Accelerating the Learning Curve: Adapting Global Expertise to Coiled-Tubing Operations in Argentina Shale Development
Abstract: World energy demand has led unconventional reservoirs to become a focal point for operators worldwide. In some regions, including North America, unconventional resources have been developed successfully, accumulating important experience and lessons learned in the process, allowing these resources to become important contributors to countries’ energy production. In an attempt to reproduce this effect in other regions, operators are also looking into important unconventional reservoirs outside North America. Cu… Show more
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Cited by 4 publications
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Vaca Muerta Coiled Tubing Operations Success and the Development of Future Extended Reach Operations
Advanced horizontal drilling, multi-stage hydraulic fracturing techniques and other innovative technologies have helped make the Vaca Muerta shale oil and gas resource economically viable. Well Operators developing this resource are continuously revising drilling programs and well designs to better exploit this valuable resource. One option in this development is to increase the length of the horizontal section of each well to add hydraulic fracture stages. This option can potentially increase production significantly with minimal incremental drilling and completion costs. In response to Operator requests, Service Companies are now seeking improved technologies and equipment to enable them to provide more effective service in extended horizontal well environments. Utilizing refined, custom-engineered Coiled Tubing (CT) string designs to perform certain intervention techniques and procedures appear to be an economic and efficient solution in this shale development phase. Anticipated high-angles in deviated well sections, along with the extended horizontal length of the planned wells formed an expectation that conventional CT designs would not be able to service new well designs. The frictional wall contact force between the coiled tubing and the wellbore, which promotes helical buckling, was greater than the axial compression force limit of the typical coiled tubing designs being used in the area; therefore, a customized taper design was necessary for the expected extended lateral, high pressure wells. An iterative collaboration between the well Operator, CT Service, and CT Manufacturing Companies took place to purpose-build a CT string design with extended reach capabilities while considering logistics and CT equipment available in the area. An extensive CT string design evaluation, which analyzed tubing forces, downhole buckling, and lock-up behavior in different planned wells, was performed to determine the optimum combination of tubing grade, taper design, wall thickness and section lengths to ensure the likelihood of reaching target depths with adequate weight-on-bit (WOB) for milling operations. Bottom Hole Assemblies (BHA), fluids and cleanout efficiencies were also analyzed in this study. The use of a proprietary technology from the CT manufacturer facilitated the required wall thickness transitions to strategically place specific thicknesses along the length of the string to enhance force transmission to the end of the tubing, increase strength and stiffness where needed, and reduce fatigue accumulation, and weight. Field results demonstrated that the use of custom-engineered CT design, extended reach tools and fluid additives, aligned with strict operational practices, has had a great impact on the economics and efficiency of post fracture plug mill-out operations in the Vaca Muerta region. This study documents the improved CT extended reach applications reliability to strategically support this unconventional shale development. Outlined in this study is the evolution of a unique, engineered coiled tubing design, considerations and operation details which helped set and push the limits of extended reach CT interventions, utilizing available CT equipment and technology in the Vaca Muerta shale.
Vaca Muerta Coiled Tubing Operations Success and the Development of Future Extended Reach Operations
Advanced horizontal drilling, multi-stage hydraulic fracturing techniques and other innovative technologies have helped make the Vaca Muerta shale oil and gas resource economically viable. Well Operators developing this resource are continuously revising drilling programs and well designs to better exploit this valuable resource. One option in this development is to increase the length of the horizontal section of each well to add hydraulic fracture stages. This option can potentially increase production significantly with minimal incremental drilling and completion costs. In response to Operator requests, Service Companies are now seeking improved technologies and equipment to enable them to provide more effective service in extended horizontal well environments. Utilizing refined, custom-engineered Coiled Tubing (CT) string designs to perform certain intervention techniques and procedures appear to be an economic and efficient solution in this shale development phase. Anticipated high-angles in deviated well sections, along with the extended horizontal length of the planned wells formed an expectation that conventional CT designs would not be able to service new well designs. The frictional wall contact force between the coiled tubing and the wellbore, which promotes helical buckling, was greater than the axial compression force limit of the typical coiled tubing designs being used in the area; therefore, a customized taper design was necessary for the expected extended lateral, high pressure wells. An iterative collaboration between the well Operator, CT Service, and CT Manufacturing Companies took place to purpose-build a CT string design with extended reach capabilities while considering logistics and CT equipment available in the area. An extensive CT string design evaluation, which analyzed tubing forces, downhole buckling, and lock-up behavior in different planned wells, was performed to determine the optimum combination of tubing grade, taper design, wall thickness and section lengths to ensure the likelihood of reaching target depths with adequate weight-on-bit (WOB) for milling operations. Bottom Hole Assemblies (BHA), fluids and cleanout efficiencies were also analyzed in this study. The use of a proprietary technology from the CT manufacturer facilitated the required wall thickness transitions to strategically place specific thicknesses along the length of the string to enhance force transmission to the end of the tubing, increase strength and stiffness where needed, and reduce fatigue accumulation, and weight. Field results demonstrated that the use of custom-engineered CT design, extended reach tools and fluid additives, aligned with strict operational practices, has had a great impact on the economics and efficiency of post fracture plug mill-out operations in the Vaca Muerta region. This study documents the improved CT extended reach applications reliability to strategically support this unconventional shale development. Outlined in this study is the evolution of a unique, engineered coiled tubing design, considerations and operation details which helped set and push the limits of extended reach CT interventions, utilizing available CT equipment and technology in the Vaca Muerta shale.
