Deployment System

Introduction

More than 70% of the oil produced today comes from fields more than thirty years old. Hence even marginally improving the performance of wells that are already producing is a cost-effective way to offset natural decline, extend field life and improve hydrocarbon recovery. Production logging efforts aimed at evaluating wells and recommending effective well interventions are essential ways to increase productivity. Gathering data for use in production optimisation modelling has for many wells been regarded as impossible or too expensive compared to the potential for increased production so developing new ways to reduce these costs is of the utmost interest for the oil and gas industry.

In the Norwegian sector, the introduction of wireline tractors has made a significant contribution to the reduction of well intervention costs compared to the use of coiled tubing and snubbing. For example an oil company in the North Sea, performing on a yearly basis 30 operations, can each year save as much as 20 million USD by applying tractor technology instead of coiled tubing. This equates to a 40% reduction in the cost of production logging when using wireline as opposed to coil tubing methods. Each well intervention operation has to be carefully evaluated with regards to conveyance method, though studies suggest that wireline tractor technology in many types of operation is favourable.

The main restriction to utilising tractor technology is the rig up height available on the platform, a problem exasperated by modern production platform design. Most of these platforms have just 10-15 metre total rig up height and with the tractor alone typically measuring 6-8 metres there is little left for the production logging string. This was the very problem facing a major Norwegian operator who contacted Phuel Oil Tools (Phuel) requesting the development of a system to allow longer strings to be deployed into the live well in a safe and consistent manner. Thus the Phuel Deployment System was born.

System Overview

The challenge facing Phuel was to develop not just equipment, but a system that could be utilised on any platform, with a simple and safe operating principle that could be repeatedly implemented time and time again. The result is a system comprising of a Blow Out Preventer (BOP), a deployment window and a detection system. The detection system consists of a number of bars, into which magnets are strategically placed to allow the bar to be positioned correctly in the BOP in order to seal on the bar and block well fluids from escaping to surface. A magnetic detection system is employed to provide positional information to the wireline operator so that the rams of the BOP can be set when the bar is in the correct position. The deployment window is located immediately above the BOP and when opened provides access to the top of the bar and the bottom of the tool string to make or break the connections between each string length. Click here to see the movie.

Detection system

The most critical part of the deployment operation is the communication of the string position to the wireline operator so that each section can be landed in the BOP correctly. Two simple magnetic sensors are mounted to the BOP and magnets are located in the deployment bars. A handheld display incorporates four lights that when operated by the microprocessor in conjunction with the output of the sensors, indicates the magnet position. The system allows for the deployment bar to be landed repeatedly within 1cm (0.4 in).

Work window

The deployment operation requires manageable sections of the tool string to be landed off in a BOP and sealed while further sections are added above. This would normally require that the lubricator be lifted up and the connection at the cable head broken. The action of working below an objected supported on a hoist is not acceptable under most safety policies so there is requirement to break the inner connection prior to lifting.

The deployment window can be considered as a section of lubricator with a hydraulic sleeve that when open provides access to string within. The design and operation procedure accommodates the testing of the sleeve in the closed position prior to filling the lubricator.

Combined BOP

The Deployment Quin (five ram sets) BOP will locate directly above the Christmas Tree and provides traditional wire-line valve protection plus the additional two rams to seal on the deployment bar. The shear and seal ram has the increased ability to shear through the deployment bar (when in the correctly set position) if required.

The Quin design, incorporating the standard wireline BOP and a dual deployment BOP emphasises the commitment to the system approach and allows standardisation of the rig up procedures and associated safety risk assessments.

Deployment bars

The Deployment bars provide a suitable diameter to seal against the ram seals and places the magnets in a strategic location so that when set in the BOP the end connections are available through the deployment window. They are also an integral part of the deployed tool string and in the case of electric logging must maintain the electrical connection through to the tool string sections.

As an additional safety feature the deployment bars are fitted with pressure bulkheads in the electrical conductor so that in the event of well pressure entering the tool string it will not escape to surface.

Cost Saving benefits

The use of the Phuel Deployment System in conjunction with wireline production logging (with or without a tractor) will yield significant cost savings in operational time when compared to equivalent coil tubing operations. When combined with properly designed remedial stimulation the oil company can rapidly provide increased oil or decreased water production, or both.

Time Comparison

The total speed of the whole operation determines the time the well is shut in. Reducing the production delay has great economic value. The total time is an accumulation of rig up, running of tools, rig down and occasionally lost time. The rig up/down and operations of wireline is less affected by weather conditions compared to coil tubing, which also requires heavy lifts and typically requires one more crew member. Rigging up a coiled tubing service package offshore may typically take 30-50 hours. Equivalent preparation time for a tractor deployment operation is only 8-12 hours, which includes pre-job checking of the logging equipment. The actual rig up of the deployment system does not add any significant time. When the saved total operational time is added up through the year, the cost benefit from the extra production is very significant for an oil company.

A time comparison between coiled tubing and wireline operations concluded that on average is was possible to complete six tractor runs in the time to complete one coil tubing operation. According to Expro, a wireline tractor operation and coil tubing operation ran against each other in a back-to-back log off. The wireline operation completed two runs and was rigged down before the coil tubing operation was fully rigged up.This highlights the significant savings that can be achieved with the Phuel Deployment System when using tractor technology compared to coil tubing conveyance.

Reservoir Utilisation

A deployment system that provides lower cost well interventions will allow for more extensive well logging at a much higher frequency, thereby increasing the reservoir utilisation. An accurate model of the well production system can then be developed using the gathered information to determine net pay, reservoir pressure, permeability, skin and the saturation of oil, gas or water. Once the model is validated remedial interventions can be recommended, cost estimated and viable options compared based on estimated well productivity and operators economic constraints.

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