3D Tomography Imaging Using Micro-seismic Events

Activities within a hydrocarbon reservoir, such as producing oil or injecting fluid, change in-situ stresses and pore-pressure which consequently cause micro-earthquakes. The induced microseismic events are small earthquakes producing high frequency waves which can be used to give a better understanding of the hydrocarbon reservoir. The microseismic events generated within a hydrocarbon reservoir as a result of the production activities are recorded. Then, the recorded first arrival times are used in a model based inversion process to map a detailed velocity model in the vicinity of the reservoir and hence the heterogeneity within such reservoir. The inversion process is based on a fast 3D finite-difference code using the eikonal equation to generate the synthetic travel times of first arriving seismic events of an initial model; the inversion of large 3D model is practical. The synthetic data are compared with observed data. The model is updated using a gradient based optimization approach until an appropriate match between observed and synthetic data is obtained. The methodology could lead to enhanced understanding and hence efficient management of the hydrocarbon reservoir. This in turn would enhance the understanding of fluid movements resulting in improved petroleum recovery from the reservoir.