Remote equalization device saves recovery costs for operator: particularly effective in highly deviated wells, a remote, intelligent equalization device allows the operator to have maximum pressure testing flexibility while avoiding tricky retrieval problems

A remote equalization device successfully completed an operation on Paladin Resources' Montrose platform in the UK North Sea. This allowed a well to be brought onstream in the face of a challenging situation, and it saved the operator considerable recovery costs. A problem encountered during the running-in phase of a new completion meant that communication between the tubing and annulus had been introduced. Red Spider Technology's Hydraulic RED (Remote Equalization Device) was mobilized to enable the operation to continue.

Helix RDS (HRDS), the Montrose well operator, sourced a straddle assembly to set across the communication path. However, the throughbore of the straddle meant that no wireline plug or retrievable bridge plug could be installed or retrieved through it.

Red Spider was contacted for help, and the service firm suggested utilizing a RED device below a conventional wireline set lock. The straddle was then set across the communication path. Tubing pressure was applied to 1) hydraulically set the production packer; and 2) perform various tubing integrity tests, Fig. 1.

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All tests completed successfully, and the RED was remotely opened from the surface in 8 min. Finally, the TCP (tubing-conveyed perforating) guns at the completion bottom were fired remotely from the surface. The well was brought onstream without need for further intervention, with production flowing through the open RED and straddle assembly.

The ability to leave the plug downhole meant that downtime was a matter of hours. Thus, a potentially high-cost, high-risk fishing/milling operation-was averted.

Phil Stratford, HRDS drilling superintendent, said, "The Hydraulic RED allowed us to solve a tricky downhole problem with minimum cost impact, and bring a new well onstream without delay. Red Spider was able to respond well to our short notice requirements, and the product performed exactly as specified."

INTELLIGENT EQUALIZATION DEVICE

The RED (patent pending) is gaining recognition and usage in the North Sea. It is typically run as part of a plugging assembly, such as a wireline lock or retrievable bridge plug. It is an intelligent equalization device that gives the operator an ability to perform any number of pressure tests above or below, up to its maximum rating. The number of tests can be decided upon, and varied, while the tool is in the hole. It also has the added benefit of being able to be opened at any time when desired. This gives the operator maximum flexibility in fixed or changing conditions.

The device was developed and launched by the vendor 18 months ago and has since been run in a variety of differing applications. It is deployed below a carrier device, such as a lock, retrievable bridge plug or packer and acts as a pressure-retaining barrier capable of containing pressures of 10,000 psi in either direction until opened. The device is opened by applying a pre-determined pressure for a pre-determined time. Once opened, the device cannot be closed.

UNIQUE OPERATING MECHANISM

The key to RED operation is the pressure discriminator mechanism, Fig. 2. This effectively locks the device until a pre-determined pressure/time window is met. The "command-to-open" pressure/ time band is typically set at 2,000 to 2,500 psi, and this is held for 10 min. When these conditions are met, the device will open. To prevent opening, the operator simply prevents the opening pressure/time combination from occurring.

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To define the operating window, some basic well condition data are required (i.e. the pressure differential across the device and the well temperature). This is established before the device leaves the vendor's workshop. It is set up and tested at these conditions to avoid the need for pre-installation setup on the rig floor.

The RED was developed to address operators' needs for a versatile tool that could adapt quickly to changing operational requirements. It was designed specifically to handle debris, and to allow operators to test up to the maximum rating of their tubing. It does not employ cycle counting or shear pins to operate. Thus, it allows as many, or as few, tests to be performed, as required. This is unparalleled flexibility for a plugging device.

QUALIFICATION TESTING

Rigorous qualification testing was performed during the tool's development, which covered the entire scope of its working envelope. Testing included:

* A full FMEA on the device's component parts

* Mechanical testing to prove operational functionality

* Fluid chamber testing to quantify temperature effects

* Pressure functional testing of the tool, to prove pressure integrity and the determination of the opening window at various temperatures

* In-house operational simulation, including impact testing

* Debris test simulation

* Qualification to ISO 14310 V3

* Operational rig-up, setting and function testing at an onshore test facility.

A series of tests was performed to determine the time window at temperatures from 0[degrees]C to 150[degrees]C. This allowed a detailed, accurate relationship to be established, allowing the user to accurately define the time window for any operational conditions.

