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.---------DISCLAIMER --------.,

This book was prepared as an account of work sponsored by an agency of the United States Government, NAithef the United States Government nor any aqency thereof, nor any of their employees. makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specif ic commercial product, process, or service by trade name, trademark, manuf&Clurer, or otherwise, does not necessarily constitute or imply its endorsemenc. recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

_ .. -· ·-- -DOWNHOLE STEAM GENERATION: MATERIAL STUDIES

E. K. Beauchamp, L. J. Weirick, and J. F. Muir Sandia National Laboratories

MASTER Albuquerque, New Mexico

ABSTRACT

One enhanced oil recovery tech­

nique for extracting heavy crude

from deep reservoirs by steam

flooding involves generating steam

at the bottom of an injection well.

Development of a downhole steam

generator that will produce steam

and inject it into formations at

depths greater than 2500 feet is

one objective of a Department of

Energy/Sandia National Laborator-

ies development effort--Project

! DEEP STEAM. Extensive material I

1 studies have been performed in cup-' 1 port of Project DEEP STEAM; current

j efforts are devoted primarily to

; the selection and evaluation of I

' materials for use in downhole steam

I generators. This paper presents

1 obse~ations of the performance of I 1 candidate metals and refractory

ceramics (combustor liners) during

tests of two prototypic, high pres­

sure, diesel/air combustion, dire~t

This work supported by the U. s. ,Department of Energy unde r ~nntrRrt

l~~:.- DE-AC~6-76DP00_~8~-· ____ _

contact, downhole steam generators.

The first downhole test of such a

generator provides data on the per­

formance of various metals (304L,

310 and 316S stainless steels and

! plain carbon steel) exposed for

I several weeks to a warm, aerated

I saltwa~er environment. A number of

1 corros1on mechanisms acted to cause

I

severely degraded performance of

some of the metals. Several refrac-

1 tory liner designs were evaluated I i during ground level tests of a

'!generator having a ceramic-lined

combustion chamber. Of the two

refractories employed, alumina and

silicon carbide, the alumina l ine r s

exhibited more serious surface

degradation and corrosion.

1. INTRODUCTION

Efforts aimed at achieving

greater energy self-sufficiency

j have placed considerable emphasis

on the development of alternative

energy sources. Because of the time

scales involved, however, these are

not expected to ... :.:~;,r significantly ~ m .. ........ , 10H OF THIS oocuMr 1T 1s !Jr;L::m·c

DISCLAIMER

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency Thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

DISCLAIMER

Portions of this document may be illegible in electronic image products. Images are produced from the best available original document.

""~~;: .. ~-~· r •

the energy picture in the near-term.

; . ··. ~ . :

T ~ ·, -

Activities which promise a more im­

mediate contribution toward reduced

reliance on imported petroleum in­

clude the discovery and exploitation

of new domestic oil fields and the

development of advanced techniques

for extracting more oil from produc­

ing fields. The application of

these improved recovery techniques

is referred to as enhanced oil re-

covery (EOR).

EOR includes a variety of tech-

niques which increase the recovery

of oil above that obtained through

primary recovery (pressure driven

or pumped). These are frequently

categorized as "secondary" and

"tertiary" recovery methods. Sec­

ondary recovery techniques, such as

waterflooding and immiscible gas

.,. .. , injection, are aimed at maintaining :. ; '', :- . ~

reservoir pressure at levels ade­

quate to extend production beyond

the natural cut-off point. Tertiary

recovery methods fall into two gen­

eral categories: 1) chemical meth­

ods in which an injected fluid

(e.g., hydro-carbons, carbon diox­

ide, and micellar-polymer solu­

tions) mixes with the oil effecting

miscible displacement; and 2) ther­

mal methods which are priQarily

aimed· at reducing the viscosity of

the oil through the addition of

heat (e.g., cyclic and continuous

stean injection and in situ combus­

tion).

