Abstract
Composite cores of core plugs from different heights of an exploration well core are often used for routine and special core analysis to evaluate an oil reservoir. The question is whether or not the order of the core plugs in the composite core make a difference to the absolute and relative permeability measurements? The seminal work by Huppler (1969), proposed ordering individual core samples harmonically in a composite core in order to match the overall permeability. Langaas (1998) proposed ordering the core samples in decreasing permeability for effective relative permeability measurements, based on theoretical framework of North Sea sandstones. In this paper we tested the methods proposed by Huppler and Langaas experimentally. Core samples with permeability ranging from 50 mD to 2 Darcy were used for this work. The orientation of the core samples was tested for permeability and relative permeability and compared with the theoretical model developed by Langaas. In addition to the experimental work, simulations were performed with the three different composite cores and the representative recovery factor was compared to provide the appropriate composite core arrangement.
Highlights
Composite cores of core plugs from different heights of an exploration well core are often used for routine and special core analysis to evaluate an oil reservoir
To mimic 5 different cores, the model is divided in 5 blocks in Z direction and the physical properties of each bock is adjusted based on the experimental measurements
It is evident that this arrangement resulted in comparatively more oil recovery than the Relative permeability on composite core samples were examined for different orientation of individual cores
Summary
To increase the relative accuracy of volume measurements [4]. The development of appropriate geological and reservoir simulation models rely significantly on routine and specialized core analysis (SCAL) data. In a similar approach Mohammadi et al [10] proposed ordering cores with increasing permeability along the flow direction to produce a high recovery factor for a waterflood experiment on carbonate cores. Often experiments are performed with composite cores increasing in permeability along the flow direction to supposedly reduce experimental time and cost with the objective being maximum oil recovery. This is, debatable because the additional time it takes to do coreflooding in a marginally higher vs lower permeability is insignificant compared to the time to prepare the experiment, fluids, and post experiment analysis. From comparative analysis of the results from these composite core arrangements we attempt to provide a recommendation that is suitable for depicting reservoir flooding mechanism in the lab that could aid field scale simulations
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