AnTech has designed a customized sensor system for a major oil service company for use in a well intervention operation being carried out offshore Louisiana in the Gulf of Mexico. The deepwater, high-pressure field is situated in over 6,000 feet of water, and is being developed using a permanently moored semisubmersible production and drilling facility.
Known as the Triple Sensor Tool Joint Detection System -- or MDET-S, the new system is being used to detect tool joints in risers by measuring changes in magnetic fields that are triggered when a pipe joint passes through the field.
The new MDET-S was developed to improve the safety and efficiency of deploying tubing strings under pressure. To achieve this, AnTech's client developed a hydraulic workover (HWO) system to support the deepwater GOM field. The system is located under the rig floor with heave compensation provided by the rig's riser tensioning system. The HWO solution provides a high-strength conveyance method to intervene and operate under pressure from a floating vessel in deep, high pressure reservoirs. Special rig-assist HWO equipment, combined with a purpose-built BOP stack, are being used to deploy the tubing strings under pressure.
To ensure that this is carried out safely, the technician must know when the tool joints are correctly located within the BOP stack so that the joint can be passed through the set of pressure seals into or out of the well bore.
Traditionally, locating tool joints is carried out by painstaking manual measurement and careful positioning of the tubing string, in relation to a specific visual point well above the BOP stack. The objective was to replace this manual method with a device that could automatically detect tool joints and alert the technician when the joint had moved into the field of sensors.
Successful Track Record in Subsea Detection Systems
Given its 16-year history of developing and manufacturing magnetic wellhead sensors that assist deepwater operators to position specialist equipment on the seabed and detect the end of coiled tubing in a riser, AnTech was approached to formulate a solution.
To accommodate the magnitude of the new GOM installation, AnTech expanded the number of sensors from two to six, and upgraded the existing ATEX certification.
The new MDET-S is comprised of two primary features: 1) three sets of two sensors, and 2) the control unit. The sensors detect changes in the surrounding magnetic field when a tool joint passes by. The device senses the distortion caused by the additional thickness of the metal joint. No markers are required on the pipe joints. Whenever it detects a shift of this nature in the magnetic field, the sensor emits an electrical signal, transmitting it to the control box. The control box receives the signal and responds by indicating that a tool joint has passed by a pair of sensors. The control box also transmits digital and analogue signals to an external data acquisition system that transfers the readings produced to a file located on the technician's laptop. The technician can then analyze this data and proceed, secure in the knowledge that the tool joint has reached its target destination.
AnTech appreciates that one of the critical phases of a successful deepwater operation is the safe and accurate deployment of tubing strings under high pressure conditions. "The MDET-S makes it possible for engineers to effectively 'see through steel' without manually measuring and identifying their location visually. With its ability to pinpoint the location of the tool joint through shifts in the magnetic fields surrounding the sensors, the entire process is much safer and efficient, as well as more reliable," said Toni Miszewski, Managing Director of AnTech Ltd. "It means that equipment positioning is a much more precise and controlled activity," he added.
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