Abstract
The objective of this paper is to display the Thermal induced fracture effect (TIF) observed in Villano water disposal wells by decreasing the injection water temperature by 20°F (Aug 2012) and 10°F (Dec 2013) through to the installation of air-coolers at surface. Furthermore the application of fracture surveillance workflow and the design, execution and results of a controlled temperature and pressure test in CPF disposal well (Apr 2013) are also presented.
The methodology aims to share the results obtained in two different cases ocurred at different times in Villano Field within the Hollin Sandstone formation, allowing improvement of the injectivity in the disposal wells. This work includes comparison of the results and identification of key factors in order to maintain maximum injectivity (100% Producer –Re-Injection water system). Additionally, the implementation of a monitoring program was necessary for a daily surveillance of the injection temperature and well behavior. Finally, field tests performed in another location (CPF) in which the injection temperature was controlled by a heat exchanger. The results were used to evaluate the differences between the documented cases and the Villano TIF cases.
Thermal fracture effects in Villano increased the injection rate by 34K bwpd which resulted in significant savings as new disposal well was not required. The thermal effect was reached with a low temperature reduction (20°F and 10°F), instead of the 50°F+ documented; the maximum reduction in the thermo elastic stress was around 26.5 psi/°F (Propped Fractured well) and 21.7 psi/°F (Non – propped fractured wells) which decreased the injection pressure by 530 psi 217 Psi respectively. Surveillance data suggests that the fractures will remain constant or will continue to grow by maintaining a low temperature. Documented studies advise that the effect is maintained when the temperature is increased however, tests performed in CPF disposal well confirmed that the effect is not permanent if the injection conditions are removed. In the particular cases of Villano and CPF fields, the injectivity is directly proportional to the temperature.
