An innovative technique for determining residual and current oil saturations using a combination of Log-Inject-Log and SWCT test methods: LIL-SWCT

Abstract

Abstract It is generally recognized that the determination of current oil saturation (Soc) and residual oil saturation (Sor) plays a significant role in production forecasting and the selection and management of enhanced oil recovery (EOR) methods. Failure to accurately determine either saturation state will lead to incorrect recovery estimates and poor understanding of EOR efficacy. While there exist several methods of determining Soc and Sor, each method benefits and suffers from advantages and disadvantages specific to that technique. In order to compensate for the shortcomings of any one specific method, a combination of testing procedures may be utilized. In this paper, we propose a combination of Log-Inject-Log (LIL) and single-well chemical tracer (SWCT) test methods to improve the accuracy of Sor measurement while simultaneously offering a novel approach to the determination of Soc. The proposed method is not still implemented in any field and in this case, the concept is offered, not confirmation through a field example. The LIL method has the advantage of being able to generate a vertical fluid saturation profile throughout a logged interval, but suffers from its strong dependence on porosity assumptions. Subsequently, any deviation between assumed porosity and actual porosity will result in a deviation between measured Sor and true Sor. By comparison, the SWCT test method is independent of porosity, but cannot detect vertical variations in Sor.The complimentary nature of these two test methods, as well as their operational reliance on fundamentally different principles, make them ideal candidates for a hybrid testing program to measure Sor with a high degree of quality assurance. As well, combining the LIL and SWCT test methods in a single testing program offers a novel approach to measuring Soc. The details and mathematical derivation of the theory behind the measurement of Sor and Soc via this hybrid approach are presented in this paper.