A Dynamic Sanding Prediction Model for Unconsolidated Sandstone Reservoirs with Complicated Production Conditions

Static sanding prediction models overlook the effect of reservoir pressure, water cut, water saturation and reservoir temperature on critical sanding conditions, so some differences resulted between the predicted sanding result and the practical one in the production process. In this paper, studies were performed on the influential law of dynamic factors on sanding conditions. First, the variation rules of rock strength and water saturation were fitted on the basis of experimental results. They indicated that the rock strength would decrease up to 60% with water saturation increasing from 0.15 to 0.50. Second, a dynamic prediction method was developed for critical sanding conditions in heavy-oil thermal production reservoirs by investigating the effect of reservoir pressure decrease on near wellbore stresses and the variation of reservoir thermal stress variation induced from temperature variation. And finally, an analysis was conducted on the data of injected with multiple thermal fluids of oil wells in Bohai Bay. It indicates that critical sanding pressure drawdown (CSPD) drops with the decrease of reservoir pressure and the increase of reservoir temperature can be represented by by approximate exponential law. It decreases faster in the early stages and gradually slows down. CSPD also decreases with the increase of water cut or water saturation and approximates a linear rule. For heavy oil reservoirs with thermal production, the most potential sanding is in the transitional stage of heat injection, soaking and production, i.e. the initial transitional stage to production. The production rate should be increased gradually to normal levels in this stage.