“双环三控法”在煤层气井智能排采中的应用

目前煤层气井的排采主要依靠人工调节控制来完成,这使得在产水、产气初期很容易对气井控制不及时,造成应力闭合、煤粉堵塞、地层气锁等伤害,从而影响气井产量。为此,针对煤层气井排水采气周期长、临界解吸压力不易控制、液面波动对气量影响大等排采难点,提出了"双环三控法"排采控制策略。该控制策略以控制动液面为核心,通过对套管压力、流动压力的双闭环控制以及控降液、控流压及控套压等3种控制策略,实现了煤层气井从降液、解吸至产气等不同阶段的智能排采控制。进而基于经典的"双环三控法"控制原理(以变频控制技术为主),采用现代ARM控制技术,研发了一套煤层气井智能排采控制装置,实现了对煤层气井井底流压和井口套压的双闭环控制。在中国石油华北油田公司2×10~8 m~3煤层气产能建设中的应用效果表明,运用该控制系统,排采设备能够在不同的排采阶段自动实现智能调整参数和安全生产,节约了劳动力资源,降低了煤层气井排采成本,使煤层气勘探开发更加智能化、精细化和安全化,具有良好的推广应用价值。

Application of "double-loop three-control" method in the intelligent production of CBM wells

At present, the production of CBM wells is mainly controlled manually. Once gas wells cannot be controlled in time at the initial stage of water and gas production, stress closing, slack coal plugging, formation gas locking and other damages may occur, and consequently, the production of gas wells will be influenced. In this paper, a production control strategy of "double-loop three-control" was worked out to address the challenges, such as long water drainage and gas recovery cycle of CBM wells, difficult control of critical desorption pressure, and great impact of liquid level fluctuation on gas production. This control strategy, with dynamic liquid level control as the core, realized intelligent control on the production of CBM wells at different stages (liquid reduction, desorption and gas production) by way of closed loop controls on both casing pressure and flowing pressure ("double-loop") and controls on liquid reduction, flowing pressure and casing pressure ("three-control"). Based on the theory of "double-loop three-control" (dominated by the frequency conversion control technology), an intelligent production control device was developed for CBM wells by using modern ARM control technologies. With the device, double closed loop control could be realized on bottom hole flowing pressure and wellhead casing pressure of CBM wells. This method was applied to the 2×10⁸ m³ CBM productivity construction project of PetroChina Huabei Oilfield Company. With this control system, production equipments can realize intelligent adjustment of parameters and safe operation at each production stage, with lower labor cost and production cost. Moreover, this system makes CBM exploration and development more intelligent, more accurate and safer. Therefore, it presents a better prospect of application and dissemination.