Carbonate Reservoir Characterization: Part 12
1. To what extent, the concept of type curves introduced by Ramey (1970), which refers to a log-log graph of a specific solution to the flow equation, involving the dimensionless pressure for the vertical axis and the other involving the dimensionless time for the horizontal axis – would be able to help in analyzing the pressure drawdown solution, when the drawdown test remain to be very short for the semi-log straight line to develop – in a carbonate reservoir?
Feasible to assume a carbonate reservoir to have a constant porosity, permeability, thickness and a uniform initial pressure?
Also, how could we assume a carbonate reservoir to be infinite, isotropic, homogeneous and horizontal reservoir?
What will happen, if we fail to capture the correct initial value of pressure?
2. Can we use short-term drawdown tests in order to determine formation permeability and skin effect; and to estimate the reservoir volume in communication with the well, using long-term or reservoir limit tests - in a carbonate reservoir?
3. To what extent, line source solution would remain to be meaningful in a carbonate reservoir, where, the pressure behavior of well produces at a constant rate, located in the center of a radial infinite reservoir?
4. To what extent, the information from a drawdown graph will remain to be meaningful in a carbonate reservoir during (a) front-end effects or short time data (pressure behavior being under the influence of wellbore storage, damage, unstable flow conditions in the tubing string); (b) the semi-log straight line portion, applicable to the analysis by the semi-log methods; (c) boundary effects, which include boundaries and interference effects? Feasible to clearly identify the straight-line portion of the semi-log plot in order to precisely estimate the formation conductivity (kh)?
To what extent, the concept of skin factor (that relates the pressure drop experienced by the fluid flowing towards the well to the rate of flow) would remain to be useful in a carbonate reservoir?
Does this skin factor include all the factors that affect fluid flow towards the well during the various phases?
(a) first under radial conditions over the full zone thickness in the region, away from the wellbore;
(b) where, it will converge into the completed interval in the region near the wellbore;
(c) when, it acts as radial flow through the damaged zone of thickness; and (d) during flow through perforations.
Suresh Kumar Govindarajan
https://home.iitm.ac.in/gskumar/
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