Quantitative Study Of Residual Gas In DND Low Permeability Tight Gas Reservoir

Low-permeability tight gas reservoirs are an important part of unconventional oil and gas.The reservoir properties are poor,the bottom hole pressure drops rapidly,the stable production period is short,and the residual gas distribution is complex.The residual gas is the material basis for the efficient development of gas reservoirs,so the remaining Gas research is particularly important.In this paper,the problems of thin reservoir,thin layer,heterogeneity,multi-layer mining and production status of production wells,nonlinear seepage and other factors in the low-permeability tight gas reservoir lead to complex gas distribution,etc.,firstly,through the analysis of geological characteristics and production dynamics of the study area,as well as the evaluation of interlayer and interlayer connectivity.On the basis of the above research,the physical simulation experiment of multi-layer combined production is carried out to deepen the understanding of the seepage characteristics of multi-layer combined production in low permeability tight gas reservoirs,evaluate the reserves utilization representing high permeability and low permeability cores,and analyze the influencing factors of residual gas enrichment.The new method of single well control reserve calculation based on the factors of stress sensitivity,slippage effect,starting pressure gradient and pressure crack is deduced by using gas reservoir engineering theory method,and the single well is programmed and calculated by Matlab software.Analyzing the calculation results of single well controlled reserves,DND gas reservoir has small single well controlled area and low well pattern control degree,which leads to accumulation of remaining gas in reservoir.Combined with the above research conclusions,a three-dimensional fine geological model is established by using the common constraints of dynamic and static parameters.The vertical mesh thickness of the main layer of the model is 0.5m,which can describe the properties of each layer in more detail.On the basis of this research,the residual gas is classified and statistically analyzed by numerical simulation.The residual gas formation is mainly caused by the un-operated well,the existing well pattern control edge is not used,the utilization is low or incompatible reservoirs.For different types of residual gas,adjustment schemes such as filling holes,encryption and sidetracking horizontal wells are proposed to improve the control degree of the well pattern.Comparing the prediction results of each adjustment scheme,considering the mining cost,the recommended replacement hole-filling and encryption scheme is the optimal adjustment scheme.The scheme predicts that the degree of recovery is 56.53%,which is 7.85%higher than that of the basic scheme,and the predicted production gas is increased by 3.25×108m3.