Evolution and Improvement of Coiled Tubing Interventions Across anUnconventional Project in Saudi Arabia

摘要

The procedural development implemented across an unconventional project in Middle East is explored,delving deeper into coiled-tubing(CT)design,from metallurgical properties and string specification tobottomhole assembly(BHA)and fluid selection,tailored to plug-and-perf operations involving the use ofa specialized frac plug.Further discussed is the"learning curve"generated,highlighting improvementsachieved across the"iron triangle"of operating time,cost,and quality,referring to case studies ofinterventions conducted across multiple horizontal wells.Unconventional CT interventions have always been challenged by an operator's quest to drill the longestpossible lateral to maximize per-well estimated ultimate recovery(EUR)by maximizing the number offractured clusters/stages.CT job designs across these projects usually rely on running the biggest outerdiameter(OD)CT with the largest hydraulic downhole motors available to enable the deepest reach,highestweight on bit(WOB),torque,and circulation rate.However,this conservative approach causes operationsto be overdesigned,ultimately resulting in excessive operational cost and nonproductive time.As observedfrom this experience,an engineered process enables an operator to select the correct resources to meet theoperational objectives.A successful multiwell campaign of prefrac-drift,wellbore fluid displacement,cement sheath cleanout,followed by tubing-conveyed perforation(TCP)and post-frac 32–44 plug millout was performed acrosshigh-pressure/high-temperature(HP/HT),sour,unconventional wells in Middle East.After respectiveCT interventions,the wells were successfully fractured and flowed back.Based on lessons learned andvarious corrective action items implemented,service efficiency(single run)and job time(+50% reduction)were substantially improved.This enhancement was mainly attributed to the revised surface piping andinstrumentation(P&I)rigup,CT material and dimension selection,BHA components,including custom-built mill/motor and extended-reach vibrating tool,gel and friction reducer fluid placement,reduced wipertrip frequency,etc.These optimized CT interventions created a more balanced approach to unconventional operations,wherein bigger is not always better.The CT procedure evolved,initially referencing best practices fromanalogue unconventional plays,while slowly progressing into a tailored fit-for-purpose operation.Thisapproach enabled the operator to achieve operational objectives more efficiently.