This paper will present a Coiled Tubing (CT) technology that can be used to maneuver severely washed-out open hole sections. The presence of open hole washouts is known to restrict access to pay zones during reservoir monitoring or other well intervention operations. The case study of the paper is a water injector completed with a 6-in. open hole across the pay zone. The lithology of the first 30 ft of the open hole section contains anhydrite. Due to prolonged exposure to injection water, leaching of the anhydrite layers took place. This has led to the creation of washout. The washout has been confirmed to be present below the casing shoe by analysis of a caliper log.
A prior attempt to access the open hole with CT was not successful. Accordingly, several Bottom Hole Assembly (BHA) designs were thoroughly examined to determine the appropriate CT deployment tool and carry out a planned acidizing work on the water injector well. The contemplated BHA designs were initially planned to include conventional well intervention tools or a combination of these tools such as knuckle joints, straight bars, and a hydraulic centralizer. However, these tools were ruled out due to their previous failure to access the wellbore in the case study well (knuckle joints and straight bars) or the risk of CT being stuck in the open hole (hydraulic centralizer).
After a careful consideration of all relevant parameters to the acidizing work, an open hole washout maneuvering technology was deployed. The CT conveyed technology consisted of a torque through knuckle joint, mechanical rotating tool and a bended sub. The deployment of this innovative technology was successful in passing the abovementioned washout. The CT successfully reached the well total depth and the benefits of this technology were fully realized as the open hole section of the reservoir was entirely exposed to the acid treatment
