During a virtual webinar at the OWI LATAM 2021 conference, Maxim Volkov, the Principal Domain Champion at TGT Diagnostics, spotlighted how ‘tube integrity diagnostics’ are pivotal to successful well operation, and how ‘Pulse’ electromagnetic (EM) technology can deliver the most accurate metal wall thickness measurements in all completion types, including specialised alloys with high chrome and/or nickel content.
On the importance of wall thickness measurements, Maxim explained that such figures can help deliver a safer and more precise calculation of burst pressures for tubing and perhaps more importantly, casings. Well operators need to maintain wells within the ‘Maximum Allowable Wellhead Operating Pressure’ (MAWOP), and calculating the most accurate burst pressure figures are key to achieving this.
In terms of conventional technologies, such as multi-finger callipers, flux leakage tools, ultrasound inspection, and older EM tools, there is a general lack of accuracy or capability to assess casing behind tubing. This is traditionally solved by pulling the tubing out of the well using expensive rig or hoist operations to expose the production casing as the primary metal surface. This obviously disrupts well operations and requires significant resources and energy utilisation.
New electromagnetic surveys provide a more efficient solution, and are able to supply wall thickness estimations of multiple casing strings up to 20” diameter, to an acceptable level of accuracy.
‘Pulse’ technology
The ‘Pulse’ platform is one of four technology platforms that make up TGT’s ‘True Integrity’ diagnostic system. Pulse is used by analysts and operators to provide an accurate barrier-by-barrier assessment of up to four concentric tubulars from a single through-tubing deployment. And unlike conventional systems, it works in all completion types, including dual string and corrosion resistant alloys.
Pulse combines advanced electromagnetic sensing and measurement technology with powerful modeling and analysis capabilities. Pulse features multiple coil sensors, each optimised by length and geometry to engage with a particular tube size. This enables it to assess the electromagnetic signature of each tube and establish wall thickness variations.
Using electromagnetics to diagnose the condition of multiple tubulars is the most reliable solution currently available for tube diagnostics. The technique is sensitive to metal only, and is free from scale or cement influence, helping it provide a reliable wall thickness assessment where the other technologies fail.
Also, EM diagnostics can be deployed while the well is active, with minimal impact on operations and cost.
Pulse deployment
Pulse can be deployed in multiple configurations with multiple sensors optimised for different tubing and casing scenarios. Short sensors can target tube diameters up to 4 1/2", with long sensors targeting up to 13 3/8" in diameter, and extra long targeting up to 20".
Coils transmit a repeating EM pulse and record the electromagnetic response, with each coil sensor capable of registering responses from different layers of casing and tubing in the well.
Multiple coil sensors are optimised to scan a different radius, enabling operators to determine which layer is being affected by corrosion and to what degree.
Pulse diagnostics delivers accurate results up to ±0.25mm for first tube, ±0.75mm for second, ±1.5mm for third, and ±3.6mm for the fourth metal barrier.
The utilisation of Pulse technology is helping the industry to keep wells safe, clean, and productive.
