A new application of electric wireline tractors in combination with the well milling technology has been successfully proven in an offshore Equatorial Guinea well. In July 2011 on a small, unmanned offshore platform in Equatorial Guinea, a downhole tractor and a milling tool were conveyed on electric line to remove an obstruction created by Lost in Hole (LIH) electric line cable and production logging tools (PLT). By using customized core milling bits, 13 successful milling runs were made. During this unique operation, most of the milled wireline material was recovered, and the challenges of controlling torque and milling penetration were achieved. In between milling runs, slickline fishing attempts were made in order to recover the remaining LIH wireline. After the last milling run, a major breakthrough was made when the PLT string moved downhole to a position that uncovered the proposed new completion interval. Ultimately the well was perforated and returned to production at projected gas and condensate rates. Milling of wireline and other well bore obstructions on electric line offers a cost efficient alternative technology to existing methods. Furthermore, it offers reduced Health, Environment and Safety (HES) risk benefits and logistical advantages. This paper will describe the actual process from preparation to completion of this first-of-its-kind fishing operation.

A new application of electric wireline (e-line) tractors in combination with well milling technology has been successfully proven in two wells in West Africa.In July of 2011 on an offshore platform, a downhole tractor in conjunction with a milling tool were conveyed on e-line to remove an obstruction created by Lost in Hole (LIH) electric wireline cable at 9,500ft (2,896m).In total, 13 successful milling runs were made. During this unique operation most of the milled wireline material was recovered, and the challenges of controlling rate and milling penetration were overcome. In between milling runs, slickline fishing attempts were made to recover the remaining LIH wireline. After the last milling run, a major breakthrough was made as fishing operations were successful in retrieving sufficient wireline to reach the target depth.In another case, this time in a subsea well, a flapper valve used to set a production packer needed to be opened, but despite multiple pressure cycles down the tubing, the valve remained closed. The operator had the option to pump in acid to disintegrate the valve, but due to the estimated volume of acid required, the operator wanted a different solution.The milling tool was fitted with a tungsten carbide milling bit specially designed to mill the aluminum flapper valve. The milling bit was designed with a spring-loaded skirt that kept the valve closed while the bit was exposed. This prevented the flapper valve from opening when pulling the bit backwards. After approximately 20 minutes of milling time, the valve was milled out. The operator saved at least one day of operation.Additionally, due to their lightweight nature, e-line tools offer HSE benefits and logistical advantages. This paper describes the process from decision-making to completion of these milling operations.

In 2012, for the first time ever in North Africa, a well in a dry environment utilized e-line milling technology to mill out a failed flapper. With this paper the author will describe the actual process from preparation to completion of a world's first operation. A gas well experienced a malfunctioning 7″×4.56″ 13 Cr. steel downhole flapper valve. Due to several operational challenges including limited well site access and temperatures over 150°C, there was a need for an alternative solution to mill the valve and allow access below it for future well interventions. Furthermore, due to the fact that the well was a gas producer, there was a need to avoid, or minimise introduction of any fluids in the well. The method of choice was an e-line tractor and milling assembly. Because of the size of the offshore platform this was the only feasible solution. Heavier intervention methods like coiled tubing were not possible to mobilize because of the weather conditions plus the risk of reservoir damage if introducing fluids. The e-line tractor conveyed the toolstring to target depth (2,916 m MD) where the e-line milling tool was activated and milled through the flapper valve in approximately 40 minutes. After the completion of the milling phase of the operation, another run was performed to set an access sleeve in the milled out flapper valve utilizing an electromechanical setting tool. This access sleeve ensured that entry/re-entry through the milled flapper valve would be easily accomplished each time. The installation of the access sleeve was confirmed by running a 3.25″ gauge through it. Milling of flapper valves and other well bore obstructions on electric line offers a cost efficient alternative technology to existing methods. Furthermore, it provides HSE benefits and logistical advantages by reducing the amount of required equipment and personnel.

In 2017, offshore North Africa, a well in a dry environment utilized a new application of e-line milling technology in combination with a specialized bit to mill out a failed flapper. This was the first time this special bit with the e-line milling toolstring was used to mill out a flapper valve in a dry environment. With this paper the author will describe the history behind the milling bit design, the actual operation and production improvements. A gas well experienced a malfunctioning 7"x 4.56" 13 Cr. steel downhole flapper valve. Due to several operational challenges including limited well site access and temperatures over 150°C, there was a need for an alternative solution to mill the valve and allow access below it to re-perforate the well. The operator's method of choice was an e-line tractor and milling assembly that had previous success in the same area in similar conditions. Furthermore, a new milling bit was developed that drastically reduces milling debris and eliminates potential fishing runs. Finally, heavier intervention methods like coiled tubing were not possible to mobilize because of the weather conditions plus the risk of reservoir damage if introducing fluids required to mill on CT After the completion of the milling phase of the operation, another run was performed to set an access sleeve in the milled-out flapper valve utilizing an electromechanical setting tool. This access sleeve ensured that entry/re-entry through the milled flapper valve would be easily accomplished each time. The installation of the access sleeve was confirmed by first running a drift to TD, followed by the perforating guns toolstring and re-perforating the well. Milling of flapper valves and other well bore obstructions on electric line offers a cost efficient alternative technology to existing methods. Furthermore, it provides HSE benefits and logistical advantages by reducing the amount of required equipment and personnel.

An operator in Algeria, found that when attempting to put wells on production, the lock mandrels were found to be stuck in the nipple profile. All slickline attempts failed to retrieve the mandrel. When coil tubing was deployed, one plug remained stuck in its nipple, while the second one came off its seat only to get stuck inside a Side Pocket Mandrel, about 25m shallower. The sequence of pulling and jarring resulted in both fish necks coming apart, thus rendering all subsequent fishing attempts impossible. Therefore, a decision was made to attempt to mill the mandrels using the new e-line milling technology. Another challenge was that the 2.562″ and 2. 75″ ID mandrels were made of 13 Super Chrome, and there was limited experience milling these types of completion components. Also, due to a rush mobilization, there was no time to execute a SIT. The solution presented consisted of milling first the mandrel outer sleeve, then milling the inner sleeve from the plug body which will cause the mandrel anchoring system to collapse. Special 2.2" and 2.375" milling bits were manufactured and sent to location. The e-line tractor conveyed the toolstring to target depth where the e-line milling tool was activated and milled through the mandrel sleeves, releasing the anchors. On the first well, the 2.562″ mandrel sleeves were removed using a 2.2″ bit, while the sleeves on the 2.75″ plug were milled using a 2. 375″ bit. With the sleeves removed, slickline ran in hole with a combination of magnets and scratchers (wire brush) of different sizes and fished the remainder of the plug. With full bore access on both wells, and after performing a clean-out operation, the operator could increase the gas production by 100%. This was the first time the e-line milling toolstring was used to mill and remove a lock mandrel. This paper will review a new application of e-line milling technology to remove heavy duty lock mandrels in order to allow wellbore access and improve the production.