Sand production sometimes causes the production loss. And, this gives a serious damage in the well-bore and for the ground-based instruments. In this study, we attempt to estimate the detailed behavior of sand grains around the perforation channel by a numerical simulation method coupled LBM (lattice Boltzmann method) and DEM (discrete element method). LBM is suitable for the simulation of fluid with the complicated and time-varying boundary shape. On the other hand, DEM has gotten much attention as useful solution for a large deformation problem. Therefore, this coupled method can be simultaneously simulated fluid flow in the reservoir and the behavior of the sand grains composed of the unconsolidated sandstone. As a result, because of the arching effect, amount of displacement of sand grains near the surface of perforation channel tend to be large compared with that of sand grains the end of perforation channel.
Sometimes the sand becomes the 4th component of production following oil, gas, and water. Sand production means that sand grains in the reservoir move with fluid flow and flow into the well-bore with the recovery of underground resources. It is said that this phenomenon tends to occur with three following cases.
Unconsolidated sandstone weak-bonded between sand grains.
Production under the excessive drawdown.
Dissolution of a cementing material between the sand grains by the water.
This phenomenon blocks up a tubing pipe and causes the production loss. And, this gives a serious damage in the well-bore and for the ground-based instruments. It is called sand trouble. Sand control is a technique to prevent the sand trouble directly. On the other hand, the sand management is a concept to permit sand production to some extent. In either case, it is demanded to clarify the mechanism of sand production. However, the mechanism of sand production has not clarified, and it is thought that this is indispensable for the prediction of sand production. In this study, phenomenon of sand production is simulated using a simulation method coupled LBM (lattice Boltzmann method) and DEM (discrete element method). LBM is a numerical simulation method which calculates the density distribution function of the virtual particle of fluid and solves the evolution equation of it. This method is suitable for the simulation of fluid with the complicated and time-varying boundary shape. On the other hand, DEM is useful for discontinuity body analysis, especially got a lot of attention as a solution for a large deformation problem. We think that this method is able to simulate the dynamic behavior of sand grains by considering unconsolidated formation as an aggregate of minute particles. We attempt to simulate the detailed behavior of sand grains around a perforation channel using this method. The target domain in this study is shown in Figure1.
Fig. 1. Perforation channel. (available in full paper)
2. NUMERICAL SIMULATION METHODS
2.1. Lattice Boltzmann method
In recent years, the lattice Boltzmann method (LBM) has made brilliant progress as new technique of numerical fluid dynamics.