Quantitative Prediction of Sand Production in Weakly Consolidated Sandstone through Numerical Simulation

摘要

During the oil and gas development from weakly consolidated sandstone reservoirs,sand production problem is highly prone to occur,resulting in oil production reduction,down-hole tool abrasion and even oil well scrapping.At present,analysis of sand production in oil and gas wells is mainly the prediction of critical down-hole pressure,and there are relatively few studies on the prediction of sand production volume with different practical down-hole pressures.Quantitative prediction of sand production involves elastoplastic behavior of the formation rock and fluid flow within the pores,and it is influenced and controlled by various factors such as mechanical properties of the formation,fluid properties,completion and production technologies.In order to accurately predict the volume of sand production,it is assumed that the weakly consolidated sandstone is a homogeneous isotropic porous elastoplastic medium for which the Mohr-Coulomb criterion is adopted to describe the abrupt strain softening and residual plastic flow.A finite element sand production model has been established for modeling the coupled reservoir matrix mechanical behavior and hydraulic erosion.By comparing with the results of laboratory sand production experiments of weakly consolidated sandstone,the erosion intensity coefficient in the model was determined.Parametric studies have been performed to predict the sand production volume of a realistic oilfield under different conditions.The calculation results show that the borehole diameter of weakly consolidated sandstone is enlarged after erosion for a certain period of time,and there is a change process from rapid sand production,stable sand production to slow down to the trend of no sand production.In the case of high production differential pressure,the total sand production volume is larger than the low production differential pressure.The simulation results can be beneficial for the decision-making of sand production management in weakly consolidated sandstone reservoirs.