沙特致密气藏水平井完井管柱下入难点与对策

Difficulties and Countermeasures of Deploying Completion String in Horizontal Well of Tight Gas Reservoirs in Saudi Arabia

近年来,在沙特阿拉伯,由于水平井的钻探,使产层的泄油面积明显增加,一些油气田的产量也在增长。在完井作业中,需要下入多级增产系统(MSS)完井管柱,但在致密气藏深水平井中,出现下入困难甚至管柱被卡现象。分析认为,井眼的完成、不同压力体系的多套地层、井眼的准备以及下入的技术和程序等因素,是影响管柱组合顺利下入的关键。实践证明,对于存在多套低压层的井眼,钻井设计时,技术套管应尽可能深下,封住上部低压非生产层,最好将套管鞋坐封在生产层内。应在井眼安全的情况下,将钻井液密度调低,以减轻低压层的过平衡压力;一旦发生黏卡,缓慢降低钻井液密度,并小幅活动管串,是解卡的唯一途径。在可能存在台阶的水平井段,用模拟完井管串结构的钻具组合(BHA)通井,可以消除机械卡钻风险,为大尺寸尾管顺利下入创造条件。

In recent years,the drilling of horizontal wells has enabled significant increases in drainage areas of the productive zone,and it has resulted in production increases in some oil and gas fields in Saudi Arabia.A special completion string named Multistage Stimulation Systems(MSS) is required to be run in hole during well completion.But the deployment of these assemblies into deep and long reach horizontal wells was initially problematic,such as string got obstructed and even stuck.Construction of the wellbore,deploying through multiple layers with various reservoir pressures,preparation of the wellbore before running the string,and techniques and procedures of running in hole are the key of affecting successful running of the string assemblies.Field practice has proved that intermediate string should run deep as far as possible when drilling design in the hole among multi-set low-pressure strata so as to seal upper low-pressure nonproductive formations and to set down casing shoe into productive zones.Under the condition of wellbore safety,density of the drilling fluid may be low for making overbalance pressure of the weak zones lower.Once sticking,the density of the drilling fluid should be dropped slowly and string may be moved at small range.At the horizontal hole section with steps probably,BHA simulated completion string structure may be applied to run gauge cutter with the result of removing mechanical drilling pipe sticking,which will provide condition for successful running of large-size tail pipe.