页岩气产量递减典型曲线中关键参数的确定方法

Methods to Determine the Key Parameters of Typical Production Decline Curves of Shale Gas Reservoirs

为减小页岩气产量递减预测的不确定性,分析了典型曲线应用中一些重要参数的确定方法。研究表明:在对典型曲线进行预测时,建议采用日生产历史数据为基础;求取初始月产量时,以初期产气量中最大值为基点,依次选取比其略小的29个点,然后对该30个值进行求和作为初始月产量;对于有关井状态的井,应忽略关井时间段,将再次开井的时间点前移至关井时间点,以此确定的典型曲线无需再考虑生产时率的影响。

In order to reduce the uncertainty of the prediction of shale gas production decline,the methods to determine some key parameters in the application of typical curves are analyzed.The study shows that it is suggested that daily production history data should be taken as a basis in predicting typical curves;the maximum value of initial production should be taken as a basic point in finding initial monthly production,29 points are in proper order selected which are slightly less than the basic point,and then the 30 values are summed and the summation is regarded as initial monthly production;for the wells which were ever shut in,the period when the wells were shut in is neglected,the time when the well is restarted is move backward to the time when the well was shut in,and thus the typical curves determined by this method doesn't necessarily consider the influence of production time rate.The type of production decline is an important part for shale gas play.However,such factors as workover,clean-up can lead to the complex production behavior which will cause some uncertainty for analyzing the type curve.In this paper,some methods are proposed and compared to determine the keys parameters during forecasting type curve of production decline.Analyses show that the method based on the daily data is more accurate than that based on the monthly data.The best method to evaluate the initial month production among three proposed methods is to select the maximum daily production and 29 daily production data that is just less than the maximum data from the initial production data.The initial month production is the summation of the 30 daily production data.For the production data including the shut in,the shut in period should be deleted and connected with the production data to keep the time be continuous.Based on the revised data,the type curve can be forecasted without considering the production rate.