Deep saline aquifers are considered for underground disposal/storage of fluids. Undesirable leakage of the injected fluids to adjacent layers may adversely affect underground water and/or hydrocarbon resources. Two main potential leakage pathways are identified as leaky wells and leaky faults. In recent studies, pressure transient analysis was used to characterize leakage through such pathways assuming that the pathway feature (well versus fault) is actually known. However, in general one may not know the nature of the leak. It is important to determine whether the leakage pathway is fault (planar leakage pathway) or a well (line-source leakage pathway). The flow regimes corresponding to these different features can be very different causing completely different pressure signals. In this study, we use pressure transient analysis to provide diagnostic plots to distinguish the leakage through a well from that through a fault. Our approach is based on the development of analytical models cast in the form of type curves. We use analytical models to investigate the pressure change in a system of an injection zone and an upper zone separated by a barrier layer. A method is presented based on pressure transient analysis to differentiate between leaky wells and leaky faults and to characterize the leaky well. The nature of leakage is detected using the typical type curves and finally, location and hydraulic characteristics of the leaky well are obtained.

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