Using production data to assess the effects of fractures in the void space on fluid filtration

A. A. Kolevatov^a, I. V. Afanaskin<sup>b

a</sup> Scientific Research Institute for System Analysis of the National Research Centre “Kurchatov Institute”, Moscow, Russian Federation
^b Almetyevsk State Technological University, Advanced Engineering Oil School, Almetyevsk, Russian Federation

Abstract: We analyzed data that describe the pore-space structure of a Tournaisian-age carbonate reservoir saturated with high-viscosity oil. We aimed to determine whether a fracture network acts as a flow path inside the pore space and contributes to fluid flow toward the wells. We used well and formation test data, core analysis results, acoustic broadband logs, and hydrodynamic well test data from producing and shut-in wells.
Interpretations from individual methods remained inconclusive about fracture-controlled flow toward the wells. However, core analysis and geophysical logs, including acoustic broadband data, showed no evidence of a fracture network that forms a significant flow component inside the reservoir void space. The absence of detectable fractures may result from their heterogeneous distribution, which is typical for carbonate reservoirs. As a result, acoustic broadband logs may have missed fracture zones inside the studied intervals.
We verified the preliminary conclusion about the limited role of fractures in reservoir flow through local numerical flow simulation. We matched simulated production rates to historical data, including cumulative production for the studied period. The simulation, which used adjusted relative permeability curves from the baseline project document, confirmed the hypothesis that fractures have a minimal influence on fluid flow – a hypothesis based on geological observations and field data.

Keywords: hydrodynamic well analysis, borehole surveying, high-viscosity oil fields, core analysis, relative permeabilities.