5th WCSET-2016 at Vietnam 

Technical Session - 2

Title:            Uncertainty in Reservoir rock Permeability Measurement due to instability in equipment design parameters
Authors:       Thomas Adebayo
Abstract:     Permeability is important reservoir parameters that determine the success of field exploration and production. The decision to produce a field does not only depends on the volume of oil in place but equally on the reservoir permeability. Hence, there is need to obtain accurate permeability value in order to make correct decision on oil well production. Various laboratory experiments being used have repeatability problem. Various experiments were performed over a period of two months to determine the permeability for a sandstone using water as flowing fluid in the Formation Damage System (formation evaluation) equipment and Helium gas as the fluid in the unsteady state Porosimeter-Permeameter. There is so much variation in the values of the permeability obtained and this was discovered to be due to various factors such as the temperature, confining pressure, pore pressure, fluid flowrate and the stability criteria used that have direct impact on measured permeability. It was also discovered that the confining pressure was never stable but changes with the unstable temperature. Maintaining constant temperature was also a problem due to slow heat transfer between the equipment core holder and the flowing or the confining fluid. It was concluded that all these factors that affects permeability need to be accounted for in the permeability measurement and this is only possible if the equipment manufacturers redesign the computer macros used in these computerized permeability systems such that the effect of changing temperature on the confining pressure and the corresponding permeability is corrected. Also considered were the effects of stability criteria and flowrate on the measured permeability values. Correlations were obtained as presented below in the result and discussion section and these are required to be incorporated into the Excel macro used by the equipment manufacturers. For the PorosimeterPermeameter, a relationship between the absolute permeability, confining pressure, pore pressure, slip velocity and temperature was obtained. For the Formation Damage System, the permeability equation to be used is a little more complex and Macros need to be written based on the different possible flowrates usable with the equipment. Moreover, there is need to have continuous measurement of the confining pressure as it was never constant during the period of experiments.

Keywords:  Permeability, Confining Pressure, Stability Criteria, Permeability Experiment, Equipment repeatability
Pages:        141-148

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