断陷盆地压力系统及其成藏特征——以沾化凹陷孤南洼陷古近系为例  

Pressure systems and their hydrocarbon accumulation characteristics in faulted basins:a case study of the Palaeogene in Gunan subsag of Zhanhua sag

作　　者：程付启[1] 王永诗[2] 宋国奇[3] 林会喜[4] 刘雅利[2] 

机构地区：[1]中国石油大学(华东)地球科学与技术学院,山东青岛266580 [2]中国石化胜利油田分公司地质科学研究院,山东东营257015 [3]中国石化胜利油田分公司,山东东营257001 [4]中国石化胜利油田分公司西部新区研究院,山东东营257015

出　　处：《油气地质与采收率》2015年第1期20-25,共6页Petroleum Geology and Recovery Efficiency

基　　金：国家科技重大专项"渤海湾盆地精细勘探关键技术"(2011ZX05006-003)

摘　　要：受构造演化与沉积过程的控制,断陷盆地在纵向上会发育不同的压力系统,不同压力系统的成藏条件、成藏模式及油气分布规律等方面都存在差异.为了明确该类盆地的压力分布与油气成藏特征,对沾化凹陷孤南洼陷进行剖析.根据实测及测井计算数据可知,孤南洼陷埋深3 000 m之上（Es2及其以上地层）古近系的压力系数主要为1.0-1.2,为常压系统;3 000 m之下（Es3以下地层）压力系数大于1.2,为高压系统.根据地层压力及油气分布,将研究区古近系划分为源外常压和源内高压2个油气成藏体系,前者位于烃源岩之上,以断块等构造圈闭为主,其油气成藏模式为源外断裂输导成藏,即沙三段中、下亚段油气沿断层垂向运移至沙二段及其以上地层,或直接在断块、滚动背斜等圈闭中成藏,或改为横向运移在合适圈闭中成藏,油气主要分布在油源断裂附近;后者位于烃源岩之内,以岩性、构造-岩性圈闭为主,油气成藏模式是源内高压充注成藏,即沙三段中、下亚段烃源岩生成的油气,在异常高压的驱动下直接向紧邻的砂岩体、构造-岩性圈闭侧向运移成藏,油气在高压区岩性体内聚集成藏,油藏分布受压力及岩性体的控制.Controlled by deposition process and tectonic evolution,different pressure systems generated vertically in the faulted basins. Hydrocarbon accumulation conditions in normal and in abnormal pressure systems are different,resulting in different oil and gas accumulation models and distributions. In order to ascertain the pressure distribution and reservoir forming characteristics in faulted basins,the Palaeogene series in Gunan subsag was studied in detail as an example. According to the measured and calculated data,it is known that normal pressure system with pressure coefficient less than 1.2exists in Palaeogene formations shallower than 3 000 meter(including Es2 and the strata above)in Gunan subsag,and high pressure system with pressure coefficient more than 1.2 in exists in the formations deeper than 3 000 meter(strata below Es3). According to formation pressure and hydrocarbon distribution,two hydrocarbon accumulation systems,one with normal pressure outside the source rock and the other with abnormal pressure inside the source rock,were identified in the Palaeogene in Gunan subsag. The hydrocarbon accumulation system with normal pressure outside the source rock is above thesource rocks mainly developing tectonic traps in faulted blocks,where hydrocarbons generated from the middle and the lower segments of Es3 migrated vertically into Es2 and the formations above through faults outside the source rocks,or directly migrated into the faulted blocks and rollover anticlines to accumulate,or laterally migrated into appropriate traps to accumulate. The hydrocarbons are entrapped in the fault zones near the source. The hydrocarbon accumulation system with abnormal pressure exists in the source rocks with dominant lithologic or structural-lithologic traps,where hydrocarbons were driven by the high pressure in the source rock and migrated laterally into the adjacent sand bodies or structural-lithologic traps to accumulate. The oil-bearing reservoir distribution is controlled by pressure and lithologic bodies.

关 键 词：断陷盆地 压力系统 源外常压源内高压 油气成藏特征孤南洼陷 

分 类 号：TE112.3[石油与天然气工程—油气勘探]