Abstract
Fracture calibration tests (minifracs) are very successful methods for providing estimates of the fluid efficiency, closure pressure, fracture geometry and leakoff coefficient prior to the main treatment. The pressure decline data is normally analyzed using a Nolte type method for calibration and redesign of the main treatment.
Many times it has been observed that the main treatment has a higher efficiency (less fluid loss) than the minifrac which can adversely impact the fracture treatment. This paper addresses the effect of fluid loss during fracture calibration tests on the main treatment.
An analytical method for leakoff controlled by the filter cake and/or filtrate fluid has been developed for analyzing the effect of fluid loss in the formation prior to the main treatment. The main treatment leakoff velocity and volume loss equations account for the effects of the minifrac fluid loss behavior, including filter cake, spurt loss, mobility, time of fracture creation and relative fracture planes.
This paper presents the foundation for a generalized set of equations quantifying the effects of the minifrac fluid loss on the main treatment by conservation of mass and Darcy’s law. Equations are formulated for the main treatment leakoff velocity and volume loss. Numerous figures are provided that illustrate the parametric effects of the minifrac fluid loss on the main treatment efficiency and fraction of pad volume.
