具有补给的气藏物质平衡方程及动态预测

A balance equation of gas materials with recharge capacity and their performance prediction

传统的物质平衡方法将整个气藏当作一个容器,忽略了地层的非均质性以及渗流阻力,在使用二项式产能方程和物质平衡方程对非均质低渗透气藏进行早期动态预测时,指标总是偏向乐观。针对该问题,假设气藏被一低渗透条带分为两个相互联系的相对均质区块,根据质量守恒原理,利用半透壁模型建立了具有补给的非均质气藏物质平衡方程及动态预测理论模型。该模型不但考虑了气田区域性非均质变化因素以及流动阻力,使物质平衡模型更加接近实际,又可简单快捷地预测气井动态变化趋势,揭示了两区内压力、产量随时间变化规律。实例计算结果表明:该模型能够改善早期动态预测结果,各项指标接近生产实际。

The traditional method of material balance takes a gas reservoir as a container,while the heterogeneity and seepage flow resistance of strata are commonly neglected.Therefore,the results generally tend to be optimistic when the binomial deliverability and material balance equations are employed to predict the early performance of heterogeneous low-permeability gas reservoirs.Aiming at solving this issue,we assumed that a gas reservoir could be divided into two interconnected and relatively homogeneous blocks by a low-permeability zone.According to the mass conservation law,a balance equation of gas materials with recharge capacity and a dynamic prediction model for their performance were established using the semi-permeable wall model.The proposed model has considered the regional heterogeneity and flow resistance of gas reservoirs,making the material balance model much closer to practical cases and capable of easily and quickly predicting a trend of dynamic variations in gas wells.In addition,varying rules of pressure-time and rate-time relationships in these two blocks could be revealed in this model.Data calculated from real cases indicated that the proposed model could improve the prediction result of the early performance and various indicators derived from the model were close to the production practice.Therefore,this study is of instructive significance in rational and effective development of similar gas reservoirs.