摘要
古城台缘带寒武系4期台缘丘滩体规模大、储层好，风险勘探中见到了好苗头，是塔里木盆地持续探索的重要新领域，但复杂的沉积模式、储层分布特征等成藏基本要素认识不清制约了油气勘探进程。基于岩心观察、薄片鉴定、储层岩相学和地球化学特征综合分析、地震相识别及储层预测等技术方法，解析了古城台缘带多期丘滩体的沉积结构类型和储层主要控制因素，构建出沉积构型约束下建设性成岩作用改造的储层分布模型。结果表明：寒武系台缘丘滩体内幕发育丘基、丘核、丘翼和丘坪4种微相类型，沉积能量向上逐渐增强，具有“加积型”和“前积型”2种沉积构型。早期1—2期相带具有垂向叠置结构特征，为“加积型”丘滩体，晚期3—4期相带侧向前积错叠，为“前积型”丘滩体。寒武系台缘丘滩体溶蚀孔洞优质储层发育，内部多套储层呈旋回分布，高能相带是储层发育的基础，大气淡水溶蚀是形成优质储层的关键因素。总体上丘滩体物性顶部好于下部、核部好于翼部；加积型丘滩体频繁暴露，储层呈“三明治”式垂向叠置分布，规模大；前积型丘滩体暴露时间长，储层呈“倒牙刷”式侧向错叠分布，物性好。研究认识为勘探部署中优选有利储集区带提供了重要的地质依据。
Abstract
The four stages of massive Cambrian platform-margin mound-shoal complexes in Gucheng area are the new exploration targets in the Tarim Basin with some promising reservoirs encountered during wildcatting.However, a lack of understanding on the complexity in sedimentary models and reservoir distribution as well as other reservoir forming factors has limited further exploration.Based on core observation, thin section identification, petrographical and geochemical characterization of reservoirs, seismic facies description, and etc., this paper expounds on the identification of sedimentary configuration patterns of the complexes and major factors controlling the reservoirs, and the establishment of a reservoir distribution model under constructive diagenesis constrained by sedimentary configuration.The results show that there are four microfacies (i.e.mound base, mound core, mound flank and mound flat) developed inside the complexes with the sedimentary energy gradually increasing upward, and two types of sedimentary configurations (i.e."accretion type" and "progradation type").The facies belts formed during stages 1 and 2 are "accreted" mound-shoal complexes of vertical superimposition, and those during stages 3 and 4 are "progradational" mound-shoal complexes of lateral stacking.High-quality reservoirs with dissolved pores and cavities are well developed in multiple cyclic distribution with high-energy facies belts as the basis and meteoric water dissolution as an indispensable factor.Generally, the top of the mound-shoal complexes are better in physical properties compared with the bottom, core and flank.The frequently exposed mound-shoal complexes of accretion type contain large-scale reservoirs in a vertically "sandwich-shaped" superimposition distribution; while the long-term exposed progradation type has reservoirs of better physical properties in a laterally "inverted toothbrush-shaped" staggered distribution.The results may be of geological value to the prediction of potential hydrocarbon play fairways in exploration deployment.
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