Near-Wellbore Formation Damage Effects on Well Performance: A Comparison Between Underbalanced and Overbalanced Drilling

Abstract

Summary Prediction of formation damage that occurs while drilling horizontal wells is a critical point for optimizing an oil field's development. The economic impact of near-wellbore drilling-induced damage and cleanup efficiency has led to significant progress being made in both experimental and numerical studies to assess wellbore flow properties during oil production. As a result, a numerical model has been developed to study the impact of various parameters related to the properties of drilling fluids on well inflow performance. This paper describes a numerical approach developed in this model to simulate near-wellbore formation damage caused by underbalanced drilling (UBD). It is generally expected that UBD will be of benefit by preventing formation damage. However, this benefit can be lost for various reasons. For instance, an overbalanced pressure can be applied on the formation during short periods of time for various operational reasons and can cause severe formation damage because of the absence of external cake protection and huge filtrate invasion. Another possible cause of formation damage in UBD is related to spontaneous imbibition, which induces water-blocking, which was observed while drilling tight gas reservoirs. A methodology for the modeling of possible formation damage during UBD is presented. Crossflow phenomena caused by spontaneous imbibition is taken into account to model the filtrate invasion from the well to the porous media, as the well is in production.