Objective
The present project is a continuation of the project TH 05033/81 which aimed at establishing the technologic feasibility of the pilot and led to the installation of two platforms (mid 82 - mid 83) and the drilling of wells from July 1983 on.
The object of the present project is to prepare, follow up and interprete all the test which precede the steam injection :
- water and steam injectivity test
- test of surface installations
- tests of interference between wells
- primary pumping tests
- elaboration of a geological model of the pilot area by interpreting cores, logs and previous tests.
a) Modification of drilling and completion programmes following the interpretation of results of the first three wells:
- abandonment of the cyclic injection on the GIK level which is dynamically connected to the R1 and will be used for the injection in the five-spot R1;
- abandonment of the two observation wells, problems of plugging losses and cementations encountered during the first drilling operations proving that it was difficult to guarantee simultaneously their efficiency and the absence of cross flows between the two five-spots.
b) Injectivity/productivity
The flows obtained during injection and production which were lower than those of the initial project, are imputable to the low height perforations. The difficulty of recovering and the risk of creating new short-circuits by continuous drains have led to postpone all new perforation.
The steam will be injected at a rate of 80 t/d in R1, 150 t/d in R2 and 50 t/d in R3 with a maximum head pressure of 30/35 bars so to avoid any risks of fracturation in cement zones or in sub-jacent beds.
The average oil flow before steam injection is of 10 m3/d/well.
c) Interference tests
For R1, the water injections carried out in the EMV 01 injection well showed rapid connections with the EMV 05 production well and with the wells of neighbouring platforms CC, DD and E. For R2, the water injections carried out in the EMV 03 injection well provided only one neat response in the EMV 09 well.
d) Reservoir image
The results of the punctual pressure measurements were excellent and made it possible to show in a very significant manner that the intermediate levels GIF were dynamically connected to R1. These measures also showed that the present gradient of pressures in R2 is parallel to the initial hydrostatic gradient, which proves a good vertical permeability of the reservoir, whereas in R1, the gradient is inversed, which shows a very low permeability value.
The SHDT logs proved to be extremely helpful to detect the drains in the lime and their continuity.
e) Injection patterns
In R1, the steam injection was carried out at the base of the reservoir whereas the production wells were perforated at the top so to favour the vertical crossing of the steam in the silts.
In R2, where the raise of the steam by gravity was carried out without problem due to the high vertical permeability, the injection well and the production wells werre perforated at the base of the reservoir.
f) Testing the installations
Tests relative to the installations were run in parallel with the drilling operations and the well tests. Modifications were made on the air feed systems of the boilers, on the assembling of the compressors and on one of the desalting units to ensure their functioning under conditions analog to nominal conditions.
The project comprises 4 phases :
PHASE 1 :
1.1 Productivity and injectivity tests
- water and steam injectivity tests in the first three wells
- production test on these wells after having drilled the eight other wells
- interference tests on R1 and R2 (between central injection well and peripheral production wells) by long water injection
- production tests on production wells
- depending on the results of these tests, modification of the completion programme in view of eventually making additional perforations and carry out treatment specific to this type of reservoir (selective acidification or cementations..)
1.2 Testing the installations
- Testing of heat exchangers, separators and crude processing units
- Testing of pumps
- Testing of desalting units and of the two steam generators
- Testing the utilities
- Start-up of gas feed unit for the steam generator
- and more generally, all that is necessary to start-up the installations.
PHASE 2 : Primary production through pumping
Evaluation of the potential of the wells and of each layer by long drive pumping over a long period with regular measurement of the production parameters on all wells successively.
PHASE 3 : Preparation
- Optimization of steam injection parameters (flowrate, pressure) and of production parameters in view of modifying the production and injection programmes
- Steam tracing (titrated water in R2) - Adjustment of units depending on injection and production patterns
PHASE 4 :
Utilisation of the analysis of cores, logs, interference tests and of production and injection tests to define the image of the reservoirs. Creation of a geological model.
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DEM - Demonstration contractsCoordinator
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