Well network optimization and recovery evaluation of tight sandstone gas reservoirs

Abstract

Tight sandstone gas reservoirs differ greatly in physical properties, and this kind of uncertainties severely set a limit to the steady production and efficient development of gas reservoirs. In order to effectively develop untapped reserves of tight sandstone gas reservoirs and improve their production and recovery, it is important to optimize the well pattern density for the ones with complex reservoir conditions. In this paper, a new index parameter is proposed for the optimization of well pattern density and recovery of tight sandstone gas reservoirs with complex reservoir conditions: the dynamic single-well control area (DSWCA). And the fuzzy synthetic evaluation method is used to establish the relationship between DSWCA and 7 reservoir physical parameters when there is no inter-well interference. The seven parameters are permeability, porosity, effective thickness, water saturation, threshold pressure gradient, productivity coefficient and storage coefficient. Besides, the calculated fuzzy prediction value of the DSWCA is compared with the geological well control area to determine whether there will be inter-well interference due to well pattern infilling under different physical reservoir conditions, and the variation curve of the interference probability with well pattern density is obtained. Finally, a gas recovery evaluation model is constructed combined with inter-well interference probability. The new evaluation method and model derivation comprehensively evaluate the influence of multiple reservoir physical parameters on the DSWCA and the quantitative relationship among them, thus capable of effectively calculating the DSWCA and predicting the production and recovery of the gas field beforehand from a very early stage using the related parameters. The new method, combined with a large number of physical parameter data of fractured vertical wells, was applied in the Su-6 block of the Sulige gas field and compared with the results of actual gas well production dynamics, revealing the consistency of the two results. This method is verified to be reasonable and reliable under certain conditions, and the new method for gas recovery evaluation provides new ideas for the well pattern optimization in tight sandstone gas reservoirs.