源内致密砂岩优质储层特征及控制因素分析:以川西坳陷须五段为例

Characteristics and Main Controlling Factors of High Quality Tight Sandstone Reservoir Source: Take the Xujiahe Formation (5;Member) in Western Sichuan Depression as An Example

川西坳陷的油气勘探已经从源储分离的常规油气勘探逐渐转变为源储一体的常规与非常规油气协同勘探,其中致密储层发育特征及成藏特点成为目前亟须解决的关键科学问题之一。运用石油地质学与沉积岩石学原理及分析方法,对川西坳陷须五段储层发育特征及控制因素进行研究,研究结果显示,须五段砂岩储层的孔隙度为1.371%~8%,小于10%,渗透率为(0.005~0.701)×10^(-3)μm^(2),小于1×10^(-3)μm^(2),属致密储层范畴。基于砂岩粒度大小结合储层物性以及含气性分析,须五段识别出三类优质储层,即粗砂、中砂和细砂。研究区粗砂较少发育,厚度较大的中砂和细砂在上亚段、中亚段和下亚段的三角洲前缘亚相较发育,储集空间发育微孔隙、少量微裂缝。粒度中值控制致密砂岩优质储层的发育类型、沉积相带与层序控制优质储层的发育位置,成岩作用控制优质储层的形成。

Petroleum exploration of Xujiahe Formation in the western Sichuan depression has gradually integrated conventional and unconventional petroleum systems. Petroleum reservoirs accumulated within the source beds have been new fields of petroleum exploration. In this study, the principle of the petroleum geology, sedimentary petrology and analysis method were used to reveal the reservoir development characteristics and controlling factors of the Xujiahe Formation(5;member) in the depression. The porosity of the reservoir in the Xujiahe Formation(5;member) is of 1.371% to 8.000%(< 10%), and the permeability is 0.005×10^(-3) to 0.701×10^(-3) μm^(2)(< 1×10^(-3) μm^(2)), which belongs to the tight reservoir category. Based on the sandstone grain size, the reservoir physical properties and gas-bearing properties, three types of high-quality reservoirs have been identified, i.e.coarse sand, medium sand, and fine sand. In the study area, the coarse sand is less developed, while thick medium sand and fine sand are better developed in the delta front of the upper, middle and lower subsegments. The reservoir space developed micro-pores and a few micro-cracks. Median granularity likely controlled the type of high-quality tight sandstone reservoirs, sedimentary-facies belts;the stratigraphic controlled the location of high-quality reservoirs;and the diagenesis controlled the formation of high-quality reservoirs.