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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.

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.

Conventional methods used for downhole sand or debris cleaning have considerable investments in economic costs and time. Scheduling these activities to minimize production interuptions and to maximize unrestricted flow is a constant challenge faced by production and flow assurance engineers in the Oil & Gas industry. A sand and fill cleaning decision can be expressed as an optimization problem since its purpose is to maximize the production of the well to accomplish production goals at the end of a time period. This paper presents optimization algorithms applied in dynamic programming to help in scheduling cleaning interventions for wells in order to maximize the continuous production under physical, technical and economic considerations while minimizing the investment cost of the total operation. A strategy will be presented which takes into account mainly the fixed costs but also the variable costs and sensitivity analysis that allow the model to better approximate reality. The strategy considers three options based on the costs of cleaning with either electric line or coiled tubing technology; 1) to completely remove a given volume of sand, 2) to clean to a minimum acceptable level or, 3) not to clean and allow sand volume increases to continue. The cost to perform sand cleaning with a certain technology based on a mathematical function, considers the following requirements:the relationship between volume of sand produced per unit time, Vt (flow),(Vmax-Vmin) or the interval between Vmax in which production of oil is minimized and the Vmin for maximum production,the time horizon to perfom the sand cleanings, andPoints that make the operation unfeasible such as physical restrictions in the well or operator time/cost constraints. This paper will also present two cases demonstrating the strategy to schedule cleaning interventions that achieves a set production goal.

Recently, a solution has been developed to provide for milling of nipple profiles and other downhole hardware with electric wireline. A new milling bit and milling system for the wireline miller enables nipple profiles to be opened up in diameter to allow larger intervention products to be deployed, e.g. straddle packers and insert valves. Extensive testing was conducted prior to the introduction of this service to optimize the weight on bit and torque. The result was the development of a unique version of the hydraulic stroking tool to be combined with the milling tool to provide the controlled weight on bit.A major benefit of using the wireline milling system is the ability to provide precision milling without mobilizing coiled tubing (CT) or heavy surface equipment for circulating and handling fluids. Thus, there is no risk of damaging the reservoir from the circulating fluids. In addition, this kind of intervention can be performed more cost-effectively, involving less people, less heavy lifts and therefore, reduced HSE risks.The world's first milling of a nipple profile on wireline took place in Indonesia where the wireline miller was mobilized to enlarge the nipple profiles in 10 wells. The entire operation was performed in 20 operating days and well kills were prevented, which would have been necessary if executing the operation with a conventional method, such as on CT. Major benefits included minimal reduction in production levels, precision milling with zero cuttings left in hole and no labour-intensive requirement for CT or heavy surface equipment.As of December 2009, the ID of twenty (20) Super 13 Chrome nipples have been enlarged for one operator, without a miss-run related to the new milling system.This paper will discuss the technical aspects of this new milling system as well as present the field performance gained to date through a field test and two case histories.

With today's high rig operating costs, identifying areas where new technology can be used to improve efficiency and reduce rig-time is critical to many a project's financial success. In deep water regions, new intervention solutions that are not rig dependent are especially desirable. Electric wireline deployed interventions have been shown to offer both technical and financial benefits in mechanical manipulation of downhole hardware, such as isolation valves, in that they are faster to mobilize and execute, saving the operator several days in rig-time and deferred production compared to pipe conveyed methods. Many deep water completions use down hole isolation valves for temporarily closing off production while awaiting flowline connections for first oil. These isolation valves can be shifted open or closed through surface commands while a backup (contingency) allows the valves to be mechanically shifted. Failure of these valves can result in expensive delays to production with large rig time costs to intervene. Operators in the Gulf of Mexico, West of Shetland and West Africa have been pioneers in the application of wireline conveyed mechanical solutions for isolation valve contingencies. The contingency consists of an electric wireline hydraulic stroking tool to shift the sleeve open or closed. The wireline stroker is either wireline tractor conveyed in high angles or run with only the shifting tool attached in low angles. A new intelligent shifting tool is also available for opening and closing valves on command to avoid hang ups on downhole profiles that may occur with the conventional spring-loaded shifting tools.

Many subsea completions employ a down hole isolation valve for temporarily closing off production while awaiting first oil or flow line connections. These valves are designed to be opened or closed through surface pressure pulses in the fluid column to activate stored nitrogen in the valve housing. When a valve fails to activate as expected, a reliable contingency plan must be ready or the financial consequences can be large. With the use of electric wireline tractor technology, a contingency valve opening system allows malfunctioning isolation valves to be mechanically shifted with depth precision and controlled force. This method uses an electrically powered hydraulic stroking tool to shift the valve sleeve open or closed with a selected force of 10K - 30K lbs depending on the type of valve. The stroking tool is either tractor conveyed in high angles or run with only a shifting tool attached in low angles. A new intelligent key tool replaces the spring loaded shifter, to allow the system to be run "slick" and avoid hang ups on down hole profiles that can occur with the conventional spring loaded shifting tools. An electric line deployed solution is faster to mobilize, more precise in locating shifting sleeves and less expensive than alternative solutions. A review of case histories will prove these points. Also, pre-job planning, integrated team involvement, SIT and operational recommendations will be discussed.

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.