致密砂岩气藏不同自吸压差下水锁损害

Water Lock Damage under Different Self-imbibition Pressure Difference in Tight Sandstone Gas Reservoir

普遍认为致密砂岩气藏在负压差自吸时不存在水锁损害。为此,依据现场资料设计无压差、正压差、负压差自吸条件下水锁损害实验,通过测试束缚水饱和度及当前含水饱和度,判断研究区域是否发生水锁损害。以返排后渗透率与初始渗透率比值来评价水锁损害程度,比值越大水锁损害程度越小。实验结果表明:研究区域当前含水饱和度明显高于束缚水饱和度,存在水锁损害。虽然负压差条件下水锁损害程度最小,但是水锁损害依然严重。可见,当致密砂岩气藏以负压差生产时,水锁损害同样不容忽视。

It was generally believed that there was no water lock damage under negative self-imbibition pressure difference in the tight sandstone gas reservoir. Therefore, designed water lock damage experiment under no pressure difference, positive pressure difference, negative pressure difference self-imbibition conditions, in order to determine whether the study area has water lock damage, the irreducible water saturation and current water saturation was tested. After flow back, the ratio of present permeability to initial permeability was used to evaluate the degree of water lock damage. The greater the ratio, the smaller the degree of water lock damage. The results show that the current water saturation was significantly higher than the irreducible water saturation, and the study area has water lock damage. Although the water lock damage was the smallest under negative pressure difference, but the water lock damage was still terrible. It is concluded that when tight sandstone gas reservoirs are produced under negative pressure difference, the water lock damage can not be ignored.