Project DEEP STEAM addresses the

application of a thermal EOR tech­

;nique, steam injection, to the

recovery of extremely viscous, low

API* gravity crude from deep reser­

voirs. The project was initiated in

1977 as part of a 5-year Department

of Energy (DOE) EOR research,

development and demonstration pro­

gram. (1) The objective of Project

DEEP STEAM is to develop the tech­

nology required to economically

produce heavy oil from reservoirs

at depths greater than 2500 feet

using steam injection. Two separate

areas are being addressed: -1) modi­

fication of injection well comple­

tions to improve thermal efficiency

(including development of thermal

packers and evaluation of insulated

injection strings), and 2) develop­

ment of a downhole steam generator

that will produce steam and inject

it into the formation at depth.

Extensive material studies have

been performed in support of

Project DEEP STEAJ1. Current efforts

are devoted to the selection and

evaluation of materials for thermal

packers and downhole steam genera­

tors that are capable of surviving

the severe environments encountered

during steam injection in deep

wells. These studies include both

laboratory and field type experi­

ments. This paper presents obser­

vations on the performance of

several downhole steam generator

,materials during separate tests of

i two prototypic steam generators.

! Corrosion results are reported for ' )various metals, including 3041, 310

*American Petroleum Institute

~-., I •

/~-·· ..

and 316S stainless steels (SS) and

plain carbon steel, exposed for

several weeks to a warm, aerated

saltwater environment during the

first downhole test of a high pres­

sure, direct contact steam ·genera­

tor. Also discussed is the behavior

of two refractory materials, alumi-

na (Al2o3) and silicon carbide

(SiC), exposed to the high tempera­

tures of air/ diesel fuel combus­

tion during ground level tests of

a high pressure, direct contact,

downhole steam generator having a

ceramic-lined combustion chamber.

2. DOWNHOLE STEAM GENERATOR

DESIGNS

Two prototypic downhole steam

generators have been designed, fab­

ricated and tested as part of

Project DEEP STEAM; one by Sandia

National Laboratories and the other

by Foster-Miller Associates, Inc.,

of Waltham, Mass.(2) Both designs

are of the high pressure combustion,

direct contact type. They are

cylindrical in shape and will fit

inside a 7-inch well casing. Each

contains a combustion chamber and

a steam generation zone as illus­

trated schematically in Figure 1.

An air/diesel-fuel mixture is

injected into the combustion cham­ber where it burns as it flows

through the chamber. Water is in­

jected directly into the combustion

products leaving the chamber. Vapor­

ization of the wr~tP.r. i.n the steam

generation zone produces a mixture

of steam and combustion gases (pri-

~:~~~_! __ ~.?~nd_~.£~~..:_he -~~~~-=-~t~_: ---·

exit. The Sandia designed generator

operates at firing rates between 1

and 5 MBtu/hr at pressures up to

1500 psig. The Foster-Hiller de­

signed generator is intended to

operate at firing rates from 1 to

20 MBtu/hr at pressures up to 3000

psig.

One of the principal differences

between the two generators is in

the design of the combustion cham­

ber (see Figure 1). The Sandia

design employs a cold-wall combus­

tion chamber consisting of a water­

cooled stainless steel liner, while

the Foster-Miller design contains

a longer, hot-wall combustor having

a composite ceramic liner inside a

water-cooled sleeve.

3. METAL CORROSION STUDIES

3.1 Downhole Test of the Sandia

Designed Generator

The first test of a high pres­

sure combustion, direct contact

downhole steam generator to be

carried out in a deep reservoir was

performed using the Sandia designed

prototype. The test was conducted

in the Wilmington Field, California,

and was a cooperative venture among

DOE, Sandia, the City of Long Beach,

and the Long Beach Oil Development

· Company. The generator assembly

(steam generator plus instrumenta­

tion package) was located just

above the packer at a vertical

depth of about 2050 feet. Following

the initial start-up in June 1981

the generator ran without interrup­

tion for almost 10 days. Generator

operation during this period was

very steady; the firing rate was

approximately 2.1 MBtu/hr at a pres­

sure of about 1290 psig with a

steam production rate of approxi­

mately 236 bbl/d. The next five

weeks were devoted mainly to resolv­

ing a variety of system control,

hardware, and operation problems

with little or no successful opera­

tion of the generator. This first

unit was pulled from the well in

August 1981 for examination and

analysis prior to completing fabri­

cation of the second steam genera­

tor assembly. The first unit,

therefore, was exposed to the down­

hole environment for a total of 50

days. The metal corrosion results

presented below are based on obser~

vations made during post-test exam­

ination of the first generator

assembly.

