Acid-treatment effects on openhole stability in limestone

Openhole completions in limestone without a slotted or perforated liner became popular. Unlike other formations, borehole failure in limestone is induced by shear failure after pore collapse. An acid treatment enlarges the borehole and creates a wavy borehole surface. The acidized zone can contain wormholes or enlarged pores. However, since the Young's modulus also is reduced, the reduction of rock strength does not reduce borehole stability significantly. Normally, because limestone has a relatively high UCS, it is likely that a protective slotted or perforated liner can be deleted for openhole completions.