A great number of the world's most prolific reservoirs are naturally fractured carbonate and clastic rock systems. Optimisation of production from this kind of reservoirs is a great challenge owing to complexities inherent in their characterization. These complexities arise, in part, from the need to characterize the matrix and the fracture sub-systems separately and to continually optimize the characterization process throughout the production phase to accommodate pressure depletion effects on production.
Laboratory experiments were performed on a Clashach core sample with a simulated single fracture to investigate the mechanisms for formation damage induced by pressure depletion and subsequent increase in effective stress in fractured reservoir systems.
The experimental results show that excessive pressure depletion during production resulted in increased effective stress loading on the simulated fractured formation system. The effective stress reached a critical value at which the fracture plates were brought into contact, leading to the crushing of sand grains at these contacts. The grain crushing resulted in grain accumulation in the flow streams which, in turn, led to pore throat and fracture space blockage and increased pressure drop across the fractured core system.