【摘要】 油气勘探成果已证实白云凹陷及其邻区是富烃凹陷,但对于其生烃能力到底如何?是不是一个大型富生烃凹陷?尚有争议。为此,基于油气地质理论研究进展,对该凹陷重新开展了地震解释工作,再认识其深部结构和沉积特征,以源热共控论为指导分析烃源岩热作用,评价其油气资源勘探潜力。结果表明:该凹陷是南海北部大陆边缘珠江口盆地深水区面积超过1×104km2、最大沉积地层厚度超过10 000m、新生代地层发育最全的深大凹陷,经历了裂谷期、裂后坳陷期和新构造期3期演化;该凹陷为叠合凹陷,始新世文昌组整体以滨、浅湖相沉积为主,局部发育中深湖相,早渐新世恩平组为海陆过渡相—局限海相沉积,晚渐新世为浅海相沉积,新近系—第四系为深海沉积;白云凹陷发育文昌组湖相、恩平组海陆过渡相和珠海组浅海相3套性质不同的烃源岩,其中主力烃源岩恩平组主要由煤系地层和浅海相泥岩组成;地温梯度高,热流值高,属于热凹。结论认为:该凹陷属于"源(烃源岩)足热(热流值)足"型凹陷,主凹槽以生气为主,其他部位以生油为主,油气资源量可观、勘探潜力巨大;该凹陷目前油气资源探明程度低,剩余油气勘探潜力大。更多还原

【Abstract】 The previous exploration results have proved that the Baiyun Sag and its nearby areas are rich with hydrocarbon resources,but it is still controversial whether it is really a large-scale prolific sag with a great hydrocarbon-generation capacity.In view of this,based on the research advances in the present hydrocarbon geological theory,we re-conducted a seismic interpretation to have a better understanding of its deep structures and sedimentary features and evaluate its resource potential through an integrated analysis of thermal effects of source rocks guided by the theory of " co-control of source and heat".The following findings were obtained.(1)The Baiyun Sag,a deep and large sag in the deep-water area of the Pearl River Mouth Basin,covers an area of over 10 000km2 in the continental margin of the northern South China Sea,where the maximum thickness of the sedimentary strata is more than 10000 mand the Cenozoic strata are found developed completely.(2)The Baiyun Sag experienced three phases of evolution including the rifting period,depression period and neo-tectonic period.(3)The Baiyun Sag is a superimposed sag,with the Eocene Wenchang Fm dominated by shore and shallow-lake sediments,and medium-deep-lake facies developed locally.The Early Oligocene Enping Fm was sea-land transition phase-limited Marine sediments;the Late Oligocene was shallow-sea facies;and the Neogene-Quaternary was deep-sea deposits.(4)Three sets of hydrocarbon source rocks with different petrophysical properties were developed in the Baiyun Sag which included lacustrine facies of Wenchang Fm,sea and land transition phase of Enping Fm and neritic facies of Zhuhai Fm.Coal measures strata and neritic facies mudstone in the Enping Fm is the main hydrocarbon source rocks.(5)The Baiyun Sag is a hot concave which has high geothermal gradients and high heat flow values.Co-controlled by source and heat,the Baiyun Sag is considerably rich with hydrocarbon source rocks and high heat flow values.With the main groove given priority to gas source kitchen and other parts to oil source kitchen,the Baiyun Sag has a great exploration potential although in the present state of low-degree proved reserves.更多还原