3.2 Design Environment and

Materials

The initial material selections

for the first Sandia designed down­

hole steam generator tested at Long

Beach were made on the assumption

that the only portion of the unit

which would see a combination of warm temperatures and salt water

(reservoir water) was its external

surface. The steam generator was

fabricated entirely of 310 stain­

less steel~ 304L and 316S stainless .

steels were used in abundance both

within and without the unit for

fuel, air, water, caustic, and elec­

trical conduit lines. Also, API

grade J55 pipe, which is essential­

ly plain carbon steel, was used for ---···------ ·---·· ---- ··-·----. -· --

the air and water supply lines.

These materials were cold formed

'and welded when necessary with no

stres~ relief steps. Thus, both

.residual and applied stresses were

,prevalent in the hardware through­

out the generator assembly.

3.3 Actual Environment During the

Initial Test

A short time into the first run

a teflon sealing gasket on the

packer failed, allowing access of

air to the entire external surface

of the generator assembly. In addi­

tion, it is believed that two Swage­

lok fittings at the top of the

.assembly leaked, allowing access of ' i saltwater to the interior of the

!instrumentation package welded to

I the top of the steam generator.

!These events caused a breach in the I 1

1

air line inside the instrumentation

1 package resulting in the interior I ·being bathed in warm, aerated .salt-

·water.

3.4 Corrosion Observations

3.4.1 General Corrosion Photo­

graph 2 shows the API grade pipe

above the generator assembly after

the first run. Extensive general

corrosion of the plain carbon steel

pipe is evident. This is not un­

usual since carbon steels and

aerated saltwater are not compat­

ible. The interiors of the API

grade air and water supply pipes

were corroded to such an extent

that corrosion scale clogged the

·filters repeatedly. The successful

performance of the 310 and 316

stainless steels used for the

{~~~/:~·; :: i: -.. .... ;, -·

' -~.

lt'1r...!;.:;. t~ .. : (::. !'- .. ' .....

;·---

generator and instrumentation

package housings, respectively, is

encouraging.

3.4.2 Galvanic Corrosion Examples

of galvanic corrosion which

occurred on hardware within the

instrumentation package are shown

in Photographs 3 and 4. Photograph

3 shows hose clamps which were

labeled "all stainless steel" but

·which show significant attack of

- the worm screw. The strap section

:of the clamp is 3041 SS, which per-' lformed adequately. However, the

:worm screw was made from a 400

:series, martensitic stainless which !

!_was significantly attacked. The

electrochemical potential differ­

:ence between the "noble" 3041 SS

'strap and the "base" 400 SS worm

screw accelerated the corrosion of

:the latter.

Photograph 4 shows the remains

of an aluminum spacer used as a

pipe holder and an electrical junc­

jtion and ground. It was clamped to

ia steel pipe. Galvanic interaction I

jin the warm, aerated saltwater

!caused it to corrode to ·a point

/where electrical contact was broken: i ' iln this case, the potential differ-;

;ence between the aluminum and steel

itncreaied the corrooion rate of the ~ ; alumi.num. I 1

:3.4.3 Erosion-Corrosion Photograph'

·s shows an end view of a section ofi

!the 316S SS tubing used to carry

:caustic exterior to the generator.

The thinning evident in the photo-

.. . ~ ~ .• . ;

'by the caustic and erosion of the

·corrosion product by the flow.

3.4.4 Stress Corrosion Cracking

Two examples of stress corrosion

cracking of 3041 SS materials with­

in the instrumentation package are

_presented in Photographs 6 and 7.

Photograph 6 is of a tubing cross­

section at a bend. The residual

. stresses induced in the material,

due to cold working during bending,

·provided the driving force to cause

cracking in the warm, aerated salt

solution. Photograph 7 shows a

deteriorated woven mesh support for

· a bellows tube. The wires within

:this mesh are extensively cracked.

:There are approximately 30 frac-

tures per inch of wire in the

region of greatest deterioration.

