Solving Sustained Casing Pressure Problems at the Source

Abstract

Abstract Sustained Casing Pressure (SCP) is an industry-wide well integrity problem that increases the risk of uncontrolled formation fluid flow to the environment and unwanted damage to well construction and the shallower water-bearing formations. In some instances, the SCP must be isolated to avoid excessive pressure build-up, which can have a detrimental effect on the well construction and, in the worst case, induce a well control situation. In some instances where the pressure source is shallow, low-pressure, the solution can plug from the surface by squeezing a plugging fluid into the channel, providing a flow path to the fluids causing the SCP. However, this is only sometimes the case, and if the source is unknown, high-pressure, or deep zone, the problem must be fixed at the source. Squeezing from the surface will only mask the problem and create a scenario where the pressure can no longer be monitored. One of the common reasons for sustained casing pressure (SCP) is channels or microchannels in cement behind a casing. This can be due to cement debonding from temperature and pressure cycling or even just poor cement job results during the drilling of the well. These channels allow the pressurized formation fluids to flow from the source formation to the surface. The surface area and the geometric shapes of these channels are not uniform along the depth and can create severe resistance to the flow of viscous fluids due to the small surface area. To re-establish the wellbore integrity and mitigate the SCP without compromising the well, these channels need to be plugged with permanent sealing material at or near the source of the fluid. Due to their small size and torturous flow paths, it is usually difficult and impractical to squeeze the conventional plugging material through these channels. The most suitable sealant for plugging such microchannels is free of particles, has low viscosity, is resistant to contamination, and can be set according to operational requirements. The sealants' high viscosity, solid particles, and short thickening (gelling) time prevent them from penetrating small channels to permanently cure the problem. This paper presents a solution derived from several successful operations of similar scenarios. It discusses a proven and well-developed polyester thermosetting setting resin-based solution and the deployment techniques to re-establish the well integrity by permanently plugging the microchannels in the casing annuli. It also sheds some light on the benefits of this technology in terms of safety, the environment, and economics.