Summary In Ecuador, shutoff of an underperforming interval through plug and abandonment (P&A) and perforation of a new interval are traditionally completed with a combination of wireline (WL) and tubing conveyance. An alternative method using enhanced coiled tubing (CT) is presented here; it enables a rigless and efficient workflow that leverages real-time downhole data for on-the-fly optimization. The new workflow relies on CT-conveyed technologies without requiring any additional conveyance methods. CT delivered four different services to start the abandonment by anchoring a 7-in. cast-iron bridge plug (CIBP), complete the abandonment with a low-viscosity cement plug, simulate wellbore dynamics during nitrogen pumping to generate the required underbalanced conditions for perforating, and perforate with a 40-ft ballistic payload of 4 1/2-in. guns. Coupled with real-time downhole telemetry, the enhanced CT workflow provided critical downhole conditions, including fluid levels, accurate depth placement and control, bridge plug setting confirmation, underbalanced conditions, perforating head activation and detonation, and postperforation inflow monitoring. Compared with traditional methods, the enhanced CT workflow introduces several benefits toward completing P&A of old intervals and perforation of new ones. These benefits include enabling a rigless workover (WO) intervention, eliminating the need and cost of a WO rig, reducing operational duration by 13%, and potentially reducing asset footprint and field crews by 95 and 70%, respectively. Elimination of a WO rig reduces environmental impact and the number of personnel on location (i.e., risk). The workflow also extends the reach and efficiency of the service in horizontal wells, enables underbalanced perforation, and delivers actionable real-time downhole data. These data elevate traditional P&A workflows and create a step change in efficiency. First, they allow tracking key downhole parameters that help guarantee a reliable operation of each of the tools and services. Second, they provide insights into the actual downhole conditions throughout the intervention to enable the operator and the field crews to make on-the-fly decisions to deliver a safe and optimal service. Those decisions may include fine-tuning the prescribed treatment or extending the scope of the intervention by leveraging the CT’s pump-through capabilities to maximize well performance and meet, or exceed, the operator’s objectives. The innovative combination of real-time telemetry with abandonment and perforating technologies proved a step change in operational efficiency and range, fueled by the quantity and quality of data recorded during the operation. This case study also marks the first documented perforation with 4 1/2-in. guns with fiber-optic real-time downhole telemetry. Furthermore, the integrated, rigless solution provides operators with an opportunity to extend their WO activity pipeline and free up their WO fleet for other activities.
Stuck coiled tubing (CT) is a main operational risk leading to delays, deferred production, or even loss of a well. Despite general commonalities, each CT recovery can face unique challenges including managing high pressure, working under limited spatial or lifting constraints, establishing well control, or handling a cable inside the CT. This study consolidates learnings and proposes a general workflow for a basic stuck pipe scenario, rig-up, recovery pressure control equipment and well control, CT free point evaluation, bottomhole assemblies (BHAs) and workflows for cutting and freeing the CT pipe downhole, and recovery of the CT at surface. A consolidation of published case studies provides specific examples of the hardware, workflows, and operational considerations. In addition, presentation of a recent case study extends the discussion to the challenges introduced by the presence of a cable in the stuck CT and its respective solution. This case study reviews the planning and execution of a CT recovery, including the use of decision trees to guide the decision-making process. It details fit-for-purpose hardware for safely anchoring the cable; packoffs for accessing, tensioning, and recovering it with slickline; an opening for deploying the wireline cutting BHA; and valves for pressure testing and well control. That workflow successfully freed 6,818 ft of stuck CT and allowed recovering the pipe without a workover rig on location, eliminating 11 days of rig time during subsequent tubing pulling. This is the first documented such recovery case worldwide based on a thorough literature review.
Summary Stuck coiled tubing (CT) is a main operational risk leading to delays, deferred production, or even the loss of a well. Despite general commonalities, each CT recovery can face unique challenges, including managing high pressure, working under limited spatial or lifting constraints, establishing well control, or handling a cable inside the CT. This study consolidates learnings and proposes a general workflow for a basic stuck pipe scenario, rig up, recovery pressure control equipment (RPCE) and well control, CT free point evaluation, bottomhole assemblies (BHAs) and workflows for cutting and freeing the CT pipe downhole, and recovery of the CT at the surface. A consolidation of published case studies provides specific examples of the hardware, workflows, and operational considerations. In addition, the presentation of a recent case study extends the discussion to the challenges introduced by the presence of a cable in the stuck CT and its respective solution. The case study reviews the planning and execution of a CT recovery, including the use of decision trees to guide the decision-making process. It details fit-for-purpose hardware for safely anchoring the cable; packoffs for accessing, tensioning, and recovering it with slickline (SLK); an opening for deploying the wireline (WL) cutting BHA; and valves for pressure testing and well control. That workflow successfully freed 6,818 ft of stuck CT and allowed recovery of the pipe without a workover rig on location, eliminating 11 days of rig time during subsequent tubing pulling. This is the first such documented recovery case worldwide based on a thorough literature review.
