The operator’s concerns
Retrieving the 5 1/2-in production tubing during plugging and abandonment operations adds operational complexity and costs, and increases exposure to HSE hazards. Through-tubing cementing around gauge cables increases risks that leak paths could form over time.
What the operator tried first
The operator's scientists developed a novel testing apparatus to evaluate cement systems for P&A and zonal isolation applications, determining that unmodified Class G cement and a blend containing metal oxide–based expansion material delivered acceptable isolation performance for normal abandonment operations. However, ongoing experimental work suggested that enhancements to the conventional systems would be beneficial for sealing.
What Schlumberger recommended
CemFIT Heal system expands to seal microannuli after setting, has a low Young's modulus to withstand normal wellbore stresses, and repairs itself upon contact with oil or gas that may seep through any isolation defects that may occur later in the life of the well.