高温高压非常规储层渗透率脉冲法测量及分析

Analysis of measurement error of permeability pulse method for high temperature and high pressure unconditional reservoirs

随着超深层致密砂岩气藏、页岩气藏等非常规气藏的大规模开发,非常规储层渗透率测试难度大、时间长、精度低等问题逐渐凸显。为提高在高温高压条件下测量储层岩石渗透率的准确性,依据高压脉冲渗透率测试原理,假设一维可压缩流体,且高压下岩石具有可压缩性,优化求解过程并推导出高压脉冲渗透率完整且实用的表达形式;考虑储层高温高压地层环境,设计并开展高温高压脉冲渗透率测试实验。提出压差保持程度概念,用以揭示压力脉冲衰减不同时段的变化特征。开展了高压脉冲渗透率与孔隙压力、压差保持程度、标准克氏渗透率以及常规脉冲渗透率的误差分析研究。结果表明:压差保持程度在20%~50%的压差衰减实验数据可准确计算岩样的脉冲渗透率。保持有效应力不变,不同渗透率范围的岩样所受高孔隙压力的影响不同。高压脉冲渗透率与其他渗透率相比,更加接近实际高温高压地层环境下的岩石渗透率。该渗透率测试方法快捷、准确,具有其独特的优势,是深层非常规气藏储层物性测试评价的有效手段。

With the large-scale development of ultra-deep tight sandstone gas reservoirs,shale gas reservoirs and other unconventional gas reservoirs,the problems of unconventional reservoir permeability testing have been gradually highlighted,such as difficulty,long time and low precision.In order to improve the accuracy of measuring reservoir rock permeability under the conditions of high temperature and high pressure,this paper,based on the principle of high-pressure pulse permeability testing,assumed the reservoir as one-dimensional compressible fluid,and the rock is compressible under high pressure.This paper optimized the control equation solution process,and deduced an improved complete and practical expression of high pressure pulse permeability.Considering a high-temperature and high-pressure formation environment of the reservoir,the pulse permeability test experiment of high temperature and high pressure was designed and carried out.The concept of pressure difference retention degree was proposed for the first time to reveal the variation characteristics of pressure pulse decay in different periods.The error analysis of high-pressure pulse permeability and pore pressure,pressure difference retention degree,conventional Klinkenberg permeability,and conventional pulse permeability were carried out.The results show that the experimental data of pressure difference decay can be used to accurately calculate the pulse permeability of rock samples with pressure difference retention degree ranging from 20%to 50%.The effective stress remains unchanged,the rock samples with different permeability ranges are affected differently by high pore pressure.Compared with other permeability,the high-pressure pulse permeability is closer to the actual permeability of the rock under the high-temperature pressure formation environment.This permeability testing method is fast and accurate,and has its unique advantages,which is an effective method for testing and evaluating the physical properties of deep unconventional gas reservoirs.