川西新场地区须二段物源特征及其对储层物性的控制

Provenance characteristics and its controlling on reservoir physical properties of the second Member of the Xujiahe Formation in Xinchang area,western Sichuan Depression

结合物源特征分析川西新场地区须家河组须二段(T3x2)储层的研究较少,严重制约了须家河组天然气勘探开发进度。文中通过碎屑组分及重矿物分析等手段,结合薄片及压汞等资料对新场地区须二段物源特征、储层物性特征及二者的关系进行了研究。结果显示:新场地区须二段主要物源为东北方向的秦岭大巴山,其次是西北方向的龙门山;须二段长石岩屑砂岩的物性最好,岩屑石英砂岩次之,岩屑砂岩最差;与龙门山物源控制的储层相比,秦岭大巴山物源控制的储层富长石,富火山岩岩屑,贫沉积岩岩屑,导致其溶蚀作用、绿泥石薄膜对孔隙的保护作用更强,碳酸盐胶结作用更弱,相对优质储层占比更高;秦岭大巴山物源控制的储层中,与近物源端相比,远物源端储层的粒度、分选性、磨圆度更好,且远物源端富长石,贫沉积岩岩屑导致其溶蚀作用更强,碳酸盐胶结作用更弱;压汞资料和薄片分析显示,远物源端储层孔隙结构更好,相对优质储层占比更高。

The research on reservoir physical properties combined with provenance characteristics of the second Member of Xujiahe Formationin in Xinchang area(T3x2)of western Sichuan Depression is less,which limit the progress of gas exploration of Xujiahe Formation.Provenance characteristics and reservoir physical characteristics of T3x2 are analyzed comprehensively by means of detrital components,heavy minerals and so on,as well as thin section and mercury injection data.The results show that the main provenance of T3x2 is Qinling-Daba mountain in the northeast of the study area,followed by Longmen mountain in the northwest of the study area.The physical property of feldspathic litharenite is the best,followed by quartzarenite,litharenite is the worst.Compared with the reservoir controlled by Longmen Mountain provenance,the provenance of Qinling-Daba mountain is rich in feldspar/volcanic rock debris and short of sedimentary rock debris,which leads to stronger dissolution and better pore protection by chlorite film and weaker carbonate cementation,caused the proportion of relatively high quality reservoir is higher.Compared with the near provenance site of Qinling-Daba mountain,the distant provenance site has better grain size,sorting and grinding,and the distant provenance site is rich in feldspar and short of sedimentary rock debris,resulting in stronger dissolution and weaker carbonate cementation.Mercury injection data combined with thin section analysis show that the reservoir of distant provenance site of Qinling-Daba mountain has better pore structure and higher proportion of relatively high-quality reservoirs.