深层致密砂岩储层成岩演化对含气性的影响

Effects of diagenetic evolution on gas-bearing properties of deep tight sandstone reservoirs： A case study of reservoirs in the 1 member of the Permian Shanxi Formation in the Qingyang gas field， southwestern Ordos Basin

曹江骏 王继平 张道锋 王龙 李笑天 李娅 张园园 夏辉 于占海

Jiangjun CAO Jiping WANG Daofeng ZHANG Long WANG Xiaotian LI Ya LI Yuanyuan ZHANG Hui XIA Zhanhai YU

为研究深层致密砂岩储层成岩作用特征，分析成岩演化对储层含气性的影响，通过铸体薄片、扫描电镜、物性、测井综合解释等资料，结合前人研究成果，对庆阳气田二叠系山西组1段（山1段）进行研究。研究结果表明：①庆阳气田山1段分流河道中部多期厚层砂岩具有连续沉积型和间隔沉积型两类叠置关系，前者孔隙组合类型以溶蚀孔+粒间孔+晶间微孔为主，后者以溶蚀孔+晶间微孔为主。相较于后者，前者填隙物含量更低、物性更好、含气性更好。②压实作用是影响山1段储层含气性最主要的破坏性成岩作用，连续沉积型与间隔沉积型砂岩储层压实率分别为55.4 %与61.2 %；溶蚀作用是影响储层含气性最主要的建设性成岩作用，二者溶蚀率分别为27.9 %与19.7 %。连续沉积型砂岩储层受中等压实作用—中等胶结作用—中等溶蚀作用的成岩演化影响，破坏性成岩作用较弱；间隔沉积型砂岩储层受中等-强压实作用—中等-弱胶结作用—中等-弱溶蚀作用的成岩演化影响，破坏性成岩作用较强。③研究区山1段储层以先致密后充注为主，受成岩演化影响，连续沉积型砂岩储层较间隔沉积型砂岩储层致密化程度低，天然气充注规模大，含气性好。④引入成岩综合指数定量判断山1段储层成岩作用强度。平面上，西部主河道以间隔沉积型砂岩为主，储层成岩综合指数较低，含气性较差；东部主河道以连续沉积型砂岩为主，储层成岩综合指数较高，含气性较好。含气储层主要发育在庆阳一线以东地区。

This study aims to analyze the effects of diagenetic evolution on the gas-bearing properties of reservoirs. Using data from casting thin section observations， scanning electron microscopy （SEM） images， physical property tests， and comprehensive log interpretation， as well as previous research results， we investigate the diagenetic characteristics of deep tight sandstone reservoirs in the 1 member of the Permian Shanxi Formation （hereafter referred to as the Shan 1 Member） in the Qingyang gas field. Key findings are as follows： （1） The multi-stage thick-bedded sandstones in the middle tributary channels of the Shan 1 Member in the Qingyang gas field exhibit two types of superimposition relationships： continuous and intermittent deposition. The pore assemblages in the sandstone reservoirs of the continuous deposition type are dominated by dissolution pores， intergranular pores and intercrystalline micropores， while those in the sandstone reservoirs of the intermittent deposition type predominantly include dissolution pores and intercrystalline micropores. Compared to the intermittent deposition type， the sandstone reservoirs of the continuous deposition type exhibit lower content of fillings， more favorable physical properties， and enhanced gas-bearing properties； （2） Compaction is identified as the most significant destructive diagenesis that undermines the gas-bearing properties of reservoirs in the Shan 1 Member. The sandstone reservoirs of the continuous and intermittent deposition types exhibit compaction rates of 55.4 % and 61.2 %， respectively. Dissolution acts as the most significant constructive diagenesis that enhances the gas-bearing properties of these reservoirs. The sandstone reservoirs of the continuous and intermittent deposition types present dissolution rates of 27.9 % and 19.7 %， respectively. The sandstone reservoirs of the continuous deposition type underwent a diagenetic evolution characterized by moderate compaction， followed by moderate cementation， and then moderate dissolution， indicating weak destructive diagenesis. In contrast， the reservoirs of the intermittent deposition type experienced a diagenetic evolution from moderate to high compaction， to weak to moderate cementation， and finally weak to moderate dissolution， suggesting strong destructive diagenesis； （3） The sandstone reservoirs in the Shan 1 Member experienced reservoir tightening first and then hydrocarbon charging. Due to the influence of diagenetic evolution， the sandstone reservoirs of the continuous deposition type exhibit lower-level tightness， larger-scale natural gas charging， and more favorable gas-bearing properties compared to the intermittent deposition type； （4） The diagenetic intensity of reservoirs in the Shan 1 Member was quantitatively determined using the comprehensive diagenetic index. Regarding the planar distribution， the trunk channels to the west of the Qingyang area primarily consist of sandstones of the intermittent deposition type， with reservoirs exhibiting low comprehensive diagenetic index and poor gas-bearing properties. In contrast， in the trunk channels to the east of the Qingyang area， sandstones of the continuous deposition type are predominant， with reservoirs featuring high comprehensive diagenetic index and favorable gas-bearing properties. Therefore， gas-bearing reservoirs primarily occur to the east of the Qingyang area.

10.11743/ogg20240112