Acid Stimulation Improvement with the use of New Particulate Base Diverter to Improve Zonal Coverage in HPHT Carbonate Reservoirs

Abstract

A novel technique in acid stimulation to attain uniform and effective coverage described in this paper has been adopted to treat large multiple carbonate intervals simultaneously. This technique has been proven to improve efficiency, increase recovery, and sustain production rate. Zones Z1, Z2, and Z3 of gas bearing are targets to be produced comingled in a well. Z2 is capable to produce without stimulation while Z3 is a thick dolomite with perforation interval up to 100+ ft., and Z1 is relatively thin and exhibits tight dolomite lithology. Both matrix acidizing and acid fracturing were developed to treat Z3, but the main challenge was to overcome high permeability contrast in the long interval thereby equally stimulate the entire net pay interval. The acid stimulation method implemented has proven successful providing longer acid penetration, better etching, higher gas production, and better operating efficiency. Efficient diversion was a key for successful stimulation of Z3. The fiber-based particulate diverter has been utilized in bullhead stimulation treatments to improve zone coverage. The new diversion material comprises of a customized blend of degradable fibers and multimodal particles, designed to provide an effective isolation plug at the perforation as well as at face of the reservoir inside the fracture in a consistent manner, thereby allowing new zones to be stimulated and increase penetration distance. The diversion materials providing such temporary isolation degrades within hours after the treatment. This new diverter has been used for matrix acidizing in wells. Many conclusions can be made by analyzing the acidizing experience in this field. The new composite diverter improves the diversion process in spite of the smaller volume of diversion material used compared to treatments with only fiber-based diverter. Although the new particulate diverter was initially developed for acid fracturing applications, experience shows its excellent effectiveness in high-rate matrix acidizing treatments.