Application of the yield energy approach to prediction of sand debris production in reservoir sandstones

A novel methodology of predicting sand debris production based on the yield zone and fracture energy dissipation of experimentally produced shear fractures, created under various triaxial stress states, is presented. This technique involves determination of the lateral extent of the failed rock around a wellbore, quantifying the energy available for fracturing and applying experimentally determined comminution constants to estimate the volume and mass of debris created. In more brittle and competent rocks, grains are deformed elastically with increasing stress, storing strain energy in the process. During failure, the stored strain energy is released as heat energy, seismic energy and also in the context of sand production as comminution of grains into debris.

The proportion of energy which accounts for the generated debris is estimated from the ratio of the energy dissipated in the creation of debris (EA) to the fracture surface energy (GIIC) required for the extension of the failure surface. The fracture surface energy (GIIC) is determined from the shear stress on the failure surface and the slip along it (slip weakening curve) generated during triaxial tests. The debris will be accumulated between the failure surfaces and may be available for sand production. This technique is used to determine the propensity of sand production of several reservoir sandstones.