单井地层压力简便计算方法研究

A simplified calculation of reservoir pressure in a single well.

目前注水开发油田矿场确定单井控制的平均地层压力真值不仅关井时间较长（长于２ｄ），而且误差较大。提出改进方法：以压力导数异常变化起始点的压力值作为单井控制的平均地层压力真值；未测到压力导数后期异常变化的井，沿用原有方法确定。推导出计算注水开发井地层压力的港Ⅰ法（利用半对数直线段或外推直线段求取，包括３种计算式）和港Ⅱ法（压力恢复速度法）。在此基础上，考虑现场条件，统计大港油田３５口井实测资料，提出关井时间可由流动系数确定：流动系数大于１μｍ２·ｍ／（ｍＰａ·ｓ）为５～８ｈ；流动系数为０．１～１μｍ２·ｍ／（ｍＰａ·ｓ）为１ｄ；流动系数小于０．１μｍ２·ｍ／（ｍＰａ·ｓ）为２ｄ。应用２组各３口井的实测资料进行验证，港Ⅰ法、港Ⅱ法计算的平均地层压力与实测地层压力的误差都小于３％，且平均关井时间可比目前通用方法缩短约２ｄ。港Ⅱ法精度高、计算简单，可优先采用。提出的地层压力计算方法可普遍应用于注水开发井，并可扩展应用于注水井。图２表３参３（陈志宏摘）

The procedure to obtain the average reservoir pressure controlled by a single well used currently in oil fields developed under water flooding is time consuming (longer than 2d), and relatively larger error often occurs. A modified method is suggested, starting from the abnormal point on the pressure derivative curve the pressure corresponding to this point is taken as the true value of the average reservoir pressure controlled by this well; in a well where the abnormality in the later period of the pressure derivative curve is not obtained, the original method will then be used. Method Gang Ⅰ (straight line portion or extrapolated straight line portion on semilog coordinates to find out this point, and calculation formulas are included) and Gang Ⅱ (method of pressure build up speed) was derived to calculate the reservoir pressure controlled by a well in a water flooding reservoir. Actually measured data in 35 wells were gathered statistically and on this base it is suggested that when flow coefficient is larger than 1μm 2·m/(mPa·s), well shut in time will be 5 8h; when the flow coefficient is 0.1 1 μm 2·m/(mPa·s), 1d is required; and 2d will be required when flow coefficient is smaller than 0.10 μm 2·m/(mPa·s). Being verified by the actual data from 2 groups of wells (3 wells in each group), all these pressures obtained by methods Gang Ⅰand Gang Ⅱhave an error of smaller than 3% and the average well shut in time is shortened by an average of 2d. Method Gang Ⅱhas a high accuracy and is easy in calculation and can be used in preference. This method can be used in production wells and can be generalized to use in injection wells as well.