柴西南昆北油田切6区路乐河组储层孔隙结构及物性特征

路乐河组(E₁₊₂)是柴达木盆地昆北油田切6区主要含油气层系,储层特征(特别是孔隙结构和物性特征)认识不清严重阻碍了油田的开发。综合运用岩心、薄片、扫描电镜、压汞及实验测试等,对该区储层孔隙结构及物性特征进行研究,明确储层物性的控制因素。研究表明:路乐河组储层岩性以砾岩和砂岩为主,岩石类型主要为长石砂岩、长石岩屑砂岩,成分成熟度较低;储层孔隙类型包括原生孔隙、次生孔隙以及裂缝,以原生粒间孔为主,占总孔隙的70.3%;孔隙喉道形状主要为缩小型状和管束状,孔隙直径主要分布于20~40 μm,根据压汞曲线形态将孔隙结构分为4类,以Ⅱ类和Ⅲ类孔隙结构为主;路乐河组储层为特低孔低渗储层,孔渗相关性较好,储层物性受岩性、沉积相和成岩作用等综合控制。储层物性较好的岩性为不等粒砂岩和细砾岩,沉积微相为分流河道和河口坝,压实作用、胶结作用使储层物性变差,而溶蚀和破裂作用较好地改善了储层物性。

Reservoir Pore Structure and Property Characteristics of Lulehe Formation in the Q6 Area,Kunbei Oilfield

Lulehe Formation (E₁₊₂) is the main hydrocarbon-bearing sequence in Q6 area of Kunbei Oilfield, but the inadequate understanding in the reservoir characteristics (especially pore structure and physical properties) has seriously hindered the oilfield development. Reservoir pore structure and properties characteristics in this area were studied by using the cores, thin sections, scanning electron microscope (SEM), mercury intrusion and experimental analysis, with the aim to clarify the controlling factors of reservoir properties. The Lulehe Formation comprises mainly conglomerate and feldspar-(lithic) sandstones with low composition maturity. Reservoir pore types include primary/secondary pores and fractures, with the primary inter-granular pores accounting for 70.3%. The pore throat is mainly narrow and tubular, and the pore diameter is mainly of 20 μm to 40 μm; According to the shape of mercury intrusion curve, the pore structures are divided into four types (I to IV), and the pore structure is mainly Type II and Type III. Reservoirs in the Lulehe Formation are of ultra-low porosity and low permeability with good pore-permeability correlation. Reservoir properties are controlled by the lithology, sedimentary facies and diagenesis. The reservoir properties of unequal grains and fine conglomerates, distributary channel and estuary dam microfacies are better. Compaction and cementation have worsen the reservoir properties, whereas dissolution and fracture have improved the reservoir properties.