3.4.5 Corrosion Fatigue When the

mesh support shown in Photograph 7

failed, it caused the pressure load

within the air line to transfer to

the inner stainless steel bellows.

Within a short time the bellows

cracked due to corrosion fatigue,

'a mechanism of corrosion caused by

attack of the environment coupled

with fatigue crack growth due to i

i pressure loads.

!3.4.6 Combined Corrosion Mechanisms ; i

.Photograph 8 shows three glow plugs:

the two outer plugs were uocd. in

the generator to ignite the diesel/

air mixture while the center plug

.is a new one shown for comparison.

·The used plugs failed due to a I

:combination of corrosion events. I

:First, the tip of the glow plug graph was caused by the combined

action of corrosion of the tubing I !

1 :(rnconel 601 sheath) eroded/ ' _____ j -~

".·,!.;,' .-..-j.{;~~,-;:1 ~c. l c.:: ........ (

:(; ~.-~ :, \ .. '

corroded away. The loss of the tip

allowed access of water/steam into

the plug interior. The water/steam

reacted with the magnesia insula­

tion to form a magnesium hydrate

which expanded against the metal

sheath causing a hoop stress which

led to radial stress corrosion

cracking. The circumferential crack

which led to separation of the glow

plug occurred in a region of

reduced sheath thickness. This

thinned zone is believed to have

been caused by preferential corro­

sion of the outside of the sheath

such as might occur at a water­

vapor interface.

3.5 Changes Made in the Second

Steam Generator Assembly

In order to reduce or eliminate

the corrosion problems encountered

with the first downhole steam gener­

ator (described above), a number of

changes have been made in fabricat­

ing and testing the second unit.

First, a new packer with a differ­

ent casing seal material was in­

stalled to provide a better seal

and thus prevent leakage of air or

combustion gases into the annulus

surrounding the generator assembly.

However, since there is still a

possibility of a packer leak,

materials for the second generator

assembly were chosen with the ex­

pectation that warm, aerated salt­

water would again be the environ­

ment outside the unit. Inconel 600

was chosen for tubing applications

external to the generator assembly

since it is conpatible with the -------- -------------- ----.

("

:environment. All other tubing, both

'inside the instrumentation package

and above the unit, was 316S stain­

less steel.

To prevent leakage of annulus

fluids into the instrumentation

package, as occurred with the first

unit, thicker walled tubing was

used with the Swagelok fittings. To

further reduce the potential for

corrosion inside the instrumenta­

tion package, new hose clamps were

used which were all 316 SS (both

strap and worm screw), and the alum­

inum spacer and the flexible (mesh

supported bellows) air and water

lines were eliminated.

To effect a significant reduc­

tion in the caustic corrosion prob­

lem in the immediate vicinity of

the generator (where temperatures

are highest), Inconel 600 tubing

was used for the caustic line to

,a point just above the unit. From

;there to the surface, the caustic I

:line was 316S SS as before (caustic I ;erosion in this portion of the line

was not a problem with the first

unit).

No change was made in the glow

l

plugs as the Inconel 601 sheath is

the best available for the normal

!environment to which the plugs are

exposed. Also, it is possible that

:the abnormal environments associ­

.ated with loss of feedwater flow

;and back-flushing with reservoir

ifluidi could have caused, or at

!least contributed to, the observed

!damage.

Efforts have also been made to

,s : 1··· .. ~ '-'.

;_,:.:· ~-- .. ;_ ~'\ ·, .

"'-.: · ........ ! • ----·--------"-'"""' -·-·--·--·-·---.... -_,__ ...... ----,.·-- ·-- --- ··- --- .. -· ··- -·-

!reduce general corrosion of the during steady-state operation.

l,~.~ • • --

!plain carbon steel air and water

:supply lines (both internal and

jexternal). Sodium sulfite has been I

ladded to the feedwater for chemical

'Scavenging of dissolved oxygen. In

:addition, the annulus water has

[been treated continuously with !

sodium sulfite and a filming inhib­

itor. A refrigeration type air

dryer has been added to the air

supply system to further reduce the

moisture content of the compressed

air provided to the generator.

