Geological interpretation of channelized heterolithic beds through well test analysis

Well test analysis is a valuable tool to measure the dynamic response of a reservoir through determination of the hydraulic connectivity and effective permeability of the reservoir. Analytical models in well test analysis, are developed based on a simple geological structures, to provide reasonably good approximations for the description and performance of such reservoirs. Nevertheless, most prolific reservoirs such as channelized systems consist of sedimentological features with high degrees of heterogeneity that influence the pressure transient response where using conventional analytical models may result in misleading interpretations. The focus of the current study is on reservoirs which depositional environment corresponds to a main channel feature incising into heterolithic beds in lateral continuity. Analysis of the pressure response demonstrated that it can be used as a tool to predict the equivalent isotropic horizontal permeability of the channel. We explored that the ratio of well test permeabilities between the radial flows can lead to the identification of a secondary geological body next to channel. Thus, it can be used to find the distance of the interface between channel and heterolithic. The results of this study showed that particular features of pressure and its derivative curves from a channel-heterolithic system are useful well testing signatures for reservoir characterization. Therefore, we proposed an algorithm for the recognition of pressure trends and the development of relationships to be used for well test interpretation of heterogeneous oil and gas reservoirs.