川东—川南地区茅口组岩溶储层分类识别及有效性评价

川东—川南地区中二叠统茅口组受暴露和风化淋滤的影响发育了独特的早成岩期风化壳岩溶储层，具有较大的勘探开发潜力。由于岩溶储层的孔隙结构特征、纵横向分布规律、测井响应特征等极为复杂，导致其测井有效性评价难度较大。在储层分类的基础上，结合岩溶发育模式，开展了茅口组3套典型储层的测井有效性评价方法研究。结果表明：①茅口组顶部储层的有效性与铝土质泥岩等风化残积物的充填程度密切相关，茅一段—茅三段铀含量较高储层的有效性与地层水的活跃程度密切相关，茅一段—茅二段似层状分布储层的有效性与泥质灰岩对潜水面的控制作用密切相关。②岩石放射性强度在一定程度上直接或间接反映了茅口组岩溶储层的发育和有效性，因此自然伽马和自然伽马能谱测井在岩溶储层有效性评价中具有重要作用。③受岩性、断层、岩溶侵蚀程度等因素的影响，不同构造中水平潜流带和深部缓流带的分布范围不同，因此储层的主要发育深度也不相同。该研究成果对于风化壳岩溶储层的有效性识别具有一定的借鉴意义。

Classification and effectiveness evaluation of karst reservoirs of Maokou Formation in eastern and southern Sichuan Basin

Influenced by exposure and weathering leaching,Maokou Formation of the middle Permian in eastern and southern Sichuan Basin has developed unique eogenetic weathering crust karst reservoirs,which has great exploration and development potential.Due to the complex characteristics of the pore structure,vertical and horizontal distribution and well logging response,it is difficult to carry out logging effectiveness evaluation.On the basis of reservoir classification,combined with karst development model,the logging effectiveness evaluation methods for three sets of typical reservoirs of Maokou Formation were studied.The results show that:(1)The effectiveness of the reservoirs developed in the top of Maokou Formation is closely related to the filling degree of weathering residual deposits such as auxetic mudstone.The effectiveness of the reservoirs with higher uranium content in Mao 1 member to Mao 3 member is closely related to the activity of the formation water,and the effectiveness of bedded reservoirs developed in Mao 1 member to Mao 2 member is closely related to the control of the argillaceous limestone on the water table.(2)The radioactive intensity of rocks directly or indirectly reflects the development and effectiveness of the karst reservoirs in Maokou Formation,so natural gamma ray logging and natural gamma ray spectral logging play important roles in the evaluation of the effectiveness of karst reservoirs.(3)Influenced by lithology,fault,karst erosion degree and other factors,the distributions of horizontal undercurrent zone and deep slow current zone vary in different structures,and the main developed depth of reservoirs is also different.The study results can be used for reference for the validity identification of karst reservoirs.