页岩气井投产初期单井最终可采量计算方法——以四川盆地CN气田为例

EUR evaluation method for producing shale gas wells in early stages:Case study of CN Gas Field in the Sichuan Basin

随着国内外页岩气的规模开发,越来越多的页岩气储量资产走向国际资本市场,气井最终可采量(EUR)的计算成为热点,但仅凭气井投产初期有限生产资料难以判断储层压裂改造效果,导致气井EUR计算误差大,无法判断勘探开发投资效益。为此,建立“校正气井产量百分位典型曲线预测法”,即运用流动形态法筛选井区内处于生产中后期气井作为样本井,根据样本井历史产量与EUR分布建立校正的产量百分位典型曲线,以此曲线实现井区内投产初期气井EUR的准确计算。研究结果表明:①运用流动形态诊断方法定量确定生产阶段,能够显著提高生产中后期气井EUR计算精度;②校正的产量百分位典型曲线能够代表井区气井的产量发展趋势,能显著提高投产初期气井EUR计算精度。因此,“类比”为页岩气投产初期EUR计算方法的关键,其能够定量确定井区内气井生产阶段,并通过“EUR百分位图版”与“产量百分位典型曲线”将生产中后期气井的生产规律合理类比应用于投产初期气井EUR的计算,方法可靠度高。研究提出的基于EUR百分位图版与产量百分位典型曲线的气井投产初期EUR计算方法,填补了这一领域技术空白。

With the large-scale development of shale gas at home and abroad,more and more shale gas reserve assets are entering the international capital market,the calculation of gas well EUR has become a hot spot.However,it is difficult to judge the effect of reservoir fracturing only based on the limited production data at the initial stage of gas well production,resulting in large calculation error of gas well EUR and unable to judge the investment benefit of exploration and development.To this end,a“corrected gas well production percentile typical curve prediction method”is established,which uses the flow morphology method to screen gas wells in the middle and late stages of production in the well area as sample wells.Based on the historical production and EUR distribution of the sample wells,a corrected production percentile typical curve is established,and this curve is used to accurately calculate the EUR of gas wells in the early stages of production in the well area.The research results indicate that:(1)Using flow morphology diagnosis method to quantitatively determine the production stage can significantly improve the accuracy of EUR calculation for gas wells in the middle and later stages of production;(2)the corrected production percentile typical curve can represent the production development trend of gas wells in the well area,and can significantly improve the accuracy of EUR calculation for gas wells in the early stages of production.Therefore,the key technology for calculating the EUR of shale gas production in the early stage is“analogy”,which can quantitatively determine the production stage of gas wells in the well area.Through the“EUR percentile map”and the“typical production percentile curve”,the production laws of gas wells in the middle and later stages of production can be reasonably analogized and applied to the calculation of the EUR of gas wells in the early stage of production.The method has high reliability.The innovation of this study lies in the first proposal of a EUR calculation method based on the EUR percentile map and typical production percentile curves for gas wells during the early production stage,filling the technical gap in this field.