Abstract
Water injection is a valuable method for produced water disposal and for reservoir pressure support. A disadvantage of water injection operations is the injectivity loss which can occur due to rock and fluid characteristics, formation damage caused by fines migration and by oil and solid particles present in the water. Optimal injection rates can't be achieved when injectivity loss occur. Nevertheless, the injectivity loss can be mitigated by water injection with fracture propagation pressure (IFPP) which aims to restore injection capacity.
To study this process, a geo-mechanical simulator for fracture modeling combined with a commercial reservoir simulation package is used to model and to optimize the operational conditions of water-injector wells. The fracture is represented by a virtual horizontal well and analytical formulations for hyperbolic decline of permeability represent the effect of formation damage around the injector well.
This paper aims to study some water injection cases to verify in which situations the IFPP use is convenient. The simulation model studied is a synthetic reservoir with a five-spot pattern. Three scenarios are considered with oil type variation (41, 31 and 21 API degrees).
Those scenarios are proposed to reproduce some possible situations that can happen in real field, where formation fracturing pressure can be reached by the effect of the injectivity loss or due to rock and fluid characteristics. The IFPP acting is evaluated using the net present value (NPV) and cumulative oil and water productions.
The results showed that the IFPP study becomes into an optimization problem of injection rate, where the fracture can or cannot occur. It is shown that IFPP, in general, anticipates oil production for cases of intermediate and high oil viscosity, turning a quite advantageous method. Studies in light oil indicate that the technique is only interesting when there is significant injectivity loss, which the IFPP aids in injectivity restoration. It is shown that IFPP can be advantageous, not only in cases where injectivity loss occurs, but also in cases without injectivity loss, in order to anticipate the oil production.
