DAK method for natural gas Z-factor calculation can yield relatively more accurate result compared with other methods and therefore is widely used in the petroleum industry.However,our analysis shows that the method generates results with large errors when both pressure and temperature are high.The paper presents a modification of the method based on optimization.Also presented here is an analysis of the relative errors of the calculation results on a two-dimensional plane consisting of isobars and isotherms.The results indicate that, compared with the original DAK method,the revised method can further improve the accuracy of Z-factor for natural gas.%天然气偏差因子计算的DAK法是较为精确的方法之一,目前在油气工业界广泛应用.研究认为,当压力和温度均较高时,DAK法计算结果误差仍较大,依然存在进一步提高计算精度的空间.基于最优化方法,对计算天然气偏差因子的DAK方法进行了修正,并在等压线和等温线构成的二维平面上对计算结果的相对误差作了分析.结果表明,修正后的DAK法与原DAK方法相比,进一步改善了天然气偏差因子的计算精度.
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