Broachment Studies Considering Fracture Propagation in a Well Containment Analysis

Abstract

Well Containment Analysis – WCA - is a set of integrity analysis criteria in a shut in scenario performed during the well design phase. The installation of a capping and shut in of the well shall not induce hydrocarbon leakages to the seabed. One of the integrity analysis criteria within WCA is a situation in which the well, in a blowout scenario, is closed with the capping, and a fracture is then initiated at a specific casing shoe of the well, propagating through shallow formations. The analysis ensures that the time for fracture propagation to reach the mudline is longer than the time to drill a relief well and have the well controlled. When considering a situation of a fracture propagation in a blowout scenario after capping and controlling the well there are two main possibilities: (I) a shallow reservoir can absorb the hydrocarbon flow from a deeper reservoir, (II) the time required for the fracture propagation to reach the seabed is greater than the time needed to control the well in blowout situation, guaranteeing that there is no fluid broaching to the seabed. When considering the time for fracture propagation, a safety margin is needed due to uncertainties in the geological data. This work aims to present a few case studies where well projects didn’t attend WCA analysis considering P90 pore pressure scenario and needed further analysis to ensure attendance of well integrity. In this situation, studies were done considering fracture propagation beginning after the well closure due to a hypothetic blowout, trying to analyze if hydrocarbons would broach to the mudline, and if so, how much time such an event could occur. Study results show the impact of geology and geomechanics on fracture propagation. There are situations in which the fracture remains confined due to the presence of a shallower reservoir and others where the fracture broaches to the mudline in a short amount of time. This analysis has the potential to turn the concept of well integrity more flexible, allowing the well designer to combine, in a tentative optimal way, a safe and feasible design in more challenging scenarios.