The tool was also tested to grade V3, as per ISO 14310 6.5.2.5 (Petroleum and natural gas industries; Downhole equipment; Packers and bridge plugs). Grade V3 is aimed at testing packers or bridge plugs, where axial loads are expected in conjunction with pressure and temperature effects. This grade was the basis for the test, except for axial loading, which would not inherently be an issue for the RED when attached to an anchoring device. The plug was successfully opened after completing the test.

FLEXIBILITY, ADAPTABILITY AND DEBRIS TOLERANCE

The RED is particularly suited for use in highly deviated wells, and where debris is present or expected. It is designed to save the operator rig time and operational costs. It provides the following benefits:

* Ability to test to maximum pressure. The device can be tested to its maximum pressure rating, as many times as required. It allows multiple testing to occur without the risk of premature shearout

* Flexibility. The range of pressure testing does not have to be predetermined. This provides good operational program flexibility.

* Opened when required. The device can be opened at any time, when required, by applying a predetermined pressure from above.

* Flow-through. The well can be brought onstream without pulling the device. Once opened, there is a large flow area through the equalization ports (which is greater than the flow area through the carrying device). This provides early access to production revenues.

* Adaptability. It can be operated in both overbalanced and underbalanced conditions--changing well conditions can be accommodated.

* Remote operation. It can be run in long-reach and highly deviated wells, where retrieval intervention is difficult.

* Debri-tolerant. It is suited to conditions where sand or debris accumulation is expected from above. It reduces the likelihood of intervention and bailing.

WIDE APPLICATIONS FOR USE

This RED can be used in a wide range of differing applications. For example, it can be shallow-set for tree testing and change-out, or deep-set for packer setting and tubing testing. It has applications for subsea plugging jobs, where intervention costs are high. The device is particularly suited to extended reach or horizontal wells, where carrying device retrieval may be problematic.

The device is being considered by a Norwegian operator for an application that requires pressure testing of a well prior to fraccing or stimulation operations being carried out. When testing is complete, the device will be opened, and the frac balls will be pumped through the equalization ports to the target area.

INITIAL SUCCESS IN NORWAY

The hydraulic RED saved money for Statoil on its first operational job as part of the plugging assembly during equalization and retrieval operations. A hydraulic master valve (HMV) was found to be in need of repair on one of the wells at Gulfaks field. To safely carry out this operation, a means of isolating the well was required prior to undertaking the operation. A 7-in., retrievable bridge plug assembly was to be run as the shallow barrier, and the client wanted a means of remotely equalizing the device prior to pulling.

Equalization of a plugging assembly is typically achieved by one of the following methods--pressuring up and shearing out a mechanical plug; intervening into the well and pulling an equalizing prong; or applying multiple pressure sequences to a pressure cycle plug to shear it out.

All of these methods have their own challenges that can lead to problems, such as premature shearout of the equalizing assembly; plugging due to debris settlement; or application of a higher pressure than that of the test pressure, to shear out the equalizing mechanism.

Statoil recognized these issues and saw that they could be avoided by using the RED. The device was attached directly beneath the 7-in. retrievable bridge plug that was run and set at 62 m (203 ft). The plug was pressure-tested from above, then inflow-tested by bleeding off the pressure above. This effectively resulted in a pressure differential from below to above the plug of 154 bars.

Frank Skjerping, lead well engineer at Gullfaks, said, "Due to repair on the HMV, a shallow barrier plug was required. Prior to pulling the plug, the equalizing device was opened by pressuring up the well above the plug to 330 bars and waiting for 10 min. After 10 min. had passed, the wellhead pressure dropped to 150 bar, indicating successful equalization. The plug c/w hydraulic RED was then retrieved to surface. The feature with this equalizing device is that one can pressure-test as many times as you like without opening the valve. No pressure cycling is required."

The device functioned as designed, enabling the operator to equalize across the plugging assembly without intervening into the well or exceeding previous test pressure, to hydraulically shear out a conventional equalizing device. This resulted in time savings and reduced HSE exposure, allowing flexibility to accommodate program changes

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Mike Reid is director of Product Development at Red Spider Technology in Aberdeen, Scotland. He graduated from The Robert Gordon University in Aberdeen, with a BSc degree in mechanical engineering and worked as a slickline operator for Camco before joining Petroline as a tool designer in 1986. He left in 1989 to start his own company, Well Equip Ltd. (an oil tool design business), which grew rapidly before merging with Petroleum Engineering Services Ltd (PES) in 1996. PES was subsequently acquired by Halliburton, and Mr. Reid was assigned as project designer to Well-dynamics, a J.V. between Shell and Halliburton focusing on intelligent completion systems. He has several patent applications to his name.

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