厄瓜多尔Oriente盆地DF油田白垩系M1层沉积特征

Sedimentary characteristics of the upper Cretaceous M1 sandstone in the DF oilfield,Oriente basin,Ecuador

应用沉积学理论,根据岩心、测井、录井和地震资料,分析厄瓜多尔Oriente盆地DF油田白垩系M1层M1SS砂岩组沉积微相特征和砂体展布规律,建立沉积模式。结果表明:研究区M1SS砂岩组发育退积式的外潮控河口湾亚相,进一步识别潮汐砂坝、潮汐水道、砂坪、混合坪和潮汐砂坝间等5种沉积微相。M1SS砂岩组沉积末期,相对海面上升至最大海泛面,而后开始下降,形成M1-Zone砂岩组小型进积式潮控三角洲平原亚相沉积,内部识别分流河道、河道间沼泽和潮坪等沉积微相。M1层储层物性主要受沉积微相控制,潮汐砂坝砂体叠置且储层物性最好,是研究区最有利的储集相带。

The upper Cretaceous M1 sandstone in the DF oilfield is rich in petroleum resource,but little research has been done about this area.To identify facies belts with the favorable reservoir conditions through the study of sedimentary microfacies and reservoir physical properties.Based on the comprehensive analysis of cores,well loggings and seismic data,the M1 SS member of the upper Cretaceous M1 sandstone was considered to have formed in outer tide-dominated estuary,five lithofacies types were identified,including tidal bar,tidal channel,sand flat,mixed flat and interbar,and characteristics of these five microfacies were described.At the same time,the paper clarified the microfacies distribution characteristics and space-time evaluation of each layer.At the end of M1-Zone member,the relative sea level raise to the maximum flooding surface,then began to fall,a small-scale regressive tide-dominated delta plain,including distributary channel,marsh and tidal flat,developed at the final infill phase of the large tide-dominated estuarine system,and the depositional model map was built.The reservoir physical properties of the upper Cretaceous M1 sandstone were controlled by microfacies,and in the area of interest,the physical properties of tidal bars were clarified to be the best and the next were tidal channels.Integrating reservoir physical properties of microfacies and the distribution characteristics of sand bodies,the most developed area of tidal sand bars was considered as the most favorable reservoirs.