Distribution of favorable lacustrine carbonate reservoirs: A case from the Upper Es4 of Zhanhua Sag, Bohai Bay Basin

Based on core thin sections, logging and seismic data, the distribution of favorable lacustrine carbonate reservoirs is predicted in the upper Es4 of the Zhanhua Sag, Bohai Bay Basin. In the upper Es4 of the Zhanhua Sag, four categories of carbonates are developed, i.e. bioclastic limestones (dolomites), intraclastic limestones (dolomites), arenaceous limestones (dolomites) and argillaceous limestones (dolomites). With core calibrated logs, the electrical characteristics interpretation criteria for various carbonates are established, and the lithofacies sequences of the exploratory well are reconstructed. According to overlying pattern of high-frequency cycles, the short-term cycles of bioherm, carbonate bank and semi-deep lake are divided, and high resolution isochronous formation framework is built. On the basis of the facies characteristics of well tie sections and palaeo-landform background, the carbonate depositional model is established, namely, the reef and bank carbonates are deposited from the largest expansion period to the stable period of lake basin, bank carbonates are mainly distributed on the upper side of synsedimentary faults on the gentle slope or deposited in fault-step lowland on the steep slope while the reef carbonates mainly on fault-step highland on the steep slope. Favorable reservoir types include reef bioclastic limestone (dolomite), bank bioclastic limestone (dolomite), intraclastic limestone (dolomite) and arenaceous limestone. It is possible to predict the distribution of favorable reservoirs according to the depositional model, palaeo-landform analysis and seismic amplitude attributes.

摘要：运用岩心薄片、测井、地震等资料和技术手段，预测渤海湾盆地沾化凹陷沙四上亚段湖相碳酸盐岩有利储集层分布。研究表明，沾化凹陷沙四上亚段发育生物碎屑灰/云岩类、内碎屑灰/云岩类、砂质灰/云岩类、泥灰/云岩类等4大类碳酸盐岩。用岩心刻度测井，分区建立了不同碳酸盐岩类的电性解释标准，重构探井岩相序列，并依据高频旋回的叠置样式，划分了生物礁、碳酸盐岩滩和半深湖等短期旋回类型，据此建立了高分辨率等时地层格架。综合分析多条连井剖面相特征及古地貌背景建立了碳酸盐岩沉积模式，即礁、滩类碳酸盐岩主要发育于湖盆扩张的鼎盛期至稳定期，缓坡带同沉积断层上盘以滩类为主，陡坡带断阶高地为礁相、断阶低地为滩相。有利的储集层类型有礁相生物碎屑灰/云岩及滩相生物碎屑灰/云岩、内碎屑灰/云岩、砂质灰岩等，依据沉积模式、古地貌分析与地震振幅属性可预测有利储集层分布。图89表3参21