苏里格气田岩石相控制的致密砂岩储层质量差异机理

针对致密砂岩储层非均质性极强、孔隙结构复杂、井间产能差异明显、储层质量差异机理不明确等问题,以苏里格西区南部下石盒子组盒₈段的致密砂岩储层为例,综合利用岩心、测井等资料,探讨岩石相控制的致密砂岩储层质量差异机理。结果表明:岩石相通过影响成岩演化序列控制储层质量,细砾岩-含砾粗砂岩相的储层质量最好,渗透率大于1.00 mD,主要发育粒间孔-缩颈型喉道,粗砂岩相的储层质量次之;根据岩石相及塑性岩屑含量,将储层成岩演化序列分为粗岩相(细砾岩-含砾粗砂岩相与粗砂岩相的统称)、富含刚性颗粒的中砂岩相、富含塑性颗粒的中砂岩相及细砂岩相4类;粗岩相经历了弱压实—强胶结—强溶解的成岩序列,物性最好,多呈孤立透镜状分布于条带状分流河道砂体中,这一分布特征是导致井间产能差异明显的主要原因。研究成果可为优质储层的预测及致密砂岩气藏的勘探开发提供理论指导。

Quality Difference Mechanism of Tight Sandstone Reservoir Controlled by Lithofacies in Sulige Gasfield

In view of the extremely strong heterogeneity, complex pore structure, significant productivity difference between wells and unclear reservoir quality difference mechanism of tight sandstone reservoir, the quality difference mechanism of tight sandstone reservoir controlled by lithofacies was discussed according to comprehensive core and logging data by taking the tight sandstone reservoir in the Member 8 of the lower Shihezi Formation in southern Sulige Gasfield. It is found in the study that the results show that the reservoir quality was controlled by lithofacies by affecting the diagenetic evolution sequence, and the reservoir quality of the fine conglomerate - pebbled coarse sandstone facies was the best, followed by that of the coarse sandstone facies, with a permeability greater than 1.00 mD, and mainly developed with intergranular pores - necked throats;according to the content of lithofacies and plastic debris, the diagenetic evolution sequence of reservoirs was classified by four categories: coarse lithofacies (collective term of fine conglomerate - pebbled coarse sandstone facies and coarse sandstone facies), medium sandstone facies rich in rigid particles, medium sandstone facies rich in plastic particles, and fine sandstone facies;after experienced diagenetic sequence of weak compaction, strong cementation and strong dissolution, the coarse lithofacies had the best physical properties, and were mostly distributed as isolated lenses in sand in striped distributary channel. This distribution feature is the main reason for the obvious difference in productivity between wells. The study results provide a theoretical basis and guidance for the prediction of high-quality reservoirs and the exploration and development of tight sandstone gas reservoirs.