Thermoelastic Fracturing on Water Injectors as Part of Injectivity Enhancement in Giant Offshore Carbonate Field. Case Study

Abstract

Water Injection is part of secondary recovery mechanism which aims to increase oil recovery by increasing or maintaining the reservoir pressure and provide additional pressure support. Most of the time water injection is controlled under matrix injection below the fracture pressure in order to avoid the creation of fractures and risk of bypass oil. However, there are two different mechanisms of fracture creation in water injection: poroelastic fracturing and thermoelastic fracturing. First one will activate above fracture point, while the second one creates below the original fracture point and most of the time missed in reservoir field development Normally fractures can be categorized in 3 groups: –Fractures induced due to increase of injection pressure above pore pressure. (Poroelastic fractures)–Fractures induced due to drilling activities (Overbalance drilling)–Fractures induced due to injection of cold water. Fractures which are induced due to difference in temperature between injected fluid and rock fluid called thermoelastic fractures. Thermoelastic fracturing is controlled primarily by the difference in temperature between reservoir rocks and injected fluids. This paper will focus on thermoelastic fractures and its propogation along the formation. The analysis performed in a giant offshore carbonate field in Middle East on a well level as well as field level through injection modules. This paper will describe the mechanisms of thermoelastic fracturing and methodology to identify this type of fractures in water injectors through several cases studies.