高含水期大孔道渗流特征及定量描述方法

Seepage characteristics and quantitative description of large pore pathways at high water cut stage

受注入水长期冲刷作用影响,疏松砂岩油藏在特高含水期易发育大孔道,大孔道的存在造成无效水循环,影响水驱开发效果,故大孔道识别与定量描述对高含水期提高采收率措施有重要意义。文章分析了大孔道中的高速非达西渗流特征,依据高速非达西渗流的识别标准,建立了大孔道识别标准,并在考虑注水开发过程中渗透率随冲刷孔隙体积倍数变化的基础上,建立了油藏模拟系统,并给出了大孔道定量描述方法。最后选取孤东油田七区西馆上段Ng6^(3+4)开发单元作为典型油藏,进行了大孔道识别与定量描述研究。结果表明,在典型油藏的模拟区域储层内大孔道所占的比例较小,主要分布在注水井周围或注采井间。考虑了注采井距、注采压差、渗透率等指标所建立的大孔道识别标准能够有效的在油藏模拟系统中应用,并能准确、定量的描述大孔道。

The identification and quantitative description of large pore pathways are of great significance to improve the measures of oil recovery at high water cut stages.Since the large pore pathways,usually developed in unconsolidated sandstone oil reservoirs at high water cut stage under the long-term injected waterscouring,can cause ineffective water cycle,and compromise the effect of water injection on recovery enhancement.Thus the study analyzed the seepage characteristics of high-velocity non-Darcy flow in the large pore pathways,to set up diagnostic criteria for large pore pathways according to the standards used to identify the high-velocity non-Darcy flow,and established an oil reservoir simulation system based on permeability,which changes with the pore volume expansion during scouring through water injection.And a quantitative description of the large pore pathways was given.Finally,the Ng6 3+4 development unit in the upper member of the west Gudong oilfield was selected for reservoir simulation to identify large pore pathways and to carry out the quantitative description of the pathways.The results show that the proportion of large pore pathways,mainly distributed around the injectors or between injectors and producers,is relatively small in the simulated reservoir.In conclusion,the diagnostic criteria of large pore pathways,taking into account of the injector-producer spacing,injection-production pressure difference and permeability,can be effectively applied to the oil reservoir simulation system and the resultant quantitative description of the large pore pathways is accurate.