Abstract
The main purpose of this work is to present an interpretation method for injectivity test in a two-layer reservoir that can be extended to a multilayer approach, based on new analytical solutions to the well pressure response. The developed formulation uses a radially composite reservoir approach and considers that the water front propagation may be approximated by a piston-like flow displacement. The reservoir is assumed to be laterally infinite and properties such as permeability and porosity may be different in each layer. The solutions were developed in the Laplace domain and then inverted to real domain using the Stehfest Algorithm. The proposed formulation was then validated by comparison with a numerical flow simulator. Results showed a good agreement between the numerical simulator and the analytical model. Also, a sensitivity study was done by comparing the results of different scenarios varying oil viscosities and injection flow rate to assess how these properties affect the pressure and pressure derivative profiles.
Highlights
The injection of water into oil reservoirs in order to extract relevant information regarding the characteristics of the reservoir has become an interesting alternative to conventional well testing, given that it has many advantages
The accuracy of the analytical model detailed in “Conceptual model” section was determined by comparison with a commercial flow simulator
Based on the solution for pressure change during injectivity tests in single-layer reservoir, it was possible to develop a formulation to a multilayered reservoir
Summary
The injection of water into oil reservoirs in order to extract relevant information regarding the characteristics of the reservoir has become an interesting alternative to conventional well testing, given that it has many advantages. In addition to bringing greater safety to the procedure, the method helps to reduce CO2 emissions to the environment, since there is no need to gas/oil flaring which happens in a conventional well testing. It brings a new parameter to the problem since the system changes from a single-phase flow to a twophase flow. The conventional and injectivity tests are completely different; the injectivity well testing presents enough information to perform the pressure behavior analysis. It is possible to obtain different reservoir properties according to what it is requested or necessary to the study of the reservoir (Neto et al 2020a).
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