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任何引起井筒附近流线发生改变的流动限制,都会产生正表皮系数。一般用试井解释计算的表皮系数来确定某口井的总流动效率,这从理论上讲是正确的。通常,将试井中得到的较大正表皮系数作为能否进行增产措施以提高单井产能的依据。但应注意,这里用到的假设,近井区的地层伤害程度,在较大范围内都是相同的。但往往这些措施不是非常有效,这是由于计算出来的表皮系数实际上是个复合变量。它不仅仅是近井区地层伤害的函数,它还与射孔几何参数、井斜、产层部分打开和其它与相态和流量相关的参数有关。因此,要得到近井区真实的表皮系数,必须将试井表皮系数分解为几个部分。另一方面,试井解释得到的渗透率和表皮系数具有相关性,其中一个变量的误差会直接影响另一个变量。所以对选定的渗透率—表皮系数模型,需要结合一些附加的输入数据来减小计算的不稳定性。只有通过正确的模拟,才能选择合适的增产措施,这对高产能气井尤为重要。因为这类井真实的与地层伤害有关的表皮系数,通常只是试井计算出来的总表皮系数的一小部分。本文提出了如何利用试井解释计算不同部分表皮系数和具有代表性的平均地层渗透率的方法,并用几个实例时其进行了分析。
Any flow restriction that causes a change in streamline near the wellbore will produce a positive skin factor. It is theoretically correct to generally interpret the calculated skin factor using a well test to determine the total flow efficiency of a well. In general, the larger positive skin factor obtained from a well test is used as a basis for the ability to increase production to improve single well productivity. However, it should be noted that the assumptions used here are that the degree of formation damage in the near well is the same over a large area. However, these measures are often not very effective, because the calculated skin factor is actually a compound variable. It is not only a function of formation damage in the near-well region, it is also related to perforation geometry parameters, well inclination, partial section opening, and other parameters related to phase and flow. Therefore, in order to obtain the true epidermal coefficient near the well, it is necessary to decompose the well test skin factor into several parts. On the other hand, permeability obtained from well testing is correlated with skin factor, and the error of one variable directly affects the other. So for the selected permeability-skin coefficient model, some additional input data needs to be combined to reduce the computational instability. Only through the correct simulation can we select the appropriate stimulation measures, which is especially important for high productivity gas wells. Because the true skin factor associated with formation damage in this type of well is usually only a small fraction of the total skin factor calculated from the well test. This paper presents how to use well test interpretation to calculate the different part of the skin coefficient and representative of the average permeability of the formation method, and with a few examples of its analysis.