23rd World Gas Conference

UNDERGROUND GAS STORAGE IN AN

UNDERSATURATED OIL FIELD IN ARGENTINA

Amsterdam, June 7 th – 2006

J.J. Rodríguez - J.M. Morisseau - P. Santistevan

PRESENTATION SCOPE

PART 1

• LOCATION

• PURPOSES OF THE UGS PROJECT

• GEOLOGY & RESERVOIR

• SURFACE FACILITIES

PART 2

• PILOT PROJECT GOALS

• COMPRESSION SYSTEM

• GAS BUBBLE EVOLUTION

• PRELIMINARY RESULTS

• QUALITY, SAFETY & ENVIRONMENTAL PROTECTION

CONCLUSIONS

UGS FACILITY

REFERENCES

(1) Depleted gas field(2) Depleted oil field

PORTO ALEGRE

CORNEJO

TUCUMAN

MONTEVIDEO

SAN SEBASTIAN

BUENOS AIRES

METHANEX

SANTIAGO

CUIABA

SANTA CRUZ

TALTAL

TOCOPILLA

LOMA LA LATA

SAN PABLO

DIADEMA [1]

[2]

ARGENTINA

BRAZIL

URUGUAYLUNLUNTA CARRIZAL

LOCATION

CONNECTION TO MAIN AND SECONDARY GAS PIPELINES

Neuquina Basin

to Buenos Aires

to Chile

Mendoza

Lunlunta CarrizalUGS

SummerWinter

Centro Oeste Trunk Gas

Pipeline (TGN)

Ecogas Pipeline

LUNLUNTA CARRIZAL UGS PURPOSES

� To comply with Repsol YPF obligations under the nat ural gas

sale contracts in the region of Mendoza

� To improve the oil exploitation in Lunlunta Carrizal field

(secondary recovery)

� To optimize natural gas and oil production in the fields l ocated in

Neuquina Basin

GEOLOGY & RESERVOIR

�STRUCTURE: Lunlunta Carrizal structure is an anticline with two apexes separated by a structural low

� CAPROCK: Claystones and volcanic rocks from Punta de l as Bardas formation

�RESERVOIR: includes sandstones and conglomerate (Flu vial deposit)

Depth: 2,400 meters below g.l.Porosity : 18 %Permeability : 70 mD Original Pressure : 230 BarCurrent Pressure : 100 Bar

