断陷盆地斜坡带大型油气田成藏条件--西湖凹陷平北缓坡断裂与岩性控藏有利区  

Conditions for the formation of large oil and gas reservoirs in the slope belts of rift basins:Fault-and lithology-controlled accumulation zones in the Pingbei slope of Xihu Sag

作　　者：江东辉[1] 蒲仁海[2] 苏思羽 范昌育[2] 周锋[1] 杨鹏程[1] JIANG Donghui;PU Renhai;SU Siyu;FAN Changyu;ZHOU Feng;YANG Pengcheng(Sinopec Shanghai Offshore Oil&Gas Branch,Shanghai 200120,China;Department of Geology,Northwest University,Xi'an,Shaanxi 710069,China)

机构地区：[1]中国石油化工股份有限公司上海海洋油气分公司 [2]西北大学地质学系

出　　处：《天然气工业》2021年第11期33-42,共10页Natural Gas Industry

基　　金：国家自然科学基金项目“非常规油气开发地球物理理论与方法研究——课题一:中国非常规油气储层特征、分类与典型地质模型建立”(编号:41390451)。

摘　　要：西湖凹陷平湖构造带烃储层条件优越,但由于断层十分发育,导致该区平北缓坡仅发现“断、小、贫、散”油气藏。为了明确大型油气藏的成藏条件及勘探方向,基于三维地震资料,结合油气成藏地球化学特征,系统研究了准区域盖层厚度,砂层厚度,断层断距,断层纵、横向封闭性等与油气成藏的关系,进而预测了大型油气成藏的勘探有利区。研究结果表明:①断裂对油气成藏具有双刃剑作用,小断裂有利于断层纵向封闭,但不利于横向封闭,大断裂有利于横向封闭,但不利于纵向封闭;②在准区域盖层足够厚和保证断裂纵向封闭的条件下,断距越大越有利于砂体被侧向泥岩遮挡成藏,大断距断层和三角洲前缘砂体是平北缓坡大型油气成藏的主控因素;③古近系始新统平湖组下段下亚段油气有利成藏区沿平西大断距断裂东盘分布,平湖组下段上亚段和平湖组中段大型岩性油气藏沿孔雀亭构造南部三角洲前缘朵状砂体区分布。结论认为,断裂、砂体和盖层3个关键控藏要素及其有效配置是平北缓坡形成有利非背斜圈闭油气藏的重要前提;该认识为该区油气的深化勘探指明了方向,对其他地区复合圈闭油气藏勘探具有借鉴意义。Pinghu structural belt in Xihu Sag has favorable hydrocarbon reservoir conditions,but the faults there are quite developed.As a result,only"faulted,small,poor and scattered"oil and gas reservoirs are discovered in Pingbei slope of this area.In this situation,to clarify the hydrocarbon accumulation conditions and exploration directions of large oil and gas reservoirs.Based on 3D seismic data,combined with geochemical characteristics of hydrocarbon accumulation,this paper systematically researches the relationships between the quasi regional cap rock thickness,sandstone thickness,fault throw and lateral and vertical sealing capacity of faults and the hydrocarbon accumulation and predicts the areas favorable for the formation of large oil and gas reservoirs.And the following research results are obtained.First,the faults in this area are a double-edged sword for hydrocarbon accumulation.Small faults are beneficial to vertical sealing of faults,but not to lateral sealing;while large faults are beneficial to lateral sealing,but not to vertical sealing.Second,when the quasi regional cap rock is thick enough and the fault is sealed vertically,the larger the fault throw is,the more beneficial it is for the sand body to be shielded by the lateral mudstone to form a reservoir.Large throw faults and delta front sandbodies are main factors controlling the formation of large oil and gas reservoirs in Pingbei slope.Third,the favorable hydrocarbon accumulation areas in the lower submember of Lower Member of Pinghu Formation are distributed along the east block of Pingxi large throw fault,and the large lithologic reservoirs in the upper submember of Lower Member of Paleogene-Eocene Pinghu Formation and the Middle Member of Pinghu Formation are distributed along the lobate sand body area of delta front in the southern Kongqueting structure.In conclusion,three key reservoir controlling factors of faults,sand bodies and cap rocks and their effective allocation are the important guarantee for the formation of favorable non-anticline

关 键 词：断陷盆地 西湖凹陷平北缓坡 古近系始新统平湖组 控藏因素 断层封闭性 复合圈闭 油气成藏有利区 

分 类 号：P618.13[天文地球—矿床学]