Determination of Residual Oil Saturation (Term Paper Sample)

Determination of Residual Oil Saturation
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Introduction
It has been well established and known that only portion of the original oil-in-oplace is economically recovered by conventional methods. Due to macroscopic and microscopic phenomena, considerable amount of hydrocarbon is unrecovered or trapped during multiphase flow in porous media. Determination of residual oil saturation is therefore an important requirement fro studying and understanding the behavior of field during water flooding and beyond. Before embarking on a tertiary recovery scheme, it is imperative getting to know the residual oil saturation of the reservoir in order to access its technical feasibility and profitability. This paper ought to consider the general concepts of residual oil saturation determination methods using different environmental remediation projects. Basing on the background information of this study, many investigations were done pertaining multiphase fluid flow by petroleum industries. They were interested in determining the volume of oil that would be trapped and not recoverable from oil reservoirs. There are varieties of engineering methods to estimate the residual oil saturation.
Core Analysis
For a long time, petroleum industries have had their interests on the volume of oil that remains in the reservoir after the production process has been completed. The industries therefore conducted laboratory experiments designed to imitate reservoir conditions. The common laboratory method for determining residual oil saturation in core analysis has it that a rock core should be completely saturated using a non-wetting phase or rather the oil displacing water. This is done by applying oil pressures in an approximation of 2300 feet of water. This oil capillary and saturation pressure then dictates the maximum oil saturation and the imbibition’s test starting point. Water is then imbibed in the same core until oil expulsion has ended and high pressures of 500 to 100 psi are required. At the end of the experiment, the resulting oil saturation is the residual oil saturation. The interpretation is therefore that the residual oil saturation results from a water flood of the reservoir.
This method is advantageous to petroleum industries since it produces higher estimates for residual saturation. This is because laboratory methods force larger initial NAPL saturation throughout the entire pore space of the sample and displace water from smaller pores. It is widely available and has excellent accuracy. It is disadvantageous in that it requires a new well at the course of the experiment and is poor to fair core recovery hence making it difficult to get in situ Residual Oil Saturation.
Interwell Residual Oil saturation method
This method measures the formation resistivity by generating electrical current and measuring potentials among pairs of open -hole wells geometrically distributed throughout the whole field. In the year 1971, a well-to-well tracer test was developed to measure the residual oil saturation. In this method, at least two tracers having different partition coefficients between oil and water phases are injected. During the movement of the tracer fluid through the reservoir, one tracer is retarded more than the other. The average interwell residual oil saturation is determined by monitoring the degree of separation of the tracers at the observation well.
The well-to-well method is simple and is subjected to accuracy since it is based on observations. On the other hand it has its disadvantages. The first disadvantage is that the field test and improvement is required and also the method requires long time to obtain the results hence it is time consuming.
Gravity Logging Technique
This method uses wellbore gravity measurements with procedures and steps to be followed in log-inject log operation. First, a borehole gravity log survey is made after the formation has been fille...