Key words: permeability, porosity, build-up curve, skin effect, reservoir heterogeneity, near wellbore zone, diffusion, flow through equation.
The paper reviews the results from the research on the effect of formation damage in the near well bore area due to the flow of reservoir fluids with suspended fine particles on the behavior of pressure build-up curves. The scope of the research and its tasks included the mass transfer solution for a porous media considering the changes in the pore space geometry with time subject to various factors. The analysis of a numerical simulation model showed a significant decrease in the reservoir porosity and permeability in the near wellbore zone of the formation. The study of the diagnostic build-up curves in a log-log scale revealed the fact that the models created in commercially available industry software programs do not give a unique solution for the permeability value in the near-wellbore zone, altered by colmatage but rather provide the average permeability value of the formation. The variability of the inverse dynamic model apart from the known and pre-set property changes was proved to be related to the changeability of the field data (such as pressure, production rates) as well as physical and chemical properties of in-situ and flowing fluids. Thus the correct estimate of the formation permeability and porosity requires definition of the associated parameters relevant for data processing and interpretation for a particular well under study, along with routine well test operations to detect their relative changes which contribute to the increased robustness and reliability of the reservoir characterization studies.
