构造抬升对高、低煤阶煤层气藏储集层物性的影响

Effects of tectonic uplift on physical properties of high and low rank coal reservoirs

构造抬升对高、低煤阶煤层气藏储集层物性的影响具有显著差异。低煤阶煤层主要为基质型孔隙,高煤阶煤层主要为裂隙型孔隙。煤岩储集层原地受力分析表明,构造抬升使得基质承受的压力降低。构造抬升模拟实验及煤基质、裂隙渗透率应力敏感性实验表明,构造抬升后煤层压力传导加速,割理开启,渗透率变大;基质渗透率比裂隙渗透率的应力敏感性弱。分析认为:构造抬升对高煤阶煤储集层物性影响明显,地层压力降低,割理、裂缝开启,裂隙渗透率显著增强;高煤阶煤层强烈抬升会使其渗透率增大,造成气体大量散失,对煤层气聚集不利;低煤阶煤层储集层物性受构造抬升影响较弱,由于构造抬升,压力降低,煤层气运移速率增大,对煤层气开采有利。

The influences of tectonic uplift on the physical properties of high and low rank coal-bed methane （CBM） reservoirs are different. Low rank coal-beds have mainly matrix-type pores and high rank coal-beds are mainly cleat type. The stress analysis of coal reservoirs indicate that the matrix pressure decreases with the tectonic uplift. The uplift simulation and the sensitivity experiment of the matrix and cleat permeability show that tectonic uplift makes the coal seams pressure deliver faster, cleats open, and the permeability increase. The sensitivity of the cleat permeability is more obvious. The uplift affected the physical porosities of the high rank coal reservoirs. The strong uplifting of high rank coal sequences makes the permeability increase and the CBM diffuse, which is disadvantageous to the CBM enrichment. The uplift has less influence on the physical properties of low rank coal-beds and makes the pressure decrease and the migration speed of CBM increase, which is favorable for the CBM development.