柴西北地区油泉子油田浅层油藏异常低压形成机制  

The formation mechanism of lower pressure in the shallow reservoirs of Youquanzi,northwestern Qaidam basin

作　　者：喻廷旭[1] 汤达祯[1] 许浩[1] 汪雷[1] 王凯 

机构地区：[1]中国地质大学(北京)能源学院,北京100083 [2]中国石油青海油田分公司,甘肃敦煌736202

出　　处：《油气地质与采收率》2014年第5期32-35,112-113,共4页Petroleum Geology and Recovery Efficiency

基　　金：国家自然科学基金青年项目"三塘湖盆地侏罗系低压油藏形成机制研究"(40802027);中国石油股份公司风险创新基金项目"柴西北中浅层低压油藏形成机制研究"(0706d01040102)

摘　　要：柴西北地区油泉子油田浅层油藏具有明显的异常低压特征,基于其压力分布特征,从地层流体性质、封闭机制、沉积特征、构造演化等方面深入剖析异常低压形成的主控因素,查明浅层低压油藏封闭条件和形成机制及其压力演化与成藏耦合关系。结果表明,油泉子油田浅层Ca Cl2型地层水、高矿化度、低变质系数、轻质低粘度原油物性共同反映出研究区浅层油藏具有良好的封闭条件,湖盆咸化沉积的塑性较高的含膏质泥岩以及物性渐变带、沥青封堵作用为浅层低压系统垂向和侧向封闭提供重要保障。运用EASY%Ro法和地层对比法对研究区喜马拉雅运动晚期构造抬升剥蚀厚度恢复结果表明,其剥蚀厚度达2 700 m,剥蚀作用导致储层孔隙反弹增大和流体降温收缩,从而使得油藏压力降低,经计算其压力分别降低了14.1和7.4 MPa。油泉子油田浅层油藏异常低压的形成是沉积配置、构造演化及油气成藏等多种地质因素综合作用的结果。The shallow reservoirs of Youquanzi oil field in the northwest Qaidam basin are characteristic of abnormal low pressure.Based on the study of low pressure distribution, the main controlling factors of low-pressure reservoirs formation in the Youquanzi were analyzed including fluid features, seal mechanism, structural evolution and sedimentary characteristics. The seal conditions, formation mechanism and the relationship between pressure evolution and hydrocarbon accumulation in the shallow reservoirs were discussed.The study results show that: the formation water type is Ca Cl2 with high salinity and low ratio of Na+and Cl-, which reflects a good sealing capability; additionally, the light density and low viscosity of crude oil also reflect good sealing conditions of the shallow reservoirs.The plastic gypsum mudstone deposited in saline lacustrine, the bitumen plug, the thrust fault plane and the reservoir heterogeneity provide both vertical and lateral sealing conditions. Methods of EASY%Roand stratigraphic correlation were used to estimate the late Neogene denudation thickness of Youquanzi with a result of 2 700 m. Influenced by the intense tectonic uplift, the pore rebounded and the temperature decreased, which lead to a pressure drop of 14.1 MPa and 7.4 MPa respectively. The abnormal low pressure of the shallow reservoirs in Youquanzi oilfield is controlled by multi effects of sedimentary assemblage, tectonic evolution and hydrocarbon accumulation.

关 键 词：异常低压 形成机制 构造抬升 孔隙反弹 油泉子油田 

分 类 号：TE112.31[石油与天然气工程—油气勘探]