顶板致密砂岩气对深部煤层气井产气效果的影响——以鄂尔多斯盆地神府区块为例

摘要/Abstract

摘要： 鄂尔多斯盆地东缘神府区块深部煤层与致密砂岩层紧密叠合,深部煤层气开发过程中存在顶板致密砂岩气向煤层运移的现象。迄今,关于顶板致密砂岩气对深部煤层气开发影响的研究仍然较为匮乏。以神府区块8+9号煤及其顶底板为研究对象,开展了不同砂岩覆盖比例（井控范围内顶板砂岩对煤层的覆盖比例）的深部煤层气直井排采数值模拟研究,并从储层压力传导、气体解吸与扩散和渗透率动态变化3个方面,探究了顶板致密砂岩气运移对煤层气井产气效果的影响及其作用机制。结果表明：深部煤层气开发过程中,顶板致密砂岩气向煤层运移并贡献了深部煤层气井部分产气量,且随顶板砂岩覆盖范围增加,致密砂岩气的产气贡献增高,相较于顶板为泥岩的情况,砂岩覆盖比例为40%、60%和80%时,致密砂岩气对累计产气量的贡献依次提高了11.43%、23.54%和29.35%;在压裂裂缝控制范围外,砂岩层中气、水产出更快,扩大了砂岩层压降幅度与压降范围,间接促进了压裂裂缝控制范围外的煤层卸压,提高了煤层气解吸与扩散速率,进而增强煤基质收缩效应,并促进煤储层渗透率回升,而煤储层渗透率的回升将进一步促进储层压力传导和气体解吸与扩散,从而提升煤层气井产气效果。

关键词: 神府区块, 深部煤层气, 致密砂岩气, 储层压力, 渗透率

Abstract: In the Shenfu block located on the eastern margin of the Ordos Basin, the deep coal seam is intimately interlayered with the tight sandstone layer. During the development of deep coalbed methane, a notable phenomenon has been observed whereby tight sandstone gas from the roof migrates into the coal seam. To date, studies on the impact of roof tight sandstone gas migration on deep coalbed methane production remain scarce. Taking the No.8+9 coal seam and its roof and floor in the Shenfu block as the study object, a numerical simulation of vertical well drainage was conducted for deep coalbed methane under different sandstone coverage ratios (i.e., the proportion of roof sandstone covering the coal seam within the well control range). This study investigated the roles of reservoir pressure conduction, gas desorption/diffusion, and dynamic changes in permeability in governing the influence of roof tight sandstone gas migration on the gas production performance of deep coalbed methane wells and explored its underlying mechanism. The results show that during the development of deep coalbed methane, the migration of roof-tight sandstone gas into the coal seam contributes to the gas output of deep coalbed methane wells. With the increase of roof sandstone coverage, the contribution of tight sandstone gas to cumulative gas production correspondingly increases by 11.43%, 23.54%, and 29.35% at sandstone coverage ratios of 40%, 60%, and 80%, respectively, In comparison to cases with a mudstone roof. Outside the control range of hydraulic fracturing, gas and water production from the sandstone layer occurs more rapidly. This enlarges both the magnitude and spatial extent of the pressure drop within the sandstone layer. As a result, pressure relief is indirectly facilitated in the coal seam, enhancing the rates of gas desorption and diffusion. Additionally, it strengthens the shrinkage effect of the coal matrix and promotes the recovery of permeability. The improvement in permeability further augments the reservoir pressure conduction and gas desorption/diffusion, thereby improving the gas production performance of coalbed methane wells.

Key words: Shenfu block, deep coalbed methane, tight sandstone gas, reservoir pressure, permeability

中图分类号:

TE37

王小东,王宇川,梁萧磊等. 顶板致密砂岩气对深部煤层气井产气效果的影响——以鄂尔多斯盆地神府区块为例[J]. 油气藏评价与开发, 0, (): 2025041001-2025041001.

WANG Xiaodong,WANG Yuchuan,LIANG Xiaolei, et al. Influence of tight sandstone gas in roof on gas production in deep coalbed methane wells: A case study of Shenfu block in Ordos Basin[J]. Petroleum Reservoir Evaluation and Development, 0, (): 2025041001-2025041001.

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