摘要
针对水平段长度超过2 000m的深层长裸眼水平段超深井,因投产周期长、管柱结构复杂而对井壁稳定要求很高的特点,进行了完井液密度对井壁稳定性方面重要性的研究.为了保证井壁稳定性,通过数值建模、Drucker-Prager强度破坏及有效塑性应变井壁失稳判断准则,来模拟分析不同生产差压对有、无裂缝情况下井眼稳定性的影响,形成了一套保证井壁稳定的完井液密度确定方法.研究结果表明:①在无考虑裂缝的情况下,沿水平井最大主应力方向的水平井稳定最好及随井斜角的增大,井眼的稳定性逐渐增强;②在考虑裂缝的情况下,沿水平最大主应力方向、倾角为90°的裂缝发育时,水平井最稳定,随裂缝走向由水平最小主应力方向变化为水平最大主应力方位时,水平井的井眼稳定性依次变好,随裂缝倾角增大,水平井稳定逐渐增强.
Abstract
Completion-fluid density is essential for borehole stability in deep marine openhole horizontal wells with the horizontal length over 2,000 m due to long cycle time and complex string structure highly needed for the stability whose re-lation to both trajectory azimuth and borehole inclination should be taken into account.Therefore,the influence of produc-ing pressure differences on the stability was analyzed for those wells with or without fractures through numerical simulation and two Drucker-Prager criteria to estimate both strength failure and effective plastic strain.In addition,one method for density evaluation was created for stability assurance.Results show that(i)there exists the best stability in some horizontal wells without fractures along the direction of maximum principal stress,and this stability is increased with the increased in-clination;and(ⅱ)there exists the most stable wells in the others with fractures whose dip of 90° goes the maximum princi-pal stress.The fracture strike that moves to the direction of the stress from that of minimum stress makes the stability somehow better.And this borehole stability grows with the increased dip.In fact,this method has been applied to Pz3-4D well successfully to verifying simulation ending,which may provide a novel solution for stability improvement in deep open-hole horizontal wells.
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