Improving Well Productivity and Sustainability in a Horizontal ExploratoryWell by Multistage Fracturing-A Case Study

摘要

Objective/Scope:The main objective is to find a way to increase the well production and sustain theproduction by connecting the reservoir through several stages of fractures spaced throughout the horizontaldrain hole.Method,Procedures,Process:Exploratory wells targeting Mauddud reservoir were normally drilledvertically and stimulated in a conventional way using matrix acid treatment,which proved a goodhydrocarbon potential,but with low productivity.A study was conducted in one the lower cretaceousreservoir(Mauddud)which recommended the option of drilling a horizontal well in the mentioned reservoirand applying multi-stage acid frac for productivity enhancement and sustainability.The target carbonatereservoir is tight,has a porosity of approximately 12-20% and permeability between 0.05 to 2 md.Thefirst horizontal well for Maudddud reservoir was drilled up to a measured depth of 11,171 ft MD with ahorizontal section of 2,752 ft.It was completed with swell packers and seven frac sleeves for multi stagefracturing job in the horizontal section.Designing and execution of multi-stage frac in a horizontal well istechnically more challenging than the conventional vertical well.Minifrac was performed to find the fracture pressure,closure pressure and understand the net pressureneeded to extend the fracture.Based on the mini-frac results,the main frac design was modified.Main Fractreatment was carried out in seven stages,each stage was performed individually and the fractured stage wasisolated using frac balls with different sizes.Acid and gel mixing was performed continuously on locationto enable continuous pumping operation,which minimized the time between stages.After a successfulmultistage frac treatment,the well was flowed back for cleanup and recovered all spent treatment fluid.Later Coiled Tubing(CT)with milling tool was used to mill the ball and seats to provide full bore accessthrough the frac sleeves.Subsequently production logging tool(PLT)survey was carried out in horizontalsection using CT to confirm the effective contribution from each stage.Results,Observations,Conclusions:Horizontal exploratory well was drilled,completed and fracturedsuccessfully with seven stages led to a sustainable oil production after installing ESP.The flow results after the multistage frac showed that there is tremendous increase in production but with some decline.The PLTresult showed the contribution profile for each stage and the cross flow status.Production enhancementand sustainability achieved from this well encouraged KOC to drill more horizontal wells for Mauddudreservoir with similar multistage completion and frac strategy to meet the production targets.Novel/Additive Information:This paper highlights the well design,the effectiveness of multi stagefracturing,well performance analysis,lesson learned and results of the multistage completion & acidfracturing.