A new solution to reservoir saturation logging in highly deviated and horizontal wells leverages a light system using coiled tubing (CT) equipped with fiber optics to overcome reach limitations and provide real-time acquisition of downhole reservoir information. The advantages of the methodology in terms of technical capabilities and efficiency have been demonstrated in wells in Mexico where acquisition of once-inaccessible logging information opened new avenues in the production management of the area. The conveyance of logging tools via wireline cable or wired CT presents significant reach and pumping limitations in highly deviated or horizontal wells. The combination of a recent downhole module development and the use of lighter CT package equipped with fiber optics addresses these conveyance and operating challenges. The optical telemetry link supports real-time logging without the need for wireline surface equipment, and the new downhole module provides power to a wide range of logging tools, including the power-demanding reservoir saturation tools. The lighter system overcomes weight limitations, and logging can be performed in any type of well profile. The new module significantly increases the voltage output from the downhole source to the logging toolstring, thus enabling the use of power-demanding components that were previously unusable with CT systems. It also extends the downhole operating logging time for traditional production logging tools by up to six times over that of previous methods. As the production of mature fields in Southern Mexico is gradually decreasing and water has become an increasing issue, operators in the area are currently performing major workover operations to rejuvenate the fields. This novel approach enabled acquisition of reservoir saturation data in several wells in which this information could not be acquired previously because of reach limitations. The newly acquired data enabled identification of bypassed hydrocarbons in those wells. With this information, the operator could selectively shut off the water-producing zones while opening new hydrocarbon-bearing ones, thus significantly reducing water production and prolonging the life of the wells. The introduction of the innovative methodology not only significantly broadens the range of logging interventions that can be performed, it also enables accessing reservoir data that, in some cases, have been inaccessible for a long time, and which can be key to the optimization of production management of entire fields.
Coiled tubing (CT) milling of downhole plugs in large monobore completions is considered one of the most challenging CT workover operations, especially when conducted in offshore environments where intervention workflows are driven by efficiency gains for operators and service companies alike. Experience gained from milling operations using CT instrumented with real-time data enabled measurable improvements in efficiency. Post-job data analysis offered additional insights to improve methodologies and further unleash untapped efficiencies. Real-time bottomhole assembly data were collected during plug milling operations using a positive displacement motor. Critical downhole readings, such as CT internal and annular pressure, axial force (thrust), and torque were monitored during the operation to identify tagging of isolation plug targets, onset of milling, and stalls. The real-time data not only added confidence to event confirmation, but also increased the accuracy in estimating efficiency metrics such as rate of penetration (ROP) and stall recovery duration. Post-job analysis calculated the error and shortcomings associated with estimating event detection based on surface measurements. Additionally, error in event detection was tied back to inaccuracies in estimating efficiency metrics when relying on surface measurements alone. Analysis of downhole measurements in CT milling improves the precision of event detection and enables rapid reactions. Target tagging reflects instantly in thrust, and motor activation reflects synchronously in downhole differential pressures and torque, which together provide certainty of motor engagement on the target. Stalls reflect in differential pressure and torque spikes that coincide with motor specifications. ROP more than doubled by leveraging these event detection techniques throughout milling operations. New torque-thrust signatures were also identified to detect material interfaces. Changes in signature behavior indicated when the bit milled through one target and reached the next. This is particularly useful when the operator must mill through a target but stop at a subsequent, contiguous one. Post-job data also suggested that some events may have been mistaken as stalls during the operation, with downhole data confirming they were false positives. Finally, at operating conditions in the case study, a 7-second lead-time window was identified to anticipate and react to stalls. This highlights the importance of access to real-time downhole information, such as differential pressure, to avoid both stalls and false positives, and ultimately, to make breakthroughs in operational efficiency. Integrated analysis of downhole measurements during CT milling lent visibility to actual ROP, stall rates, and stall recoveries. These constitute important baselines against which any improvement in efficiency must be compared. The methodologies proposed here for event detection, with special attention to stall anticipation and milling interface detection, pave the way for smarter, more efficient operations.
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