Prediction of Paleogene reservoirs based on structural evolution analysis: taking Shahejie Formation in the middle part of Liaoxi Uplift as example
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摘要:
辽西凸起中段古近系沙河街组缺乏规模性圈闭,储层横向变化快、预测难度大,滚动勘探一直难有较大突破。针对构造、储层问题,采用基于构造演化分析的古近系储层预测方法,综合运用裂变径迹构造反演和空间平衡剖面技术,开展构造演化精细分析,改变传统地层沉积模式,提出辽西凸起高部位发育沙河街组地层的新认识,指导构造解释调整,新增沙河街组勘探层系和有利目标;结合构造约束下的叠前同步反演技术,准确预测沙河街组优势储层发育区,有效指导井位部署和钻探。近年的勘探实践证实了方法的有效性,研究区新增2个千万方级含油气构造,有力支撑了渤海油田的增储上产,也为类似区域的古近系储层研究提供了借鉴。
Abstract:Two problems are encountered in the middle part of Liaoxi Uplift, with regard to the reservoir prediction for Shahejie Formation: the lack of large-scale traps and the rapid lateral variation in reservoirs, which have made reservoir prediction difficult and limited the progress of rolling exploration. In order to solve these problems, we turned the way of research to carry out the Paleogene reservoir prediction upon structural evolution. Using the methods of fission track structure inversion and space balance profiling, detailed study of structural evolution was conducted. This approach abandoned the traditional stratigraphic deposition model, and proposed a new way of thinking for the Shahejie Formation. It is assumed that the Shahejie Formation might occur as well in the high part of Liaoxi uplift. Based on the new understanding, new exploration strata and favorable targets in Shahejie Formation are re-selected. Combined with the pre-stack synchronous inversion technology under structural constraints, the development area of the dominant reservoirs in Shahejie Formation was accurately predicted, and the well position deployment and drilling were effectively performed. The exploration practice in recent years has proved the effectiveness of the new understanding. Two new gas oil-bearing structures of ten million cubic meters of reserves have been discovered in the study area, which strongly supported the increase in oil and gas reserve and production of the Bohai Oilfield, and also provided a reference for the study of Paleogene reservoirs in similar areas.
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表 1 辽西凸起中段基于裂变径迹恢复构造活动史
Table 1. Restoration of tectonic activity history based on fission track in the middle part of Liaoxi uplift
A构造
年代/Ma孔店组沉积期66~50.5 沙四段沉积期50.5~42 沙三段沉积期
42~38.0沙一二段沉积期38.0~32.0 东三段沉积期32.0~30 东二段沉积期30~27.4 东一段沉积期27.4~23.3 馆陶组沉积期23.3~12 抬升量/m 865.7 181 −11.4 −82.8 −37.1 −25.7 31.4 762.8 B构造
年代/Ma晚白垩世+孔店组沉积期75~50.5 沙四段沉积期50.5~42 沙三段早期42~40.0 沙三段晚期40.0~38.0 沙一二段沉
积期38.0~32.0东三段沉积期32.0~30 东二段沉积期30~27.4 东一段沉积期27.4~23.3 馆陶组+明化镇组沉积期23.3~5.3 抬升量/m 727.7 162.8 25.7 −265.7 −325.7 −100 −188.5 −151.4 1314 C构造
年代/Ma孔店组沉积期66~50.5 沙四段沉积期50.5~42 沙三段沉积期42~38.0 沙二段沉积期38.0~34.1 沙一段沉积期34.1~32.0 东三段沉积期32.0~30 东二段沉积期30~27.4 东一段沉积期27.4~23.3 馆陶组早期23.3~16.9 抬升量/m 602.8 165.7 −51.4 −77.1 −37.1 −111.4 −77.1 780 717 -
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