Importance of fracture geometry and conductivity in improving efficiency of acid fracturing in carbonates

The success of a stimulation technique is often measured by its stimulation ratio. This paper, however, presents a novel way of calculating the value that can be added from acid fracturing. A methodology predicting the effect of acid fracturing in carbonate reservoirs has been developed. This accounts for fracture geometry and for acid fracturing job specifications. Acid fracturing is typically conducted in carbonate reservoirs, which make up approximately 70% of the worldwide hydrocarbon reserves. Acid fracturing is a complex process depending on multiple factors which are different in nature, making mathematical models unreliable. Due to the stochastic process inherent in acid fracturing, modeling has been met with difficulty, especially in calculating conductivity. The modeling data analysis includes the sensitivity study with respect to fracture length and fracture width, as well as the importance of efficient acid transport. The post-stimulation production data is used to calculate the cumulative production parameter which is the cumulative production over a given period of time. It can also be compared to the production of an un-stimulated case. The cumulative production parameter offers a unique way to calculate acid fracture value. This parameter gives a tangible value which translates to production over time. More importantly, the proposed model allows fractures from different reservoirs to be accurately compared, helping production engineers make better decisions and estimate the acid treatment efficiency.