丽水—椒江凹陷月桂峰组地震—沉积响应及烃源岩特征

Response of Seismic-sedimentary Facies and Characteristics of Yueguifeng Formation Source Rock in Lishui-Jiaojiang Sag

丽水—椒江凹陷月桂峰组属古新世早期沉积,为凹陷主力烃源岩层。依据地震反射波的振幅、连续性、内部结构和外部形态等特征,在月桂峰组识别出6种主要的地震相类型:中高频弱振幅连续平行—亚平行席状相、低频强振幅较连续亚平行席状相、变振幅连续—较连续前积相、中振幅较连续—断续楔状相、中强振幅杂乱相和中弱振幅较连续充填相。然后再结合研究区钻井资料及区域构造背景,进行地震相—沉积相分析。结果表明:研究区月桂峰组是断陷型湖泊沉积环境,主要发育扇三角洲、水下扇、三角洲、湖泊等多种沉积相类型。进而结合钻井岩样分析,得出月桂峰组湖相泥岩属中—好烃源岩,主要发育于丽东次凹、丽西次凹中北部和椒江凹陷的中央洼陷带,有效烃源岩厚度可达1 000余米,面积总共为4 974.8km2。优选了处于源岩中心或邻近源岩中心的凹中隆及斜坡构造带作为下一步勘探工作的重点目标区域,为今后的勘探工作提出了有益的建议。

The Yueguifeng Formation as a main source rock in the Lishui-Jiaojiang sag is formed in the early Paleocene.Based on features of amplitude,continuity and internal structure of seismic reflection wave as well as its external shape,six seismic facies types for the Yueguifeng Formation in Lishui-Jiaojiang sag are identified as follows：Medium-high frequency weak amplitude high continuity subparallel or parallel sheet facies,weak frequency high amplitude medium continuity subparallel sheet facies,variable amplitude medium-high continuity progradation facies,medium amplitude weak-medium continuity wedge facies,medium-high amplitude disorderly facies,and weak-medium amplitude medium continuity filling facies.According to areal distribution,drilling and regional structural background,seismic facies is transferred into sedimentary facies by seismic interpretation.The results show that the Yueguifeng Formation was deposited in the rift lacustrine environment,associated with fan delta,subsea apron,delta and lacustrine faicies.In combination with core sample measurement,we consider that the lacustrine mudstone of Yueguifeng Formation is good and general quality source rock,mainly distributed in the central area of Lishui east subprime sag,north-central of Lishui east subprime sag and Jiaojiang sag,with thickness more than 1 000m and area about 4 974.8km2.We identity some favorable areas in the uplift and slope structural belt nearby the source rock center as the important target regions in the further.Some beneficial advices are proposed for further exploration.