A few studies considered the role of rock strength on fracture conductivity retained at elevated closure strengths. Based on experimental results and field data, many correlations were derived with a consideration of both the surface roughness and rock mechanical properties. These studies found that acid fracture conductivity is sometimes lower with longer acid contact times than with shorter ones. This is apparently the result of the weakening of the rock structure along the face of the fracture with increased acid exposure, such that the conductivity decreases more rapidly with increasing the closure stress.

Based on extensive literature survey of three types of carbonate rocks, it was found that chalk has the lowest rock embedment strength and the fractures closed at much lower stresses compared with limestone or dolomite. Dolomite has the highest rock embedment strength and best conductivity results compared with other rocks tested.

A sensitivity analysis was performed to determine the effect of rock embedment strength, and dissolved rock equivalent conductivity on the fracture conductivity. The results of this analysis showed that dissolved rock equivalent conductivity determines the maximum conductivity at a closure stress equal to zero, while the value of rock embedment strength determines the decline in conductivity with increasing the closure stress. This analysis shows that the value of dissolved rock embedment conductivity doesn't affect the difference that exists in some of the developed correlations, while the value of rock equivalent strength has a significant impact on this difference. Finally, the rock embedment strength is a key parameter that affects the fracture conductivity. This paper discusses current correlations to predict fracture conductivity, and addresses the influences of several key parameters on the fracture conductivity.

You can access this article if you purchase or spend a download.