气藏动态优化配产方法研究和应用

An Approach for Dynamic Production Optimization in Gas Reservoirs

针对气田生产中存在的配产不合理,造成稳产期短,最终采收率低,经济效益低等一系列问题,提出了一套动态优化配产方法。该方法对气藏—井筒—地面集输整个生产系统进行模拟,可以考虑气井积液、携液能力、冲蚀等流动限制,即单井产气量上下限的限制,及处理站的日处理水量能力,日净化气能力限制,以采收率最高或经济效益最大化为目标,建立优化数学模型,并考虑到气藏压力随着累产气量的增加发生变化,建立一段时间内的配产模型。该问题为含有等式及不等式约束的非线性优化问题,目前没有固定算法求解非线性优化问题,针对该优化问题,采用可变容差法求解,逐步加强近乎可行性的限制,直到可行性被接受为止,最终实现模型求解,将下游用气需求合理分配到各气井。使用该方法对实际气田生产进行了配产和预测,验证了方法的可行性。该方法综合考虑流体在气藏、井筒、地面的流动,考虑气藏条件变化对配产的影响,所获得的配产量是整个系统的最优产量。

In a gasfield, many problems may often occur during a production, for example, unreasonable production, short period of stable production, and low ultimate recovery ratio and economic benefits. So, an approach for dynamic production optimization is presented. This approach just simulates the whole system from gas reservoir to wellbore further to surface gathering, and takes some factors into consideration, such as liquid loading, liquid- carrying capacity, erosion, and the upper and lower limit of gas production for individual well; and the limit of both daily water treatment capacity and daily purified-gas capacity for treatment stations. Furthermore, aiming to realize the highest recovery ratio and the largest economic benefit, it establishes an optimal mathematic model in which takes one situation that reservoir pressure changes with an increase of cumulative gas production into consideration. At present, a method called flexible tolerance is used to solve nonlinear optimization and can realize that the gas demand from downstream users will be reasonably assigned to different gas wells. This dynamic production optimization approach has been applied to field production and forecast.