Simulation Study of Water Coning in Iranian Fractured Reservoirs

The water coning which is created by imbalance between gravity and viscous forces is the most important reason of water production in many oilfields. There are different controllable and uncontrollable parameters affecting this phenomenon; in this study some simulation models were constructed to analyze the effect of different parameters in a radial single-well model. Furthermore, some studies were done using multi-well models in order to investigate the effect of them.A systematic parameter study has been carried out. It was determined that oil layer thickness, perforation thickness, fracture permeability and its anisotropy, especially horizontal fracture permeability, production rate, matrix permeability, mobility ratio and storativity have the major role in water coning phenomenon; also it was determined that fracture spacing and aquifer power has negligible effect on water coning in fractured reservoirs. The change of breakthrough time of water cone respect to each effective parameter has been studied and each trend was shown, so it seems necessary to optimize the conditions before adjusting the location of wells and determining production program. Multi-well studies showed that the trend of dependency of water coning on each parameter is similar to the single-well model, however coning simulation in field scaleis a unique problem for each field. In the other word it is necessary to have all data correspond to reservoir, well location, and production history completely for a successful simulation, because a small pressure drawdown exerted by a far well will affect the cone shape and its breakthrough time. The significance of this work is the study of coning phenomenon in carbonated reservoirs. Carbonated reservoirs having fractures in different scales are very different than conventional sandstone reservoirs. In this work in addition the all critical parameters, the role of single-well versus multi-well in coning phenomenon have been investigated and the results are discussed.