石油与天然气地质 ›› 2024, Vol. 45 ›› Issue (1): 281-292.doi: 10.11743/ogg20240119

• 方法技术 • 上一篇    

源外层系油气运聚关键环节研究与评价方法

张宏国1(), 杨海风1, 宿雯1, 徐春强1, 黄志1, 程燕君2   

  1. 1.中海石油(中国)有限公司 天津分公司,天津 300459
    2.山东科技大学 地球科学与工程学院,山东 青岛 266580
  • 收稿日期:2023-09-03 修回日期:2023-12-10 出版日期:2024-02-01 发布日期:2024-02-29
  • 第一作者简介:张宏国(1986—)男,高级工程师,油气运聚与渤海油气勘探。E‑mail: zhanghg2@cnooc.com.cn
  • 基金项目:
    中海石油(中国)有限公司科研项目(ZZKY-2019-TJ-01);中海油”七年行动计划”重大科技专项(CNOOC-KJ 135 ZDXM 36 TJ 08 TJ)

Key stages in hydrocarbon migration and accumulation in layers outside source rocks and the evaluation methods related: A case study of the lower member of the Minghuazhen Formation, Bozhong Sag, Bohai Bay Basin

Hongguo ZHANG1(), Haifeng YANG1, Wen SU1, Chunqiang XU1, Zhi HUANG1, Yanjun CHENG2   

  1. 1.Tianjin Branch of CNOOC (China) Limited,Tianjin 300459,China
    2.College of Earth Science and Engineering,Shandong University of Science and Technology,Qingdao,Shandong 266580,China
  • Received:2023-09-03 Revised:2023-12-10 Online:2024-02-01 Published:2024-02-29

摘要:

油气运聚是源外层系规模性成藏的关键之一。利用渤海湾盆地渤中地区丰富的三维地震和钻井数据分析,从断裂带深层垂向输导、馆陶组二次汇聚及明化镇组下段(明下段)侧向分流3个主要运聚环节分析入手,对明下段砂体烃柱高度进行分析。研究认为,烃源超压-断层活动耦合作用是断裂带垂向输导的关键,在烃源充足条件下断裂带分形维数大于0.7时,油气垂向输导能力较强;富砂型层系形成的早期油藏控制油气二次汇聚能力,利用馆陶组圈闭面积和有效幅度等计算汇聚系数,当馆陶组汇聚系数大于700 km3时,对应明下段具备发育大、中型油田的基础;断层的泄压控制浅层砂体侧向分流环节,利用砂体高部位和低部位断-砂接触面积计算泄压系数,当明下段砂体泄压系数大于2.0时,砂体烃柱高度可超过30 m。3个主要运聚环节紧密配合,是富生烃凹陷源外层系高丰度油藏形成的必要条件。

关键词: 分形维数, 汇聚能力, 高丰度油气藏, 油气运聚, 明化镇组下段, 渤中凹陷, 渤海湾盆地

Abstract:

Hydrocarbon migration and accumulation are critical for large-scale reservoir development in layers far from the source rocks. Using abundant 3D seismic and drilling data, we delve into the primary driving forces for hydrocarbon migration and accumulation in three major stages in the Bozhong Sag, Bohai Bay Basin, namely the deep vertical transport along fault zones, secondary convergence in the Guantao Formation, and lateral diversion along sand traps in the lower member of the Minghuazhen Formation. Furthermore, we predict the hydrocarbon column heights within sand bodies in the lower member of the Minghuazhen Formation. Key findings are as follows. First, the coupling between overpressure in source rocks and fault development is crucial to the vertical hydrocarbon transport along fault zones, reflecting a high vertical transport efficiency with a fractal dimension exceeding 0.7 on the condition of abundant hydrocarbon sources. Second, the buoyancy pressure of old oil reservoirs in sand-rich sequences serves as the main driving force for the secondary hydrocarbon convergence. Convergence coefficient calculated using the size and effective range of traps, is in line with the scale of reserves. The lower member of the Minghuazhen Formation has the potential for the formation of large- to medium-scale oilfields when the convergence coefficient of the Guantao Formation exceeds 700 km3. Third, fault depressurization determines the lateral hydrocarbon diversion in shallow sand bodies. The depressurization coefficient is calculated based on the fault-sand contact area in both the high and low parts of the sand bodies. The results show that the hydrocarbon column heights within sand bodies in the lower member may exceed 30 m when the depressurization coefficient is greater than 2.0. These findings underscore that the three major stages are interlocking, which is a necessary condition for the formation of high-abundance hydrocarbon reservoirs in strata outside source rocks in a hydrocarbon-rich sag.

Key words: fractal dimension, convergence efficiency, high-abundance hydrocarbon reservoir, hydrocarbon migration and accumulation, lower member of the Minghuazhen Formation, Bozhong Sag, Bohai Bay Basin

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