致密砂岩气藏储层微观孔隙结构特征及其对产能的影响

致密砂岩气藏复杂的微观孔隙结构是影响储层储渗能力及其产能的本质因素,本文通过铸体薄片观察结合压汞曲线形态及特征参数对苏里格西部苏48区盒8、山1段孔隙结构特性及其影响要素进行了研究。结果显示,孔隙组合类型分为3种：Ⅰ类：溶孔-粒间孔型、Ⅱ类：晶间孔-溶孔型、Ⅲ类：微孔型。其中,Ⅰ类孔隙结构物性好,储集渗透能力强,孔隙度高于10%；Ⅱ类孔隙结构物性较差,孔喉半径分布集中范围较窄；Ⅲ类构成的储层物性较差,该类孔隙结构储层的气、水的渗流阻力较大,通常不构成有效储层。分析实验结果后认为,孔隙结构特征的主要影响因素为埋深与成岩作用。随埋深增加,压实作用增强,在强压实作用下颗粒间接触关系逐渐呈紧密接触,孔喉缩小、排驱压力增加。交代作用、溶蚀溶解等成岩作用对储层的物性有建设作用。碎屑组成以及填隙物含量差异导致孔隙类型发育的不同,从而影响储集性能,最终引起产量变化。高孔渗段产气量较高,低孔渗井段受毛细管阻力影响,气驱水不彻底从而气水同产。

Microscopic pore structure characteristics of tight sandstone gas reservoir and its influence on productivity

s: The complex micro-pore structure of tight sandstone gas reservoir is the essential factor affecting the reservoir reservoir capacity and seepage capacity. In this paper, the pore structure characteristics and its influencing factors of Bo 8 and Shan 1 in Su 48 area in Western Sulige are analyzed by casting thin section observation combined with mercury injection curve shape and characteristic parameters. The results show that there are three types of pore assemblages: type I: dissolved pore-intergranular pore, type II: intergranular pore-dissolved pore and type III: micropore. Among them, Class I pore structure has good physical properties, strong reservoir permeability, and porosity is higher than 10%; Class II pore structure has poor physical properties and narrow pore throat radius distribution range; Class III pore structure has lower pore and permeability, and the gas and water seepage resistance of this kind of pore structure reservoir is larger, usually does not constitute an effective reservoir. After analyzing the experimental results, it is concluded that the main influencing factors of pore structure characteristics are burial depth and diagenesis. With the increase of burial depth, the compaction effect increases. Under the action of strong compaction, the contact relationship between particles gradually shows close contact, the pore throat shrinks and the displacement pressure increases. Diagenesis, such as metasomatism, dissolution and dissolution, can improve the physical properties of reservoirs. The difference of clastic composition and filling content leads to the difference of pore type development, which affects the reservoir performance and ultimately leads to the change of production. Gas production is high in high porosity and permeability section, and gas-water co-production is caused by capillary resistance in low porosity and permeability section.