Evaluation of Well Performance Using Data from Fiber Optics Sensors, in Wells of the Pilot Polymer Flooding Test. Orinoco Basin, Venezuela

Abstract

Abstract In the case of this pilot test using polymer flood, evaluating the performance of injector wells was one of the main priorities. Losing injectivity is recognized as one possible cause of poor performance in the case of enhanced oil recovery processes, so estimation of the length of the well that contributes with injection, the identification of by passed zones, the diagnostics of the well behavior, and recommending solutions for a future project, were part of the objectives stablished at design of the project. For those reasons, we chose to complete the wells using a distributed temperature sensor (DTS). After installation of fiber optic sensors system in the wells associated with the project, the acquired data was analyzed using different techniques: Comparison of the effective length obtained from the static model with the one obtained from fiber optic sensors, and also pressure test analysis, later the distribution of the injection rate in each case was obtained. Initially it was necessary to establish a base behavior: Real-time measurements of pressure and temperature, characteristics of the injected fluid, and petrophysical evaluation of the completed intervals, which was used as departure point for studies performed. Maintaining a good injectivity in polymer injection projects normally is a major concern, in this case we present a real case of a polymer injection project in an extra heavy oil reservoir, which is producing oil with an average viscosity of 4150 cP at reservoir conditions. Polymer solution with a concentration of 1600 ppm was injected since 2017 and the injection is maintained so far without important reduction in the injectivity index. An estimated of the injection interval was established, and also estimation of the injection distribution in the horizontal section. The estimation was then validated with the results of the measured surface rate, and pressure transient test analysis. In average 30 % of the horizontal section of the well were receiving polymer solution, and then thanks to this new information zones not receiving polymer solution were identified. The results were used to improve the reservoir simulation models, and as diagnostic tool for pilot test. This paper describes how a better understanding of the connection between the well and the reservoir, can improve the reservoir simulation models, decision making process, and well performance evaluation. Also the importance of determine the possible not swept areas in the reservoir, which could result in low volumetric swept efficiency, and as a consequence low recovery factor. Finally the results presented here could be useful to the general interest of engineers dedicated to polymer flooding projects.