Simulation Experiment Of Depletion-drive Development On Overpressured Gas Reservoir In Kela 2 Gas Field

The production characteristics of overpressured gas reservoirs are different from normal pressure gas reservoirs. The elasticity drive energy of overpressured gas reservoirs is much stronger than the others. While the pressure is declining during the process of overpressured gas reservoirs development, the rock metamorphose may be obvious under compressed, which will affect on the production characteristics of gas reservoirs in many aspect. Kela 2 Gas Field is a overpressured gas reservoir and it is the major resource of West Gas To East Project. What changes of the rock and reservoirs will be during the process of development is the fours of experts' attention. So through some new experiments, the effects of overburden pressure on porosity and permeability of reservoir rock have been studied, and the performance status of development on overpressured gas reservoirs could be simulated. The tested pressure is up to 72.8 MPa It can availably simulate the process of Kela 2 Gas Field development.The effect of overburden pressure on permeability varies considerably for different reservoir rocks, causing less reductions in permeability for high-permeability rocks and greater reductions for low-permeability rocks. The permeability loss is even more noticeable in fractured samples. And the effect of fracture connection on permeability is remarkable. Lone short fracture has little effect on formation conductivity.The physical properties of Kela 2 reservoirs formation are better. When the reservoir pressure reduces and net overburden pressure increases, the porosity and permeability are not dramatically reduced by compaction. The integration permeability of formation only reduces 18.2% as the reservoir pressure changes from 74.35MPa to 10MPa. Reduction of production by compaction and compression is not serious as well as permeability, which is only 11.8%.The simulation experiment could be useful for analyzing the relationship of pressure(P/Z) and cumulative gas produced(Gp), and estimating the deviation that the dynamic reserves of gas reservoir be calculated depends on the production data during early-phase. It is also to help for analysis the effect of the water influx from associated aquifer on the development of overpressuredgas reservoirs. The results of this simulating experiment indicate that errors of dynamic reserves are 6.3% in Kela 2 Gas field. This calculated data is extrapolated from the curves with P/Z and Gp during early-phase under the condition is not considered the effect of margin and bottom water to gas reservoir production. The final recovery ratio be determined that is 80% from depletion to abandoned pressure during this gas reservoir production on the results of simulating experiment.