烃源流体—储集岩协同演化模拟实验及地质启示——以川西地区上三叠统须家河组为例

Co-evolution simulation experiment of source rock fluid and reservoir rock and its geological implications:a case study of Upper Triassic Xujiahe Formation, western Sichuan Basin

流体—岩石相互作用是致密砂岩油气藏形成的重要影响因素,深入研究流体—岩石相互作用对储层致密化的影响机制对厘清优质储层的分布规律尤为重要。以川西上三叠统须家河组为例,开展了封闭环境条件下,Ⅲ型烃源流体—长石石英砂岩储层协同演化模拟实验。Ⅲ型烃源岩生成的大量CO_(2)在140℃或170℃储层地温条件下会导致砂岩储层中碳酸盐胶结物发育,是砂岩储层致密化的主要影响因素;烃源流体的滞留效应对储层致密化至关重要;封闭成岩体系下,致密油气勘探应以寻找有利于原生孔隙形成与保存的有利沉积相砂体为指向,在半开放—开放体系成岩环境下,应以寻找酸性流体优势运聚区次生孔隙发育的储层为指向。

Fluid-rock interaction is critical for the formation of tight sandstone reservoirs,contributing to illustrate the distribution of high-quality reservoirs.In this study,a simulation experiment on the co-evolution of typeⅢsource rock fluids and feldspar-quartz sandstone reservoirs under sealed condition was carried out with the samples from the Upper Triassic Xujiahe Formation in the western Sichuan province.A large amount of CO_(2) generated leads to the development of carbonate cements in sandstone reservoirs at temperature of~140 or 170℃,indicating the main factors for sandstone reservoir densification.The retention effect of hydrocarbon fluids plays a key role for reservoir densification.In the closed diagenetic system,tight oil and gas exploration should focus on locating favorable sedimentary sand bodies that are conducive to the formation and preservation of primary pores;while in a semi-open or open system,it should be directed to reservoirs with secondary pores in the dominant migration and accumulation areas of acid fluids.