Accumulation of hard scale in the production tubing will not only affect the well accessibility it will also lead to a dramatic decline in production rate and locking the allocated production. Maintaining wells accessibility to wellbore for well intervention operations in order to run logs, water shut-off jobs, well securement operation,…etc. is part of well integrity and performance assurance program. The traditional operation approaches in other areas and reservoirs include isolating the active reservoir prior to operations are not suitable for all cases especially when formation damage is expected to take place. The implementation of underbalance mechanical de-scaling operations using coiled tubing; will lead to restore wells to production faster, regain well productivity and avoids the formation isolation stage.

The candidate oil producer; located in Southern Area of Ghawar Field; had accumulations of hard Iron Sulfide scale inside the tubing at different depths. Acid de-scaling operation using bullheading technique utilizing 20% HCL went vain to restore well accessibility and productivity. Hence, the underbalanced coiled tubing de-scaling operation was successfully executed for the first time ever in an oil well in Saudi Arabia. The operation consisted of two CT runs executed in underbalanced conditions, where the first CT run was with milling tool and second CT run was with jetting tool. It is worth to mention that the well is equipped with two different tubing sizes (6,500′ of 4 ½″ & 300′ of 3 ½″ TBG). This variation on the tubing size resulted in operation optimization as will be illustrated on the paper.

This paper will illustrate the operation in terms of planning, risk assessment, execution, results and well performance prior and after restoring well accessibility and productivity. Moreover, the paper will highlight the optimization done during the field operation execution after obtaining extra information from the first run using milling tool.

This operation has resulted in cost saving of more than $1 MM, 30% production gain and restoration of the well full accessibility.

Keywords:
paraffin remediation, downhole intervention, Hydrate Remediation, scale remediation, hydrate inhibition, production enhancement, Production Chemistry, remediation of hydrates, aquifer water, operation
Subjects:
Production Chemistry, Metallurgy and Biology, Inhibition and remediation of hydrates, scale, paraffin / wax and asphaltene, Completion Installation and Operations, Well Intervention
Copyright 2016, Society of Petroleum Engineers
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