川东北地区优质碳酸盐岩储层改造机制探讨

川东北普光气田优质碳酸盐岩储层主要为礁滩相白云岩,储集空间类型以次生粒内孔、粒间孔为主,并伴有明显的构造形迹。研究表明,次生孔隙主要形成于深埋阶段的2期溶蚀作用:第1期发生于中成岩早期埋藏阶段,大量的石油充注之前,对应于早中侏罗世(J1-2);第2期发生于中成岩晚期,对应于晚侏罗—早白垩世(J3—K1)的干气阶段。有机质热演化过程中形成的有机酸和膏盐地层中硫酸盐热化学成因(TSR)的H2S水溶液分别构成了这2期溶蚀作用的酸性流体介质。根据储层的显微岩石学特征和成岩作用标志可以识别和确认埋藏溶蚀作用。储层岩石中大量的构造形迹是中新生代多期构造运动的产物,其中燕山运动早期和中晚期2期构造运动与2期溶蚀作用时间相吻合,形成的裂缝、微裂缝提高了岩石的渗透率,使得酸性流体沿裂隙和早期的残留孔隙渗入岩石中发生非选择性溶蚀,形成了裂缝-溶孔"组合"。构造应力作用促进了埋藏溶蚀作用的进行,两者的相互作用成为储层改造和优化的重要方式。因此,根据储层形成的这种机制,利用"相控分布-构造应力+溶蚀改造"的储层发育模式,可以对优质碳酸盐岩储层进行预测。

Reformation mechanism of high-quality carbonate reservoirs in northeastern Sichuan Basin

The high-quality carbonate reservoirs in Puguang Gas Field of the northeastern Sichuan Basin are mainly dolomites of reef-bank facies.Secondary intragranular and intergranular pores work as the main reservoir spaces,accompanied with significant tectonic track ways.The secondary pores generated from 2 stages of dissolution during burial history.1) The 1st stage of dissolution took place during the early burial period of mesodiagenesis,which corresponded to the early and middle Jurassic and was followed by bi...