It is important to determine fluid distribution after injecting certain volume of fluid into a reservoir. Material balance method combined with Darcy’s and EOS (Equation of States) can be used to calculate fluid distribution analytically or numerically. By knowing porosity and permeability distribution in the reservoir, one can predict prefer fluid front direction. The information is important for successful field flooding.
Some oil and gas companies have done pilot flooding before full-field flooding projects or EOR projects. This is to ensure the oil recovery can be achieved efficiently and effectively. A more robust technique has been done to acquire complete data of fluid distribution by means of a 3D seismic survey.
Logging tools also have been used to log fluid distribution around wellbore such as the C-O log. Frequently, the operators find oil potential behind water coning wells.
In the present patent by SLB, an electromagnetic logging tool is used to determine fluid distribution around the wellbore. The logging tools are run first to get baseline data. Then electrolytic fluid containing electrically conductive particles (metallic powders or carbon nanotubes) is injected into the reservoir. The logging tools measure electromagnetic waves response as a function of time. The key point here is the electrically conductive particles must generate sufficient electrical resistivity (conductivity) contrast between the injected fluid and the existing fluid.
Measurements also can be run on the surface (Figure 1). Two transmitters and one receiver are required to produce vertical areal fluid distribution. The distance between the transmitters is commensurate with a vertical depth of investigation. More transmitters and receivers on the surface are required for other directions. By combining in-well logging data and surface measurement data, it is possible to map 3D fluid distribution as a function of time. By doing so, one can conclude preferable fluid front directions (Figure 2).
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