靖边气田气井产能方程的建立

产能方程是进行气藏工程计算的基础,靖边气田在求解产能方程时,前期主要采用修正等时试井、系统试井方法。由于修正等试试井受到井口装置的限制,对于已投产气井操作难度大;系统试井则受到储层条件的限制,不能够准确确定各种气井的产能方程,给气藏工程计算带来很大困难,而“一点法”只需要测试一个工作制度下的稳定产量和该产量相对应的稳定流压,在大幅减少测试工作量及测试周期的同时,可得到气井的产能方程。从二项式产能方程出发,推导了“一点法”产能方程的理论公式,传统“一点法”公式在α值的选取上没有进行气井分类,在计算过程中产生了误差,因此文章通过收集靖边气田修正等时试井资料,分类计算了气井的α值,建立了适合于该气藏的新的经验公式,这完善和补充了传统“一点法”经验公式法,更符合气藏的实际。还对采用新方法计算的产能方程进行了应用,结果表明所求产能方程符合实际地质情况。

DERIVATION OF JINGBIAN GASFIELD WELL PRODUCTIVITY EQUATION

Productivity equation serves as the basis for gas reservoir engineering calculation. To derive Jingbian Gasfield productivity equation, correction isochronal testing and systematic well testing are normally used at early stage of development. Correction isochronal testing is difficult to apply on gas wells in production due to wellhead device and systematic well testing alone cannot render accurate productivity equation for various types of gas wells as restricted by reservoir condition, which causes much difficulty for gas reservoir engineering calculation. As a contrast, "Single Point Method" requires only the measurement of the value of steady production under one working system and its corresponding stable flow pressure to produce well productivity equation. Meanwhile, testing workload and cycle are reduced greatly. Theoretically "Single Point Method" productivity equation is deducted from binomial productivity equation. Conventional "Single Point Method" productivity equation does not vary the value of α with well classification and error occurs during the course of calculation. In this regard, this paper gathered correction isochronal testing data of Jingbian Gasfield, determined the value of α matching gas category and established new empirical equation specific to Jingbian reservoir, which is an improvement of and supplement to conventional "Single Point Method" empirical equation and reflects the real situation of gas reservoir. Productivity equation derived with a new calculation method has been put into practice and its outcomes match the real geological situation.