Special Report: Healthy wells
Proactive well integrity management with through-barrier diagnostics, by Ken Feather, chief marketing officer of TGT Oilfield Services
Proactive integrity management is a key focus area for exploration and production operators, and rightly so. Well integrity is fundamental to enabling maximum well system performance, and minimising cost and risk for the operator.
A well is usually delivered intact when new but issues like leaking connections or poor cement isolation can exist from the start and these of course need immediate and regular integrity diagnostics surveillance.
Then, as the well becomes exposed to harsh working conditions underground over many years, integrity breaches will occur, with these needing diagnosis and addressing early on.
Inside the tubing diagnostics
Through-barrier diagnostic systems – a capability TGT scientists and engineers have been pioneering for years – are vital for this task as they can evaluate most of the well system from inside the tubing.
Through-barrier diagnostic systems sense dynamic well behaviour and certain well properties behind well barriers – and consequently evaluate the condition and performance of the well system from inside the tubing. Such systems can determine the wall thickness of individual tubulars in up to four concentric pipe strings to track corrosion in each pipe. They can also locate fluid movement behind the pipe – essential in determining annulus integrity or locating barrier leaks.
Through-barrier diagnostic systems cleverly harness heat, acoustic and electromagnetic [EM] energy to perform certain measurements downhole and engage sophisticated processing and modelling to transform these measurements into insightful and useable answers.
It’s important, however, that through-barrier diagnostics keep up with current well integrity challenges.
High-chrome tubulars are increasingly prevalent in the Middle East as a means of combatting corrosion but also challenging for ordinary EM well inspection systems to operate, due to a decrease in ferrous content and conventional EM signals decaying too quickly.
High chrome deployments
With this in mind, TGT recently conducted three successful high-chrome deployments with its EmPulse well inspection system – one a yard test with a 28% chrome pipe with built-in mechanical defects, and the two others live wells with high hydrogen sulphide and 28% chrome tubulars.
In the first case, the high-speed EM sensor technology and ‘time-domain’ measuring techniques correctly identified man-made defects and in the two live wells they recorded the status of three concentric well barriers.
Another well integrity challenge is cementing – particularly in deeper and longer reach wells – where cementing techniques and sealing abilities are being pushed to the limit. In such cases, ‘spectral diagnostics’ is a technology that tracks fluid movement behind pipes within several casing strings and identifies leaks and flowpaths.
Key to spectral diagnostics is its ability to utilise high-fidelity downhole sound analysis systems to capture the frequency and amplitude of acoustic energy generated by liquids or gas moving through integrity breaches and restrictions.
Understanding well integrity
While the meaning of ‘well integrity’ is often debated, it has one unifying principle – that of containment – ensuring that the right fluids connect safely and productively via the wellbore to surface, and that they don’t stray along unwanted flowpaths either inside, or worse still outside the well system.
Since most integrity failures happen behind tubing or casing, it’s incumbent upon through-barrier diagnostics to deliver the well system insights that Middle East operators need to ensure safe and productive operations. It’s reassuring to know that technologies are evolving to meet these challenges.