复杂断陷盆地低渗透油藏形成条件及油气富集规律——以海拉尔盆地贝尔凹陷贝中次凹南二段为例  

Accumulation conditions and hydrocarbon enrichment laws of low-permeability oil reservoirs in complex rift basins:A case study from the second member of Nantun Formation of Beizhong sub-sag in Beier Sag of Hailar Basin

作　　者：李婷婷[1] 邓海[1] 邹伟奇 LI Tingting;DENG Hai;ZOU Weiqi(Exploration and Development Research Institute of Daqing Oilfield Co Ltd,Daqing 163712,China;No.6 Oil Production Plant of Daqing Oilfield Co Ltd,Daqing 163114,China)

机构地区：[1]大庆油田有限责任公司勘探开发研究院,黑龙江大庆163712 [2]大庆油田有限责任公司第六采油厂,黑龙江大庆163114

出　　处：《大庆石油地质与开发》2021年第4期32-37,共6页Petroleum Geology & Oilfield Development in Daqing

基　　金：国家科技重大专项“大庆油气持续有效发展关键技术研究与应用”(2016E-0202)。

摘　　要：海拉尔盆地贝尔凹陷为典型陆相断陷盆地,其中贝中次凹南二段富含大面积低渗透油藏。为了搞清低渗透油藏形成机制,明确油气富集规律,通过岩心、测井、地震资料分析,从沉积相带、烃源岩评价、储层结构、成藏模式等方面对南二段低渗透油藏形成条件及主控因素进行了研究。结果表明:贝中次凹南二段暗色泥岩累计厚度大于150 m,Ro一般大于0.7%,干酪根类型以Ⅰ型为主,排烃强度普遍超过2×10^(6)t/km^(2),是最主要的生油岩;南二段砂体横向连片,纵向多层叠加,孔隙度平均为8.4%,渗透率平均为0.4×10^(-3)μm^(2),属于低孔、特低渗型储层,储集空间以原生粒间孔、溶蚀孔隙及微裂缝为主,具有良好的储集性能;贝中次凹南二段油藏“源—储”一体共同控制低渗透油藏分布,油气多为近距离成藏,主要分布在扇三角洲前缘砂体的优质储层区,反向断层与扇体、油源有效组合下富集成藏。Hailar Basin is a typical continental rift basin and the second member in Beizhong sub-sag is rich in low-permeability oil reservoirs.In order to make clear of the forming conditions of the low-permeability oil reservoirs and its enrichment lows,based on the core,well logging and seismic data,the forming conditions and main controlling factors of the low-permeability oil reservoirs in the second member of Nantun Formation(K_(1)n_(2))of Beizhong sub-sag are studied from the aspects of sedimentary facies belt,source rock evaluation,reservoir structure and accumulation pattern.The results show that the cumulative thickness of the dark mudstone is more than 150 m,R o is generally greater than 0.7%,the main kerogen type is TypeⅠ,and the hydrocarbon expulsion intensity is over 2×10^(6)t/km^(2),so it is the most significant oil source rock.K_(1)n_(2)sandbody is widely spread laterally and superimposed vertically,its average porosity and permeability are 8.4%and 0.4×10^(-3)μm^(2)respectively,so it belongs to low-porosity and ultra-low permeability reservoirs;the reservoir space is mainly composed of primary intergranular pores,dissolved pores and micro-fractures with good accumulating performances.Both source rocks and reservoirs control the distribution of the low-permeability oil reservoirs in K_(1)n_(2) of Beizhong sub-sag,meanwhile,the oil and gas are generally accumulated nearby the source rock and mainly distributed in the high-quality reservoir of the fan delta front sand body;the effective combination among the reverse fault,fan body and oil source is favorable for the tight oil enrichment.

关 键 词：断陷盆地 贝中次凹 南二段 低渗透油藏 形成条件 富集规律 海拉尔盆地 

分 类 号：TE122.1[石油与天然气工程—油气勘探]