The current increasing trend in the oil and gas industry to secure future reserves drives a demand for increasingly complex well design in highly deviated, horizontal and even ERD with various downhole hardware.
A way of optimizing mechanical inventions is the utilization of establishes downhole wireline technology in order to make it possible to perform reliable, economical and flexible interventions. Especially, it will make a cost effective alternative to traditional intervention method and coil tubing.This paper is seperated in two main parts. First is a basic concept of wireline tractor and then the applied fuction of wireline tractor with scale milling techology will be discussed. Wireline tractor and its essential compartible downhole equipments, wireline stroker and wireline key, will be discussed in the first part include benefit and adventages of the application of these technologies by way of actual case history. Moreover, use of wireline tractor in production logging tool programe will be discussed.
Wireline tractor milling operation at high-temperature condition will be described in the second part include surface equipment normally used, operating plan, result, and discussion of pro and con compare with coil tubing. All of this base on history case of Asgard field. The case histories provided substantiate the benefit that this new technology is able to provide to the global operating community, regardless of environment and well type.Introduction Due to increasing of oil and gas demand nowsaday, complex completion designs for maximizing production of hydrocarbon for as long as possible are created. For complex reservoir, well design and production strategy must be evaluted carefully. So the conventional wireline technology can’t be used to operate in these kinds of wells.
For example highly deviated wells, horizontal wells, and extended reach drilled (ERD) wells. Downhole wireline tractor technology is invented to serve this problem. The manipulation and/or replacement of downhole hardware components in conjunction with wireline stroker and wireline key (intelligent shifting tool) applications makes it possible to perform reliable, economical, and flexible intervention such as opening/ closing SSDs or valves, setting and retrieving plugs, straddles and GLVs, also in horizontal and ERD well. Moreover, wireline tracter can be applied with milling tool for scale milling job in high temperature well.
This operation has been performed at Åsgard since 2003.The Modular Downhole Tractor (MDT) The modular downhole tractor is a wireline deployed system use to convey wireline tool, sumassembly or perforating gun into difficult-to-access areas. There are 3 main equipments of MDT that are wireline tractor, wireline stroker, and wireline key.Wireline Tractor Wireline trator services were commercially introduced in 1996, aiming to provide a highly cost-effective alternative to coil tubing and snubbing interventions in horizontal and high-angle wells. This technology was primary used for conveyance of diagnotis logging tools and traditional operation such as perforation and plug setting. Because it achieved a reliable track record, wireline tractor was applied with other technologies for do a specific job in, especially, horizontal and high-deviated well.
As shown in figure 1, wireline tractor is modular enabling a number of sections, which are electronics section connect with actuator and drive arm/wheels below. In order to provide the maximum force to drive the passenger tool combination along the well, wireline tractor use DC powerd in control panals and communications section while the remaning parts and functions are hydraulic. So it can drive both up and downhole. When actived, the wheels are hydraulically deployed out of the body and start to rotate automatically. Each wheel rotates by its own independent hydralic motor. The tool centralized it self once the wheels contact casing.
The cummative traction force deploys the passenger tools into the wellbore. When it reachs the target, the tool is powered down.Wireline Stroker Conventional wireline jars are usually used in vertical and slightly deviated wells during retrieval of plug or activated some downhole assembly. In case of high angle and horizontal well, a special tractor jar, which is call wireline stroker, has been designed.
It connects below wireline tractor. As shown in figure 2, wireline stroker is devided into electronic section and hydraulic section. The upper section is used as command reciever while the lower section allows mechanical operation to be carried out. When combined with a wireline shifting tool, the wireline stroker applied the required force to shift downhole valves or SSDs.
The maximum axial force is upto 33,000 lbs bi-direction. Additionally, the force provided can be replace the use of explosives in packer setting application, which increase operational safety, provide environmental benefit and easier logistic.Wireline Intelligence Shifting Tool Wireline key is used as special shifting tool, it connect below wireline stroker. As shown in figure 3, the wireline key contains a pair of keypads arranged at 180-degree angle. The tool is activated by axial force generated from wireline stroker, which is controlled from surface. When activated, a hydraulic pump extends the keypad with a specific profile out of the tool body, which allows them to latch onto a matching shifting profile.
For example latch on SSD key profile, the sliding sleeves are pushed or pulled until it closed or opened completely. If it deactivated the keypads are retracted into the tool body. Wireline key enable access through minimum restrictions because it can shift selectively. So the operator can do multiple jobs in the single run if it uses the same key profile. It provides operational time saving and allows flexibility for completion engineer to design wells with lots of downhole hardware without shifting mechanial restriction.
Use of Wireline Tractor on Logging Program Wireline tractor technology is now a conveyance method for Production logging tool (PLT) in horizontal wells. The logging jobs were completed safely and successfully at flowing and shut-in conditions. Usage of DC motor in tractor technology allows logging tool to operate at different speeds due to surface controller. Normally, most of the horizontal wells are drilled and logged using logging while drilling (LWD) technology, which have some limitation.
Once PLT with wireline tractor runs, the wellbore profile is clearly understood. The wireline tractor is a good deployment solution and alternative for horizontal logging application. It has proved its flexibility and reliability to overcome the severe well trajectory and different sizes of washout in openhole applicationSucessful Case Historywith Wireline Tractor Technology Case I, in late 2006 at Norway, a lowest SSD located at the depth of 4,334-m MD with an angle exceed 70°. It was programmed to close by wireline tractor, wireline stroker, and intelligent wireline shifting tool. Two upward strokes were performed during the operation in single, the first upstroke is to close the sleeve and the second upstroke is to verify that the sleeve is completely closed.
