川东北普光气田鲕粒白云岩储层粒内溶孔的成因  

Origin of Intragranular Dissolution Pores of Oolite Dolomite Reservoirs in Puguan Gasfield,Northeastern Sichuan Province

作　　者：王恕一[1] 蒋小琼[1] 管宏林[1] 鲍云杰[1] 

机构地区：[1]中国石油化工股份有限公司勘探开发研究院无锡石油地质研究所,江苏无锡214151

出　　处：《沉积学报》2010年第1期10-16,共7页Acta Sedimentologica Sinica

摘　　要：普光2井下三叠统飞仙关组储层鲕粒白云岩中,常见铸模孔、新月形、半月形溶孔和环状溶孔,溶孔常具定向特征,前人多认为这些溶孔为早期成岩的大气淡水溶蚀。研究发现,这些溶孔常与压性缝、碎裂(粒)化伴生,而溶孔无明显变形,表明是形成于构造挤压之后的埋藏溶孔。埋藏溶孔有二期,一期中有沥青充填,另一期无沥青充填,前者形成于石油侵位之前,后者形成于侵位石油演化为沥青之后。研究认为:构造挤压作用于岩石时,应力首先使鲕粒中结构薄弱点—同心圈层之间产生裂缝,当应力集中于上端,使鲕粒上端优先沿同心圈层发育裂缝,随应力增大裂缝沿同心圈层向下延伸,乃至形成圆形"脱壳"裂缝,在后期酸性流体进入时沿这些裂缝优先产生溶蚀,形成偏于上端的定向溶孔,以及沿同心圈向下溶蚀形成新月形、环状溶孔,挤压和(或)溶蚀更强,则发育成铸模孔。The most common types of pores in the oolite dolomite reservoirs of the Lower Triassic Feixianguan Formation are moldic pores,crescentiform dissolution pores,lune dissolution pores and annular dissolution pores in Well Puguang 2 in Puguang Gasfield. The pores are directionally arranged. It was always believed that the pores were formed in early meteoric freshwater environments. However,the dissolution pores,with no clear deformation,are often associated with extrusion fractures,disintegration or crushed particles,indicating origin of burial dissolution after tectonic compression. The dissolution pores can be divided into two stages：the first one filling bitumen was formed before oil emplacement,the second one without bitumen occurred after oil turning into bitumen. It was considered that if structural compressional stress acted on the rocks,it could firstly cause cracks among the concentric layers of oolites where was the weak structural positions. When the stress was concentrated on the upper part of the oolites,it would develop cracks along the concentric layers by priority. The cracks were extended downward along the concentric layers as the stress increased,and which even circular and uncoating cracks could be formed. The late acidic fluids prefer to dissolute the oolites along the fractures,resulting in the formation of directional pores in the upper part of the concentric layers. With downwards dissolution along the fractures,the crescentiform pores and annular pores were developed and even moldic pores were formed as a result of increasing pressure and （ or） stronger dissolution.

关 键 词：川东北 普光气田 鲕粒白云岩 储层 粒内溶孔 

分 类 号：P618.130.21[天文地球—矿床学] TE122.222[天文地球—地质学]