Cementing Bullheading Simulator for Well Plugging and Abandonment with Coupled Well-Reservoir Modeling

Abstract

Abstract Oil & Gas E&P operations are known for its financial and operational risks. In regard to environmental regulations, an O&G well must comply not only with the restrictions for its operational life, but also to those conceived for its decommissioned life. One such restriction involves guaranteeing that different Oil and Gas zones are kept isolated from each other after the well is decommissioned, i.e., abandoned. One of the various techniques deployed in these cases is Cement Bullheading, consisting of pumping cement down the well, so that cement plugs the porous media making it impermeable, and therefore, isolated. A cement bullheading well abandonment simulator equipped with a coupled well and reservoir model was developed to assist in the decision-making of well decommissioning processes. The numerical model covers the whole cement path, starting at the Oilrig tank, down to the reservoir, modeled through hoses, risers, tubulars, completions and rock formation. Different models of fluids are considered, such as biphasic fluids, cement paste and cement/foamed fluid. Changes in Well Injectivity are computed based on the pressure reservoir response (3D FEM Simulator) along with cake formation, which depends on the adopted filter cake model. Thermodynamic effects are also addressed during the operation, considering heat exchange between well components and reservoir, including fluids, casings, and rock formation. The main simulator output are time dependent curves, along the whole cement path, for pressure (casing and rock stress operational limits), temperature, fluid position, flowrate and when using foam fluids, the nitrogen injection rate. Results are checked against field data and so far are very promising.