珠江口盆地白云凹陷烃源岩评价及油气资源分布预测  

Evaluation of source rocks and prediction of oil and gas resources distribution in Baiyun Sag,Pearl River Mouth Basin,China

作　　者：高阳东 朱伟林[2] 彭光荣 龙祖烈 汪旭东 石创 陈聪 黄玉平 张博 GAO Yangdong;ZHU Weilin;PENG Guangrong;LONG Zulie;WANG Xudong;SHI Chuang;CHEN Cong;HUANG Yuping;ZHANG Bo(Exploration and Development Department of CNOOC China Limited,Beijing 100010,China;State Key Laboratory of Marine Geology,Tongji University,Shanghai 200092,China;Shenzhen Branch of CNOOC(China)Co.Ltd.,Shenzhen 518054,China;CNOOC Deepwater Development Limited,Shenzhen 518054,China)

机构地区：[1]中海石油(中国)有限公司勘探开发部,北京100010 [2]同济大学海洋地质国家重点实验室,上海200092 [3]中海石油(中国)有限公司深圳分公司,广东深圳518054 [4]中海石油深海开发有限公司,广东深圳518054

出　　处：《石油勘探与开发》2024年第5期986-996,共11页Petroleum Exploration and Development

基　　金：自然资源部“十四五”全国油气资源评价项目“中海油矿业权区及周边空白区油气资源评价”(QGYQZYPJ2022-3);中国海洋石油集团有限公司“十四五”重大科技项目“南海北部深水区勘探关键技术”(KJGG2022-0103-03)。

摘　　要：基于对珠江口盆地白云凹陷已钻井岩心样品的有机地球化学分析,明确白云凹陷烃源岩发育特征;重构凹陷现今地温场,恢复构造-热演化过程,在此基础上通过烃源岩热模拟实验和数值模拟,预测白云凹陷资源类型、规模和分布。研究表明:①白云凹陷发育古近系浅湖相规模烃源岩,沉积期为弱氧化环境,生源以陆源高等植物为主,藻类等具有一定贡献,为油气兼生型烃源岩;②白云凹陷现今地温场显示地温梯度主体为(3.5~5.2)℃/100 m,整体呈现从西北往东南方向增高的趋势,不同洼陷地温梯度差异较大;③新生代以来白云凹陷经历了始新世和中新世两期明显的伸展拉张过程,经受两期加热升温事件,加快烃源岩成熟演化,基底古热流主体在距今13.82 Ma时达到最高值;④盆地模拟结果显示,白云主洼烃源岩成熟度明显高于其他洼陷,始新统文昌组现今整体处于高成熟—过成熟阶段,始新统恩平组现今达到成熟—高成熟阶段;⑤热模拟实验表明,文昌组浅湖相泥岩具有较好的生干酪根裂解气能力,且气产率高,具有宽窗持续生气的特征;恩平组浅湖相泥岩具有较好的生轻质油能力,晚期仍具有一定的干酪根裂解产气能力,但与文昌组浅湖相泥岩和恩平组三角洲煤系泥岩相比,气产率相对偏低;⑥数值模拟结果表明,白云主洼烃源岩生烃较早,生烃强度明显高于其他洼陷,平均约为1200×10^(4) t/km^(2),油气资源主体分布在主洼,主力烃源岩层位为文昌组三段和四段;⑦在运聚单元划分与评价的基础上,优选4个有利区带,分别为①号番禺30鼻状构造带、③号流花29鼻隆带和荔湾3鼻隆带、②号白云东凹缓坡带以及⑧号白云1低凸起。By conducting organic geochemical and spore-pollen and algae combination analyses of the samples taken from the drilled wells in Baiyun Sag of Pearl River Mouth Basin,China,the development characteristics of hydrocarbon source rocks in the sag are clarified.Reconstruct the current geothermal field of the sag and restore the tectonic-thermal evolution process to predict the type,scale,and distribution of resources in Baiyun Sag through thermal pressure simulation experiments and numerical simulation.The Baiyun Sag is characterized by the development of Paleogene shallow lacustrine source rocks,which are deposited in a slightly oxidizing environment.The source rocks are mainly composed of terrestrial higher plants,with algae making a certain contribution,and are oil and gas source rocks.Current geothermal field of the sag was reconstructed,in which the range of geothermal gradients is(3.5–5.2)℃/100 m,showing an overall increasing trend from northwest to southeast,with significant differences in geothermal gradients across different sub-sags.Baiyun Sag has undergone two distinct periods of extensional process,the Eocene and Miocene,since the Cenozoic era.These two periods of heating and warming events have been identified,accelerating the maturation and evolution of source rocks.The main body of ancient basal heat flow value reached its highest at 13.82 Ma.The basin modelling results show that the maturity of source rocks is significantly higher in Baiyun main sub-sag than that in other sub-sags.The Eocene Wenchang Formation is currently in the stage of high maturity to over maturity, while the Eocene Enping Formation has reached the stage of maturity to high maturity. The rock thermal simulation experiment shows that the shallow lacustrine mudstone of the Wenchang Formation has a good potential of generating gas from kerogen cracking with high gas yield and long period of gas window. Shallow lacustrine mudstone of the Enping Formation has a good ability to generate light oil, and has ability to generate kerogen

关 键 词：珠江口盆地 白云凹陷 古近系 烃源岩评价 构造-热演化 油气资源潜力 

分 类 号：TE122[石油与天然气工程—油气勘探]