柴达木盆地西部地区渐新世沉积特征与油气成藏模式  

Oligocene sedimentary characteristics and hydrocarbon accumulation model in the western Qaidam Basin

作　　者：黄成刚[1,2] 常海燕[2] 崔俊[3] 李亚锋[3] 路艳平 李翔[2] 马新民[2] 吴梁宇[1,2] 

机构地区：[1]中国石油天然气集团公司油藏描述重点实验室,甘肃兰州730020 [2]中国石油勘探开发研究院西北分院,甘肃兰州730020 [3]中国石油青海油田公司勘探开发研究院,甘肃敦煌736202

出　　处：《石油学报》2017年第11期1230-1243,共14页Acta Petrolei Sinica

基　　金：国家重大科技专项"前陆冲断带及复杂构造区油气成藏规律;关键技术及目标评价"(2016ZX05003-006);中国石油天然气集团公司重大科技专项"柴达木盆地建设千万吨油气田综合配套技术研究"(2011E-03)资助

摘　　要：对柴达木盆地西部地区渐新世下干柴沟组上段的沉积特征与成藏模式进行分析。系统地开展了岩石学和矿物学研究、古地貌分析、碳氧同位素与微量元素地球化学研究、地震剖面精细解释与"蚂蚁追踪"裂缝预测、成藏模式研究以及高产控制因素分析,提出英西地区渐新世下干柴沟组上段为一个"半开放—半封闭"的半深湖相咸化沉积环境,基质晶间孔储油、盐下应力聚集造缝、盐层封盖造就了英西地区特殊的成藏模式。研究结果表明:(1)岩性以深灰色或灰黑色等暗色色调为主并混积盐类矿物,主要受控于沉积环境;(2)下干柴沟组上段沉积前的古地貌为一个发育湖障壁岛的"西低东高"的局限湖泊;(3)碳、氧同位素数据点落于开放性湖泊与封闭性湖泊之间;(4)Sr/Ba平均值为2.01、均大于1,Sr/Cu平均值为109.04、远大于5,U/Th平均值为0.62、均小于1,指示了咸化、干旱和还原环境;(5)ΣREE平均值为87.67×10-6,分布范围为(39.41~162.67)×10-6,且存在Eu负异常;(6)盐下主力产层的压力系数可高达2.2,"自源-超压系统"导致应力聚集造缝的推论与"蚂蚁追踪"裂缝预测成果和岩心观察结果完全吻合。The sedimentary characteristics and hydrocarbon accumulation model in the upper member of Oligocene Xiaganchaigou Formation,Western Qaidam Basin are analyzed in this paper.Comprehensively based on the petrology and mineralogy research,paleo-geomorphology analysis,carbon-oxygen isotopes and microelement geochemistry research,seismic-profile fine interpretation and＂ant-tracking＂fracture prediction,hydrocarbon accumulation model research and high-yield controlling factor analysis,it is put forward that the upper member of Oligocene Xiaganchaigou Formation in Yingxi area is a saline sedimentary environment of＂semi open-semi closed＂semi-deep lake facies,and the special hydrocarbon accumulation model in Yingxi area is resulted from oil storage in the matrix intracrystalline pore,fracture forming by under-salt stress accumulation and salt formation seal-capping.Research results show that firstly,the lithology is dominant by dark colors including dark grey or ash black with the mixed sedimentation of saline minerals,mainly controlled by sedimentary environment.Secondly,the paleo-geomorphology prior to the sedimentation in the upper member of Xiaganchaigou Formation is a limited lake＂lower in the west while higher in the east＂with the development of lake barrier island.Thirdly,the data points of carbon-oxygen isotopes fall between an open lake and a closed lake.Fourthly,Sr/Ba values are all greater than 1 with an average of 2.01,the average value of Sr/Cu is 109.04,far greater than 5,and U/Th values are all less than1 with an average of 0.62,indicating a saline,arid and reducing environment.Fifthly,the average value of∑REE is 87.67×10-6 with the distribution range of（39.41-162.67）×10-6,and Eu negative anomaly exists.Sixthly,the pressure coefficient of main under-salt producing formation can be up to2.2,and the deduction of＂self-originating-over-pressured system＂resulting in the fracture formed by stress accumulation is completely consistent with the results of＂ant-tracking＂fracture prediction a

关 键 词：半开放—半封闭 咸化湖 白云岩 超压造缝 成藏模式 英西地区 柴达木盆地 

分 类 号：TE122.1[石油与天然气工程—油气勘探]