考虑差异化相渗的致密气藏开发效果分析

压裂改造是低渗致密气藏增产的重要措施,而考虑地质-工程一体化的气藏开发动态预测是致密气藏开发的热点问题。大规模水力压裂也会造成改造区相渗与未改造区相渗出现差异,并且不同储集层类型也对应着不同的相渗关系。因此,基于差异化相渗的致密气藏一体化模拟研究具有重要意义。从工程-地质一体化建模流程入手,考虑基质和裂缝的相渗差异,并结合3种储层地质及相渗关系形成了考虑差异化相渗的模拟流程,该模拟方法能有效解决前期返排阶段产水量拟合效果较差的问题。通过考虑差异化相渗的一体化模拟对低渗致密气藏3种储层类型的开发特征和开发效果进行了分析,并建立无因次压降与采出程度的关系图版,用于评价气藏不同时期的开发效果。研究表明,残余气饱和度的高低决定了气井开始产气的滞后时间,残余气饱和度越低,气井返排期越长;在考虑差异化相渗的情况下,含水饱和度对采收率影响最为显著、渗透率次之,孔隙度与有效厚度影响较小。通过本文的研究揭示了不同储集层物性对开发效果的影响规律,对指导致密气藏高效开发具有重要的理论及实践意义。

Development Effect Analysis of Tight Gas Reservoir Considering Differential Relative Permeability

Fracturing is an important measure to increase production of low-permeability tight gas reservoir, and gas reservoir development performance prediction considering geological engineering integration is a hot issue in tight gas reservoir development. Large scale hydraulic fracturing will also lead to the difference of phase permeability between the reformed area and the unmodified area, and different reservoir types also correspond to different phase permeability relationships. Therefore, the integrated simulation of tight gas reservoir based differential on dissimilatory relative permeability is of great significance. This paper starts with the engineering geological integrated modeling process, introduces the differential relative permeability embedding method, and combines the three types of reservoir geology and relative permeability relationship to form a simulation process considering differential relative permeability. This simulation method can effectively solve the problem of poor fitting effect of water production in the early flowback stage. Through the simulation considering differential relative permeability, the development characteristics and development effects of three types of low-permeability tight gas reservoirs are analyzed, and the chart between dimensionless pressure drop and recovery degree is established to evaluate the development effects of gas reservoirs in different periods. The simulation results show that the residual gas saturation determines the lag time of gas production. The lower the residual gas saturation is, the longer the flowback period of the gas well is. Through the research of this paper, the influence law of different reservoir physical properties on development effect is revealed, which has important theoretical and practical significance for guiding the efficient development of tight gas reservoir.