川中北斜坡地区沧浪铺组一段颗粒滩特征及分布

Characteristics and distribution of grain shoal in the first Member of Canglangpu Formation in the north slope area of central Sichuan Basin

基于岩心、薄片、测井及地震资料的综合分析,围绕川中北斜坡地区寒武系沧浪铺组一段颗粒滩特征及分布规律开展研究,认为:1)区内滩体岩性以鲕粒灰岩及在此基础上受不同程度白云石化作用改造的残余鲕粒云岩、云质鲕粒灰岩、灰质鲕粒云岩为主;颗粒滩在自然伽马曲线上以箱形、漏斗形响应为主,地震反射上以丘状杂乱、中弱振幅、中低频的a类地震相响应最优,b类地震相次之。2)纵向上,沧一段颗粒滩单体厚度不大,表现为多套频繁叠置、累计厚度具有一定规模的特征;横向上,滩体连续性较好,可对比追踪;平面上,三维地震资料精细刻画显示滩体北西—南东向展布,呈现整体连片、局部分异的特征。3)滩体发育受到海平面及古地貌的双重控制,位于研究区东侧的相对古地貌高带及裂陷槽边缘地带是沧浪铺组颗粒滩发育的主要区域,也是下一步勘探工作的主要方向。

Based on the comprehensive analysis of core,thin section,logging and seismic data,the characteristics and distribution law of grain shoal in the first Member of Cambrian Canglangpu Formation in the north slope area of central Sichuan Basin are studied.The comprehensive analysis shows that:(1)the shoal lithology in the area is mainly composed of oolitic limestone and the oolitic dolomite,dolomitic oolitic limestone and calcareous oolitic dolomite reformed by different degrees of dolomitization on this basis;in GR logging curve,the response of grain shoal is mainly box-shaped and funnel-shaped.The response of Class a seismic facies with disordered mound shape,medium and weak amplitude and medium and low frequency is the best,followed by Class b seismic facies.(2)In the longitudinal direction,the monomer thickness of grain shoal in the first Member of Cambrian Canglangpu Formation is not large,showing that multiple sets are frequently overlapped,and the cumulative shoal thickness has the characteristics of a certain scale.Laterally,the shoal body has good continuity and can be tracked by comparison.On the plane,3D seismic data show that the shoal body is distributed in the near NW to SE direction,showing the characteristics of overall contiguity and local differentiation.(3)The development of the shoal body are controlled by both sea level and geomorphology,and the relative geomorphic high zone and the margin of the rift trough located in the east of the study area are the main areas for the development of grain shoal in the Canglangpu Formation,which is the main direction of the next exploration work.