邻水–大竹地区飞仙关组储层特征及主控因素

Reservoir Characteristics and Main Controlling Factors of the Feixianguan Formation in the Linshui-Dazhu Area

摘要: 邻水–大竹地区飞仙关组储层岩性组合复杂、孔缝洞配置关系多变，有效储层识别及主控因素认识仍需进一步细化。基于岩心观察、薄片鉴定、扫描电镜、物性测试、压汞分析及测井解释资料，对研究区飞仙关组储层特征、综合分类及主控因素进行分析。结果表明：飞仙关组储集岩主要包括鲕粒灰岩、生屑灰岩、砂屑灰岩、泥晶灰岩、粉晶–细晶白云岩、鲕粒白云岩、灰质白云岩和白云质灰岩，其中鲕粒灰岩、颗粒白云岩和粉晶–细晶白云岩储集意义相对突出。储集空间以粒间溶孔、粒内溶孔、晶间孔、晶间溶孔、铸模孔、微裂缝和局部溶洞为主，未完全充填裂缝可改善孔隙和溶洞连通性。储层整体表现为低孔、低渗特征，储层段孔隙度主要集中于2%~6%，渗透率总体偏低但离散性较强；飞二段储层段数量、孔渗条件和储层段厚度均优于飞一段和飞三段，为研究区主要有利储层段。压汞资料表明，储层孔喉结构可划分为粗孔粗喉、中孔细喉、细孔微喉和微孔微喉四类；依据孔渗物性、毛管压力、孔喉半径、束缚水饱和度、孔隙类型和岩石类型，可将储集岩划分为I类好储层、II类较好储层、III类差储层和IV类非储层。综合分析认为，高能颗粒滩和鲕滩沉积控制有利储集岩发育基础，白云石化和溶蚀作用改善孔隙结构及孔喉连通性，压实、胶结和多期充填作用降低储层有效性，构造裂缝主要改善低孔低渗储层渗流能力。

Abstract: The Feixianguan Formation reservoirs in the Linshui-Dazhu area are characterized by complex lithological assemblages and variable pore-fracture-vug configurations, and the identification of effective reservoirs and their main controlling factors still requires further refinement. Based on core observation, thin-section identification, scanning electron microscopy, petrophysical testing, mercury intrusion analysis and logging interpretation, this study investigates the reservoir characteristics, comprehensive classification and main controlling factors of the Feixianguan Formation in the study area. The results show that the reservoir rocks mainly include oolitic limestone, bioclastic limestone, sandy-grained limestone, micritic limestone, silty-fine crystalline dolomite, oolitic dolomite, lime-bearing dolomite and dolomitic limestone. Among them, oolitic limestone, grain dolomite and silty-fine crystalline dolomite have relatively favorable reservoir significance. Reservoir spaces are dominated by intergranular dissolved pores, intragranular dissolved pores, intercrystalline pores, intercrystalline dissolved pores, moldic pores, microfractures and local vugs. Unfilled or partially filled fractures can improve the connectivity among pores and vugs. The reservoirs generally show low porosity and low permeability. The porosity of reservoir intervals is mainly concentrated between 2% and 6%, and permeability is generally low but highly dispersed. The second member of the Feixianguan Formation has better reservoir abundance, porosity-permeability conditions and reservoir thickness than the first and third members, and therefore represents the main favorable reservoir interval in the study area. Mercury intrusion data indicate that the pore-throat structures can be divided into four types: coarse pores with coarse throats, medium pores with fine throats, fine pores with micro-throats, and micro-pores with micro-throats. According to porosity-permeability properties, capillary pressure, pore-throat radius, irreducible water saturation, pore types and rock types, the reservoir rocks can be classified into type I good reservoirs, type II relatively good reservoirs, type III poor reservoirs and type IV non-reservoirs. The comprehensive analysis suggests that high-energy grain shoals and oolitic shoals provide the depositional basis for favorable reservoir rocks, dolomitization and dissolution improve pore structures and pore-throat connectivity, compaction, cementation and multi-stage filling reduce reservoir effectiveness, and tectonic fractures mainly enhance the seepage capacity of low-porosity and low-permeability reservoirs.