Methodology to optimize the control rules of intelligent injector wells for managing WAG-CO2 injection

Author(s)

Guilherme Nunes Lopes

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia Mecânica
• Defense date: 2023-03-30

Examining board members

Denis José Schiozer; Vinicius Eduardo Botechia; Valmir Francisco Risso

• Advisor: Denis José Schiozer

Abstract

One of the main challenges for the production of pre-salt fields is a significant amount of CO2 that must not be emitted into the atmosphere. The WAG-CO2 injection process can be an alternative to give an ecologically sustainable destination to CO2 and can increase oil recovery in pre-salt fields. The optimization of the WAG-CO2 injection strategy can be important to improve the oil recovery and the net present value (NPV) of the field. Due to process uncertainties, Inflow Control Valves (ICV) can provide operational flexibility, allowing to manage field injection/production more efficiently. In the literature, more attention is usually given to the ICV of producing wells, but the control of ICV of injection wells should also be the focus of research work. This work proposes a methodology to optimize the control variables of WAG-CO2 injection wells with intelligent completion in early stages of field development. The optimization method employed is nominal for each representative model (RM) of the uncertainty scenarios. One of the challenges of the process is to optimize the management rules to maximize the chosen objective function and guarantee the total recycling of the produced gas, which proved to be one of the relevant constraints of the case. The optimized control variables are related to the WAG-CO2 injection strategy and the control rules of the ICV of the injection wells. The selection of the WAG-CO2 injection strategy consists of defining the fluid, gas or water, to open each well during the platform ramp-up period, the duration of the WAG-CO2 injection half-cycle and the injection fluid from each well in the first WAG-CO2 bank. To optimize the ICV two reactive approaches were used. The first aims to optimize the control of ICV based on the gas-oil ratio (RGO) value monitored in the zones of the production wells correlated with the injectors under analysis; the second based on the equalization between the accumulated volume of gas injected between zones, aiming at a better sweeping efficiency. The developed methodology was applied to a benchmark case called UNISIM-II-D, based on the Brazilian pre-salt trends. The application followed the steps of the methodology proposed by Schiozer et al, (2019), with optimization for a base case and applications in representative models of uncertainties. Compared to a base injection strategy, the methodology was able to increase the field's financial return for all MR, with an average increase in Expected Monetary Value (EMV) of approximately US$ 100, improving gas injection management in the field (AU)

• FAPESP's process: 19/11881-4 - Optimization techniques applied to decision making process with intelligent wells in carbonate reservoir
• Grantee: Guilherme Nunes Lopes
• Support Opportunities: Scholarships in Brazil - Master