4. CERAMIC LINER PERFORMANCE

The ceramic shown schematically

as the combustion chamber liner of

the Foster-Miller steam generator

design in Figure 1 was actually

a composite structure consisting of

a sintered ceramic inner tube 3

feet long and 3 inches I.n.·with

an outer layer of either ceramic

felt or a castable ceramic. Table

1 includes sketches of the various

prototypic liners tested in the

Foster-Miller program.

The primary function of the

ceramic combustor liner is to pro­

vide a thermally insulating barrier

which will permit a high tempera­

ture to be maintained on the inner

surface (adjacent to the flame)

while· limiting the temperature on

the metal parts and minimizing heat

flow to the water jacket. The liner

must be able to survive the stress­

es produced in rapid temperature

excursions during start-up and shut­

down as well as those resulting

from radial and axial gradients > .

It

must also be thermally and chemic­

ally stable in the combustor

environment.

From a thermal stability stand­

point (resistance to thermal shock

and high melting point), the best

choices of commercially available

ceramics seem to be SiC and silicon

nitride (Si3N4).(3) On the other

hand, Al2o3 and zirconia (Zro2)

should be more stable chemically

than SiC and Si3N4 in the low

oxygen partial pressures that might

exist in the combustor.< 4) Not

enough was known about the com­

bustor environment to validate a

selection among these candidates.

Instead, both Al2o3 and SiC, the

two materials readily available in

tubes of the proper size, were

tried in different combustor

designs.

Each of the combustor liner con­

figurations was tested by Foster­

Miller in a prototypic steam gener­

ator that was operated inside a

pressure vessel capable of simulat­

ing downhole conditions. Operating

parameters are given in Table 1.

In addition, the best performing

design, employing a SiC liner, was

operated in a 5-day test of the com­

plete Foster-Miller downhole steam

generator system (Series 6). This

quasi-field test was conducted at

the DEEP STEAM test site at Sandia

National Laboratories. The genera­

tor was mounted near the top of a

test well (120 feet deep) cased

with 7 inch diameter well casing.

t .

.. · r-' ----··--:--··-·~-- ------·------··-- ...................... ·- -·-

For the first 93 hours of th-e--t~s-t · · 1 stresses on the interior surface of

the firing rate was nominally 5

MBtu/hr. During the last 21 hours

this was increased to 7.5 MBtu/hr

and then to 10 MBtu/hr. The associ-

ated steam generation rates were

175-330, 430-550, and 695-725 bbl/d,

respectively. The total test time

'for this SiC liner (including Test

Series 5) was over 150 hours.

Performance of the ceramic

liners was evaluated primarily by

post-test examination of failure

;surfaces and microstructure. Frac-

tographic analysis of the failure

-surfaces permitted a determination

of the direction of local mechani­

cal stresses during failure as well

as estimates of relative magnitudes.

This information was compared with

calculated stresses obtained from

. .. thermal and stress analysis of the

structures.

4.1 Alumina Combustor Liner

The first designs tested used

Norton AN498A porous alumina tubes

as liners. For Test Series 1,

Norton CA333 castable alumina was

cast between the alumina tube and

the water jacket to give rigid sup­

port to the tube. No failure was

observed after the first run but,

in subsequent runs, fragments

spall~d off the inner surface of

the tube and were carried out of

the combustor. These fragments

were roughly lenticular in shape,

0.5 to 1.5 inches in diameter and

0.1 to 0.2 inch thick. The shape

suggested that failure had occurred

because of planar compressive . :- • ~·-: .= r.~ -

I

i the tube.

Examination of these spall frag­

ments revealed that the alumina had

become very friable, so that it

crumbled under finger pressure. In

the Scanning Electron Microscope

(SEM), failure surfaces of the

alumina showed features like those

in Figure 9. These are apparently

growth features, probably a result

. of vapor phase transport involving

the more volatile suboxides of

Al2o3.< 5 ) In some areas, enhanced

growth features such as the whis­

kers shown in Figure 10 were found.

These whiskers were almost certain­

ly produced by vapor deposition.

