海底泵举升系统回流管道内钻井液举升效率

海底泵举升系统是无隔水管钻井液回收(riserless mud recovery,RMR)钻井技术的核心设备,该系统将钻井液和钻屑通过回流管道泵送至钻井平台,能够有效解决深水钻井作业所遇到的泥浆密度窗口过窄的难题,同时能够降低对海洋钻井平台的要求。回流管道作为钻井液和钻屑返出海面的通道,其设计的合理性关系到整个举升系统能否有效运行。结合由钻井液和钻屑组成的混合流体在回流管道内的流动特性,建立回流管道内混合流体流动的控制方程,探究混合流体的流态判别方式,分析回流管道内钻井液举升效率的影响因素。研究成果有望为海底泵举升系统回流管道的设计提供理论依据。

Study on Lifting Efficiency of Drilling Fluid of Submarine Pump Lifting System in Return Line

The subsea pump lifting system is the core equipment of the non-watershed double gradient drilling technology (RMR), which pumps drilling fluid and cuttings through the return pipeline to the drilling platform, which can effectively solve the problem that window of mud density is too narrow in deepwater drilling operations and meanwhile can reduce the requirements for offshore drilling platforms. The system has been successfully applied commercially abroad. The return pipeline serves as a passage for the drilling fluid and cuttings to return to the surface of the sea, which of its rationality designing is related to the effective operation of the entire lifting system. In this paper, by combining the flow characteristics of the mixed fluid composed of drilling fluid and cuttings in the return pipe, the governing equation of the mixed fluid flow in the return pipe is established, the flow state discrimination mode of the mixed fluid is explored, and the drilling fluid in the return pipe is analyzed. The factors affecting the lifting efficiency are expected to provide a theoretical basis for the design of the return pipeline of the subsea pump lift system.