Objective
During gas production from gas reservoirs and underground gas storage the produced reservoir water has to be removed on the surface and disposed as waste. By injection of special polymer solutions into gas reservoir layer an in-situ water blocking will be created. This results in:
- production of additional gas
- reduction in technical expenditure on gas production
- reduction in associated water production, which is detrimental to the environment.
Polymers with properties, which block water selectively and do not restrict the flow of gas have to be found and tested in gas wells. Experience existing for the treatment of oil wells should be extended by novel developments to gas producing wells. Optimal technologies will be concluded from analysis of carried out polymer treatments for further application.
The treatment of Salzwedel 85 results in excellent production parameters : original gas rate, blocking of water production of about 17 months until June 1994. This case indicates success rate of 100%.
Treatment of Mellin 184 in gas field Salzwedel remains without production results because a technical failure in tubing prevents gas flow. This failure should be resolved in 1994. After treatment in Buchholz the gas injectivity during summer period 1993, but also the gas production during production period 1993/1994 were clearly improved. Watergas ratio under the values of former years. The gas saturation of storage layer is higher at the end of gas production period.
After acidizing (against bacteria) the well Buchholz 17 reached the high gas injectivity.
The wells Engelbostel 1020 and Kalle S 106 treated in 1994 show an improved gas injectivity.
Realization of the project is subdivided into three phases :
1) Test (lab, simulation model, comparison of methods and injection processes)
The water shut-off technologies are based on 3 principles :
a) gel block
b) polymer adsorption
c) porous gels
and are tested in core-flood experiments for different geological and thermodynamic conditions, whereby the porous gels will be included as new systems.
For each candidate field the chemical system and treatment technologies are adapted after collection and evaluation of field/well data. After that comparison of methods, selection of technologies and elaboration of engineering design follow.
2) Field operation
Treatments are carried out in selected gas production wells with medium to high water cut of several reservoirs with different geological and thermodynamic conditions.
Special well tests and measurements are realized before and after treatment.
3) Comparison of technologies
The evaluation of technologies is done on the basis of decrease of water cut and of duration of this effect.
Experience gained from treatment and production performance may lead to changes in the design of chemical systems and to repeat tests.
For various types of reservoirs (with respect to the composition of formation water, mineralogy of rocks with different pore structure and degree of fissuring, pressure and temperature conditions) the most advantageous conditions for the application of eligible technologies should be defined after rigorous diagnosis of the treatment and test results and if necessary after adjustment of the chemical systems. An essential task is the further use of promising technologies in European and other companies.
Worldwide 20 to 30% of all gas wells are producing water; there is enormous interest for technologies able to reduce water production.
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DEM - Demonstration contractsCoordinator
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