Summary A technological breakthrough within the application of wireline technology has been achieved. In August 2008 on an offshore platform on the Norwegian continental shelf, a wireline tractor and a new wireline milling system were used to mill and remove a permanent bridge plug at 4,147 ft measured depth (MD). The operator decided to mill out the plug on electric wireline and worked closely with the service company to develop this novel solution. Having developed and tested several bits and milling tools, results showed that by combining the wireline miller with hydraulically provided weight on bit (WOB), it would be possible to mill out the retaining rings of the plug, which would cause the plug to collapse. The milling-control unit allows the WOB to be adjusted for each application and also controls the reactive torque—the force generated when the milling bit engages the plug. The service company was able to develop the solution within the client's parameters and in accordance with the timeline set out for this project. The offshore operation was completed in 3 days, to the operator's satisfaction. In another platform well, a permanent bridge plug had been set in 2003 in the sealbore between two screen sections [3-ft seal- bore, 67° well angle, 4.75-in. inner diameter (ID)]. The plug was set in order to isolate the somewhat higher water cut in the lower reservoir zone to prolong oil production from the well. In 2006, the well drowned after a 2-week-maintenance period. Two years later, a coiled-tubing (CT) gas lift operation was carried out with good results. It was then decided to remove the permanent bridge plug to reopen for production before another CT gas lift operation was carried out. A method for milling the permanent bridge plug was developed on the basis of lessons learned from the other plugmilling operation and by extensive testing at the service company's facilities. The operation was completed successfully in 13 days. This new application for milling completion hardware and other wellbore obstructions offers a cost-efficient alternative to existing methods. The success of the milling operation is a significant achievement and has pushed the limits for what is possible on electric wireline. This paper will examine two cases of milling bridge plugs on electric wireline and the technical challenges that had to be overcome in offshore operations.The first case used the well stroker as WOB, and the second cased used the well tractor as WOB.

This paper describes the use of Well Tractor® technology to convey services for recovery of stuck drillpipe in circumstances where conventional methods were considered economically or technically unfeasible. In the first case, the drillpipe became stuck while running in and circulation was subsequently lost. After 100 jarring cycles were performed it was decided to attempt a fishing operation using the 2 1/8" Well Tractor enabling the retrieval of the radioactive logging source. The retrieval tool was deployed on Well Tractor, which enabled the radioactive source to be successfully recovered from the bottom hole assembly (BHA). The drillpipe was subsequently backed-off using Well Tractor to convey the explosives. In the second case, drilling losses to the formation were experienced and it was decided to pump lost circulation material. However, during pumping the drillpipe plugged up completely. At the same time flow was recorded on the annulus side and the drilling BOP annular preventer was closed with subsequent pressure build-up below. A 2 1/8" Well Tractor was successfully run inside the DP to first gauge and subsequently punch holes in the drillpipe to open for circulation, thereby allowing pumping of heavy mud and regaining well control. Introduction The number of horizontal and extended reach drilling (ERD) wells worldwide is dramatically increasing. Now it is possible to drill and complete ERD, long horizontal and designer wells with no greater difficulty than what was considered an acceptable risk level for vertical wells a few years ago. However, when the requirement for intervention in these types of wells become important, it has until recently been impossible to reach a target depth in the horizontal section of the well with normal wireline techniques, since the method relies on gravity to convey the tool and cable to its target depth. Traditionally, the only option for live well intervention has therefore been to employ coiled tubing or snubbing methods to reach into the horizontal section of an horizontal well. Today an alternative to these two methods is available. The necessary force to push a downhole wireline toolstring into the horizontal section of a well can be provided by using the Well Tractor. In many cases and particularly in wells with high well head pressure, coiled tubing and snubbing operations are impractical and involve a large amount of costly equipment, personnel and rigtime. In other cases it is logistically not possible to access the wellsite with a coiled tubing or snubbing unit due to physical constraints, as typically seen onboard a semi submersible or a small wellhead platform with limited deck space. The only method which easily can be adopted is often limited to wireline conveyed services. This fact combined with the relatively short lead-time for mobilization of the Well Tractor and associated equipment, makes it an ideal alternative for emergency mobilisations. Well Tractor was initially introduced to cover cased hole applications like PLT, perforation, cement bond logging etc. and has since moved into open hole operations and lately to drill pipe freepoint/back off operations (Figure 1.). Based upon Well Tractor's flexible hydraulic system, the technology is well suited for operation inside drill strings and completions with changing ID, e.g. drill pipe connections, x-overs, landing nipples, through patches, PBR's etc. So far, 5 operations in the North Sea have been carried out through drill pipe in conjunction with stuck pipe. The cost savings have been considerable, as the only viable alternative has been to cut the drill pipe several 1,000 ft above the depth to where the Well Tractor has conveyed tubing puncher and back-off services. This is especially applicable in wells where the circulation for one reason or another has been lost, preventing pumping down an explosive cutter or back-off bar on wireline.

