川西北地区三叠系须家河组深层储层特征及主控因素

川西北地区三叠系须家河组深层碎屑岩是重要的天然气勘探领域，储层质量对气藏发育规模至关重要。应用岩心、露头、地震和测井等资料，对川西北地区三叠系须家河组储层特征及其主控因素进行了分析，并对有利储层发育区进行了评价。研究结果表明：①川西北地区三叠系须家河组深层有效储层属低孔低渗储层，主要发育于三角洲水下分流河道、河口砂坝等微相，岩性以粗砂岩和含砾细砂岩为主，储集空间主要为原生孔、粒内和粒间溶蚀孔及裂缝。②研究区有效储层的发育主要受沉积微相、成岩作用和构造破裂作用等因素控制。水下分流河道砂体最为有利；溶蚀作用形成溶蚀孔隙，并对原生孔隙进行改造，有效提高了砂体物性；构造破裂作用产生的构造裂缝对有效储层的形成具有重要影响。③研究区须家河组三角洲前缘水下分流河道发育大面积砂体，较多的原生孔隙在早期快速埋藏过程中得以保存；在后期埋藏成岩过程中，烃类生成过程中产生的有机酸使得岩石产生了大量溶蚀孔隙；喜山期构造运动形成的大量裂缝优化了储层物性。④川西北地区三叠系须家河组相对优质储层主要分布于老关庙—文兴场—柘坝场、中台山、黎雅庙及剑门关等4个区域。

Deep-reservoir characteristics and main controlling factors of Triassic Xujiahe Formation in northwestern Sichuan Basin

The deep clastic rocks of Triassic Xujiahe Formation in Northwest Sichuan are important areas for natural gas exploration,and reservoir quality is very important to the development scale of gas reservoirs. The reservoir characteristics and main controlling factors of Triassic Xujiahe Formation in northwestern Sichuan Basin were analyzed by using core,outcrop,seismic and logging data,and the favorable reservoir development areas were evaluated. The results show that:(1)The deep effective reservoirs of Triassic Xujiahe Formation belong to low porosity and low permeability reservoirs,which are mainly developed in delta underwater distributary channel and estuarine bar. The lithologies are mainly coarse sandstone and pebbly fine sandstone,and the reservoir space mainly includes primary pores,intragranular and intergranular dissolved pores and fractures.(2)The development of effective reservoir is mainly controlled by sedimentary microfacies,diagenesis and structural fracturing. The underwater distributary channel sand bodies are most favorable. The dissolved pores formed by dissolution and the transformation of primary pores effectively improve the porosity and permeability of sand bodies. The structural fractures produced by fracturing play an important role in the formation of effective reservoirs.(3)A large area of sand bodies are developed in the underwater distributary channel of delta front of Xujiahe Formation in the study area,and many primary pores were preserved in the early rapid burial process. In the process of late burial diagenesis,the organic acids produced in the process of hydrocarbon generation caused a large number of dissolved pores. A large number of fractures formed by Himalayan tectonic movement improved the reservoir physical properties.(4)The relatively high-quality reservoirs of Triassic Xujiahe Formation in northwestern Sichuan Basin are mainly distributed in Laoguanmiao-Wenxingchang-Zhebachang,Zhongtaishan,Liyamiao and Jianmenguan area.