Studies of Fractures Induced During Cyclic Steam Injection

Abstract

Abstract Induced fracturing during cyclic steam injection was studied in two heavy oil reservoirs in California. In a shallow, unconsolidated sandy-conglomerate, steam induced fracturing was chaotic, with multiple events occurring over a period of days. Predominantly horizontal fractures appeared to open and close in various locations and at various times. Not all of the temperature events observed in observation wells that suggested fractures correlated with changes in the injectichon pressure. No model for steam flow in this reservoir could be developed. In a deeper, less permeable, more consolidated formation, two vertical fractures simultaneously opened along the wellbore at different depths at the start of injection and remained open during injection and production. The fractures were co-planar and were separated by a shaly interval. Multiple fracturing events were not observed. A simple thermal conduction model was developed that successfully matched the measured data and allowed the effective reservoir permeability to be estimated.