During the production phase of the PW1 well, an unintentional operation depressurized the annulus A below its design limit, resulting in a progressive casing collapse from the surface casing to the tubing. Therefore, it was not possible to abandon the well conventionally. This complex abandonment scenario demanded for a rig to drill an intervention well (IW1) and set up the safety barriers. The IW1 well was successfully drilled, intercepting the production well (PW1) at 3,056-m (TD) through a 1.10-m long slotted window. The whole operation was monitored via PDG from the PW1, making possible to identify the exact moment that the interception occurred and safely displacing the cementing fluids, while avoiding the risk of fracturing exposed formations. Numerical simulations and real time monitoring of the injection pressure demonstrated the success of the operation with excellent adherence between the plan and the execution phases.
Due to the restrictions imposed by the characteristics of the PW1 reservoir, production tubing and its accessories, such as, slotted liner, ESP, NRV and DHSV, it was necessary to evaluate plugging materials that could be displaced through those restrictions without reaching the fracture limit of formation at the IW1 casing shoe. Ultrafine cement, pure resin and combinations of both were selected for their ability to pass through restrictions and resist to contamination by fluids present in the well, while also developing compressive strength to provide zonal isolation. Optimized plugging formulations were evaluated by passing them through artificial porous media, which simulated the PW1 well restrictions.
After 87 operational days, the PW1 well was successfully abandoned. A 79-m long cement plug was set in the annulus A and inside the tubing. The safety barrier was established and verified with pressure tests according to the regulatory criteria imposed by the National Agency of Petroleum, Natural Gas and Biofuels (ANP).
