三塘湖盆地牛圈湖南-马中地区西山窑组一段储层特征及主控因素

RESERVOIR CHARACTERISTICS AND MAIN CONTROLLING FACTORS OF XISHANYAO FORMATION IN NIUJUANHUNAN-MAZHONG AREA,SANTANGHU BASIN

新疆维吾尔自治区东北部三塘湖盆地马朗凹陷牛圈湖南-马中地区中侏罗统西山窑组一段勘探潜力巨大,马朗凹陷具多类型储层特征共生的特点,目前对于牛圈湖南-马中地区储层特征及主控因素研究较少。以牛圈湖南-马中地区西山窑组一段为研究对象,利用490余口井1270件普通薄片、1197件铸体薄片、扫描电镜1197件、49块样品的压汞数据等进行储层特征及主控因素研究。结果表明,牛圈湖南-马中地区西山窑组一段储集砂岩岩性主要为长石岩屑砂岩,其次为岩屑砂岩,填隙物主要为胶结物,胶结物均值4.78%;主要孔隙类型为剩余原生粒间孔,其次为晶间孔和粒间溶孔。储层孔隙度均值12.23%,渗透率4.21×10^(-3)μm^(2)。压汞曲线分选系数均值1.5,最大孔喉半径1.4μm,孔喉分选较差,为小孔隙喉道。沉积微相和成岩作用共同影响储层物性,沉积微相是主控因素,水下分流河道储层物性最好,河口坝微相次之;成岩作用对于储层物性具有两面性,其中压实作用、胶结作用分别平均减少孔隙度19.03%,4.78%,溶蚀作用平均增加孔隙度1.53%。成岩阶段位于早成岩B期至中成岩A期,经历压实作用与胶结作用减孔后,主要由溶蚀作用增加孔隙度,所以可以形成较好储层;研究结果为挑选优势储层提供有效依据。

The Malang Sag in the Santanghu Basin of northeast Xinjiang is notable for the coexistence of multiple reservoir types,with the first member of the Middle Jurassic Xishanyao Formation(J_(2)x^(1))in the Niuquanhunan-Mazhong area showing significant exploration potential.Despite this potential,there have been few studies on the characteristics and main controlling factors of the reservoir in this area.This paper investigates the reservoir characteristics and controlling factors of the first member of the Xishanyao For-mation in the Middle Jurassic through the analysis of extensive data from over 490 drilling wells,1,270 thin sections,1,197 cast thin sections,1,197 scanning electron microscopy samples,and 49 sets of mercu-ry compression data collected from the Niuquanhunan-Mazhong area.The results reveal that the reservoir sandstone of the first member of the Xishanyao Formation in the Niuquanhunan-Mazhong area is primarily feldspar lithic sandstone,with lithic sandstone being the secondary type.The average interstitial material content between the clasts is 4.78%,predominantly composed of cements.Diagenetic analysis indicates that the main pore types in the sandstone are residual primary intergranular pores,followed by intergranu-lar pores and intergranular dissolved pores.The average porosity of the sandstone reservoir is 12.23%,and the average permeability is 4.214.21×10^(-3)μm^(2).Furthermore,the sandstone reservoir exhibits poor sor-ting characteristics with small pore throats.The average separation coefficient of the mercury injection curve is 1.5,and the average maximum pore throat radius is 1.4μm.The study of sedimentary facies in-dicates that both sedimentary microfacies and diagenesis significantly impact the physical properties of the sandstone reservoirs,with microfacies being the predominant factor.Among the various microfacies,the underwater distributary channel reservoirs exhibit the best physical properties,followed by the estuarine bar facies.Diagenesis has both positive and negative effects on reservoir physical properties.Compaction and cementation reduce the reservoir porosity by 19.03%and 4.78%,respectively,while dissolution in-creases porosity by 1.53%.Comprehensive diagenetic analysis shows that the diagenetic stage of the reser-voir rocks ranges from early diagenetic stage B to middle diagenetic stage A.The porosity of the rocks is reduced by compaction and cementation and increased by late-stage dissolution,which can create favorable reservoir spaces.The findings of this study provide an effective basis for selecting superior reservoirs in the Malang Sag,enhancing the understanding of reservoir characteristics and the main controlling factors,and guiding future exploration and development activities in the region.