Abstract
In the event of mud complete loss circulation while drilling through fractured Dolomite formation, the economical drilling fluids technique was to continue drilling with lime treated water and pump mud cap in the annuals, although this technique overcomes the need and cost of mixing drilling fluids on fly, but it caused several problems that led to stuck pipe and lose the directional tool / BHA in the hole. The manuscript describes a study performed to analyse the root cause of stuck pipe incident and presents a detailed success case of utilizing customized non-damaging drilling fluids.
While drilling in well BG-1832 located in southeast Kuwait field through fractured Dolomite formation (Shuaiba) a complete lost circulation has been encountered and the decision made to continue drilling with water in inclination of 90 degree. Once total losses occurred the variations between ECD and ESD was very low indicating that annular friction losses below the loss circulation zone was minimal. This support the theory that all the drilled cuttings are properly lifted from bottom and carried to loss circulation zone and not fluctuating above the loss zone. Due to cuttings accumulation and differential pressure it led to stuck pipe and lost the directional tool / BHA in the hole. The well has been side-tracked and non-damaging WBM has been utilized to drill 8 ½″ hole side-track, which improved the holing cleaning and successfully drilled the hole and a achieved the well target successfully as per plan.
The customized non-damaging drilling fluids was designed taking the following objectives in consideration:
Enhanced hole-cleaning efficiency at critical angles
Minimized risk of stuck pipe across depleted formations with high porosity and permeability
Minimal damage to reservoir section during drilling phase
Reduced the drilling hours by improving ROP and minimizing the required time for wash up and ream down prior connections.
Reduced the required mixing time by 70% comparing to conventional non-damaging Calcium Carbonate water base mud.
This paper presents a real case study of applying a customized drilling fluid to reduce the non-productive time by mitigated the risk of stuck pipe and losing expensive tools in the hole. It confirms the theory of the hole cleaning in total lost circulation, and includes a full drilling fluids analysis, hydraulic engineering study, lab test and performance / economical comparison.
