柴达木盆地昆北油田路乐河组沉积相及储层特征

Characteristics of the sedimentary facies and reservoirs in Lulehe Formation of the Kunbei oilfield in Qaidam Basin,China

昆北油田位于柴达木盆地西南区的昆北断阶带,路乐河组是该油田重要的产油层系。通过对路乐河组的岩性、沉积构造、粒度、重矿物和测井相研究,认为路乐河组是一套退积型的辫状三角洲沉积,发育辫状三角洲平原、前缘亚相,微相类型包括(水下)分流河道、席状砂、河口坝、泛滥平原、分流间湾等;沉积相平面展布呈自南西向北东的扇形,平面上发育两期分支体系;储层岩性包括砾状砂岩、中粗砂岩及细砂岩等,储层成分成熟度中等,结构成熟度低,储集空间以原生粒间孔为主,见少量次生溶孔、成岩粒内缝;储层物性整体较好,属中低孔、中低渗型储层。压实作用是储层物性的主控因素,储集性能主要受沉积相带、杂基含量和成岩作用控制。

Sedimentary type and reservoir characteristics of Lulehe Formation are important in exploration due to its primary role in the Kunbei oilfield.The Kunbei oilfeld is located in the Kunbei step-fault zone of the south-west part of Qaidam Basin.The reservoir is generally studied using cores,thin sections,well loggings and testing data on the basis of stratigraphy in this paper.It is revealed that the Lulehe Formation rock is a set of retrogradating braid delta sediments.The plain and front subfacies are developed in this area,including distributary channels,sheet sands,mouth bars,flood plain and interdistributary bays.The sedimentary facies,including two branches,is a fan originated from the south-west and expands to the north-east.The reservoir rocks include pebbly,moderate,coarse and fine sandstone with moderate compositional maturity and low textural maturity.The reservoirs with intermediate porosity and low permeability mainly consist of original intergranular pore spaces with few dissolved pore and intergranular cracks.Integrated with regional structure style,well testing data and production rate,sand bodies located in Ⅲ sequence are favorable accumulation areas;distributary channels are the most favorable facies which control hydrocarbon＇s accumulation of single wells and reservoir boundary.