An Environmentally Friendly Alternative for The Conventional Acids Used in Matrix Acidizing and Acid Fracturing of Carbonate Reservoirs

Abstract

Oil and gas industry has been using acidizing techniques in carbonate formations to remove unwanted substances, reconnect the flow path and introduce a new flow channel in order to increase oil production. These techniques have been developed and applied to maximize oil production while bypassing the near wellbore damage. Commonly used acids such as hydrochloric acid (HCl) and hydrofluoric acid (HF) damage equipment. Furthermore, their additives such as corrosion inhibitors, surfactants, and iron control agents are harmful to oil field workers and they are not environmentally friendly. Moreover, transportation of such fluids to the well-head and neutralization of the flow-back products is costly. The Ultra Series FF-01 is both an environmentally and equipment friendly alternative to the products available in the market presently. The Ultra Series FF-01 is very acidic, its pH is less than 1, and has a slower reaction rate compared to HCl. It can work up to 72 times longer than hydrochloric acid. Most importantly, it is biodegradable and is non-corrosive to the field equipment. Core-flooding tests show the Ultra Series FF-01 was able to generate wormholes in low permeability cores at low injection rates. On the contrary, 15% HCl with stronger dissolution capability at the surface of the core sample, was unable to generate wormholes under the same condition. Furthermore, acid fracture conductivity measurement tests show conductivity after etching by the Ultra series FF-01 was significantly better compared to that obtained with 15% hydrochloric acid with additives, for all values of closure stress, when the leak-off pressure was set at 100 psi lower than the system pressure.