Browsing by Subject "seismic modeling"
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Item Numerical modeling of time-lapse seismic data from fractured reservoirs including fluid flow and geochemical processes(2009-05-15) Shekhar, RaviFractured reservoirs, especially in low permeable carbonate rocks, are important target for hydrocarbon exploration and production because fractures can control fluid flow inside the reservoir. Hence, quantitative knowledge of fracture attributes is important for optimal hydrocarbon production. However, in some cases fractures can cause leakage of injected CO2 during enhanced oil recovery (EOR) or CO2 sequestration. Furthermore, CO2 can geochemically interact with reservoir fluids and host rock. Hence, time-lapse monitoring of the progress of CO2 in fractured reservoirs is also very important. In order to address these challenges, I have developed an integrated approach for studying fluid flow and seismic wave propagation in fractured media using Discrete Fracture Network (DFN) models. My seismic simulation study suggests that CO2 saturated reservoir shows approximately ten times more attenuation than brine saturated reservoir. Similarly, large P-wave velocity variation in CO2 saturated reservoir and amplitude variation with offset (AVO) results for our example model predicts that CO2 is easier to detect than brine in the fractured reservoirs. The effects of geochemical processes on seismics are simulated by time-lapse modeling for t = 1000 years. My modeling study suggests that intra-aqueous reactions are more significant during injection of CO2 for t = 6 years, while slower mineral reactions dominate after pressure equilibrium is achieved that is from t = 6 to 1000 years. Overall both types of geochemical reactions cause change in reflection coefficient of 2 to 5%, which may be difficult to detect in some cases. However, the significant change in the seismic properties at the boundary of the CO2 front can be used to detect the flow path of CO2 inside the reservoirs. Finally, a method for generating stochastic fracture models was extended and improved to more realistic field model for seismic and fluid modeling. My detail analysis suggests that fractures generated by isotropic stress field favor orthogonal sets of fractures in most subsurface rocks that can be converted to seismic model, similar to DFN study. The quality and validity of the models is assessed by comparisons to DFN models, including calculations of fractal dimension measures that can help to characterize fractured reservoirs.Item Static Load Balancing using Non-Uniform Mesh Partitioning based on Ray Density Prediction for the Parallel Wavefront Construction Method(2014-08-01) Alyabes, Abdullah FahadThe Wavefront Construction (WFC )method, which was developed based on ray theory, is one of the most efficient tools in seismic modeling. The main idea of this method is to propagate a wavefront represented by rays in a computational mesh that is interpolated whenever an accuracy criterion is violated. Recently, a parallel WFC was developed using the Standard Template Adaptive Parallel Library. However, due to wavefront density adaptivity, the parallel implementation exhibits inefficient performance owing to load imbalances between multiple processors.This paper applies a static load balancing approach based on a method for predicting future loads for a synthetic salt dome model, in order to improve the performance.The approach utilizes a preliminary conventional ray simulation to estimate the cost (future load) of each cell in the WFC's initial wavefront mesh.Then it applies a non-uniform mesh decomposition that results in a more efficient parallel WFC. Our implementation shows better and stable scalability in most WFC simulations. Overall, this paper contributes to understanding the behavior of wavefront mesh adaptability and predicting earth model complexities, and it serves as a guide for achieving the ultimate goal, a fully load-balanced parallel WFC.