0 m

21

44

67

82

93

124

173

189

350

345

40

99

G.L. (120m a.s.l.)

100

120

140

160

GR0 0 101000gAPI

K% 100

Th

0 200ppm

R deep0.05 5000Ohmm

WF Near

200 1300usVp

5000 0

Susc

1E SI 10000

m/s

40

60

80

180

200

220

240

260

U

0 ppm

GAMMA RAY RESISTIVITY SONIC Magn. SUSC."Villa Senni"

366+-4ky

"Pozzolane Nere"407+-4ky

"Pozzolane Rosse"457+-4ky

"Vallerano" lava460+-4ky

Air-fall sequence488+-2ky

"Tufo del Palatino"528+-1ky

"Tufo di Acque Albule"526+-1ky

"Fioranello" lava

"Tufo Pisoliticodi Trigoria"561+-1ky

Sand 1

Sand 2

Clay

("M. Vaticano")

NOTES:-Ages of volcanic units after Karner et al. (2001).-Small gray intervals are paleosols.

Sed

imen

tary

seq

uen

ce (

Plio

-Ple

isto

cen

e)

Seismometer position

*

*

d=

96m

md

=7

6m

m(f

rom

30

0m

)d=

178

mm

d=

15

2m

md=

123m

m

P=6%

P=10%

P=22%

P=20%

2 %4 %6 %

0 %

Data Number: 105

N30˚330˚

60˚300˚

90˚270˚

120˚240˚

210˚ 150˚

180˚

N

Tyrrhenian Sea

Adriatic Sea

Alban Hills

N

Ischia

Phlegrean FieldsVesuvius

Northern Apennines

Vulsini

Mt.Amiata

41

42

43

44

Ernici

39

40

45˚Na b

1 2

3 4

Sabatini

Vico

11 12 13 14 15 16˚E10

100 km

Figure 1

6

Rome

5

a

b

Apulian foreland

Roccamonfina

ba c d

Italy

a

b

borehole televiewer

We have recognized 213 fractures from

the analysis of borehole televiewer data

and have analysed them with "Daisy3"

(http://host.uniroma3.it/progetti/fralab/).

Figure shows the poles of 105 fracture

planes.

Breakout analysis has been performed

with dipmeter data: 7 breakout

intervals of small size, for a total length

of 38m, point out a minimum

horizontal stress oriented N88W±22°.

Downhole logs were performed (by ICDP-OSG, GFZ Potsdam) along

the borehole to measure some physical parameters of the volcanic

rocks. The figure shows the borehole stratigraphy from core analysis,

in the left side, compared to log data, on the right. In the first column

Gamma Ray followed by Potassium, Uranium and Thorium

concentrations; then electrical resistivity, P-wave velocity and

magnetic susceptibility. From resistivity, mean porosity values of

main volcanic units were estimated.

The drilling was performed by an italian company

(SO.RI.GE. s.r.l.) using wireline technique with continuous

coring down to 350m depth with a recovery of about 99%.

As this area is characterized by high gas concentration in

water (mainly CO2 and H2S), a blowout preventer was

installed, and combustible gases and H2S were monitored

continuously for safety reasons.

wireline logs

BoreholeStratigraphy

ABSTRACTAlban Hills are a Quaternary volcanic district located in Central Italy, SE of Rome, defined as "dormant" or "quiescent" volcano. Recently, many detailed

investigations have been performed under the auspices of Italian "Dipartimento della Protezione Civile", involving different branches of earth sciences. In the

framework of two different Italian projects, in 2006 a scientific borehole was drilled in this area to better define the shallow crust structure under the

volcanic complex, the present-day stress field and its evolution in recent times by means of down-hole measurements and core analysis. Moreover, finally the

hole became a station of the Italian seismic network, hosting a broad-band seismometer at depth that will allow good seismic recordings in a very urbanized

area. The drilling site was selected mainly because of its features: it is located in the area where most of the seismic swarms occurred; where an uplift was

recognized by geodetic investigations and satellite images analysis; gas concentrations (mainly CO2 and H2S) in the aquifers are high; gas leak at surface

occurred in the past causing casualties; local tectonics is peculiar and seems quite different from the regional trend and there is, however, still a lack of

active stress data. Here we summarize the drilling project, its aims and the main results but in particular we focus on the wire-line logs that allowed

characterizing some physical properties of the main volcanic units of this Quaternary volcanic district. Wire-line drilling produced a complete stratigraphic

record of the volcanic units (tuffs and lavas) down to the Plio-Pleistocene sedimentary basement (clays and sands) and stopped at 350m depth into few

meters of sands. Pressurized fluids held in the sandy unit at the hole bottom, capped by the overlying shales, caused a blow-out while the first hydrofracturing

test was starting. This event prevented us from continuing the planned hydrofrac tests, but deep fluids (mainly gases) were sampled and analysed providing

useful information to better understand the complex fluid flow and its likely connection to a deep-seated magma chamber (see Pizzino et al., this session). Six

down-hole logs were performed by ICDP Operational Support Group (GFZ-Potsdam) using slim tools: gamma-ray, resistivity, sonic, magnetic susceptibility,

borehole televiewer and caliper. From the latter we recognized and analysed borehole breakouts, fractures and faults that helped to interpret the main

tectonic features and the present-day stress field. The others allowed to characterize some in-situ physical properties of the stratigraphic units. In-situ

measurements were also compared and/or joined to laboratory analysis on core samples for a better definition of the rock parameters and comprehension

of the behaviour of the main volcanic units under different P and T conditions and their seismic response (see e.g. Vinciguerra et al., this session).