X-ray emission analysis in the SEM

showed that these features are

essentially only alumina •

In the combustor tested in

_Series 2, the porous Norton tube

was separated from the water jacket

by a layer of Johns~Manville cera­

blanket (ceramic felt) which per­

mitted the tube nearly free expan-

i sion. During testing, the tube

!fractured into roughly rectangular

segments approximately two inches

on a side. Additional cracks

extended part way through these

segments. These partial cracks had

started at the inner surface of the I

'tube and extended toward the outer

'surface. Only modest force was l !required to complete these frac-1

itures and expose the failure sur-

ifaces for examination. In contrast

:with the first tube, the inner sur­

·face remained hard and strong •

• f e f ,, "-' • ; ~ '

. I • :~' '•

---·~·- -----.. ·4------ ---·---·-·-··----.-....... __ ..., ________ , SEM examination of the failure

isurfaces revealed few grains with

1 surfaces characteristic of brittle

fracture. Most of these grains

~were in the region that was frac­

;tured after the segment was removed

·from the combustor. Much of the i :failure surface near the inner sur-

face of the tube showed structural

features like those in Figure 9.

All the evidence--the propaga­

tion of the cracks from the inner

surface toward the outer, the fact

that the incomplete cracks stayed

open after the tube had cooled down /

and the nature of the failure

surface--indicates that failure

occurred because of non-uniform

shrinkage of the alumina. The

porous alumina body sintered and

shrank, faster near the inner sur­

face because of the higher tempera­

tures there, giving an effect like

mud-flat cracking.

Although the types of failures

in the two Norton porous alumina

tubes were different, both were

associated with the presence of

open porosity. In the first tube,

failure occurred because of weaken­

ing of the grain boundaries,

apparently a result of attack by

combustion gases through the pores.

In the second tube, the presence of

open pores provided the driving

force for sintering which fractured

the ceramic.

To eliminate the problems

associated with porosity, a high

density, high-purity McDanel

alumina tube was selected for the .. ! ~

I third prototype combustor. In an

I attempt to reduce the axial

I stresses which analysis indicated

I were high in a monolithic tube,

1 this tube was cut into axial seg-1 . ments two inches long and bonded

: into the combustor with Norton

· CA333 castable alumina. In this

combustor design, a stainless steel

sheath separated the alumina tube

and castable layer from the sur­

rounding water jacket. It was

·expected that the higher compliance

of this design, compared with one

in which the ceramic was bonded

·directly to the water jacket, would

decrease thermal stress levels.

However, subsequent stress analysis i :showed that creep would probably

occur in the stainless steel sheath

in the first heating cycle, so that

tensile stresses would be generated

in cooling and in subsequent runs.

Four runs of about 0.9 hour dur­

ation were made on this combustor

beginning with a low firing rate,

1.25 MBtu/hr, for the first run and

increasing incrementally to about

2.5 MBtu/hr in the final run (Test

Series 4). No cracking was ob­

served after the first run. However,

after the second run some cracks

were observed, and in succeeding

runs they increased in number and

severity. During the fourth run,

some pieces of the end tubes broke

loose and were expelled from the

combustor.

Fractographic examination of

expelled fragments and others

removed from the tube after testing

....

L •.

revealed that most of the fractures

initiated at the inner surface of

the tube and propagated radially

outward. Orientation of the cracks

indicated both axial and circumfer­

ential tension. Most surfaces were

blackened with carbon, indicating a -. reducing environment had been main-

tained, at least in the final run.

In some areas, at the inner surface

of the tube, a closely spaced net­

work of shallow cracks ran into the

alumina. In those areas, the alum­

ina was markedly weakened so that

grains and clusters of grains could

be removed from the surface. SEM

examination of the fracture sur­

faces in these weakened regions

showed severe grain boundary ero­

sion and some growth features like

those seen in the porous Norton

tubes (Figure 9).

On one fragment which had been

pried loose from the combustor

assembly after testing, some of the

castable ceramic remained as an

adherent layer. Crystallite morphol­

ogy and Ca to Al ratio, as deter- ·

mined from X-ray emission and com­

pared with observations by Givan et

al,(6) indicated crystals adjacent

to the outer surface of the McDanel

tube had been exposed to tempera­

tures. of at least 2200°F, while

those 0.1 inch radially out from

that surface saw temperatures of

1450°F to 2200°F. These tempera­

tures agree well with those

obtained in thermal analysis.

