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EFFECTS OF WATER INJECTION UNDER FRACTURING CONDITIONS ON THE DEVELOPMENT OF PETROLEUM RESERVOIRS
Juan Manuel Montoya Moreno
Departamento de Engenharia de Petróleo – Faculdade de Engenharia Mecânica –UNICAMP Caixa Postal 6122 – Cep 13081-970 Campinas – SP – Brasil moreno@dep.fem.unicamp.br

Eliana Luci Ligero
Departamento de Engenharia de Petróleo – Faculdade de Engenharia Mecânica -UNICAMPCaixa Postal 6122 – Cep 13081-970 Campinas – SP – Brasil eligero@dep.fem.unicamp.br

Denis José Schiozer
Departamento de Engenharia de Petróleo – Faculdade de Engenharia Mecânica - UNICAMP Caixa Postal 6122 – Cep 13081-970 Campinas – SP - Brasil denis@dep.fem.unicamp.br

Abstract. Waterflooding is the most frequently used method in the petroleum fields to increase oil recovery. The injectedwater maintains the reservoir pressure above the bubble point of fluid and displaces the oil to the producer wells. However, water injection is associated to a technical problem called injectivity loss, which occurs due to deposition of different types of solid particles in the porous media around the injector wells. Actions to avoid injectivity loss have an important economic impact, especially inoffshore projects, where high oil production rates are required. One possible solution to this problem is to inject water above the fracture propagation pressure, bringing up high conductivity channels from injectors. The fracture growth from injector wells can have a significant impact on reservoir performance (sweep efficiency, oil production rates, oil/water ratio and recovery factor).However, there is a risk associated to water injection under fracturing conditions if the fractures grow up in the direction of the producer wells, resulting in recycle of water. Due to the importance of the problem and to the difficulties to model the problem, some different approaches can be applied to this problem. In this work, two alternatives are presented to model the fracture propagation in apetroleum reservoir: (1) grid refinement and transmissibility modifiers and (2) virtual horizontal wells. The impact of injectivity loss on the oil production and the net present value are studied in order to show that the problem can be modeled, representing an initial point to future research in this area. Keywords: Waterflooding, injectivity loss, fracture propagation, hydraulic fracture,reservoir numerical simulation. 1. Introduction Water injection has been the most used recovery method in petroleum industries due to its advantages: operational simplicity, low cost and favorable characteristics of displacement. The injected water displaces oil from porous media to producer wells and maintains the reservoir pressure above of saturation pressure, increasing the recovery processefficiently. During the injection process, large quantities of water are introduced into the reservoir, which involves many complex variables (Singh, 1982). Some important variables are the geological characteristics that influence the water injection performance, the well localization and consequently the production strategy, the fluid properties like viscosity that is related directly to the waterinjection efficiency, technical variables such as injection pressure, water quality and water processing systems and economic variables. Water injection has high initial investment and the project conditions for the injection are more complicated in offshore operations. According to Palsson et al. (2003), the operational conditions in an offshore field are complex and have narrow economic limits. Theproduction cost of maritime fields are elevated and many water injection projects are implemented quickly to support the pressure as recovery mechanism to maintain high oil production rates. Another important characteristic of offshore fields is the average project life that is smaller than onshore projects (Singh, 1984 and Palsson et al., 2003). Either offshore or onshore operations, injector...