Caliper calibration

Four-arm caliper

Structural map of Italy showing the

Quaternary volcanoes of the Roman

Comagmatic Province (modified after

Patacca et al., 1990; Marra et al, 2004). 1)

Surface (a) and subsurface (b) Thrust fronts;

2) Extensional faults; 3) Strike-slip faults; 4)

Volcanoes and volcanic districts of the

Tyrrhenian margin: Roman Comagmatic

Province (a); 5) Structural arcs

characterized by active compressional

fronts (a) and inactive thrust fronts (b); 6)

Main stress regimes (after Montone et al.,

2004): a) compression (SHmax direction), b)

extension (Shmin direction), c) radial

extension, d) strike slip.

Magneticsusceptibility

Borehole televiewer

Depth ofinvestigation(cm)

150-300 (deep)

50-100 (shallow)

20-40

20-70

50-100

Verticalresolution(cm)

80

15

0.3

5 (radius)

>300 (orient)

50

20

Tool specifics

Dual Laterolog

Speectrum Gamma Ray

Borehole Televiewer

Four-arm Dipmeter

Borehole Sonic

Magnetic Susceptibility

Diam. 43 mm

Length 3.5 m

Weight 15 kg

Diam. 55 mm

Length 2.5 m

Weight 12 kg

Diam. 52 mm

Length 4.5 m

Weight 25 kg

blowoutpreventer

blowout

fluids from depthhydraulic fracturing probe

Some Hydraulic Fracturing tests had

been planned between 320 and 350

m. Unfortunately, during the phase of

probe positioning a blow-out occurred

destroying the deepest part of

borehole (300-350m, 76mm φ) and

the tests were cancelled because the

HF tool for a larger hole (96mm φ)

was not available.

On the other hand, the blow-out

allowed to sample deep fluids (gas

and water) with peculiar geochemical

features never observed in in the area

till now. They have been analysed in

situ and in laboratory to determine

their chemical and isotopic

composition, both to define their

origin and to highlight the main gas-

water-rock interaction processes

occurring at depth.

Gamma ray

Diam. 52 mm

Length 2.5 m

Weight 22 kgResistivity

Diam. 43 mm

Length 3.8 m

Weight 20 kg

Borehole sonic

Diam. 43 mm

Length 6 m

Weight 39 kg

31 2 4 6

Nemi lake

R OME

5

5 km

CA1 BOREHOLE

8 97

A riccia

A lbano lake

Tuscolano-A rtemisio

Faete Mt.

Colli A lbani

ITA LY

Location of CA1 borehole

bLOW-OUT

Borehole televiewer

Geological sketch of the Alban Hills

volcanic district modified after Marra at al.,

2003). 1) Holocene alluvial deposits; 2)

Albano Crater hydromagmatic deposits

(69-36 ka); 3) Nemi Crater hydromagmatic

deposits (150 ka); 4) Ariccia Crater

hydromagmatic deposits (200 ka); 5) Faete

phase pyroclastic deposits and associated

lava flows (grey) (308-250 ka); 6)

Tuscolano-Artemisio phase pyroclastic-

flow, air-fall deposits and associated lava

flows (black) (561-351 ka); 7) Plio-

Pleistocene sedimentary deposits 8)

Caldera and crater rims; 9) Location of

Falcognana 1 borehole (ENI).

Drilling active volcanic areas: in situ physical measurements at Alban Hills (Rome, Central Italy)

M.T. Mariucci, P. Montone, S. Pierdominici, F. Marra, F. FlorindoIstituto Nazionale di Geofisica e Vulcanologia, Roma, Italy

Drilling project was funded by:

-the Italian "Dipartimento della Protezione Civile" in the frame of the 2004-2006 Agreement

with "Istituto Nazionale di Geofisica e Vulcanologia- INGV", Project INGV-DPC V3.1;

-the Italian Ministry for University and Research in the frame of FIRB Project "Research and

Development of New Technologies for Protection and Defense of Territory from Natural

Risks", Working Package C3;

-INGV Department "National Earthquake Center", Rome, Italy;

-INGV Department "Seismology and Tectonophysics", Rome, Italy.

We thank ICDP Operational Support Group, GFZ, Potsdam, Germany.

ACKNOWLEDGEMENTS

mariucci@ingv.itEuro-conference of "Rock Physics and Geomechanics" on

"Natural hazards: thermo-hydro-mechanical processes in rocks"

Ettore Majorana Foundation and Centre for Scientific Culture

Erice, Italy, 25-30 September 2007