涠西南凹陷WA油田流一段储层特征及物性影响因素

根据岩芯和测井资料,结合薄片鉴定、扫描电镜分析,对北部湾盆地涠西南凹陷WA油田流一段扇三角洲储层沉积相和储层特征展开了详细全面地研究,并从沉积和成岩作用等方面对储层物性影响因素进行分析。结果表明:流一段为扇三角前缘亚相,包括辫流坝、辫状水道和席状砂3种微相类型。岩石类型主要为长石石英砂岩,成分成熟度中等偏高,结构成熟度中等偏低;储层空间类型主要为原生粒间孔,其次为粒间溶孔和粒内溶蚀孔。喉道形态为缩颈状和弯片状,孔喉类型主要为中孔粗喉型、中孔中喉型和中孔细喉型。孔隙结构特征为储层排驱压力较低、有效孔喉体积大,最大连通孔喉半径和中值喉道半径分布范围广,有利于油气储集。储层物性整体上表现为中孔中渗和中孔低渗特征。储层物性主要受沉积作用和成岩作用影响;沉积作用中沉积微相是影响储层物性的决定性因素,辫流坝微相为中粗砂岩,分选系数小,储层均质,储层质量最好;成岩作用中压实作用是储层物性变差的主控因素,孔隙损失12.5%~17.5%,而溶解作用改善了储层物性。综合分析认为,WA油田流一段储层以砂砾岩和粗细砂岩为主,发育的辫流坝和辫状水道微相沉积储层质量较好,可作为后续油田开发挖潜调整目标。

Reservoir characteristics and influencing factors of the Member 1 of Liushagang Formation in WA oilfield, Weixinan Depression

Based on core and well logging data, combined with thin section identification and scanning electron microscope analysis, the sedimentary facies and reservoir characteristics of fan delta in the Member 1 of Liushagang of WA oilfield in Weizhou Southwest Depression were studied in detail, and the influencing factors of reservoir physical properties were analyzed from the aspects of deposition and diagenesis. The results show that the Member 1 of Liushagang of flow is the front subfacies of fan triangle, including three types of microfacies:braided flow dam, braided channel and mat sand. The rock type is mainly arkose quartz sandstone, the composition is medium high, the structure is mature medium low. The type of reservoir space is mainly primary intergranular pore, followed by intergranular dissolution pore and ingranular dissolution pore. The throat form is neck contraction and flexural, and the main types of pore throat are mesopore thick throat, mesopore middle throat and mesopore thin throat. The pore structure is characterized by low displacement pressure, large effective pore throat volume, wide distribution range of maximum connected pore throat radius and median throat radius, which is beneficial to oil and gas accumulation. The reservoir physical property as a whole is characterized by mesopore permeability and mesopore permeability. The reservoir physical property is mainly affected by sedimentation and diagenesis. The sedimentary microfacies is a decisive factor affecting the physical properties of reservoirs. The microfacies of braid-Flow dam is medium coarse sandstone with small separation coefficient, homogeneous reservoir and best reservoir quality. Compaction in diagenesis is the main controlling factor of reservoir physical properties, with pore loss ranging from 12.5% to 17.5%, while dissolution improves reservoir physical properties. The comprehensive analysis shows that the reservoir the Member 1 of Liushagang of WA oilfield is mainly composed of sand and coarse and fine sandstone, and the developed braided flow dam and braided channel microfacies sedimentary reservoirs are of good quality, which can be used as the target for further exploration and adjustment of oilfield