Dynamic Effects of Foamy Fluid Flow in Sand Production Instability

Abstract

SPE Members Abstract As a major component in the development of better flow models for the "cold production" process in heavy oils, formation of a foamy fluid phase during flow of a liquid containing dissolved gas toward a wellbore is considered. The appearance of gas bubbles in the flowing fluid is described by the theory of nucleation. Unlike previous approaches, the foamy state is interpreted as a metastable state which starts developing at pressures below the bubble-point of a gas-fluid phase diagram. The amount of gaseous phase is determined kinetically, that is, by the rate of nucleation. Mass balance analysis for the compound foamy fluid gives the spatio-temporal evolution of the foamy zone which starts growing around the wellbore Fluid pressure in the foamy zone exhibits a steeper gradient, compared to the non-foamy flow. The conditions of sand production instability via tensile failure at the foamy front are also determined, and this constitutes a condition for liquefaction and loss of effective stress in the granular medium. Introduction Several studies show that many heavy-oil reservoirs in Alberta and Saskatchewan exhibit foamy-oil behaviour, which leads to better than expected primary production. This behaviour is accompanied by sand production, and it is also realized that sand control measures tend to massively reduce the oil production rate. These observations suggest that the sand production might be physically linked to foamy-oil flow. A new, physics-based model for massive sand production has been developed for the case of one-phase fluid flow. If pressure in a borehole in an unconsolidated sandstone under general stress is lowered below some critical magnitude, the shear yield condition may become fulfilled, and a yielded and flowing zone may start growing around the wellbore. P. 113