复杂砂砾岩储集体岩相特征及识别技术——以川西北地区为例

四川盆地川西北地区普遍发育砂砾岩储集体，具有成因类型多样、成分复杂、岩石结构差异大、储层非均质性强及不同砂砾岩体识别难度大等显著特点。为准确识别砂砾岩储集体，以剑阁、九龙山、白龙场、柘坝场及文兴场等地区为研究重点，以主要发育砂砾岩储层的上三叠统须家河组三段-下侏罗统珍珠冲段为目标层段，利用岩心观察描述、分析化验及测井资料，在深入分析砂砾岩岩相与测井曲线响应特征对应关系的基础上，建立了岩相-测井相数据库，采用多种测井响应交会法和多元分析技术（包括主成分分析法、聚类分析法）识别出砾岩、砂岩、粉砂岩和泥岩等主要岩相；根据不同砾岩相之间物性和岩石结构的差异，将砾岩相进一步细分为颗粒支撑砾岩（包括碳酸盐岩砾、石英砂岩砾、粗砾、中砾、细砾）、杂基支撑砾岩和混合支撑砾岩相。分析结果表明：①采用上述方法测井解释符合率较高（符合率为81.7%），能有效地划分储集层和非储集层；②砾岩、砂岩、粉砂岩和泥岩岩相之间易于区别，但砾质砂岩和砂岩、泥质粉砂岩和粉砂质泥岩有时难以有效区别，另外粗砾与中、细砾区分效果也较差，仅具一定参考性。

Characteristics and identification of lithofacies in complex siliceous elastic reservoirs:A case study from Northwestern Sichuan Basin

Siliceous clastic reservoirs are widely distributed in the northwestern Sichuan Basin and are featured by multiple genetic types, complex components, large texture variation, strong heterogeneity, and great difficulty in their identification. The 3^rd member of Upper Triassic Xujiahe Fm the Lower Jurassic Zhenzhuchong Fm dominated by siliceous clastic reservoirs in several areas such as the Jiange, Jiulongshan, Bailongchang, Zhebachang and Wenxingchang were taken as the major targets of study. A lithofacies log facies data base was set up based on a thorough analysis of the correlation between lithofacies and logging response characteristics. Various logging response cross plotting methods and multivariate analysis techniques were used to identify conglomerate, sandstone, siltstone and mudstone facies. In addition, according to the physical properties and rock textures, the conglomerate facies were further subdivided into grain supported, matrix supported and hybrid grain matrix supported conglomerate facies. The analysis results show that the log interpretation results are high in the coincidence rate of about 81.7% and can be used to effectively differentiate reservoirs and non reservoirs. It is effective in the lithofacies differentiation of conglomerate, sandstone, siltstone and mudstone, but ineffective in distinguishing either conglomeratic sandstone from sandstone or argillaceous siltstone from silty mudstone. Moreover, the differentiation of coarse conglomerate from moderate or fine conglomerate is also quite difficult with this technique.