套管阀关阀井下压力动态演变规律的研究

Dynamic evolution of pressure below downhole-deployment-valve

套管阀是实现全过程欠平衡钻井最为简捷、安全的技术之一,但其面临很难预测和控制关阀后井下动态压力的问题,因此常常在关阀后阀下压力急剧上升,导致无法正常开阀。造成这一客观事实的主要原因是单向封闭管流的特殊多相流动的特征参数预测模型与求解方法的不完善。因此,本文在分析套管阀使用流程的基础上,根据不同的地层介质建立了井下气液两相流动数学模型并采用数值方法得出了规律性的认识。通过数值模拟发现:孔隙性地层在较大的初始欠压值条件下,井下与地层压力平衡时间较短,套管阀下气柱压力更大;而对于裂缝性地层,因不断有钻井液向地层漏失,其地层压力平衡时间较孔隙性地层也更长。针对不同地层在条件,在使用套管阀时需严格控制起下钻作业时间(即井底压力与地层压力的平衡时间),以免由于阀下压力过大造成钻后无法正常打开套管阀。本文研究对于指导套管阀施工作业以及完善全过程欠平衡钻井流动理论均具有积极的意义。

DDV is one of the whole process underbalanced drilling simple,safe technologies.It faces the problem that downhole dynamic pressure prediction and control.Sin the pressure often rises sharply in off valve after the valve,leading to that the drill can not normally open valve.The main reason for the fact is for a one-way closed pipe flow,the special multiphase flow prediction model based on the characteristic parameters and the solution method are imperfect.Therefore,based on the analysis of DDV,the underground gas-liquid two-phase flow mathematical model is established,numerical method is adopted to come to the understanding of the laws.It is found by numerical simulation that: the larger the porous strata initial conditions of downhole pressure are,the shorter the equilibrium formation time is,and the larger the the column pressure in the DDV is;For fractured strata,as the drilling fluid constantly flow to the leakage,the equilibrium formation time is also longer than the porous strata.The results are references for sleeve valve construction operations and may improve the whole process underbalanced drilling flow theory of positive significance.