Near-Wellbore Formation Damage Effects On Well Performance - A Comparison Between Underbalanced And Overbalanced Drilling

Prediction of formation damage that occurs while drilling horizontal wells is a critical point for optimising an oil field development. The economic impact of near wellbore drilling-induced damage and clean up efficiency has led to make significant progress in both experimental and numerical studies in order 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 the well inflow performance.This paper describes a numerical approach developed in this model to simulate near wellbore formation damage due to underbalanced (UBD). It is generally expected that UBD will be of benefit from 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 it can cause a severe formation damage due to 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, experienced while drilling tight gas reservoirs.A methodology for the modelling of possible formation damage during UBD is presented. Cross flow phenomena due to spontaneous imbibition is taken into account to model the filtrate invasion from the well to the porous media as the well is producing.