Development and application of a novel approach to sand production prediction
Lamorde, Mustapha Halilu
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Sand production is a complex problem that has plagued the oil and gas industry for decades, leading to reduced productivity, wellbore instability, equipment failure and expensive sand control and management techniques. Therefore, a reliable prediction of the potential of a formation to produce sand as well as the mass and volume of the sand produced is required for an appropriate and economically effective sand management. In this thesis a novel approach (yield energy model) to predict the potential of formation to produce sand and to quantify the mass of sand produced around yielded wellbore region based on energy dissipation is presented. During drilling and hydrocarbon production, yield and fragmentation of rock around a wellbore may occur when the rock is exposed to stresses which exceed its failure criterion, creating yield zone and hence the potential for instability and sand production. Generally, in brittle rocks, grains are deformed elastically with increasing stress, storing strain energy in the process. The stored strain energy is dissipated during failure, some of which is available for the fragmentation of the rock along failure surfaces. It is argued that the major source of sand production in competent rock is associated with the debris created by slippage along shear fractures in the yielded zone along perforation wall. The potential for sand production and the mass or volume of the sand created around the yield zone is predicted by quantifying the reduction in strain energy stored in the rock as its yields around a completion on removal of completion fluid and the imposition of drawdown. The resultant sand then becomes available as a source for sand production. The yield energy model has been applied to assess the potential of several reservoir samples to produce sand and also quantify the mass of the sand produced as a result of formation instability caused by drilling and hydrocarbon production in a field specific manner. Results from laboratory testing of representative samples and field data has been utilised as input parameters. The extent of the failed zone, the sand production potential and the mass of debris have been analysed as a function of mud weights, drawdown pressures and production rates. The impact of unique production performance of different horizons on formation stability has been accounted for by employing deliverability expressions. The results have been assessed with regards to field observations and were found to be consistent.