Geomechanical Conditions of Successful Acid Fracturing Applications

Authors: N.G. Ibragimov (Tatneft OAO, RF, Almetyevsk), V.G. Salimov, R.R. Ibatullin, A.V. Nasybullin, O.V. Salimov (TatNIPIneft, RF, Bugulma)

Key words: acid fracturing, geomechanics, well productivity.

Analysis of conductivity changes of acid-etched fractures depending on influential factors has been conducted. The following conclusions have been made. Efficiency of acid fracturing increases with decrease of producing reservoir depth. Appropriate candidate formations for acid fracturing are those characterized by high Brinnel hardness and those having low fracturing pressures. Reservoir pressure drop is not allowed while operating the wells with acid-etched fractures. Instead, increase of reservoir pressure is advisable. If the stress resulting in loss of conductivity in acid-etched fractures lies within the actual range of compressional stresses (from 0 to 30 MPa in Tatarstan conditions), so the optimum value of reservoir pressure drawdown will exist ensuring maximum production rate and well productivity. Combination of horizontal wells and multiple transverse acid-etched fractures is a viable solution for reduction of compressional stress.