煤层气试井注入压降法模拟实验

 煤层气开发首先需要通过试井分析来反演地层参数,而注入压降法是煤层气开发过程中最常用的试井方法。为进一步扩展注入压降法在煤层气试井中的适用性,尽量在煤层气试井过程中获得更多的地层信息,提高试井解释合格率,通过室内模拟实验的方法研究了注入压降法试井新方法。首先建立了室内模拟实验装置,通过控制注入流量的变化,获得井底压力时程变化曲线,与现场试井得到的井底压力曲线形式一致,证明室内模拟实验能够复现现场试井过程。实验首次提出并采用一次试井过程中多级流量注入的方法,获取井底压力不同阶段的变化曲线,结果表明,多级变流量注入时井底压力增加的幅值与注入流量的增加呈非线性关系。实验模拟过程可控制注入流量,充分反映井底压力变化,以此获得更多的数据资料,为后续试井资料解释提供更充分的信息,以便提高试井解释准确率和合格率。同时还可通过控制和改变地层参数(如渗透性)进行实验,从而在已知地层参数前提下,达到校验试井理论解释模型的合理性和准确性的目的。

Simulated Experiments on the Method of Injection/Falloff Well Testing for Coal Bed Methane

Before carrying on a reasonable exploitation of coal bed methane, it is necessary to take the inverse computation for the parameters of coal bed by well testing analysis. The method of injection/falloff is the most commonly used in coal bed methane well testing. In order to expend the applications of the injection/falloff method in well testing and to gain more information about the coal bed, the injection/falloff well testing process is reconstructed in terms of an experimental system designed in the laboratory. The change of pressure on well bottom is obtained by controlling injection flux. It is indicated that the experimental result is consistent with the in-situ result. The method of multi-level injection is presented in the simulated experimental study to gain more information involving the pressure change on well bottom at different stages. The results show that the pressure on well bottom is nonlinearly increasing with the increase of injection flux. By controlling the injection flux, the simulated experimental process is able to sufficiently response the pressure change on well bottom, and to obtain more digital information about well bottom for further well testing interpretation. In the meanwhile, this kind of experiments could be carried out to verify the rationality and accuracy of the proposed model for theoretical interpretation by controlling and changing the given parameters of well bottom.