准噶尔盆地玛湖地区深层致密砾岩储层发育特征及成因

Development characteristics and genesis of deep tight conglomerate reservoirs of Mahu area in Junggar Basin

为明确准噶尔盆地玛湖地区深层致密砾岩储层发育规律及主要成因,利用已钻深井各项资料和数据对其进行系统研究,确定了储层的基本特征和有效储层成因。结果表明:储层以细砾岩和中细砾岩为主,属扇三角洲分流河道砾岩;储层为典型低—特低孔、渗深层致密砾岩储层;砾石成分主要为凝灰岩和中酸性火山熔岩构成的火山岩,胶结物主要为浊沸石和方解石;经历了压实、胶结和溶蚀3类成岩作用,前两者兼具破坏和建设双重作用,而溶蚀作用的结果是普遍发育由沸石类、碳酸盐类胶结物和泥质杂基溶蚀形成的粒间溶孔及长石和暗色矿物溶蚀形成的粒内溶孔构成的次生孔隙富集带;与中浅层不同,储集空间由次生孔隙和裂缝双重介质构成;有效储层成因主要为岩石成分、溶蚀作用、裂缝系统和异常高压:岩石成分是内因,提供充足物质基础;而溶蚀作用、裂缝系统和异常高压是外因,溶蚀作用形成次生孔隙富集带,裂缝系统提升储层渗流能力,异常高压实现孔隙的有效保持和增加。4个因素共同控制深层致密砾岩相对优质储层的形成与分布。

In order to clarify the development rules and main origins of deep conglomerate reservoir in Mahu area of Junggar Basin, the basic characteristics and effective reservoir origins of the reservoir are determined by systematic research with various materials and data of deep wells. The results show that: The reservoir is mainly fine and medium fine conglomerate, belonging to fan delta distributary channel conglomerate;The reservoir belongs to typical deep tight conglomerate reservoir with low to ultra-low porosity and permeability;The gravel is mainly composed of volcanic rock that is composed of tuff and intermediate acid volcanic lava, and the cement is mainly laumontite and calcite;It has experienced three types of diagenesis: Compaction, cementation and dissolution. The first two has dual effects of destruction and construction, and the result of dissolution is the widespread development of secondary pore enrichment zones that are composed of intergranular solution pores formed by the dissolution of zeolite, carbonate cements and argillaceous matrix, as well as intragranular solution pores formed by the dissolution of feldspar and dark minerals. Different from the middle and shallow layers, the reservoir space is composed of secondary pores and fractures: The effective reservoir is mainly caused by rock composition, dissolution, fracture system and abnormal high pressure;The rock composition is the internal cause and provides sufficient material basis, while the dissolution, fracture system and abnormal high pressure are the external cause;The dissolution forms a secondary pore enrichment zone, the fracture system improves seepage capacity of the reservoir, and abnormal high pressure can effectively maintain and increase pores. Four factors control the formation and distribution of relatively high-quality deep tight conglomerate reservoirs.