致密砂岩气藏开发传质过程的时间尺度研究

致密砂岩储层在空间上具有强烈的尺度性,包括致密基块孔喉尺度、天然裂缝尺度、水力缝尺度以及宏观气井尺度,这种多尺度结构对气藏流体在储层空间分布和流动中起控制作用。致密砂岩气藏开发传质过程包括基块孔喉尺度的解吸、扩散和渗流，还有天然裂缝和水力裂缝尺度的渗流。气体在不同空间尺度中的流动具有时间效应,在裂缝中流动较快,在孔隙和喉道中流动较慢,而微孔中的扩散更慢,且易受外界环境变化的影响。基于4种尺度下气体的传质过程,推导了各个尺度下不同传质过程的特征时间计算公式,得到了对应空间尺度下的时间尺度范围,结果表明,基块中的扩散和渗流过程在时间尺度上分别为101~1010s和100~106s，而天然裂缝和人工裂缝中在时间尺度上为10-2~101s。指出致密砂岩气藏开发要注意储层保护与改造并举，采用特殊结构井、多层合采井和钻加密井等技术。

STUDY ON TEMPORAL SCALES OF MASS TRANSFER PROCESSES IN DEVELOPING TIGHT SANDSTONE GAS RESERVOIRS

Tight sandstone gas reservoirs are characterized by strong Spatial Scales, including matrix pore and throat scale, natural fracture scale, hydraulic fracture scale, and macro gas well scale. The distribution and flow of fluids are controlled by this multi-scale structure in the gas reservoirs. Mass transfer processes in the tight sandstone gas reservoirs consist of desorption, diffusion and percolation in the matrix pore and throat scale, and percolation in the natural fracture and hydraulic fracture scales. Gas flow in different scales has time scale effect and is easily influenced by circumstance changes. Gas percolation is faster in fractures and slower in pores and throats, and gas diffusion in matrix is the slowest. Based on the gas mass transfer processes in four spatial scales in tight sandstone gas reservoirs, formulae for calculating the characteristic time of the different modes of gas transfer in different scales are derived, and the ranges of spatial and temporal scales are specified. Results show that the time scales of matrix gas diffusion and percolation are 10^1-^10^10 seconds and 10^0-10^6. seconds, and the time scale of natural fracture and hydraulic fracture scales is 10^-2- 10^1 seconds. Such time effects result in lack of gas supply from tight matrix to natural fractures. Therefore, employing both damage control and stimulation should be emphasized, and using special wells, multilayer commingled production and infilling wells will promote the economic exploitation of tight sand gas reservoirs.