南海深水区白云凹陷烃源岩热演化与油气资源潜力预测

Thermal evolution of source rock and prediction of petroleum resources potential in Baiyun Depression, deep-water area of the northern South China Sea

基于钻井、测井、地震及地质等资料及盆地数值模拟技术,结合成因法及类比法,对南海深水区白云凹陷现今地温场特征、烃源岩热演化、烃源岩排烃强度、烃源岩排烃量以及已发现油气田石油、天然气聚集系数进行了系统研究,进而综合预测白云凹陷油气资源潜力。研究表明,白云凹陷地温梯度较高,介于34~67℃·km^(–1)之间,均值为40℃·km^(–1),有利于有机质的成熟与烃类生成;各烃源岩现今均处于成熟生油或过成熟生气阶段,烃源岩成熟度从珠海组顶面到文昌组底面增幅较大,文昌组烃源岩底面过成熟面积占凹陷面积的53.7%;各烃源岩排气强度均大于排油强度,且恩平组上段为主力排烃层位;文昌、恩平及珠海组3套烃源岩总排烃量为1143×10~8m^3油当量。且结合石油、天然气聚集系数预测白云凹陷保守资源量为25.2×10~8m^3油当量。

Based on the data of drilling,logging,seismic,geology and basin modeling,we analyzed the characteristics of geothermal,source rock maturation,hydrocarbon expulsion,and accumulation coefficient by using the analogy and genetic methods.Then,prediction of petroleum resources potential in Baiyun depression is carried out.The results show that the Baiyun Depression presents high geothermal gradient,ranging from34to67℃·km-1and with an average of40℃·km-1,which is favorable for organic matter maturation and hydrocarbon generation.Each source rock has been in the stage of mature or post mature,and the source rock maturation increases from the top formation of Zhuhai to the bottom formation of Wenchang;the area of post mature is53.7%in the bottom formation of Wenchang.The strength of gas expulsion is bigger than the strength of oil expulsion,and the upper formation of Enping is the major formation of hydrocarbon expulsion.The hydrocarbon expulsion of three source rocks is1143×108m3,and prediction of petroleum resources potential in the Baiyun Depression is25.2×108m3combining the accumulation coefficients of oil and gas.