In the last decade, the number of horizontal wells drilled in North America has risen dramatically. As a result, there has been an associated increase in the use of the plug and perforation system and the ball-drop system used to complete these horizontal wells. After the fracturing treatment has been completed, the bridge plugs or ball seats are subsequently milled out via the use of coiled tubing (CT). During the plug or ball-seat milling phase, it is difficult to control weight-on-bit at the end of the CT. If the injector releases too much weight at surface, then the weight-on-bit is too high and the downhole motor can experience a stall. Alternatively, if the injector is not releasing enough weight at surface, then there is insufficient weight-on-bit to mill out the plug or ball-seat. Given that these operations are performed in horizontal wells, it is difficult to predict the optimal weight-on-bit without the presence of real-time downhole measurements. The current data acquisition software used on CT field operations does not analyze or interpret the data - - it only records the measurements. As a result, it is an arduous process to identify trends in pressure, depth or CT string weight changes over an extended period of time. However, analyzing changes in these variables is critical for optimizing the CT milling operation. This paper focuses on an innovative technique for analyzing real-time CT job data that can be used to calculate the required surface weight needed to achieve the optimal weight-on-bit. Furthermore, the technique also enables real -time interpretation of CT job data to confirm that the mill is making the desired progress. This technique has been implemented as a utility within a leading CT modeling software package. This paper will also present field case studies that demonstrate how the new CT interpretation utility software has optimized the milling efficiency in horizontal wells.
The horizontal well count increase during the past decade and associated surge in coiled tubing intervention services has prompted high-paced research into optimization of coiled tubing (CT) milling efficiency. One of the products produced by this research was a new, state-of-the-art, dynamic CT modeling software module that was aimed at increasing CT plug-milling efficiency in extended-reach wells. This dynamic CT modeling software was introduced last year (Yeung, J. et al. 2015) with the expectation that it would deliver numerous benefits to its users. This paper will focus on the subsequent implementation, lessons-learned and benefits associated with use of this new software module. Specifically, this paper will analyze case histories of plug-milling operations that utilized the new dynamic software modeling module versus similar operations performed on offset "control wells" where historical plug-milling techniques were applied. Weight on bit (WOB) measurements recorded by a downhole load cell tool are compared to the WOB values predicted by the dynamic modeling software, so that the predicted WOB values from the software can be analyzed. Following review of the field data from multiple wells, the dynamic modeling software module has proven to significantly enhance the efficiency of CT plug-milling operations. This improvement was a direct result of the CT operator acting on key decision-making data that was provided by the software. In addition, the WOB prediction accuracy of the modeling software was validated against WOB measurements from a downhole tool. During this project it was also observed that proper training and presentation of documented results from use of this new software tool will serve to enhance the adoption rate in the field. Finally, this paper documents the estimated financial benefits that the software can deliver to the bottomline. While introduction of dynamic CT modeling software provided the potential to enhance CT plug-milling efficiency, there was much speculation as to how well it would actually perform in the field and the actual amount of benefits that could be achieved. There was also a concern regarding the amount of time required for field users to become proficient with use of the software module and how quickly field personnel would adopt it. This paper addresses all of these issues.
Coiled tubing (CT) is frequently used in horizontal wells to mill out hydraulic fracturing plugs before bringing new completions online. However, the maximum depth CT may reach while milling plugs can be a major limiting factor for final completion depths. CT reach limits are normally attributed to friction lockup during these milling operations and can reduce effective pay zone penetration if not considered during the well design. In these cases, several common well features typically contribute to the majority of the low force transfer factors leading to insufficient set-down force and helical lockup. This paper will discuss key parameter variations found from a case study of several horizontal well designs, and analyze their impacts on typical coiled tubing reach capabilities using a tubing forces model. Features analyzed include: kick-off build rate, vertical sections and simple deviations down to the heel, trajectory changes in the horizontal section, well completion geometry, and required weight on bit (WOB).• Quantitatively identify well features and possible variations that significantly impact CT reach • Identify limiting factors for these features such as flow requirements during fracturing or production, wellsite location, lease boundaries, TVD of the payzone, etc.
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