川中地区下二叠统白云岩储层测井评价

Well logging evaluation of the Lower Permian dolomite reservoir in central Sichuan Basin

四川盆地川中地区下二叠统茅口组和栖霞组发育裂缝—孔洞型白云岩储层,多口井测试获高产工业气流。但茅口组热次盆相白云岩岩性复杂、富含硅质、非均质性强,测井储层精细评价困难;栖霞组白云岩受岩溶及多期构造作用影响,缝洞发育,储层厚度薄,基质具有低孔隙、低渗透特征,储层评价及产能预测难度大。通过综合分析常规测井、成像测井、阵列声波测井资料,结合地质录井资料,建立白云石、方解石和硅质岩等复杂岩性及非均质构造识别标准,解决了茅口组硅质白云岩岩性识别问题;基于成像裂缝、孔洞参数、斯通利波能量衰减、核磁孔隙结构参数建立了储层定量判别标准及图版。该方法在川中地区下二叠统储层评价中取得了良好的应用效果,测井解释符合率超过80%,为川中地区下二叠统天然气储量申报提供了技术支持,为川中地区高石梯—磨溪—龙女寺地区立体勘探、寻找规模储量与资源接替领域提供了支撑作用。

The fracture-cavity dolomite reservoirs develop in the Lower Permian Maokou Formation and Qixia Formation in the central Sichuan Basin, and have contributed high-yield industrial gas flow during testing of several wells. However, the Maokou Formation dolomite of hydrothermal sub-basin facies is complex in lithology, rich in siliceous content, and strong in heterogeneity, bringing challenges to fine reservoir evaluation. The Qixia Formation dolomite reservoir is thin and contains fractures/cavities, with low porosity and low permeability matrix, which were resulted from karstification and multi-stage tectonic movements, making the reservoir evaluation and production capacity prediction difficult. Through the comprehensive analysis of conventional logging, imaging logging, and array acoustic logging data, together with geological logging data, the identification standards for complex lithologies （e.g. dolomite, calcite, and siliceous rock） and heterogeneous structures were established to facilitated the lithological identification of siliceous dolomite in the Maokou Formation. Based on the fracture/cavity parameters obtained by imaging logging data, Stoneley wave energy attenuation, and NMR pore structure parameters, the quantitative reservoir discrimination criteria and charts were defined. This meth- od was satisfactorily applied in the Lower Permian reservoir in the central Sichuan Basin, with the logging interpretation coincidence rate over 80%, which provides a technical support for the declaration of the Lower Permian natural gas reserves in the central Sichuan Basin. This method also supports the stereoscopic exploration and finding large-scale reserves and replacement resources in the Gaoshiti-Moxi-Longn0si area of the central Sichuan Basin.