The Challenges to Retrieve a Stuck Coiled-Tubing Pipe Without Downhole Check Valves in a High-Pressure Well: A Case Study from Argentina
(300 words) This paper describes the lessons learned during the completion phase of an unconventional well in Argentina. Where a coiled tubing was used to perform a plug drill out campaign. The article describes the procedure of how the CT service provider followed to release a stuck pipe, the well barrier regains and its recovery. The potential solutions were analyzed by the engineering teams from both CT service provider at local and headquarter levels and the local vendors. The fact of cutting the pipe after getting stuck and unsuccessful retrieval attempts result on losing the well control barriers inside the CT pipe. There was a need to regain the well control before proceeding with the retrieval process. The use of a mechanical agents to plug the pipe was assessed, it was considered internal mechanical plugs that due to logistics will result in excessive times. Therefore, the team looked into the chemical solutions, and cement plug was also visualized but discarded due to tendency of laying down in the horizontal section of the wellbore; Finally, a high viscous resin that is fast setting time was evaluated as the optimal solution to set a plug inside the CT, which was the key to success on the safe retrieval operation. The Argentinian well was completed with 57 stages isolated by 56 dissolvable plugs over 3000 m of the horizontal section. After removing all the plugs in the horizontal section down to total depth. CT pipe was being retrieved to surface performing the final wiper trip, when it got stuck. After several unsuccessful release attempts. The decision was to cut the CT pipe at surface to allow the wireline to perform the downhole cutting. Wireline (WL) rigged up on top of the injector head and performed a tubing puncher run, 3 m below the cutting depth. Then, WL perform a second run at the free point, at a depth of 3900 m, deploying a chemical cutter to release the CT pipe. Once the CT pipe was confirmed free, the resin service company, proceed to install their high-pressure lines in the top of the injector head and proceed to pump 6.7 bbls of resin at a pump rate of 1.5 bpm, displacing it with 5 bbls of gel and 30 bbls of water leaving the bottom of the plug 500 m above of the new CT end. After the thickening time, a pressure test of the plug was done up to 8000 psi for 30 minutes followed by an inflow test of 6 hours, after the successful completion of both, the retrieval of the CT pipe was followed. This project describes the design and execution process of pumping a resin plug, without previous experience within our organization at global basis, that is suitable to regain well control on CT pipes that lost the downhole safety valves after being cut due to a stuck condition.
Novel Coiled Tubing Post-Fracturing Cleanout of Unconventional Wells Without Downhole Motor: A Case Study from Argentina
Unconventional wells that are completed with plug-and-perf fracturing techniques require coiled tubing (CT) to mill the plugs. In Argentina, CT must mill upwards of 60 plugs to bring the well into production. The CT downhole motors are leading contributors to service quality incidents because: 1) they mill challenging materials over extended periods of time, and 2) they limit the pump rate, which reduces cleanout effectiveness and increases the risk of stuck pipe. A completion campaign selected soluble plugs instead of composite ones to improve efficiency. Initial CT runs were still completed with a milling bottomhole assembly (BHA) to address the risk of low plug solubility. However, as evidenced during the initial campaign runs, the plugs dissolved nearly completely, leaving only the steel buttons inside the well. Those buttons required a high pump rate to carry them to surface. Given the excellent plug dissolution and the fluid velocity requirement to clean out buttons, the BHA was simplified to an extended reach tool (ERT) and a customized, high-rate jetting nozzle, thus eliminating the downhole motor. The new and simplified BHA extended the pump rate limit from an average of 3.8 to 4.5 bbl/min with no adverse effect on circulating pressure. The operator observed a tenfold increase in the number of plug buttons recovered at surface, which reduced the risk of stuck CT pipe during interventions in those wells. The cleanout speed was also increased, reducing total operating time by 25%, costs, and diesel consumption. A special procedure was developed for the cases when the BHA encountered consolidated sand and plug debris during the operations, a situation that occurred an average of three times per well. To clean those accumulations, the pump rate was increased to generate high jetting energy and stronger ERT agitation, and the CT was run in hole at slow speed until tagging the solids. This procedure allowed passing all the restrictions found during the execution of the CT cleanout jobs. This approach also made it possible to clean wells with known casing deformations, a common situation in Argentina unconventional wells. Over the course of 44 wells, 13 were cleaned with the simplified BHA. This new approach addressed the two main sources of nonproductive time before initiation of the project: BHA failures decreased from 16% to 8% and no CT stuck pipe event occurred. This is the first published case study of a post-fracturing cleanout in an unconventional well without the use of a downhole motor and which, instead, combined soluble plugs and a tailored BHA. Eliminating the downhole motor in this application significantly improved operational reliability and efficiency. The use of this simplified BHA to clean the well down to total depth is only possible with a good dissolution performance of the plugs present in the well.
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