准噶尔盆地玛湖凹陷百口泉组储层水敏效应及主控因素

Water-sensitive effect and main controlling factors of Baikouquan Formation reservoir in Mahu Sag, Junggar Basin, China

对准噶尔盆地玛湖凹陷下三叠统百口泉组细/小砾岩与含砾粗砂岩储层的水敏效应进行评价,并对其主控因素及规律进行分析。结合基础物性测试、岩矿成分、孔隙结构分析,以及水敏实验,对不同岩性的水敏效应进行评价,探讨其主控因素,并利用填砂模型进行单一因素研究,以验证水敏主控因素分析的正确性。研究结果表明:细/小砾岩的物性与孔隙结构较差,但是喉道分选性优于含砾粗砂岩;研究区水敏损害的主要因素为矿物水化膨胀,次要因素为颗粒运移。由于含砾粗砂岩较好的物性,增加了黏土与流体接触的概率,且较差的喉道分选性及胶结程度,易造成喉道封堵,导致其水敏指数远大于细/小砾岩;渗透率是水敏效应的主控因素,细/小砾岩的敏感性指数随着克氏渗透率的增加而急剧增加,而含砾粗砂岩的敏感性指数随着克氏渗透率的增加而缓慢减小,填砂模型的单因素分析验证了其主控因素的合理性。由于渗透率与润湿性的协同作用,对于细/小砾岩而言,第一次伤害率与第二次伤害率无明显差异,但是含砾粗砂岩的第一次伤害率明显大于第二次伤害率。

The water-sensitive effects of fine/small conglomerate and pebbled coarse sandstone reservoirs in the Lower Triassic Baikouquan Formation in Mahu Sag, Junggar Basin are evaluated, and the main controlling factors and rules are analyzed. Based on the basic physical property test, rock and ore composition, pore structure analysis and water sensitivity experiment, the water sensitivity effects of different lithologies are evaluated in order to determine the main controlling factors and the sand filling model is used to conduct a single factor study to verify the correctness of the analysis of main controlling factors of water sensitivity. The results show that the physical properties and pore structure of fine/small conglomerate are poor, but the throat sorting is better than that of pebbled coarse sandstone. The main factor of water sensitivity damage in the study area is mineral hydration expansion and the secondary factor is particle migration. The good physical properties of pebbled coarse sandstone increase the probability of clay and fluid contact, but its poor throat sorting and cementation degree is easy to cause throat sealing, resulting in much higher water sensitivity index than that of fine/small conglomerate. Permeability is the main controlling factor of water sensitivity effect. In fact, the sensitivity index of fine/small conglomerate increases sharply with the increase of the Klinkenberg permeability, while that of the pebbled coarse sandstone decreases slowly with the increase of the Klinkenberg permeability. The rationality of the main controlling factor is verified by the single factor analysis of the sand filling model. Due to the synergistic effect of permeability and wettability, there is no significant difference between the first damage rate and the second damage rate for fine/small conglomerate, but the first damage rate of pebbled coarse sandstone is significantly greater than the second damage rate.