利用气井测试资料建立湍流系数的新公式

气井的高速湍流系数β是确定非达西流动常数D和附加湍流表皮因子St的重要参数。对于一口新的气井,在稳定生产条件下,根据关井测试压力恢复曲线,可以利用Horner法确定气层有效渗透率K和视表皮因子Sa。视表皮因子由完井表皮因子Sc和湍流表皮因子St两部分组成,即Sa=Sc＋St,只有先确定了St,才能确定Sc的数值,并用于判断实施增产措施的必要性。由于St=Dqg,因而,需要寻找确定D值的方法。然而,迄今为止,在利用单点测试资料确定D值时,均采用地面实验室一维岩心多点测试资料求得的β值和K值所建立的相关经验公式。该相关公式用于气井不稳定测试,确定D和St的数值,显然是不合理的。利用气井多点测试资料,由二项式求得β值和关井后由压力恢复曲线求得K值,建立β与K的相关经验公式,可用于确定D和St的数值。实例应用表明,该方法是有效的。

A new formula for establishing turbulence coefficient from testing data of gas wells

High velocity turbulence coefficient β in gas well is a very important parameter to determine non Darcy flow constant D and additional turbulence skin factor St.For a new gas well,the effective permeability K and apparent skin factor Sa can be calculated by Horner method of buildup curve.Apparent skin factor consists of completion skin factor Sc and turbulence skin factor St,that is Sa=Sc＋St,and value Sc can only be determined after the value St is determined firstly so as to judge the necessity of stimulation.Because St=Dqg,the method to determine value D should be needed.However,the related empirical formula of value β and value K are all obtained by multi-point testing data of one-dimension cores in the laboratory on the ground,and then value D is determined by single-point testing data combined the correlation with unstable testing data.There is obviously error in this method.A new correlation of β and K is established in this paper to determine value D and St,in which value β is calculated by binomial and value K is followed by pressure buildup curve based on multi-point testing data of gas wells.The application example shows that this method is effective.