Prediction of Thermal Induction Fracture During Waterflooding in a High Pressure High Temperature Field in Offshore Brazil
Antonio Luiz Serra de Souza1
1 Petrobras
Resumo
Reservoir Geomechanics has become a relevant subject for the petroleum industry during the last decades. There are many benefits on improving geomechanics understanding, including: better characterization of reservoir volume deformation and impact on rock permeability (compaction and dilation); prediction of surface subsidence; reducing risks of fault reactivation; and fracture propagation during waterflooding or other improved oil recovery process. In Petrobras, Reservoir Geomechanics is a fundamental tool to develop fields with large number of faults/fractures, which is the case of several offshore sandstone and carbonate reservoirs. Amongst all of those phenomena, one important to be considered during a waterflooding project is the possible occurrence of a thermal induced fracture in a injection well due to the temperature difference between the reservoir and the injected water. This difference reduces the initial stress state of the reservoir, also decreasing the fracture pressure, and the induced fracture will propagate at a lower pressure than those calculated by isothermal methods. In this case, the system operates with Injection with fracture propagation pressure, a technique widely used by petroleum operators in order to keep the predicted injection rate, but sometimes also avoided to minimize geomechanical risks, like an impact in sweep efficiency or communication between different layers or even exudation. This work describes a methodology to estimate the impact of a fracture propagation in a waterflooding project in an offshore brazilian High Pressure High Temperature (HPHT) field. The object is to study the possible conditions that a thermal induced fracture can occur and estimate the main parameters that affect the process, like horizontal and vertical penetration of the fracture, propagation pressure and so on. The Mechanical Earth Model (MEM) was developed in two stages: the main geomechanical parameters were obtained by lab and log data and correlations available in the literature; an
Palavras-chave: Reservoir Geomechanics; Hydraulic Fracture; Thermal Induced Fracture