基于物质平衡方程的页岩气井产能预测方法

页岩气井产能受地质和压裂改造参数综合影响,在开发初期,难以确定可靠的地质模型来预测气井产能。为了快速、准确地预测气井产能,在研究页岩气物质平衡方程和产能方程的基础上,考虑吸附气和异常高压气藏岩石弹性能量影响,建立了基于物质平衡方程的页岩气井产能预测方法,该方法需要参数较少,可在开发初期快速对页岩气井产能进行预测。涪陵地区X1井实例计算表明:该方法综合考虑了页岩气吸附气解吸、异常高压气藏岩石弹性能量的影响,产能预测结果准确、可靠;吸附气对气井累产气量影响明显,约占总累产气量17%,对定产生产气井的稳产期影响不大;吸附气的贡献在2.5~4年逐渐体现出来,定压放喷生产初期产量高,地层压力下降快,吸附气的产出贡献比控制产量的定产生产方式要早;考虑岩石弹性能量的影响,气井稳产时间和累产气有所增加,但影响不明显。

Productivity prediction method of shale gas well based on Material balance equation

The productivity of shale gas well is influenced by geological and fracturing parameters. It is difficult to predict the gas well productivity through the reliable geological model in the early period of development. Based on shale gas material balance equation and productivity equation, a fast productivity prediction method considering the impact of adsorbed gas and rock elastic energy for shale gas well is established, this method needs less parameters, it can be used to predict the productivity of shale gas wells at the early stage of development. The calculation example of X1 well in Fuling area shows that the productivity prediction results calculated by the method considering the impact of adsorbed gas and rock elastic energy are accurate and reliable. The adsorbed gas has obvious influence on the accumulated gas production, the adsorbed gas accounted for about 17% of the total accumulated gas production, the adsorbed gas has little influence on the stable production time of the shale gas well with fixed production; the contribution of adsorbed gas will gradually reflect in 2.5 to 4 years, the production rate of shale gas well with fixed pressure is high in the early period, and the formation pressure decreases quickly, so the contribution of adsorbed gas reflects earlier. Considering the influence of elastic energy of rock, the stable production time and accumulated gas of gas well increase, but the influence is not obvious.