As more and more longer extended reach (ER) wells are being drilled in the middle east, coiled tubing (CT) interventions are becoming a predominant challenge in terms of reaching total depth (TD). A major requirement for the operators is that CT reaches TD cost effectively to perform stimulation or any mechanical intervention. This paper discusses case histories for two extended reach wells where a 2-inch CT achieved 100% accessibility with the use of special CT lubricant.
There are many methods to enhance CT reach, but the simplest and most cost-effective method is the use of metal friction reducing lubricants. The methodology of using the lubricant is either based on filling the entire well with the lubricant solution during run-in hole or selective placement in specific intervals. Selective placement of lubricant is further cost efficient but can be compromising if the target depth is not reached during the actual job. However, by performing pre-job tubing force analysis and modelling various scenarios, it is possible to optimize the volume of lubricants required with minimized risk on the outcome.
In the first case history, full use of lubricant was applied from the beginning of CT run to successfully access TD in one of the longest well of the field with a TD in excess of 24,000 ft. and lateral length 14,000 ft. Pre-job modelling performed with offset data in similar completions predicted an early friction lock. After the first run, lubricant solution placement was optimized by conducting a thorough tubing force analysis (TFA) that helped understand friction profiles and helical pitch development determining the optimum intervals for pumping lubricants. Post job force match showed that the lubricant reduced the effective coefficient of friction (COF) by more than 30%. In the second case history, CT was able to reach TD of around 27,100 ft after lubricant placement was optimized and it reduced the COF by up to 50% from assumed base case.
The case histories presented in this paper demonstrate the benefits of using the special CT lubricant in reducing CoF and enhancing accessibility for CT in ER wells. It also discusses a methodology to optimize lubricant placement in ER wells with help of pre-job modelling on a proprietary CT simulator.