神府解家堡区上古生界致密砂岩储层特征及主控因素

神府解家堡区构造上位于鄂尔多斯盆地东缘晋西挠褶带,上古生界自下而上发育本1段、太2段、山2段和千5段等多套致密砂岩储集层.储层岩石类型以石英砂岩、岩屑石英砂岩、长石石英砂岩、岩屑砂岩和长石岩屑砂岩为主,自下而上储层石英含量呈递减、岩屑和长石含量呈递增趋势.储集空间类型以粒间溶孔、粒内溶孔、晶间孔和微裂缝为主,储层最大孔隙半径总体偏小,孔隙中值半径较小,排驱压力中等,储层孔隙以小孔—微孔为主.本溪组海相障壁—潮坪沉积、太原组浅水三角洲沉积、山西组三角洲沉积和石千峰组陆相辫状河沉积演化序列下,岩石成分成熟度和结构成熟度自下而上降低,储层空间展布呈层多而薄、砂—泥—煤岩交互特征.成岩作用类型以压实、胶结、溶蚀作用为主,局部发育高岭石化和微裂缝.以沉积相带、岩石类型和成岩作用类型作为3个控制端元,以孔隙度和渗透率为标准,上古生界致密砂岩储层可划分为4个大类和10个亚类,优势相和强溶蚀、弱胶结作用下的Ⅰ类储层孔隙度大于8%,渗透率大于0.5 mD,是最优质储层.

Characteristics and main controlling factors of tight sand reservoir in Shenfu block,Ordos Basin

Shenfu block is tectonically located in the Jinxi fold belt of the eastern Ordos Basin. where tight sand reservoirs are well preserved. such as Ben-1. Tai-2. Shan-2 and Qian-5. Rock types of these reservoirs are mainly quartz sandstone. lithic quartz sandstone. lithic feldspar sandstone. lithic sandstone and feldspar lithic sandstone. showing quartz decreasing and lithic+feldspar increasing trends from the bottom to the top. Reservoir space is mainly composed of inter-grain dissolution pore. inner-grain dissolution pore. inter-crystalline pore and microfracture. Reservoir porosity is dominated by small and micro pores. with low pore radius and medium driving pressure. The distribution of reservoir space is characterized by multi-but-thin layers and interlayers of sand-mud-coals. A gradually decreasing of component maturity and structure maturity has been discovered from the bottom Benxi Formation barrier tidal flat deposition. through Taiyuan Formation shallow delta deposition and Shanxi Formation delta deposition. to Shiqianfeng Formation braided river deposition. Diagenesis is mainly controlled by compaction. cementation and dissolution. with local kaolinization and micro-fracture. With sedimentary facies. rock type and diagenesis as three controlling end members. and porosity and permeability as criteria. Late Paleozoic tight sand reservoir in Shenfu block can be divided into four types and ten sub-types. Ⅰ-type reservoir with better sedimentary facies. strong dissolution and weak cementation is considered as the best reservoir. which has high porosity > 8% and high permeability > 0.5 mD.