Determination of the Fracture Pressure from CO2 Injection History

Fracture pressure of geological formations is a major controlling parameter for many engineering operations, such as drilling, water injection, CO2 geological sequestration and gas storage. Fracture pressure is usually obtained based on analytical calculations and/or interpretation of water injection tests. This paper presents an approach to determine the actual fracture pressure of a sandstone reservoir at In Salah, Algeria. The injection data were employed and plotted in various domains. In this way, the transition from matrix injection to fracture injection could be determined, which was not evident from initial analysis of injection data. Therefore, iterative analysis of injection data plays an important role in understanding the performance of a reservoir during the early stages of an injection project. Further analyses of data showed that fracture pressure of formation increased with time. This implies that fracture pressure is a dynamic parameter in reservoirs with limited permeability and may reflect the history of pore pressure development in the target formation.