Abstract: In the high-steep structural belt of the eastern Sichuan Basin, gas reservoirs of the Maokou Formation in Wolonghe structure block were discovered between the 1980 s and 1990 s by following the exploration model in South Sichuan. The natural gas production reached 44.13×10⁸m³, accounting for 72.57% of the explored reserves. However, no major exploration breakthroughs have been made in recent years. By analyzing the influencing factors of reservoir development, it is determined that the Maokou Formation reservoir in Wolonghe structure block is mainly reformed by later karstification and dolomitization. Among them, dolomitization plays a role in construction of the reservoir, and the karst fracture-cavern body is the key to finding gas reservoirs of the Maokou Formation in the study area. But the application effect of conventional prediction methods for karst reservoir is not good, and it is difficult to predict the regional distribution of karst reservoir thickness. The seismic prediction technology put forward for karst reservoirs in this study include the following analytical steps. (1) According to the development condition of karst geology, paleogeomorphology research is carried out to delineate the favorable areas for karst reservoir development. (2) Based on the geophysical response characteristics of karst reservoirs, a new seismic prediction technique of karst is developed to further delineate the karst development zones in the favorable karst areas. (3) According to the logging response characteristics of karst reservoir, the development zone of karst reservoir is adopted as the facies control condition, and the P-wave velocity data volume of karst is obtained through the facies-controlled stochastic inversion. (4) The regional distribution regularity of karst reservoirs is quantitatively characterized by integrating paleogeomorphology, development zone and P-wave velocity body of karst. The research results show that the time domain thickness and reservoir thickness of the predicted karst coincide with those of the drilled wells up to 88%, which effectively realizes the seismic prediction of the karst reservoirs of the Maokou Formation in Wolonghe structure block. The seismic prediction technology of karst reservoirs helps to open up the prospects for exploration of the Lower Permian Maokou Formation in Sichuan Basin.

Key words: karst, Maokou Formation, seismic prediction, paleogeomorphology, Wolonghe structure, Sichuan Basin

摘要： 在四川盆地川东高陡构造带，20世纪80—90年代沿用蜀南勘探模式发现了卧龙河构造区块茅口组天然气藏，累计产量达44.13×10⁸m³，占已探明储量的72.57 % ，但近年来却未再取得较大的勘探突破。通过分析储层发育的影响因素发现，卧龙河构造区块茅口组储层主要受后期岩溶及白云石化改造，其中，白云石化对储层起建设作用，岩溶缝洞体是该地区寻找茅口组气藏的关键，但常规的岩溶储层预测方法应用效果不佳，岩溶储层厚度平面分布的预测难度大。研究中提出岩溶储层地震预测技术的分析步骤包括：①从岩溶发育的地质基础入手，开展古地貌研究，圈定岩溶发育有利区域；②基于岩溶储层的地球物理响应特征，开发岩溶地震预测新技术，在岩溶发育有利区进一步圈定岩溶发育带；③根据岩溶储层的测井响应特征，采用岩溶储层发育带作为相控条件，并通过相控随机反演获得岩溶的纵波速度数据体；④综合古地貌、岩溶发育带和岩溶纵波速度体，定量表征岩溶储层的平面展布规律。研究结果表明，预测岩溶的时域厚度和岩溶储层厚度与实钻井的符合率达88 % ，有效地实现了卧龙河构造区块茅口组岩溶储层的地震预测，形成的地震岩溶储层预测技术有助于打开四川盆地下二叠统茅口组的勘探局面。

关键词: 岩溶, 茅口组, 地震预测, 古地貌, 卧龙河构造, 四川盆地