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Coupled Geomechanics-Transient Fluid Flow Model to Predict Intact Zone Failure Mechanism and Sand Production: Case Study in Field X

Abstract

Sand production, caused by the formation failure due to in-situ stress and fluid flow, is prevalent during production of oil and gas from unconsolidated sandstone reservoirs. It is important to understand sand production from reservoirs since it can be very harmful to the facilities (excessive erosion, plugging, well sand-up, separator fill). Understanding the causes of sand production in a field helps to accurately predict sand production rates. In Field X, sand production prediction analysis is proposed to recognize sand rate, sand volume, and sand occurrence time. In this research, static and dynamic approaches are coupled. It captures rock deformation and failure mechanism and the transport aspects during transient flow near the wellbore. Rock strength evolution from intact zone to plastic zone is employed due to variety changing of friction angle and matrix cohesion caused by water invasion and unconfined compressive strength. At sand face near the wellbore, role of drawdown and bottom hole load condition is considered to model loose grain transportation through perforation tunnel in radial case. Generalized pressure transient solution is applied to determine wellbore storage effect. During sand lifting inside wellbore, tubing performance curve is adapted to quantify sand transportation. Results of this research in Field X can predict sand production potential of a produced well through the sand production rates profile over time. It also shows the maximum sand rates and volume, and determines at what time the sand firstly produced. Using a set of a particular field data shows that sand will start produced at 36 month while the maximum sand production rate is 0.0031061 liter/day at 60 month. In the presence of fluid flow, the amount of sand produced is directly related to the flow-induces change in volumetric plastic strain around the wellbore. Transient fluid flow and wellbore storage will effect tubing pressure curve and create heavier fluid column during sand production. Sensitivity analysis is concluded that unconfined compressive strength gives major effect comparing to friction angle, poro-elastic constant, permeability, fluid viscosity, drainage radius, and wellbore storage.