Simulation of Mud Loss in Formations with Fracture Network

Based on the Monte Carlo random modeling theory, a 3-D discrete fracture network formation model has been established in an effort to solve the mud loss problem taking place in complex fractured formations. Using the Bingham model drilling fluid, a model describing the mud losses in networked fracture formations was established. This model took into consideration the linear deformation of the fractures. The model was calculated using finite element method to simulate the behavior of mud losses. Studies showed that this model was able to dynamically simulate the flowrate, rate of mud losses and total volume of mud losses inside a fracture. In fractures that were near the borehole wall, the mud flowrate was high, while in fractures that were far from the borehole wall, the mud flowrate was low. After logarithm transformation, the rate of mud loss curve showed obvious irregular fluctuation phenomenon, quite different from the behavior of mud losses in a single fracture. This phenomenon can be used to identify a formation with networked fractures. The stress sensitivity of fractures had greater effect on mud losses. Taking into account the stress sensitivity, the volume of mud losses increased. The volume of mud losses calculated from numerical simulation was close to the theoretical volume of mud losses, indicating the high reliability of the model established. Field application showed that the studying results can be used to find out mud losses into networked fractures. A mud loss control program based on this study was successfully used in controlling a mud loss just in one shot.