毛塞几比盆地南部白垩系阿尔布阶—土伦阶海相烃源岩有机相特征及其发育主控因素

doi:10.3969/j.issn.1672-7703.2023.02.010

摘要/Abstract

摘要： 对毛塞几比盆地南部陆架边缘Z-1井与X-1井白垩系阿尔布阶、塞诺曼阶、土伦阶原油与烃源岩样品进行了系统的有机地球化学特征分析。Z-1井阿尔布阶烃源岩TOC平均为1.9%，I_H平均为283mg/g，R_o平均为0.88%；Z-1井塞诺曼阶烃源岩TOC平均为2.1%，I_H平均为456mg/g，R_o平均为0.81%；Z-1井土伦阶烃源岩TOC平均为3.4%，I_H平均为538mg/g，R_o平均为0.66%。X-1井阿尔布阶烃源岩TOC平均为1.3%，I_H平均为246mg/g，R_o平均为0.67%。根据原油与烃源岩样品的有机地球化学特征及沉积特征共划分出6类有机相，包括前三角洲贫氧腐殖有机相、三角洲前缘贫氧腐殖有机相、浅海贫氧腐泥—腐殖有机相、半深海厌氧腐泥有机相、半深海贫氧腐泥有机相、深海贫氧腐泥—腐殖有机相。通过有机相特征分析，建立了阿尔布阶、塞诺曼阶—土伦阶烃源岩发育模式，重点探讨有机质来源、古海洋生产力、水体氧化还原条件、沉积作用等因素对烃源岩发育的影响，明确了大洋缺氧事件为优质烃源岩发育的关键控制因素。从阿尔布期到土伦期，有机质从以陆源高等植物与海洋藻类混合来源为主向以海洋藻类来源为主过渡，海洋藻类丰度逐渐增加，古海洋生产力逐渐升高，微生物作用对有机质影响增强。阿尔布期到土伦期沉积环境发生明显变化，水体环境整体上还原性增强；在塞诺曼期—土伦期过渡阶段，水体含氧度快速下降，含盐度快速上升，可能与塞诺曼期—土伦期缺氧事件有关。研究成果明确了毛塞几比盆地白垩系海相烃源岩的有机相特征及其发育关键控制因素，对于落实烃源岩层系、圈定烃源岩分布、指导油气勘探具有重要意义。

关键词: 毛塞几比盆地, 白垩系, 阿尔布阶—土伦阶, 海相烃源岩, 有机相, 主控因素, 缺氧事件

Abstract: The organic geochemical characteristics of crude oil and source rocks in the Cretaceous Albian, Cenomanian, and Turonian from wells Z-1 and X-1 in the southern continental margin of MSGBC Basin are systematically analyzed. In Well Z-1, the average values of TOC,I_H, and R_o of the Albian source rock are 1.9%, 283 mg/g, and 0.88%, those of the Cenomanian source rock are 2.1%, 456 mg/g, and 0.81%,and those of the Turonian source rock are 3.4%, 538 mg/g, and 0.66%, respecitvely. In Well X-1, the average values of TOC, I_H, and R_o of the Albian source rock are 1.3%, 246 mg/g, and 0.67%, respectively. Based on the organic geochemical and sedimentary characteristics of oil and source rock samples, six organofacies are classified, i.e., predelta dysoxic humic organofacies, delta front dysoxic humic organofacies, shallow marine dysoxic sapropelic-humic organofacies, bathyal anoxic sapropelic organofacies, bathyal dysoxic sapropelic organofacies, and pelagic dysoxic sapropelic-humic organofacies. By analyzing the organofacies characteristics, source rock deposition patterns during the Albian and Cenomanian-Turonian are constructed, and influence factors are discussed, including organic matter source, marine paleo-productivity, redox condition, and depositional process, among which the oceanic anoxic event was the key controlling factor for the deposition of high-quality source rocks. From Albian to Turonian, the organic matter source changed from a mixture of terrestrial higher plants and marine algae to marine algae, showing an increasing abundance of marine algae, increasing marine paleo-productivity, and enhancing bacteria modification on organic matter. From Albian to Turonian, the depositional environment changed tremendously, and the reductive water environment was enhanced. In the transition period during Cenomanian-Turonian, the water oxygen content decreased rapidly, while the salinity increased rapidly, which might be related to the Oceanic Anoxic Event. The study results enable to determine the organofacies characteristics and the key controlling factor of the Cretaceous marine source rocks in MSGBC Basin, which have great significance to identify source rock series, delineate the distribution of source rocks, and guide the petroleum exploration in the basin.

中图分类号:

TE112.113

詹鑫, 赵红岩, 杨松岭, 孔令武, 李丹, 逄林安, 杜威, 张鹏浩, 刘正. 毛塞几比盆地南部白垩系阿尔布阶—土伦阶海相烃源岩有机相特征及其发育主控因素[J]. 中国石油勘探, 2023, 28(2): 102-118.

Zhan Xin, Zhao Hongyan, Yang Songling, Kong Lingwu, Li Dan, Pang Lin’an, Du Wei, Zhang Penghao, Liu Zheng. Organofacies characteristics and key controlling factor of the Cretaceous Albian-Turonian marine source rocks in the southern MSGBC Basin[J]. China Petroleum Exploration, 2023, 28(2): 102-118.

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