Kvitebjoern is a Statoil operated gas and condensate field that lies in block 34/11 in the Norwegian North Sea. The reservoir lies about 4,000 meters down, and features high pressure and temperature conditions (770 bar and 160 deg C). 34/11-A-9 T2 well was drilled as a gas producer by end of October 2009 and completed in February 2010. During the final completion phase, it was not possible to open the High Pressure/High Temperature (HP/HT) isolation ball valve set in the 9 7/8" liner at 6245.7 m MD / 3795.8 m TVD through pressure cycling.After several failed attempts to open the isolation ball valve with wireline using mechanical override tools, it was decided to punch above it to allow well production passing the outside of the valve through the annulus between 9 7/8" liner and the 5 ½" tail pipe. However, the production performance was poor. A feasibility study was carried out to evaluate available methods for opening or milling out the valve with the objective to improve the production characteristics. The well is an exploration well and an important objective for the operation was also to allow access for future production logging tools.The decision was then taken to mill the stuck-closed isolation ball valve using Coiled Tubing (CT).The operation presented several critical challenges. Statoil had not performed any HP/HT CT operations and the available experience was limited.To minimize uncertainty relating to depth determination during the milling operation, it was decided to use a telemetry system run at its operational pressure and temperature limits to provide real time Casing Collar Locator (CCL) reading in addition to downhole pressure and temperature data.

A technological breakthrough within the application of wireline technology has been achieved. In August 2008, on an offshore platform in the Norwegian Continental Shelf, a wireline tractor and a new wireline milling system were used to mill and remove a permanent bridge plug at 4,147 ft MD. The operator decided to mill out the plug on electric wireline and worked closely with the service company to develop this novel solution. Having developed and tested several bits and milling tools, results showed that by combining the wireline miller with hydraulically provided weight on bit (WOB), it would be possible to mill out the retaining rings of the plug, which would cause the plug to collapse. The milling control unit allows the WOB to be adjusted for each application and also controls the reactive torque, the force generated when the milling bit engages the plug. The service company was able to develop the solution within the client's parameters and in accordance with the timeline set out for this project. The offshore operation was completed in three days to the operator's satisfaction. In another platform well, a permanent bridge plug had been set in 2003 in the sealbore between two screen sections (3 ft sealbore, 67 degree well angle, 4.75" ID). The plug was set in order to isolate the fairly higher watercut in the lower reservoir zone to prolong oil production from the well. In 2006, the well drowned after a two week maintenance period. Two years later, a coiled tubing (CT) gas lift operation was carried out with good results. It was then decided to remove the permanent bridge plug to re-open for production before another CT gaslift operation was carried out. A method for milling the permanent bridge plug was developed based on lessons learned from the other plug milling operation and by extensive testing at the service company's facilities. The operation was successfully completed in 13 days. This new application for milling completion hardware and other wellbore obstructions offers a cost-efficient alternate technology to existing methods. The success of the milling operation is quite an achievement and has pushed the limits for what is possible on electric wireline. This paper will examine two cases of milling bridge plugs on electric wireline and the technical challenges that had to be overcome in offshore operations. The first using the well stroker as WOB, the second using the well tractor as WOB.

A new application of running wireline stroker technology in combination with wireline milling technology has been proven successful in the Norwegian Sector of the North Sea. In August 2008, on an offshore platform, a wireline stroker and wireline milling rotational unit were used to mill out and remove a permanent type bridge plug at 1,264m (approximately 4,147 ft) MD (50° deviation).The 3.25" high expansion bridge plug was inadvertently set in the tubing in March 2008 at 1,264 m. It was decided to attempt to mill out the plug on electric wireline to regain production from the well. A study was initiated to evaluate if it would be feasible to develop a wireline conveyed stroker and milling system capable of removing the plug. During a two months design period, several different bits and milling tools where designed and tested. It was confirmed that by combining a wireline miller with a modified wireline stroker to act as feed control, it should be possible to mill out the retaining rings and collapsing the plug. The milling system included a control unit allowing the WOB (weight on bit) to be optimized for each application. In addition it also controls the reactive torque and force generated when the milling bit engages the plug.The offshore operation was successfully completed in three days. The milling tool has proven to be an effective solution to down hole problems that require milling of metal or hardened materials. The technical solution was developed within the design parameters and in accordance with the timeline set out for the project. This new method for milling well completion hardware and other well bore obstructions offers a cost-efficient alternative technology to existing methods using coil tubing or snubbing. The success of the milling operation is a significant milestone and has pushed the limits for what is possible to achieve on electric wireline.By applying new technology, the well was quickly put back in production. The operation was conducted as a live well intervention without the need for using the drilling derrick. This paper will examine the challenges and solution chosen in an operation of milling a bridge plug on electric wireline.