First Successful Hydraulic Fracture Treatment Offshore Abu Dhabi – Implementation of Pseudo-Stable Fracturing Fluids as a Key to Awaken Deep Pre-Khuff Clastics Production Performance

Abstract

This paper describes the application of pseudo-stable fracturing fluids as a key technology to improve fracture conductivity and production performance in the first successful hydraulic fracture treatment pumped offshore Abu Dhabi. The primary target reservoir is the Pre-Khuff clastics Fm., a deep tight gas sandstone that can be found at depths exciding 16,000 ft with temperatures above 350° F. Even though our industry has a long-standing history in fracture stimulating high temperature reservoirs, the rheological behavior of fracturing fluids for optimum performance still remains to be highly controversial. It is well-known that at elevated temperatures fracturing fluids tend to prematurely break, losing its viscosity alongside the capability to transport proppant and develop fracture width that may lead to early treatment termination. What is rarely mentioned is that fracturing fluids break spontaneously at high temperature in oxygen rich environments (such as in a laboratory) nevertheless, when there is a lack of oxygen, fluids do not break effectively. Reservoirs are strong oxygen reducing environments because of the presence of iron, organic matter and hydrocarbons, having a negative effect on fracturing fluid rheology degradation, fluid cleanup and fracture conductivity. At the same time, there is still little consensus regarding the rate and magnitude of thermal exchange between the fracturing fluid and the reservoir high temperature conditions that will affect its rheological properties. Contrary to popular belief, fracturing fluids do not heat up to reservoir conditions as fast as suggested by many software applications and there is no need for large viscosity stability windows to efficiently transport proppant without premature screenouts. In this case history, a physics-based fracturing fluid design was utilized to successfully place ~ 100 tons treatments implementing a 15 minutes viscosity stability window which, under traditional standards, will not survive harsh downhole conditions and temperatures over 350° F. Post-frac production increased by 500%, reaching stable commercial rates after the first fracture treatment, proving that the implemented fluid design philosophy is correct and extremely efficient in developing high performing fracture treatments.