东海西湖凹陷中南部HY区天然气碳同位素分布控制因素及充注模式  

Controlling factors of natural gas carbon isotope distribution and its charging models in the HY area in the central and southern Xihu Sag,East China Sea Basin

作　　者：丁飞 邹玮 刘金水 刁慧 张武 赵洪 于仲坤 Fei DING;Wei ZOU;Jinshui LIU;Hui DIAO;Wu ZHANG;Hong ZHAO;Zhongkun YU(Shanghai Branch of CNOOC Ltd.,Shanghai 200335,China)

机构地区：[1]中海石油(中国)有限公司上海分公司,上海200335

出　　处：《天然气地球科学》2024年第11期2029-2039,共11页Natural Gas Geoscience

基　　金：“十三五”国家科技重大专项(编号:2016ZX05027-001);“十四五”全国油气资源评价项目(编号:QGYQZYPJ2022-3);中国海洋石油集团有限公司重大科技专项(编号:KJZX-2023-0101)联合资助。

摘　　要：HY区是东海西湖凹陷中南部重要的天然气勘探区,勘探程度不高,天然气成藏机制认识不足制约了勘探的进一步拓展。为明确天然气成藏过程,综合利用天然气、烃源岩及储层等分析化验资料,以天然气碳同位素为研究对象,对其分布控制因素进行分析,建立了HY区天然气充注模式,指出了有利勘探方向。结果表明:①HY区天然气为有机成因的煤型气,成气母质为腐殖型干酪根;②烃源岩干酪根碳同位素组成及热演化程度是控制HY区天然气碳同位素平面分布的主要因素;天然气横向运移特征不显著,呈现下生上储、垂向运移、近源充注特征;③早、晚2期油气充注与储层致密化时间的先后关系是影响碳同位素垂向分布的重要原因:第1期储层尚未致密化,碳同位素呈“上轻下重”分布,第2期深部储层致密化,碳同位素组成呈“上重下轻”分布;④HY区存在早、晚2种天然气充注模式:早期充注模式主控区,天然气充注强度和圈闭有效性决定气藏规模,深、浅层皆为有利勘探层段;晚期充注模式主控区,天然气充注强度、圈闭有效性和储层物性决定气藏规模,浅层以常规勘探为主,深层低渗—致密层段以寻找有利“甜点”储层为主。HY area is an important natural gas exploration area in the central and southern Xihu Sag of East China Sea Basin,with a relatively low level of exploration.Insufficient understanding of the natural gas reservoir formation mechanism has constrained further exploration expansion.Integrated utilization of laboratory data of natural gas,source rocks,and reservoirs were used to clarify the process of natural gas accumulation.Taking natural gas carbon isotopes as the research object,the controlling factors of its distribution were analyzed and the natural gas charging model was established in the HY area,and the favorable exploration directions were pointed out.The following research results are obtained.First,the natural gas of HY area is coal-type gas,derived from humic-type kerogen.Second,the carbon isotope composition and thermal evolution degree of kerogen in source rocks are the main factors controlling the planar distribution of natural gas carbon isotopes in the HY area.The lateral migration characteristics of natural gas are not significant,showing downward generation and upward storage,vertical migration,and near source charging characteristics.Third,the relationship between the early and late stages of gas charging and the time of reservoir densification is an important reason for the vertical distribution of carbon isotope.The first stage reservoir has not been densified,and the carbon isotope is“light in the upper and heavy in the lower”distribution.In the second stage of deep reservoir densification,the carbon isotope is“upper heavy and lower light”distribution.Fourth,there are two kinds of natural gas charging modes,early and late,in HY area.In conclusion,the intensity of natural gas injection and the effectiveness of traps determine the scale of gas reservoirs in the early charging mode dominated area.Natural gas charging intensity,trap effectiveness and reservoir physical properties determine the scale of gas reservoirs in the late charging mode dominated area.

关 键 词：西湖凹陷 HY区 天然气 碳同位素 充注模式 

分 类 号：TE122.113[石油与天然气工程—油气勘探]