A Coupled Model To Predict Interformation Flow Through an Abandoned Well

Abstract

Summary This paper presents a novel approach for predicting flow between two formations coupled by an abandoned well. A steady-state, abandoned-well model is derived analytically and applied with a "series of steady states" to create the transient flow response. The model is verified by comparison to the results of a transient, analytical, interformation well model for a single injector given by Avci. This model is the first to include true pressure losses in the abandoned wellbore calculated from established equations for turbulent or laminar pipe flow, plugs, and a casing perforation. The model can also predict flow behind pipe through an open or plugged annulus or a fracture in the annular plug. Finally, the model is the first to incorporate the effect of pressure variations on well flow caused by production or injection in the overlying formation. Application of the model in a single-phase simulation demonstrates the impact of location and condition, rock and fluid properties, initial pressures, and well operations in the coupled formations on the abandoned-well flow. Evolving pressure distributions in the coupled formations may move flow up or down the hole. Pressure losses in the wellbore or behind pipe (through plugs) are shown to preclude flow. The model is also applied to a field case to demonstrate its use as a prediction tool for abandoned-well flow. As opposed to the limited analytical solutions or complex numerical-simulation methods currently available, the new abandoned-well model provides a simple means to determine flow for realistic field conditions.