大型致密砂岩气藏水平井产能评价与新认识

Productivity evaluation and new understanding for horizontal well of large scale tight sandstone gas

压裂水平井技术是开发致密砂岩气藏的有效手段,已经在苏里格气田取得了良好应用效果,但存在生产规律认识不清、产能评价困难、生产工作制度不合理等问题,影响了水平井部署和生产管理。为此,深入研究了苏里格气田地质和水平井生产特征,评价了水平井产能并形成了新的认识,建立了考虑长期稳产的水平井合理产量确定方法。研究结果表明,苏里格气田历年投产水平井初期递减率很高,中后期递减率变低,符合衰竭式递减规律,且新完钻井的初期递减率逐年增大;水平井日均产量与无阻流量呈幂函数关系、与单井控制储量呈线性关系;提出了用单井控制储量指导压裂水平井合理配产的经验方法,以实现单井长期稳产。研究结果对致密气藏产能建设有积极意义。

Fractured horizontal well technology is an effective means to develop tight sandstone gas reservoirs.While horizontal wells development have achieved excellent performance in Sulige Gasfield,there are practical problems including difficulty in production characteristics,productivity evaluation and unreasonable production system,which influence horizontal well deployment and production management.For this,the gas field geology and horizontal well production characteristics were studied firstly.Then,productivity of horizontal wells was evaluated.Finally,reasonable production rate of horizontal wells considering longterm stable production is established.Results show that the initial decline rate of the horizontal wells in the Sulige Gasfield is very high in the different years,the decline rate in the middle and late stage is low,and the decline rate in the early stage of the new drilling increases year by year.The production of single well decreases rapidly in the early stage and gradually slows down in the middle and late stages,which is in line with the decrement law of exhaustion.The relationship of reasonable horizontal well production and absolute open flow rate is power function.Reasonable production proration gradually decreases with the increase of absolute open flow.The relationship of reasonable horizontal well production and well-controlled reserves is linear relation.It is the first time that single well controlled reserves are used to guide the rational distribution of fractured horizontal wells in order to achieve long-term stable production of single well.The research results have positive significance on the production of tight gas reservoirs.