STRUCTURAL MAP

GAS BUBBLEAREA

Safety well

Injection / withrawal well

Gas Reservoir

Caprock

Aquifer 1

Aquifer 2

Aquifer 3

Oil Producer well

Gas Monitoring well

Water Monitoring well

Oil

Aquifer 3

UGS CROSS SECTION

Gas monitoring well Aquifer monitoring well

UGS WELLS

Injection / Withdrawal well

SURFACE FACILITIES

PART 2

• PILOT PROJECT GOALS

• COMPRESSION SYSTEM

• GAS BUBBLE EVOLUTION

• PRELIMINARY RESULTS

• QUALITY, SAFETY & ENVIRONMENTAL PROTECTION

� Working gas: 120 M Std. m 3

� Cushion gas: 150 M Std. m 3

� Maximum pressure: 210 Bar

� Gas injection flow rate: 0,30 / 0,90 M Std. m 3/d

� Maximum gas withdrawal: 1,0 M Std. m 3/d

� Gas Injection wells (available) : 12

� Gas Monitoring wells: 12

PILOT PROJECT GOALS

Coo

ler

Sep

arat

or

Oil

gas

Eco

gas

Pip

elin

e

ManifoldInjection/ Withdrawal

Gas Injection --------------

Gas Withdrawal --------------

Oil + Gas Production --------------

Eco

gas

pipe

line

Coalescer Filter

FIL 118

K-100 A

K-100 B

K-200

Coalescer Filter

FIL 115

ManifoldSG-140

LC-2

Gas / Oil Separator

K-300

SG 100

SC 101

E 102

V 1

03

Joule-Thompson Plant

General Separator

Control Separator

C 105

Heater Interchange Gas-Gas

COMPRESSION SYSTEMC

usto

dy T

rans

fer

Sta

tion

LUNLUNTA CARRIZAL GAS PLANT

GAS / LIQUIDS SEPARATORS & FILTERS

UNDERGROUND GAS STORAGEIN LUNLUNTA CARRIZAL OIL FIELD

0

50.000

100.000

150.000

200.000

250.000

300.000

350.000

400.000

450.000

500.000

550.000

600.000

650.000

700.000

Oct-05 Nov-05 Dic-05 Ene-06 Feb-06 Mar-06 Abr-06

Inje

ctio

n ga

s flo

wra

te (

std

m3 /d

ay)

75

100

125

150

175

200

225

250

PRESSURE VARIATIONS IN THE MONITORING WELLS vs GAS INJECTION FLOWRATE

Gas Injection Flowrate

BHP LC-9 (Amerada)

BHP LC-13 (Amerada)

BHP LC-19 (Amerada)

BHP LC-19 (calculated)

BHP LC-27 (Amerada)

BHP LC-29 (Amerada)

BHP LC-71 (Amerada)

PRESSURE VARIATIONSIN THE MONITORING WELLS

GAS BUBBLE EVOLUTION

NOV - 2005

Cumul. Gas Inject: 6.920.460 m3

JAN - 2006

Cumul. Gas Inject: 26.715.260 m3

MAR - 2006

Cumul. Gas Inject : 41.027.950 m3

Gas Injection wells used: 5

Gas Monitoring wells: 12

Gas inj. flow rate (avge) : 318.000 m3/d

Cumul. Gas Inject:16.845.160 m3

DEC - 2005

APR - 2006

Cumul.Gas Inject : 41.027.950 m3

�The gas injectivity of the wells matches previous es timates� Vertical wells: 50,000 std. m 3/d per well� Horizontal well: 150,000 std. m 3/d

�As expected, gas injection was not found to impact the aquifers located above the cap rock, which is clearly positive given t he large number of wells drilled in the area.�The major mobility of the gas injected is registered in zones with high permeability of the reservoir, which are at the same tim e, areas of high water saturation.�The minimum gas saturation (Sg), necessary for a cont inuous gas bubble is about 7% of the porous volume.�Considering a reservoir thickness of 10 meters and porosi ty of 18%, the gas volume necessary (Sg: 7%) is about 40 Mm3 (std), at pressure of 100 Bar .�We estimate that 15 m on the top of the reservoir, is enough for developing a gas bubble of about 100 M Std m3 ( Sg: 1 5%).

PRELIMINARY RESULTS

Repsol YPF successfully completed (2004) the certif ication of an Integrated Management System (IMS), including the following st andards:

Quality (ISO 9001:2000)Environmental Protection (ISO 14000:1996)Safety and Work Health (OHSAS 18001:1999)

The aspects controled by the IMS are:

� Water quality control in higher aquifers, every 6 m onths.� Casing integrity in oil production Wells located in the area of gas bubble influence.� Casing protection in Gas Injection Wells, against h igh pressure.� Gas bubble control at spill points� Escape gases composition control at the Compression Plant, Waste Disposal, etc� On-line gas control (Scada): Auditable measurement system

QUALITY, SAFETY & ENVIRONMENTAL PROTECTION

� The Lunlunta Carrizal Project presents a major challeng e for Repsol YPF as it involves developing a gas bubble in an undersa turated oil reservoir composed of low-permeability sandstones.

� After injecting more than 40 Million Std. m 3 of gas into the reservoir, the gas bubble is in progress on top of the structure.

�The IMS in place at Lunlunta Carrizal Storage facility has provided us with effective control tools: no accidents since 2003, ac curate gas balancing and a precise monitoring System of the gas bubble and upp er aquifers.

� Gas production tests will be performed during Jun/Aug- 2006, in order to to assess recoverable gas volumes and productivity in dexes,

CONCLUSIONS