延长组长6低渗油藏高温高压条件下裂缝对渗吸效率的影响

Influence of crack on imbibition efficiency of low permeability reservoir in Yanchang Chang 6 formation under high temperature and high pressure condition

关键词:  长6储层  裂缝  核磁共振  高温高压渗吸  渗吸效率

Key words:  Chang 6 formation  crack  nuclear magnetic resonance  imbibition under high temperature and high pressure  efficiency of imbibition

摘要:

杏子川油区长6储层是典型的特低渗油层,具有成岩压实作用强、孔隙度低、渗透率小、溶蚀孔和微裂缝发育、孔隙喉道细小且小孔喉所占比例很大、微观非均质性强的特点。目前,对该特低渗油藏渗吸驱油研究不够深入,通过压裂的方法以及高温高压渗吸实验结合恒速压汞实验、核磁共振实验、CT扫描实验等岩心资料分析方法,研究了裂缝长度和发育程度对渗吸驱油效率的影响。研究结果表明:高温高压渗吸过程主要是小孔隙内的油水置换,水进入小孔隙将油置换到大孔隙中；含裂缝渗吸效率比基质渗吸效率高,缝长越长,渗吸效率提高就越大；在渗吸初期阶段,剩余饱和度随渗透率的增大而减小,渗吸效率随渗透率的增大而增大,效果较为明显。在开发过程中应尽量增加裂缝发育程度,增大基质渗透率,增加基质与裂缝的接触面积,以提高渗吸采收率。 

Abstract:

The Chang 6 formation in Xingzichuan oilfield is a typical ultra-low permeability reservoir with the charactors of strong diagenetic compaction, low porosity, small permeability, the development of dissolved pores and micro-fractures, large proportion of small pore throats, and strong micro heterogeneity. At present, the researches of seepage and displacement in the ultra-low permeability reservoir are not enough. Fracturing methods and high-temperature high-pressure seepage experiments are combined with constant velocity mercury injection experiments, nuclear magnetic resonance experiments, and CT scanning experiments, then the effect of fracture length and development degree on the efficiency of oil absorption and displacement are studied. The research results show that:the high-temperature high-pressure infiltration process is mainly oil-water displacement in small pores, and water enters small pores to replace oil into large pores. The infiltration efficiency with cracks is higher than the infiltration efficiency with matrix, and the longer the slit length is, the higher the infiltration efficiency is. In the initial stage of infiltration, the residual saturation decrease with the increase of permeability, the infiltration efficiency increase with the increase of permeability, and the effect is obvious. During the development process, the degree of fracture develop should increase as much as possible, the matrix permeability should increase too, and the contact area between the matrix and the fracture should also increase to improve the seepage recovery efficiency.