Revolutionizing the Oil&Gas industry from below

The answer was to develop a method small enough to be mobilized to even the smallest installations, but also robust enough to withstand the extreme environments in the oil and gas industry. Welltec® came up with a radical, new solution that runs on standard, electric wireline, today regarded as a break-through in the application of new technology. The equipment was the Wireline Well Tractor®, a 20 ft long and slender wheel-driven conveyance device that pushes wireline tool strings out into the end of the wellbore, both in open and in cased holes.

The intervention challenge
Before the invention of the Well Tractor®, methods like drill pipe, snubbing and coiled tubing were considered the only feasible ways to get down into the horizontal well bore. The drill pipe method consists of a jointed steel pipe in about approx. 30 ft lengths, screwed together to form one long pipe going back from the drilling bit at the bottom of the well to the surface of the drilling rig.

Snubbing is a method also using jointed pipe but where the drill string has to be pushed (‘snubbed’) into the well bore repeatedly and under pressure control.

Another traditional method is coiled tubing, where cable is replaced by heavy, tubes deployed from a large truck-mounted coil at surface. It is a fluid-driven solution where the fluid is pumped down inside the coil and the fluid powers a bit or bottom hole assembly that performs the operation down hole.

Common for all three types of intervention is that they work mainly via brute force, which is not a good thing when conveying sophisticated sensors and electronics. Furthermore, they require lots of heavy equipment, are extensive to rig up and/or require the use of a rig, which may amount to thousands of dollars a day. The strongest opposition, however, is the financial aspect; all of these methods are expensive, time consuming and sometimes even unable to reach the targeted point in the well.

Step change technology
With these challenges in mind, Welltec® set out to develop a wireline alternative that integrated precision, finesse and cost-efficiency. The result was the revolutionary Well Tractor® that from the beginning was backed by a leading North Sea operator who spotted the appealing potential offered by this new solution.

Replacing conventional methods with a solution that runs on electrical wireline has meant a reformation of the oil and gas industry. Due to the Well Tractor® and the possibilities to service horizontal and deviated wells, operators actually changed the way they planned and drilled their wells. What seemed impossible 20 years ago has now become part of several leading oil companies’ standard equipment for intervention in horizontal and deviated wells.

The benefits are multiple; in contrast to the conventional intervention methods mentioned above, the entire operation can be run in a rig-less environment, which eliminates the need for mobilizing heavy equipment. This leads to engaging a smaller number of personnel and reduced operational hazards. Furthermore, the required equipment is logistically easier to handle and the rig-up time is reduced considerably compared to competitive technologies.

Huge Returns on Investment
Perhaps the most significant advantage is the documented cost savings achieved through reduced expenses for personnel and work hours. A North Sea operator has calculated that they save approximately 50% on operations where the Well Tractor® is utilized instead of conventional intervention equipment. More interestingly, they have also calculated that they receive billion of dollars in value-creation due to the effectiveness of the Well Tractor®.

In some cases, the intervention feasibility has been the deciding factor for plug and abandon in horizontal wells. However, with the Well Tractor® it has been documented that the lifetime of the well and economics can be shifted favorably towards the continuous intervention and optimization of well productivity, similar to what is being done in vertical wells on slickline.

Clean technology
Apart from solving down hole challenges quickly and reliably, the Well Tractor® is designed according to principles that consider job safety and protection of the environment. It perpetuates the mitigation of risks associated with environmental impacts while reducing the carbon footprint, fuel consumption, discharges, spillages, explosives and chemicals associated with traditional oil production methods.

The ability to drill horizontally has also contributed positively to heighten the environmental aspects of operations as horizontal wells lead to fewer surface penetrations. The development of extended reach wells also helps to safeguard the environment due to the possibility to operate underneath locations with biological diversity at risk without affecting the environment. For instance, the Well Tractor® can function under the beach in Santa Barbara, under water or beneath a city without harming the environment because the surface control enables it to be operated many miles away from where the operation is actually taking place. Additionally, Welltec® often replaces traditional methods that expose wells to explosives and materials that may cause damage.

Type of jobs
Originally, the Well Tractor® was developed as a means for conveying other tools down hole, ensuring they reached targeted depth. However, Welltec® has further refined its service offerings to perform complicated interventions either alone or in conjunction with Welltec’s mechanical services. The service range spans logging, perforating, performing repairs such as opening and closing of valves or cleaning the well bore of sand or other materials, just to mention a few. Operations can also be conducted in challenging environments such as Subsea, extended reach, Arctic, heavy oil and unconventional gas environments.

Services are versatile and not limited to certain phases of a well’s life but applicable during the evaluation, drilling & completion, production and intervention phases.

In 2002, Welltec® introduced a series of associated technology: the down hole mechanical services comprising activities such as opening and closing valves; removing scale, corrosion and other obstructions; inserting and cleaning valves, other flow control components and continuous measuring devices that reside in wells. The Well Stroker®, Well Key®, Well Cleaner® and Well Miller® are designed to increase the economic lives of clients’ assets, especially in declining fields.

Benefits as seen by operators
The track record is supported by the following two case histories. A major North Sea operator experienced a build-up of scale in two gas wells. Traditionally this would have been removed by a method such as coiled tubing (CT), but in the case of these two wells, the costs were prohibitive.

The well manager says: “The development of this technology enabled us to complete the project at a fraction of the cost of CT and in considerably less time. To give you an idea of the advantages of this new technology, the scale was removed from both well bores in just 12 days – the same time it would have taken just to rig up/down the CT equipment offshore.“

To be exact, the operation took half the number of people that a CT intervention would have required and reduced the total operation costs by 60% (£300,000). Further benefits were the reduced human exposure to risks offshore and the fact that the field was able to export an additional 4 million cubic feet of gas a day.

Isolating sliding side door
Another well in the North Sea producing since 1995 was isolated with tubing including 2 sliding side doors (SSD) to control production. Attempts had been made to close both SSDs in 2003, but only the upper SSD had managed to close. A two-piece straddle was set above the lower SSD, which however did not change production. A PLT test showed there was an internal leakage in the tubing. In 2006, the straddle was retrieved and the well temporarily plugged.

The operator decided to apply the Well Tractor® and Well Stroker® to isolate the lower sliding side door with a 72 ft long straddle and to isolate hole the tubing hole above the lower straddle with a 26 ft straddle. The results of the job were impressive. Water cut was reduced from 85% to 5%, gas to oil ratio was decreased from 2000 to 200, and Q oil was boosted from 100 to 900 Sm3/d.

Future perspectives
Implementation of novel solutions is the true essence of Welltec® and there is still enormous potential to unlock. In the future, Welltec® will continue to convey their way into the business as a full-scale well service provider. The promise is to keep on designing more equipment to continue the revolution from above.

Company Contact Details:
Jørgen Hallundbæk
CEO
Tel: +45 48 14 35 14
Email: jha@welltec.com
www.welltec.com