Numerical Interpretation of Single Well Chemical Tracer Tests for ASP Injection

Abstract

Abstract A series of single well injection tests has been conducted to estimate the efficiency of Alkaline Surfactant Polymer (ASP) flooding. These injection tests comprised a Single Well Chemical Tracer (SWCT) test that was done after water injection to establish a baseline remaining oil saturation and a second SWCT test conducted after ASP injection to measure the Remaining Oil Saturation (ROS) after ASP. Analytical methods are generally used to interpret SWCT tests and to determine the remaining oil saturation. These techniques work best when the response is close to an ideal, single peak. However, the responses from the SWCT tests in our single well tests sequences are complex, showing multiple peaks. This is indicative of complicating factors such as cross-flow between layers. To understand the complex response we used numerical simulation techniques to interpret the SWCT tests. The numerical model includes the physics of ASP, such as interfacial tension reduction, water viscosity modification, and the related reduction in ROS as wells as an accurate model for tracer dispersion. The model allows full control of physical dispersion and does not require the use of numerical diffusion to mimic the effect of physical dispersion. The numerical simulation sequence involves the full single well injection test history including SWCT tests before and after the ASP injection. The key challenge in matching the tests results with the numerical simulations was to model the complex response, which was different for each well tested. Elaborate numerical simulations, different from the conventional interpretation method, were used to successfully match all tests. This paper presents the simulation work, an explanation of the parameters varied to obtain agreement between numerically predicted and actual SWCT responses and the numerical simulation tools used to match the SWCT tests.