4.2 Silicon Carbide Liners

In the first design employing

-~ r·

. t• •

-- -; ------··- ... :SiC, a Norton CRYSTAR tube was held

·in the combustor with a layer of

1 refractory fiber felt. This tube

!fractured into irregular pieces

!during the first cycle (Test Series

'3) and fell apart in the second

cycle. A thick layer (.040 inch)

of glass (Si02 formed by oxidation

of the SiC) was found on the inner

surfaces.

The most successful Foster­

Miller design featured a Carborun­

dum REFRAX SiC tube bonded into a

thin-walled stainless steel liner

with Norton CA333 castable alumina

containing 25% iron powder. This

tube was examined after four cycles

of Test Series 5, again at the end

of Test Series 5, and finally at

the end of Test Series 6. In the

first examination, a few cracks

were found near the inlet and a

thin layer of glass was found on

the tube wall. At the end of Series

5, a network of cracks was visible

over the entire tube with cracks

spaced from about 1.0 inch apart at

the tube ends to 0.3 inch apart at

the center. However, except for a

few chips expelled from cracks, the

tube remained in place.

At the end of Series 6, examina­

tion showed that a 2-3 inch section

of the SiC tube was missing from

the downstream end. In most of

this area the castable ceramic was

removed, and in a portion of the

area the stainless steel liner had

eroded away. The fracture surface

where the section of SiC was

removed was rough, irregular, and

.. '.> ~--)

r -----· -- - . - _r---. ----· ·-·-- ·- -·---gray-white in color suggesting that 5. SUMMARY

oxidation had weakened the grain

boundaries.

Even with the loss of the tube

end, the performance of the SiC was

clearly. much better than that of

any of the alumina tubes. Although

the SiC tube cracked extensively,

the mechanical constraint of the

castable ceramic, the stainless

steel sleeve, and probably the Si02 coating produced by oxidation, kept

it in place. Oxidation of the tube

to form Si02 glass was extensive.

However, the glass layer adhered,

maintaining a barrier against

further oxidation. There was no

evidence of spalling of the glass

layer which often occurs on SiC

heater elements when they undergo

similar thermal excursions; nor was

there evidence of substantial

erosion of the layer, which could

occur at temperatures high enough

and oxygen pressure low enough for

Sio2 to decompose to the volatile

monoxide.(?) The only real failure

occurred because the fragments at

the end were able to move axially

and separate from the tube. Some

form of axial constraint, perhaps a

metal collar, which would lock the

end of the tube in place, might

prevent that motion and substanti­

ally extend the life of the tube.

Two high pressure combustion,

direct contact, downhole steam gen-

i erator designs have been fabricated

and tested in separate experiments

as part of Project DEEP STEAJ-1.

Post test observations have pro­

vided information on the perform­

ance of candidate metals and refrac-

tory ceramics exposed to the severe

environments encountered during

steam injection in deep wells. A

number of corrosion mechanisms

; acted on the first steam generator

tested downhole and caused severely

, degraded performance of some of the

. metals employed. These corrosion ;

: problems are understood and pre-' lventable, and the second unit to I ! be tested downhole incorporates

· changes design~d to eliminate them. 1 Alumina performed poorly as a com­

' bustor liner material because of

: grain boundary attack by the com-

. bustion gases which resulted in

: loss of strength and eventual

disintegration. Although silicon

carbide tubes fractured, they gave

satisfactory performance provided

suitable mechanical constraint was

used to prevent fragments from

separating from the tube.

·-------------------;:--- -·· ·-··· "'• ~ I ·~ ,.._

~. :... ' • I ' ..

.·y_

;'·----··-··--·---· --·-·--4--·---· _R ___ _ . 6. REFERENCES

1. Dept. of Energy, "Technology Im­

plementation Plan for Enhanced

Oil Recovery," Draft, June 1978.

2. Project DEEP STEAM Quarterly

Reports from Jan 1 - Mar 31,

1978 (SAND78-1023, August 1978)

through Oct 1 - Dec 31, 1980

(SAND81-1199, Sept. 1981).

3. R. N. Katz, "High Temperature

Structural Ceramics," Science

208, 841 (1980).

