Single Well Chemical Tracer Method To Measure Residual Oil Saturation Numerical Simulation

a mass of oil that be reserved after primary and secondary recoverying can not be availability recovered. Exploitation is becoming more and more difficult while the newly discoverable petroleum oil is less and less. New fields were not being discovered fast enough to replace the old one as they were depleted. It became clear that the oil remaining in our developed reservoirs could be considered a valuable primary resource. The need for determining residual oil saturation (Son) has existed. SOR is a critical parameter in the evaluation of the potential for the third recovery. There are a number of recognized methods for estimating remaining oil content of reservoirs and these methods have inherent advantages and limitations. One method which was thought to be further development was the single-well chemical tracer procedure. The method is developed by Deans in later 1960's. The chromatographic effect was first proposed as a way to measure SOR. The first laboratory experiments using a chemical reaction to produce a tracer in-situ in a sand pack containing a refined oil at residual saturation has succeeded. And the was applied in fields in 1968. The technology is proprietary to Exxen produotion Research Company in 1971.lt was applied widely since advantages of the single-well method are the ability to detect the larger amount of reservoir volume and to control the depth that is sampled as compared to other methods.In the single-well chemical tracer (SOR) method for measuring residual oil saturation, injecting Ethyl acetate dissolved in brine as the primary tracer into target well, and shutting in. The primary tracer hydrolyzed into product tracer during shutting in. Then producing back the brine and tracers, the primary tracer and the product tracer have different distribution ratios between oil and brine, they would separate during the flow back. When the flow was reversed, the ethyl alcohol was produced first; followed by the unreacted ethyl acetate. The separation between the two concentration peaks was used to calculate a value for SOR because the relative amount of separation could be related quantitatively to SOR. This is equivalent to the separation obtained in an analyticalchromatographic column used to analyze mixtures. The results are used to protract the plots of tracer concentrations vs. volume of fluid produced. Getting the SOR is by matching the plots. The method's precision is 2% ?%PV.The interpretation is critical in this method. The success of the method depends on matching the plots of tracer concentrations vs. volume of fluid produced obtained from field to measuring SOR. Interpretation methods of the field data include analytic interpretation and numerical simulation interpretation. There is no analytic interpretation model to get a reliable precise at present. In numerical simulation interpretation, there had been developing three numerical simulation models to interpret the field data. The models are "ideal" one-layer model multi-layer model fluid drift model It requires more trial calculation to obtained matching the field data very well with the increasing complexity of the reservoir simulation model. As a result, the general simulation procedure becomes very unwieldy and the calculation workload will increase. So the researchers have been improving the numerical simulation arithmetic applied in the single-well chemical tracer test.The precision of the analytic model applied in the single-well chemical tracer test was affected because its ignoring the diffusibility in interpreting with analytic method. The affection is very severity in the case of "fluid drift" test.The paper reviewed the background history and actuality of the single-well chemical tracer (SOR) method for measuring residual oil saturation at first. Then describe its whole process(from library experiment to field testing) and general interpretation model after expatiating its mathematics theory method principle. Finally researched its numerical simulation model, this paper emphases on the research in th...