The Use of a Fully Coupled Geomechanics-Reservoir Simulator To Evaluate the Feasibility of a Cavity Completion

摘要

Cavity completions have been widely used to increase productivity from non-conventional sources such as coalbed methane reservoirs and “heavy” oil from weakly consolidated formations. In the 1990s, the technique was applied to conventional wells where massive sand production was allowed with the objective of creating a cavity. The benefits expected from a cavity completion are four-fold: 1) increase in PI by reducing skin, 2) increase in effective wellbore radius 3) creation of an enhanced permeability (dilatant) zone near the wellbore, and 4) decrease in pressure drop near the wellbore to values below the critical threshold for sanding. Even though there are analytical tools available for predicting the initiation of sanding for simple well configurations, there are very few models that are capable of predicting cavity stability or cavity growth for general field applications. This paper introduces results from a fully-coupled geomechanical/reservoir simulator, GMRS~R, which predicts cavity geometry evolution, sanding rates, cavity stability/instability, and production enhancement because of the creation of a cavity. In this study, GMRS~R is used to investigate the feasibility of a cavity completion in a well located offshore West Africa. This well started producing moderate amounts of sand in 1993. GMRS~R is history matched with historical production data prior to sand predictions, and is used to investigate cavity initiation and growth for the well. An axisymmetric model is used with the reservoir treated as a poroelastic-poroplastic material with hardening. Porous flow is modeled as a black-oil two phase (oil and water) flow model. For the well investigated, sensitivity studies with varying formation properties predict that sand production and cavity generation will be unstable.