Analysis Of Post - Pressure Evaluation Of Sulige Gas Field

Most tight gas reservoirs with low permeability in our country need to be fractured to achieve the requirements of industrial exploitation, and the fracturing effect is a common concern people widely focus. This paper chooses the Sulige fractured gas wells as study topic, and combines geology, percolation mechanics, numerical simulation and mathematical statistics to make the fracturing evaluation. Major work and achievements are as follows.(1) This paper had analyzed the reservoir lithology properties, space properties, fluid properties, temperature and pressure systems, and classified the reservoir, which provided the basic information for the evaluation of the hydraulic fracturing.(2) The gas-water relative permeability experiments of20cores in Sulige area were completed. Several pieces of representative relative permeability curves were normalized, and the character of different types of relative permeability curves were analyzed.(3) The stress sensitivity experiments of8cores in Sulige area were completed. The stress sensitivity coefficient of different types of reservoir were confirmed, on this basis, the relationship between the dimensionless permeability and the reservoir pressure was calculated.(4) According to the pressure buildup test data of two fractured gas wells, major fracture parameters were tentatively confirmed, which provide the basis for establishing fracturing geological models.(5) Using the commercial software, the geological models of fractured gas well were established, and the production of dynamic histories of gas wells were matched. Then the sensitivity analysis of main fracture parameter were made, and the fracture parameter which put the most important effect on the fracturing effect was found.(6) According to the steady productivity formula in consideration of the stress-sensitive, the production capacity of twenty fractured gas wells were calculated by using the fracture half-length and formation permeability and other parameters. Comparing to the absolute open flow potential of test report, we concluded that the fracture half length and formation permeability were accurate and reliable. In addition, the influence of different stress sensitivity coefficient on the fractured gas wells productivity was also analyzed.(7) The Mathematics theoretical analysis method was applied for fracturing effect evaluation. Selecting the fracture half-length as assessment indicator, construction parameters as effect factors, the weight and correlation were calculated to determine the priority and the impact of effect factors.In this paper, based on the experiments of seepage, well test data, typical well test interpretation, numerical simulation and deliverability assessment, the effective fracture half-lengths were finally obtained. On this basis, the effect of fracturing was evaluated by using the entropy theory and gray relational analysis. Then a simple and systematic fracture evaluation technique suitable for the Sulige was formed, which provide a theoretical basis for the subsequent fracturing design.