Near-Wellbore Modeling: Sand-Production Issues

Abstract

This article, written by Technology Editor Dennis Denney, contains highlights of paper SPE 109894, "Near-Wellbore Modeling: Sand-Production Issues," by Guillaume Servant, IFP; Philippe Marchina, SPE, Total; and Jean- Francois Nauroy, IFP, prepared for the 2007 SPE Annual Technical Conference and Exhibition, Anaheim, California, 11-14 November 2007. The paper has not been peer reviewed. Sand production in an oil or gas well can cause operational difficulties, but it contributes to production enhancement by improving the well inflow performance. To assess the relative magnitude of those effects and to optimize the well completion and operation, a quantitative forecast of the expected amount and rate of sand production must be made. This forecast requires a correct description of all the mechanisms involved in sand production, sand transport in particular. The proposed numerical method considers that the geomechanical problem (rock failure) interplays with the transport of sand. Equilibrium equations that control rock failure (solid mechanics) and sand transport (fluid mechanics) are solved simultaneously by an iterative coupled scheme at the wellbore scale. Introduction Sand production causes production problems and can generate safety and environmental hazards. However, it can increase the inflow performance of the well. Therefore, the option of installing downhole sand-control equipment may not always be the best economic solution for the project. Heavy-oil reservoirs can benefit from allowing sand to be produced with the oil. This technique, known as cold-heavy-oil production with sand (CHOPS), allows higher production rates than conventional techniques. Again, the productivity and ultimate delivery of the well will depend on the amount of sand produced. Therefore, the ability to anticipate the sand-production mechanisms in terms of sand rate and volumes, and anticipate sand-producing patterns in the reservoir, is required for optimized development of such fields. Two mechanisms contribute to sand production: rock failure (through which freed sand grains are generated) and transport of those free grains by the effluents into the wellbore and up to surface. Most current sand-production-risk models concentrate on the rock-failure analysis and, as such, can determine only the conditions for the onset of sand production. In the proposed model, the rock-mechanical aspects are coupled to the sand-transport problem. Therefore, interaction between the solid matrix and the slurry flow can be analyzed and translated into quantitative sand production. Paralleling development of this numerical model, a series of sand-production experiments was carried out in a purpose-built laboratory apparatus with the objectives of understanding the sand-production processes in uncemented reservoirs better and providing high-quality data sets for calibrating the model.