利用生产数据确定异常高压气藏储量

Determination of gas in place for abnormally pressured gas reservoirs from production data

气藏储量的计算是油气藏工程领域关注的热点问题。物质平衡法及其各种衍生方法被广泛应用于井控储量或气藏储量的确定,但其存在成本较高的缺点。为准确、高效地确定异常高压气藏的储量,考虑孔隙中束缚水的膨胀作用和岩石孔隙的收缩作用,从天然气渗流基本理论出发求解气体渗流数学模型,并将之与异常高压气藏物质平衡原理相结合,导出了一种利用生产数据迭代计算气藏储量的方法(VRRLT-APGR方法),并给出了迭代初值的选择方法。利用各种生产制度下的数值模拟结果以及变产量变流压现场实例验证了其有效性,若生产数据可靠,储量计算误差一般不超过5%。该方法具有严格的理论基础,考虑了气体性质的变化和气井产量的波动,对于常压气藏和异常高压气藏均适用。

Estimation of gas in place is a hot issue in the field of oil and gas reservoir engineering. Material balance method and its derivative methods are widely employed in determining gas in place or well-controlled reserves,but their costs are usually high. To determine gas in place of abnormally pressured gas reservoirs with desirable accuracy and efficiency,this paper derives an iterative calculation method taking the pore restriction of reservoir rocks and the volume expansion of bound water into account,and proposes the selection strategy for initial iteration value. The method, called VRRLT-APGR(variable-rate reservoir limits testing for abnormally pressured gas reservoirs) here, combines the mathematical model of gas flow through porous media which is solved on the basis of the fundamentals of natural gas flow, with the material balance principle of overpressured gas reservoirs. Numerical simulation data under various production scenarios and two field cases with variablerate/variable-pressure conditions are used to verify its effectiveness,and generally the calculation error for gas in place is no more than 5% under the condition that production data should be recorded reliably and credibly.VRRLT-APGR method works very well for both gas reservoirs with abnormal high pressure and those with normal pressure in virtue of its strict theoretical basis,which also takes into consideration the changes in flowrate and variations of gas properties as functions of pressure.