INJECTION OF NON MISCIBLE GAS IN FRACTURED OR THICK RESERVOIRS IN THE NORTH SEA

Ziel

The purpose of the project is to evaluate the advantages to be obtained from injecting non miscible gas in fractured or thick reservoirs, which are the types of reservoirs the most commonly operated in the North Sea for more than some fifteen years. Some of these deposits, whether fractured or not, are becoming flooded with water and production rates will drop over the next few years if the operating mode is not changed. As regards those being developed, the choice of their operating mode must be decided upon within a very short delay. Therefore, this type of evaluation is currently of prime importance.
Concerning non miscible gas injection, there is a lack of data and of physical models in particular for describing gas injection in :
- fractured reservoirs
- thick and continuous reservoirs
However some preliminary studies showed that non miscible gas can be very attractive for two reasons :
- high recovery rates can be expected,
- moderate cost of gas production is possible.
Phase I
Phase I.1
Relative permeability : Set of two-phase data has been obtained. Minimum oil saturations have been obtained for various brine/gas proportions. End-points for brine and gas relative permeabilities have been measured. Capillary pressure : three-phase capillary pressure curves in both drainage and inhibition have been obtained.
Phase I.2
Studies in reservoir conditions with Clashach sandstone. Drainage curves can be deduced from the mercury intrusion curve by scaling the interfacial tension down to 3 mN/m. Presence of connate water saturation increases the capillary pressure level.
Phase II
Studies in 1D and 3D models with binary mixture (C1-C5) as liquid and C1 or N2 as diffusing gas.
The kinetics of recovery is lower with nitrogen than with methane without water saturation. But the presence of water saturation has a much more important effect on the kinetics with methane than with nitrogen. The effect of an initial gas saturation seems to be negligible.
Studies with complex fluids : no selective vaporisation. Same tendencies as binary mixture concerning the comparison between C1 and N2 as diffusing gas.
Phase III
Reliability of equipment for air injection.
Comparison of air injection and nitrogen injection. Completion of water alternate air injection. Significant additional oil recovery. Completion of 13 tests under high pressure and temperature, using two kinds of porous media (limestone and sandstone), in secondary and tertiary conditions, with light and heavy oils. High level of oxygen consumption (802), except with light oil in limestone, has been observed. Oil production analysis indicated a rise in polar content, when oil is oxidised, generated from the heavy aromatics components of the oil.
Phase IV
Phase IV.1
Case of Alwyn Set of laboratory studies to deliver appropriate data for the field case simulation. One experiment in a vertical long core at tertiary conditions. Gas injection led to an additional oil recovery of 10% PV (16%of Sorw). Three cases of nitrogen injection were simulated over a period of 15 years. Finally results from the nitrogen injection are slightly better than those of water injection. But miscible tertiary injection recovers much more oil and gas than water injection.
Phase IV.2 Case of Ekofisk History matching of the full field has been completed, including the project of increasing water injection. A compositional model has been adapted to simulate tertiary gas injection. Several prediction cases involving various gas and water injection rates have been run. Incremental oil recovery of the order of 20% can be expected from immiscible gas injection and potentially a lot more if miscibility conditions are achieved.
The purpose of the project is to evaluate the injection of non miscible gas : methane (C1), nitrogen (N2) or air, in two types of North Sea reservoirs : fractured reservoirs and thick reservoirs.
This project consists in four phases :
Phase I : Measurement of triphasic relative permeabilities and capillary pressure.
The results expected from this work consist in finalizing the correlations to be used in the numerical simulation models taking into account all the physical laws determined at the laboratory scale.
Phase II : Quantitative evaluation of stripping improved by gaseous dispersion in fractured reservoirs.
The results expected from this work are the control of process efficiency, the evaluation of exchange kinetics, and the equivalent dispersion coefficient. These data will help to adapt a numerical compositional model.
Phase III : Air injection in thick or fractured reservoir
The main purpose of this work is to gain informations on the catalytic effect of the rock and theoxidation kinetics by air of the oil in place. The experimental results will be used in a numerical model to simulate hydrocarbon oxidation reactions by air and their consequences.
Phase IV : Simulation of non miscible gas injection in two typical types of deposits in the North Sea.
The experimental results obtained during phases I to III will be extrapoled in digital simulation of non miscible gas injection in two cases of North Sea reservoirs (thick reservoir and fractured reservoir).
The project is directed by Institut Francais du Petrole, in association with the other members of GERTH, AGIP, BRITISH PETROLEUM and PETROFINA.

Programm/Programme

ENG-HYDROCARB 2C - Programme (EEC) of support for technological development in the hydrocarbons sector, 1986-1989

Thema/Themen

1.5 - IMPROVED OIL RECOVERY

Aufforderung zur Vorschlagseinreichung

Data not available

Finanzierungsplan

DEM - Demonstration contracts

Koordinator

GERTH

EU-Beitrag

Keine Daten

Adresse

232 AV. NAPOLEON BONAPARTE
92500 Rueil Malmaison
Frankreich

Gesamtkosten