Tech 101 In this new series, TWA examines some of the most significant upstream technologies being employed today. This first installment focuses on well tractors.

Wireline tractoring technology has set world and Gulf of Mexico records for several logging applications during the initial completion and intervention of two extended-reach, deepwater frac pack wells and one extended-reach, deepwater water-injection well. This paper reviews some of the challenges involved with conventional conveyance methods in extended-reach wells, describes the planning process for wireline tractoring operations, including prejob modeling, and summarizes the results of a project.The authors will also share the lessons learned and best practices implemented. Proper utilization of this technology has led to significant cost savings for the example project. Introduction The Petronius project, located 150 mi south of Mobile, Alabama in the Gulf of Mexico, is operated by Chevron Corporation, with Chevron Corporation and Marathon Oil Corporation having a 50% working interest in the project.The project was sanctioned in August 1996 after a compliant tower and subsea development options were evaluated.The compliant tower alternative was selected based on superior well intervention capability, less complex seawater injection system designs, lower investment, and future hub potential.The 2,001-ft tall Petronius compliant tower is set in 1,754 ft of water, and is the world's tallest free-standing structure. The Petronius project targeted two main reservoirs that were delineated by seven preplatform well penetrations.Once these two original pay sands were developed, sights were set on developing potential pay much further from the platform in deeper waters. The development of these distant zones required mechanical success in difficult world-record, extended-reach processes and, of course, success in finding pay. For the past 3 years, a successful program of world-record, extended-reach deep-water well development has been ongoing.To date, there are 7 wells in the program with horizontal displacements of 14,000 ft to over 25,000 ft.This far exceeds the ~11,000-ft true vertical depth (TVD) of these wells.Fig. 1 illustrates the magnitude of the directional profile of the most challenging of these seven wells (Well #3 in this paper). This is quite an accomplishment considering the unconsolidated deepwater environment.To date, the program includes two water-injection wells and five frac pack-producing wells.Future well plans include an additional extended-reach frac-pack completion and a sidetrack of an extended-reach water-injection well.

Traditionally, deviated and horizontal wells have been challenging to service in a cost and time-efficient manner. Conventional technology requires large equipment to be mobilized and many heavy lifts in the offshore environment, sometimes with negative HSE consequences.New technology on electric wireline has made it possible to access the entire well regardless of deviation and lateral reach. Wireline tractors and new mechanical services can be mobilized in a matter of hours and only require a crew of two people for many applications. Transportation can be done by helicopter to avoid the cost and time of mobilizing a full coiled tubing (CT) spread with bottom hole assembly. Additionally, fuel consumption, emissions and fluid discharges are reduced and heavy lifts are eliminated for the offshore environment.Mechanical down hole wireline tools have also been developed to manage produced water. When wells produce up to 100% of water, mechanical tools can isolate the water to increase oil recovery. By reducing water entry at the source, the subsequent efforts and costs to address it are reduced along with the environmental risks. This paper will illustrate how HSE benefits can be achieved through several case histories. One case history will show how time and crew requirements can be reduced when a wireline tractor and milling system were deployed to remove 42 ft of barium sulfate inside two wellbores. The scale was removed from both wells in 12 days -the same time it would have taken a CT unit to mobilize and demobilize offshore. Costs were reduced by 60% and crew requirements were reduced from 23 to 12 people compared which reduced human exposure to risks offshore.Another case history will illustrate how produced water can be effectively reduced through e-line mechanical services. In an offshore well in Norway, a leak was detected in the tubing, which resulted in 85% water cut. A wireline tractor and stroker were applied to install two straddle packers in order to isolate the water-producing area. Water cut was reduced to 5% and oil production increased 800%.

An Angolan operator needed to perform a coiled tubing (CT) acid micro-wash stimulation on a subsea sand screen completion in order to improve production. The CT simulation showed that the coil would not reach the objective, which was the bottom screen, even with friction reducers, without the assistance of additional forces. The operator chose to deploy a downhole tractor to provide a pulling force to achieve the desired depth. However, this horizontal well had debris which prevented reaching the objective and required changing strategies to accomplish the job. A downhole tractor can be powered by pumping fluids down the coiled tubing, driving a turbine which powers the hydraulic systems in the tractor. The drive fluid will then pass through the tractor and out the bottom of the tool to provide the treatment. Surface testing is performed prior to the job to determine at which pumping rate the tractor will be engaged and disengaged. This testing is performed with and without treating nozzles to gauge tool performance and expected pumping rates for tractoring and treating. In this Angolan operation two runs were required to reach the bottom screen due to debris fill in the completion preventing passage during the first run. On the second run the CT provider used a nozzle that could both clean the well and treat in the same run. This operation demonstrates the effectiveness of using CT tractors, which are under-utilized in the industry, to achieve extended reach beyond the normal CT range. It also demonstrates the quick mobilization and same day deployment, as well as problem solving that can occur when service companies (CT provider and tractor provider) work closely together.

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