川中地区三叠系雷口坡组泥灰岩油气地质特征及充探1井发现意义

Petroleum geology of marl in Triassic Leikoupo Formation and discovery significance of Well Chongtan1 in central Sichuan Basin,SW China

2022年,风险探井充探1井在中三叠统雷口坡组雷三2亚段海相泥灰岩段测试获工业油气流,发现新的产油气层段和新类型油气资源,勘探取得重大发现,但对泥灰岩油气成藏认识尚不清楚,制约了勘探选区与部署。以充探1井为重点,研究剖析了雷三2亚段泥灰岩油气成藏特征。研究表明:①油气及烃源岩地球化学分析数据显示充探1井雷三2亚段泥灰岩油气来源于自身泥灰岩烃源,泥灰岩既是烃源岩、又是储集层,源-储一体;②雷三2亚段泥灰岩在川中地区为潟湖相沉积,厚40~130 m,面积约40000 km^(2),生烃强度为(4~12)×10^(8)m^(3)/km^(2),估算生烃量为25×10^(12)m^(3);③川中潟湖相区泥灰岩储集层大面积分布,西充—仪陇、资阳—简阳和磨溪南等3个地区储集层厚20~60 m,分布面积为7500 km^(2);④潟湖相泥灰岩油气具有“源-储一体、膏盐岩封盖、超压”成藏特征,属于海相非常规油气新类型,油气在生烃中心、储集层厚值区和裂缝发育复合区富集,是一个值得勘探重视的非常规油气新领域。⑤依据川中二维地震并结合三维地震解释分析,优选西充和遂宁2个有利区带,估算区带天然气资源量为(2000~3000)×10^(8)m^(3),是近期值得重视的勘探有利区。

In 2022,the risk exploration well Chongtan1(CT1)in the Sichuan Basin revealed commercial oil and gas flow during test in a new zone-the marl of the second submember of the third member of Leikoupo Formation(Lei-32)of Middle Triassic,recording a significant discovery.However,the hydrocarbon accumulation in marl remains unclear,which restricts the selection and deployment of exploration area.Focusing on Well CT1,the hydrocarbon accumulation characteristics of Lei-32 marl are analyzed to clarify the potential zones for exploration.The following findings are obtained.First,according to the geochemical analysis of petroleum and source rocks,oil and gas in the Lei-32 marl of Well CT1 are originated from the same marl.The marl acts as both source rock and reservoir rock.Second,the Lei-32 marl in central Sichuan Basin is of lagoonal facies,with a thickness of 40-130 m,an area of about 40000 km^(2),a hydrocarbon generation intensity of(4-12)×10^(8)m^(3)/km^(2),and an estimated quantity of generated hydrocarbons of 25×10^(12)m^(3).Third,the lagoonal marl reservoirs are widely distributed in central Sichuan Basin.Typically,in Xichong-Yilong,Ziyang-Jianyang and Moxi South,the reservoirs are 20-60 m thick and cover an area of 7500 km^(2).Fourth,hydrocarbons in the lagoonal marl are generated and stored in the Lei-32 marl,which means that marl serves as both source rock and reservoir rock.They represent a new type of unconventional resource,which is worthy of exploring.Fifth,based on the interpretation of 2D and 3D seismic data from central Sichuan Basin,Xichong and Suining are defined as favorable prospects with estimated resources of(2000-3000)×10^(8)m^(3).