Completions

Disconnect Tools Ease Removal of Upper Completion

Intelligent completion systems have the ability to monitor and optimize reservoir performance in real time without mechanical intervention.

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Intelligent completion systems have the ability to monitor and optimize reservoir performance in real time without mechanical intervention. Although such systems were introduced more than 15 years ago, the industry has only just begun to recognize and accept the numerous benefits derived from their implementation. Operators and service companies are now looking at new applications for intelligent completion technology including:

  • extended reach horizontal wells
  • marginally economic assets in which electric submersible pumps (ESPs) are required
  • regulatory compliance, such as nonfunctional subsurface safety valves replacements

However, these applications bring with them certain challenges. In ESP applications, ESP pumps require periodic retrieval for maintenance. With the high torque and drag in long horizontal wells, deploying intelligent completions on production tubing can become a challenge. When a workover is required to replace a nonfunctional subsurface safety valve, it can become more economical to leave the existing intelligent completion in place, and pull and replace only the upper tubing string including the subsurface safety valve.
How then can one reliably install intelligent completions in these applications? Intelligent completion disconnect tools help address these challenges.

Intelligent Completion Disconnect Tools

Recently introduced disconnect tools for intelligent completion applications by Halliburton facilitate the removal of the upper completion from the lower completion without any destructive or mechanical intervention. This leaves the intelligent completion lower assemblies, such as packers, interval control valves (ICVs), and permanent downhole gauges in the wellbore undisturbed.

Intelligent completions require hydraulic and electrical umbilicals to monitor and control the gauges and ICVs in the wellbore. Besides providing tubing-to-annulus integrity, disconnect tools must also reliably disconnect (demate) and reconnect (wet mate) the umbilicals without affecting the functionality of the downhole intelligent completion equipment. Two variants of the disconnect tool are the hydraulic and the electro-hydraulic. The electro-hydraulic provides the ability to multidrop gauges on a single I-wire and hydraulically actuate ICVs in the lower intelligent completion.

Design

These disconnect tools are exclusively designed for intelligent completion applications. The tool comprises two halves: the receptacle and the disconnect sub (Fig. 1). When the two halves are wet mated, hydraulic and electrical continuity is achieved from the surface down to the ICVs and gauges.

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Fig. 1—The disconnect tool for intelligent completions.

The tool design provides for six hydraulic channels to run five ICVs using the direct hydraulics (N+1) downhole control system or up to 12 ICVs using an alternative downhole control system. The hydraulic channels on the receptacle have spring-loaded ball checks that prevent any contamination of the hydraulic control line fluids when the disconnect tool is demated. In the hydraulic-only version of the disconnect tool, the hydraulic channels are protected by a sleeve when running in or pulling out of hole. This sleeve moves out of place when the two halves are mated, thus allowing for the respective hydraulic channels to line up and provide the required hydraulic continuity. The hydraulic channels are isolated from each other and annulus or tubing with field replaceable thermoplastic/elastomeric seal stacks. These seal stacks are compatible with oil or water-based control fluids and most types of wellbore fluids.

The electro-hydraulic version, in addition to six hydraulic channels, allows for multidropping downhole pressure/ temperature quartz gauges. Electrical continuity is achieved through concentric electrical connectors housed in the receptacle and the disconnect sub. The electrical connectors are protected by a sleeve when demated and slide out of the way to allow for electrical wet mate to take place when the two halves are mated. Seals prevent wellbore fluids from contacting the electrical connector when mated.

The tool design provides for three optional latch mechanisms—snap, shear, and anchor—which are field configurable depending on the application. Metal-to-metal seal connectors are used for terminating the hydraulic and electrical umbilicals to the disconnect tool.

Qualification Testing

Robust design validation testing is paramount to help ensure a reliable product. Failure mode effect analysis (FMEA) of the design was conducted and the results used to tailor the qualification test program. Each component was individually qualified before conducting a full scale test. The following is a summary of the qualification testing that was carried out.

Electrical Connector

  • Fit and tolerance stack-up test
  • Electrical performance test: measure voltage and resistance after mating/demating
  • Soak test: short term/long term in completion brine
  • Mate/Demate test: dry mate and wet mate 10 times
  • Debris test: wet mate/demate in sand slurry

Hydraulic Seals

  • Hydraulic unload test: unstab 10 times with 500 psi in hydraulic lines
  • Hydrostatic test: subject tool to 8,000 psi at 140°C
  • Movement test: simulate tool movement due to thermal effects
  • Debris test: wet mate/demate in sand slurry

Full-Scale Test

  • Hydrostatic test: 8,000 psi at temperature/pressure (burst/collapse)
  • Shock and vibration test
  • Integration test: test functionality with ICV and gauge simulator

Completion Design

The disconnect tool is placed directly above the intelligent completion production packer. The packer provides centralization and anchors the receptacle, thus ensuring reliable mates and demates of the upper completion. A shear or anchor latch is required for the initial deployment of the lower intelligent completion assembly. An anchor or suitable shear ring rating needs to be chosen to help ensure the production packer can be set hydraulically without prematurely releasing the disconnect sub. When the upper completion is to be retrieved, rotation or an overpull on the tubing string and/or tubing pressure assist is used to shear the ring and disengage from the lower completion. On recompletion, a snap latch version is used to allow for multiple mates and demates to allow the production tubing to be spaced out and the tubing hanger landed.

Field Trial

A successful field trial of the electro-hydraulic disconnect tool for a major client in Latin America was recently conducted. The objective of the field trial was to reliably disconnect an ESP in the upper completion from the lower intelligent completion that had two ICVs and two dual sensor pressure/temperature gauges. After deploying the lower intelligent completion string and hydraulically setting the production packer, the gauges and ICVs were function tested before disconnection. Subsequently the tubing string was pulled to shear the 70K shear ring. The upper completion was disconnected and pulled out of hole. The subsequent run in hole with the upper completion and ESP reconnected to the lower completion at the same time landing the tubing hanger. The gauges and ICVs were function tested successfully. As of this publication, the well has been producing for the past 7 months with full functionality in the intelligent completion.

Operational Considerations

Wellbore cleanup is critical to the successful mating of the disconnect sub into the receptacle. It is recommended to run junk basket/dirt magnet tools before running the intelligent completion. The disconnect tool is tolerant of wellbore fines, but any large debris can prevent the disconnect sub from engaging the receptacle and damage seals. Circulating down the tubing before engaging the receptacle aids in engaging successfully.

Accurate space-out of the completion string is critical. Unlike floating production seals, the disconnect sub must be latched within the receptacle to ensure electrical/hydraulic channel integrity. Similarly, an adequate tubing movement analysis should be done to determine proper weight down required so that the disconnect sub does not disengage the receptacle during varying well conditions.

As the disconnect tool design evolves, future applications such as deepwater ESP/intelligent completions may become a reality. Safety valve replacements or monitoring of plugged and abandoned appraisal wells in deep water may be other areas in which the disconnect tool finds application.