致密储层渗透率测试的稳态与非稳态法对比研究

渗透率是油气藏储层评价、产能计算及制定合理的开发方案所需关键参数之一。针对常规稳态法测试致密储层岩石渗透率效率低下、试验过程易受环境温度影响等缺点，使用脉冲衰减渗透率测试仪对39块致密岩石稳态法克氏渗透率与非稳态脉冲衰减渗透率进行系统的对比研究，分析岩样渗透率、试验操作方法及有效应力组合方式等因素对测试结果的影响。研究结果表明，相同净围压条件下致密岩石脉冲渗透率小于克氏渗透率，脉冲渗透率平均约为克氏渗透率的47.26%，岩样渗透率越小，则两种渗透率之间的差别越大。误差分析表明，脉冲渗透率试验初期岩样短时间承受的9 MPa高围压和其高围压、高孔隙压力组合的有效应力施加方式对脉冲渗透率测试结果具有一定程度的影响，但仍无法完全解释两种渗透率的总体误差。数学拟合表明，取自同一区块的露头砂岩岩样脉冲与克氏渗透率相对误差与脉冲渗透率具有较好地对数函数关系，由数学推导获得该露头砂岩储层岩石脉冲渗透率与克氏渗透率的转换关系。

Comparative study of tight reservoir permeability using steady-state and unsteady-state methods

Permeability is one of the most important parameters required for reservoir evaluation, well production calculation and developing a reasonable development program. Obtaining the accurate permeability is helpful for effectively exploiting tight petroleum reservoirs. Due to the shortcomings of conventional steady-state permeability measurement method such as long experimental process and easily affected by the environmental temperature, this paper has conducted comparative study of permeability of 39 block rocks of tight reservoir using both steady-state and unsteady-state techniques. Meanwhile, those factors which affecting experimental results accuracy have also analyzed including permeability, experimental operation method and the way of combination of effective stress. The experimental results show that the unsteady-state pulse transient decay technique consistently underestimates the steady-state Klinkenberg-corrected permeability. Pulse decay permeability is only about 47.26% of the steady-state permeability in average. The difference between the above two different kinds of permeability increase with the decrease of the rock samples permeability. Error analysis suggests that the high effective about 9 MPa loaded on the rock sample before the pulse decay permeability measurement and the combination of high confining stress and high pore pressure can induce a portion of experimental error, but still not fully explain the overall error between the pulse decay permeability and the steady-state Klinkenberg-corrected permeability. Finally, mathematical fitting result shows that the relative error and the pulse decay permeability has a good logarithm function.