Nipple Profile Milling With Electric Wireline Interventions
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Cited by 5 publications
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This paper will present a record North Sea electric line milling operation carried out during March 2010, the success of which enabled access to the reservoir section, with subsequent interventions leading to a significant uplift in production.The Operator was experiencing high water cut in one of its wells; previous interventions in other wells connected to the same reservoir indicated a high probability of scale. The plan was to log, isolate the watered out zone and then re-perforate in order to increase oil production rate. Electric line Tractor Milling equipment was mobilised as contingency, should well access be an issue, which happened to be the case. In order to keep the bit clear during milling, cuttings were flowed back to surface. Progress was made until the surface choke packed off and flow was no longer achievable, the toolstring had to be retrieved whilst choke and lines were cleared. The scale sheath was eventually broached and the decision made to continue in hole in order to drift, as well as providing the capability of dealing with any further scale that may be present; the Tractor Miller was started once more with a minimum of resistance encountered. Target depth was attained, all Tools were then retrieved to surface with no issues.The overall objective was achieved, resulting in a significant increase in production. One hundred and twenty one (121 metres, 390 feet) of calcium carbonate scale was removed during the operation, validating the use of light well intervention techniques when removing scale. This paper will discuss the technical aspects of e-line milling and challenges overcome during this particular operation.
This paper will present a record North Sea electric line milling operation carried out during March 2010, the success of which enabled access to the reservoir section, with subsequent interventions leading to a significant uplift in production.The Operator was experiencing high water cut in one of its wells; previous interventions in other wells connected to the same reservoir indicated a high probability of scale. The plan was to log, isolate the watered out zone and then re-perforate in order to increase oil production rate. Electric line Tractor Milling equipment was mobilised as contingency, should well access be an issue, which happened to be the case. In order to keep the bit clear during milling, cuttings were flowed back to surface. Progress was made until the surface choke packed off and flow was no longer achievable, the toolstring had to be retrieved whilst choke and lines were cleared. The scale sheath was eventually broached and the decision made to continue in hole in order to drift, as well as providing the capability of dealing with any further scale that may be present; the Tractor Miller was started once more with a minimum of resistance encountered. Target depth was attained, all Tools were then retrieved to surface with no issues.The overall objective was achieved, resulting in a significant increase in production. One hundred and twenty one (121 metres, 390 feet) of calcium carbonate scale was removed during the operation, validating the use of light well intervention techniques when removing scale. This paper will discuss the technical aspects of e-line milling and challenges overcome during this particular operation.
Unique Milling Bit Deployed via E-Line Intervention Enables Operator to Achieve Early Production
This paper presents the significant benefits accomplished from the utilization of robotic, electric-line (e-line) intervention to mill out a malfunctioning flapper valve versus the use of coiled tubing (CT). In addition, it will discuss the flexibility and control features of e-line based, intervention technology towards addressing short lead time and design modifications required to meet dynamic well challenges. On the West Coast of India a well was completed using a flapper valve as the method of isolating the completion while being installing it into the well. A standard practice in the field, the flapper valve has been utilized successfully for a decade without any failures. Hence, during the current operation, contingencies to overcome a mechanical failure to open the valve were not on board. And unfortunately, in this particular well, the flapper valve failed to open as per SOP. After multiple days spent on attempting to cycle open, attempts were then made with slickline to determine if debris accumulation was an issue. When this proved false, it was concluded that the flapper valve was mechanically stuck. After evaluation of solutions incorporating CT and e-line interventions, it was determined that standard milling operations would pose additional challenges for the well due to the design of the completion below the flapper valve which incorporated a 2.56" restriction. If the milled portion of the flapper valve was not retrieved there was consequential risk that the well could become plugged by the coupon. After an extensive review with the PMT JV (Panna, Mukta and Tapti Joint Venture) plus the Design and Engineering team of a service provider, it was agreed that the probability of retrieving the milled fIapper valve coupon with standard bits was low. However, the service provider suggested a unique, star shaped milling bit that enabled milling a coupon which was small enough to pass through the restriction should it not be captured. E-line milling was selected due to several reasons including the finer control, efficiency of operations and minimum debris generation. The newly designed ‘star’ bit enabled milling a small coupon and subsequently expanding that hole to the desired OD of 2.7" which would enable access for future interventions as needed. The total time from the identification of the problem to designing, manufacturing, testing the new bit, transporting it to India and executing the solution was less than 45 days. This enabled the well to be intervened upon while the rig was on the platform. The operation itself was carried out within 45 hours vs the 120 hours projected for CT, leading to a cost saving of ~ 750,000 USD. This unique methodology also enabled early onset of production, avoiding a delay of ~ three months. This was the first time this new mill bit was applied and the first time that this type of flapper valve had been milled out. Existing, standard bit designs were not sufficient to accomplish this solution nor were conventional approaches satisfactory in today's economic climate.
An automated wireline milling solution targeted for removal of wellbore obstructions of a varying type, from scale to metal, with built-in capabilities of autonomous cruise navigation between consecutive obstacles, is presented. This paper highlights design features that made a step change in the efficiency and usability of milling services. Control challenges are still common in downhole milling technology. Changes in milling target composition, cuttings accumulation around the target, drag forces from production flow, and other variations can reduce system efficiency and result in lost time or failed interventions. In the case of wireline milling technology, inclusion of intelligent on-board electronics in the downhole equipment presents an opportunity to actively control the milling process to optimize rate of penetration and implement additional protections to reduce operational risk. We describe a robotic toolstring that automatically and independently controls a wireline tractor using real-time feedback from a milling cartridge and other on-board sensors. Embedded control algorithms implement intuitive workflows derived from the combined experience of multiple experts in well intervention. With this automated wireline milling system, the user can initiate the milling process by defining certain milling parameters and then can monitor progress in real time while the downhole robotic tool regulates weight on bit and the milling motor. This new automated downhole control system significantly improves torque-on-bit and weight-on-bit controls yielding superior performance, such as rate of penetration and usability. Dynamic load conditions are handled in a high-speed distributed control loop downhole to get most of bit torque capacity across the entire speed range defined by the motor power curve. Tractor push force is adjusted quasi-instantaneously with changes in cutting conditions. Control responsiveness along with software solutions for tracking of motor stall preconditions and a torque limiter greatly reduce the occurrence of motor stalls arising due to the bit wedging in highly reactive targets. With stall avoidance and an automatic backing-off feature to reengage the bit in case of a sporadic torque spike, direct involvement of an operator is significantly minimized compared to the previous tool generation. Head-voltage stabilization is another factor positively impacting the overall power stability and performance of electromechanical tools downhole. Safety features are also in place to prevent cable twisting and protect assets from overcurrent and overtemperature conditions. The progressive design of the automated milling tool boosts operational efficiency and autonomy, minimizes human mistakes, and reduces risk of getting stuck during the service. Case histories demonstrate the first field jobs and system integration tests performed with this new tool.
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