4. L. Y. Sadler et al, "Evaluation

of Refractory Liner Materials

for Use in Non-Slagging, High

Btu Coal-Gasifier Reactors,"

Ceramic Bull.~ (7), 705

(1979).

5. L. Brewer and A. W. Searcy,

"The Gaseous Species of the

Al-Al2o3 System," J. Am. Chern.

Soc. 21., 5308 (1951).

6. G. v. Givan et al, "Curing and

Firing High Purity Calcium

Aluminate-Bonded Tabular

Alumina Castables," Ceramic

Bull.~' (8), 710-13 (1975).

7. A. F. McLean et al, "Brittle

Materials Design, High Tempera-

ture Gas Turbine," AMMRC-CTR-

75-8, Interim Report, April

1975.

i ... ~------------·--------~- ·-· _____ .,· ... ~ ....

Table 1. Foster-Miller Ceramic Liner Configurations and Test Conditions

Total Firing Run Number

Test I Rate Pressure Time of Liner Liner Ceramic I Backing I Fabrication Series (HBtu/hr) (psig) (hr) Cycles Construction Configuration Material Material Method

1 I 1.25 I 175 1.6 6 ~'W:~ Monolithic A12o3 Castable: Cast to () :\ r-i ' . •

3" ID x 3/8" Norton Norton water wall AN498A CA333 jacket I 'l'"'t

... ... -

I I I ~i~~-'~Vbl I Monolithic I

"1 .. 2 I 1. 25 I 175 1.3 4 () -t\

A12°3 Blanket: Placed in ,, --.. 3" ID x 3/8" Norton Johns- water wall AK498A Manville jacket

cera blanket ~~;:1;-:f@J

3 1.25 175 0.9 2 ~'I~ u '.f.)\ .-.~ mt Monolithic SiC Blanket: Placed in

2-3/4" ID x Norton Johns- water 3/16" wall CRY STAR Manville jacket

cera blanket

Cast in 4 I 1.25-2.5 I 300 I 3.5 I 4 I ~~~~~t~~ I 2" cylinders Alt3 Castable: steel

3-1/8" ID x Me anel Norton sleeve 3/16" wall 998 CA333 0. 025 in.

air gap

cast- Cast 5 I 5.0 I 250-1000 I 40 I 16 I ~'t;~ ~~.~~ I Monolithic SiC able, 25% steel

3" ID X 1/2" Carborun- iron powd. sleeve wall dum Norton 0.025 in.

REFRAX 20 CA333/25 air gap 6 I 3.5-lo.o I 900-1300 I 115 I 19 I ~\~~-~1""~'t'f;f I I mesh

r· • ;. ,;·:. r.t-~~ .. - """~,r.- /.,.' ,.. - ~- - +

~- -.r-- .. ~ . ,.. . . ...

WATER WATER

t FUELAIR F1EL

~~~--~~Hl~ ~~ I

FUEL/AIR MIXTURE

' I COMBUSTION

~HAMBER

{

STAINLESS STEEL LINER

CERAMIC]. LINER

1DETAILS IN

TABLE 1

STEAM GENERATION ZONE

SANDIA DESIGN FOSTER-MILLER DESIGN

Figure 1. Schematic of Two Prototypic, High Pressure, Direct Contact, Downhole Steam Generators.

·--- ------ --

:_ ,; .

- -·-;-t

Figure 2. API Grade Pipe and Steam Generator Assembly.

Figure 3. Stainless Steel Hose Clamps.

c.r , .......

•' --' r.~

Figure 4. Aluminum Spacer.

Figure 5. 316S StRinlPss Steel Caustic Line Showing Wall Thinning.

Figure G. 304L Stainless Steel Electrical Conduit Line Showing Cracking at Bend.

Figure 7. 304L Stainless Steel Woven Mesh Support for B~llows Tuulug.

. '•

Figure 8. Glow Plug Ignitors with Inconel 601 Sheathing.

Figure 10. Whisker Growth on Failure Surface of Porous Alumina Combustor Liner. SEM Micrograph (5 ~w bar).

, __

Growth Features on Failure Surface of Porous Alumina Combustor Liner. SEM Micrograph (5 ~m bar).