湖相—浅水扇三角洲叠置砂体沉积模式

沙湾凹陷三叠系百口泉组沉积相研究程度较浅,为了更好地预测有利砂体的分布范围,根据钻井、测井、地震及岩心等资料,对沙湾凹陷三叠系百口泉组砂砾岩的沉积环境和沉积特征进行了研究。研究表明,百口泉组发育扇三角洲和湖泊2种相类型,其中扇三角洲平原、扇三角洲前缘亚相最为发育;该组沉积于水浅、盆广的环境中,并由此建立了湖泊—浅水扇三角洲沉积模式,该模式表明有利储层主要为不同时期沉积的分流河道及水下分流河道叠置砂体;结合沉积相平面展布特征、沉积模式以及地层厚度分析,百二段沉积期物源供应充足,砂体相对较厚,同时由于上覆于百一段所以埋深相对较浅,物性较好,认为百二段为优势层段,并划分为3个级别。该结论对三叠系百口泉组下一步勘探及有利储层预测具有指导意义。

SEDIMENTARY MODEL OF THE SUPERIMPOSED SANDBODY IN THE LACUSTRINE-SHALLOW WATER FAN DELTA

Due to the relatively shallow research degree of the sedimentary facies of Baikouquan Formation of Triassic Shawan Sag,in order to better predict the distribution of the favorable sandbodies,according to the drilling,logging,seismic,core data and so on,the sedimentary environment and characteristics of the conglomerate in the formation were studied.The research achievements show that 2 kinds of facies:fan delta and lake are developed in Baikouquan Formation,in detail,the fan delta plain and fan delta front subfacies are best developed;the formation is deposited in the shallow water and wide basin environments,and thus the sedimentary models of the lake-shallow water fan delta are established,the pattern shows that the favorable reservoirs are mainly accumulated by the different-depositional period distributary channels and underwater distributary channels superimposed sandbodies;combined with the analyses of the planar distributed characteristics of the sedimentary facies,sedimentary model and strata thickness,the material supply in Member Bai-2 is pretty adequate and the sandbodies are relatively thicker,at the same time,because of the overlying Member Bai-1,the buried depth is relatively shallower,the physical properties are much better,so Member Bai-2 is regarded as advantaged horizon,and moreover it is subdivided into 3 levels.The conclusion has a certain guiding significance for the next exploration of Triassic Baikouquan Formation and prediction of the favorable reservoir.