A capacitance model to infer interwell connectivity from production- and injection-rate fluctuations

This paper presents a new procedure to quantify communication between vertical wells in a reservoir on the basis of fluctuations in production and injection rates. The proposed procedure uses a nonlinear signal-processing model to provide information about preferential-transmissibility trends and the presence of flow barriers. Previous work used a steady-state (purely resistive) model of interwell communication. Data in that work often had to be filtered to account for compressibility effects and time lags. Even though it was often successful, the filtering required subjective judgment as to the goodness of the interpretation. This work uses a more complicated model that includes capacitance (compressibility) as well as resistive (transmissibility) effects. The procedure was tested on rates obtained from a numerical flow simulator. It was then applied to a short-time-scale data set from an Argentinean field and a large-scale data set from a North Sea field. The simulation results and field applications show that the connectivity between wells is described by model coefficients (weights) that are consistent with known geology, the distance between wells, and their relative positions. The developed procedure provides parameters that explicitly indicate the attenuation and time lag between injector and producer pairs in a field without filtering. The new procedure provides a better insight into the well-to-well connectivities for both fields than the purely resistive model. The new procedure has several additional advantages. It can be applied to fields in which wells are shut in frequently or for long periods of time. allows for application to fields in which the rates have a remnant of primary production. has the capability to incorporate bottomhole-pressure (BHP) data (if available) to enhance the investigation about well connectivity.