMENTARY NoTEs Co-sponsored by Office, Chief of Engineers.·.

Atlantic Richfield Company and u.s. Army Corps of Engineers Exxon Company Washington, D.C. 13. ABSTRACT

The problems of obtaining frozen samples by core drilling of, perennially frozen gravel and rock were investigated. Most of the core drilling was carried.out in ice-bonded, well-graded alluvial gravel with the g~ound tem­perature near its freezing point. Both chilled compressed air and oil-based liquids were used as drilling fluids. The details of both successful and unsuccessful coring attempts are reported and related to descript~ons and photographs of samples of a wide range of quality. Drilling variables such as weight on the bit, rotational velocity, rate of penetration, fluid tempera­tures, viscosities, flow rates and pressures and mechanical details of the diamond bits are reported. To make the information more wide~y applicable, calculated values for the pressure on the bit, the lineal velocity range of the diamond points, the force per diamond point and the uphole velocity of the fluid stream are given. Some core drilling was also successfully accomplish­ed in frozen, fractured rock. The results and pertinent details of this operation are also presented. It is concluded that with careful control of the drilling variables, good samples of these difficult materials can be obtained at satisfactory drilling rates so long as the material is well­bonded by ice. Suggestions are given for improvement of equipment and methods

DD .': •• 1473 PtaPLACBS DO P'O .. M 1478, I .IAN ••• WHICH Ul Ot850LIITIK 11'01' ARMY UIJ ••

28 Unclassified Security Classification •-...... ...,...._,---~·~·iiO:;iii;------------------.... --.-------.------... -...-,a,_ __ IIC"', I 4.

Coring\ Coring bits

. Diamond bits ~ Frozen soils Permafrost Rock drills

:Underground_ surveys

KEY WORDS LINK A Llt:'K B LINK C

ROLE WT ROLE WT R 0 L._E -4--W-T~II

I

----=.I"U~.l.aB§ified.~-~-, .. ", __ , Security Classificotion