The actual time taken to close SSD was just 15 minutes. The benefit of this operation is time saving. Case II, a newly drilled horizontal well has 91.7° maximum deviation with total depth of 6272-m. This well was program to set plug and shifting SSD followed by retriving the plug.
The first run is to set plug at depth 4061-m MD by wireline trator as a conveyance. The plug was set with explosive setting tool. Total time in well was about 15 hour. The next run was combination of wireline tractor and wireline stroker for closing SSD. Total time in well was 13 hours.
The final run was made to pull the plug after testing anullus pressure.The entire operation was completed successfully with zero personal injury and zero hour lost time. Case III, an internal leakage in tubing was found in a 4979-m MD deviated well in the North Sea. Production rate from this well was about 100 sm3/day with 80% water cut and gas-to-oil ratio was 2,100.
In order to serve this problem, the straddle packer was used to isolate the leakage zone. The biggest challenge was too long leakage zone required too long straddle packer.Conventional rig counld not be used due to accommodate restriction. So it was decided to use 8-m single straddle packer to isolate SSD and installed 22-m multi-section straddle packer to isolate leakage zone as shown in figure 4. There are 5 runs of wireline tractor/stroker combination required. First, lower the straddle packer.
Wireline stroker activated the element of straddle packer in run 2 and 3. Two strokes per element were performed to ensure physical matching and proper sealing.The typical stroke time is 25 seconds. In run 4, the top packer was anchored and the final run was to install the top packer. The entire operation took a total of 32.5 hours.
The successful operation causes water cut reducing to less than 5%. Gas-to-oil ratio decreases from 2,000 to 200. Oil rate increases from 100 sm3/day to 900 sm3/day. The combination of wireline tractor/stroker was proved in repairing a well completion with reliable of considerable saving in personal, logistic and overall planning.Applying of Wireline Tractor Scale Milling Technology with RLWI Wireline tractor had been applied with scale milling tool in Smørbukk field of MidNorway in 2008 for the first time.
The newly technology came to replace the traditionally scale milling operation performed with semi-submersible rigs and coil tubing. The concept of Riserless Ligh Well Intervention (RLWI) is base on use of subsea invention well control package including a lubricator with no high-pressure riser tied back to the vessel. There are 4 main equipments of subsea lubricator system as shown in figure 5.The First is the lower intervention package (LIP), it has two barrier valves and a shear seal ram.
The second is the lower lubricator package (LLP); it has subsea grease system and workover mudule system. The third is the upper lubricator package (ULP); it has cutting ballvalve combine with lubricator tubular. The fourth is the pressure control head (PCH); it consists of wireline flow tubes and emergency packing elements. The lubricator allows deployment of tool strings up to 22-m.
The Milling Bottom Hole Assembly The bottomhole assembly consisted of a wireline tractor, rotation adapter, gearbox, shock absorber and the milling assembly. The total length of BHA was 11.3-m. The rotation adapter was connected between wireline tractor and the gearbox.
It is a hydraulic moter module recieves power from wireline tractor for providing torque and rotation to the gearbox beltrow. The wireline tractor milling concept is base on low torque and high RPM. The gearbox deliver a maximum of 90 revolutions per minutes (rpm) and maximum torque output of 160-Nm while shock absorber, under the gearbox, provide sustainable weight on bit and allow axial travel.The milling assembly consists of costomized bit and specially designed reamer for associated with wireline tractor.
As shown in figure 6, milling bit has four separate freely rotating cutting cone. It optimize for cutting grinding scale into fine particles. The reamer is placed over the bit and acts as a stabilizer for milling assembly. A rotation counter incorperated in rotational adapter is one of the most recent functionalities introduced for wireline tractor milling survice. This feature facilitates real time feedback of actual bit rotational at hold up depth.
This help operator to optimize weight on bit and RPM by adjust wireline cable tension for increaing milling efficiency.Case History The operation described in this topic was performed at Smørbukk. It is a high temperature gas condensate subsea field and produced mainly by depletion with some pressure support from gas injection. Scale plugging in linver around perforation zone had been found in 2003. It was first removed by coil tubing invention however; scale bridge hadn’t been removed completely. Until 2008, it was decided to plug off a gas break-though from the lowest reservoir zone so scale milling required again.
Wireline tractor milling in a high temperature combined to Riserless Light Well Intervention (RLWI) equipment was first performed here in order to complete this operation. Scale was tagged at 4,044-m MD and 11-m of scale was milled in the first run with in 22 hours. On the second run, 7-m of scale was milled in 15 hours. The final run 5-m of scale was milled in 10 hours.
4The wireline tractor was in good condition when it was checked on deck. A PLT was run after scale milling process in order to evaluate the contribution. X-Y caliper in the string showed no scale left in plug setting area. So the bridge plug was installed completely A major benefit during milling operation was rotation counter that mounted on wireline tractor although RLWI was time consuming operation compare to traditional surface wireline operation.
For this invention the total operating causes turn out to be approximately 50% of the estimated costs of a coiled tubing intervention form a drilling rig.ConclusionCompletion designer can create more complex well schemetic for horizontal, highdeviated, or exteneded-reach-drilled (ERD) well due to the invention of wireline tractor, wireline stroker, and wireline key. It can apply to other downhole equipment for specific function such as combine with milling tool for removing scale. The case history proved that the new technology provides substantiate the benefit especially in time saving and reparing the well. It is able to provide to the global operating community, regardless of environment and well types.
