注汞压力对致密砂岩储层物性下限分析的影响

Influence of Mercury Injection Pressure on Lower Limits Analysis of Tight Sandstone Reservoirs

最小流动孔喉半径法是目前常用的储层物性下限确定方法,它以岩芯压汞资料为基础,对岩石微观孔隙结构与渗流能力的关系进行定量分析,进而确定储层物性下限。研究表明,过高的注汞压力可能影响岩石孔隙结构状态,这引发了注汞压力的高低是否会对物性下限分析产生影响的思考,应该如何选取恰当的压汞数据来获取符合实际地质情况的物性下限值。目前,这些问题还没有得到明确和有针对性的研究。以川中P地区致密砂岩气藏为例展开了较为深入的研讨。分析结果表明,当注汞压力从30 MPa增加到200 MPa时,最小流动孔喉半径法确定的有效储层物性下限数值呈下降趋势。当注汞压力接近目的层位地层压力时,分析结果与生产测试等结论吻合较好。

The minimum flow pore throat radius method is often used to determine the lower limits of porosity and permeability of tight sandstone gas reservoirs.This method is based on mercury intrusion method.It can determine the lower limits by quantitative analysis of relationship between micro pore structure and permeability.Researches indicate that high mercury injection pressure may affect rock pore structure,which triggers the pondering over whether mercury injection pressures influences lower limits and how to choose appropriate mercury injection data to acquire lower limits suitable for practical geological situation.These problems have not been deeply discussed by far.So this paper focuses on these problems,taking the tight sandstone reservoirs in P area of the central part of Sichuan Basin as an example.The research results show the lower limit of porosity determined by minimum flow pore throat method falls when the selected mercury injection pressure rises from 30 MPa to 200 MPa.The calculated results and production testing results are in good agreement when the mercury injection pressure is close to the formation pressure.