New Non-aromatic Non-ionic Surfactants to Form a Stabilized Emulsified Acid for Efficient HP/HT Stimulation

Abstract

Matrix acidizing has been used for permeability and productivity enhancement purposes in oil and gas wells. Hydrochloric acid has been always a first choice due to so many advantages that it can offer. However, HCl in high pressure/high-temperature (HP/HT) wells is a concern because of its high reactivity resulting in face dissolution, high corrosion rates, and high corrosion inhibition costs. There are several alternatives to HCl, among them emulsified acid is a favorable choice due to inherent corrosion inhibition, deeper penetration into the reservoir, less asphaltene/sludge problems, and better acid distribution due to its higher viscosity. Furthermore, the success of the latter system is dependent upon the stability of the emulsion especially at high temperatures. The emulsified acid must be stable until it is properly placed and it also should be compatible with other additives in an acidizing package. This study presents the development of a stable emulsified acid at 300 °F (150 °C) through investigating a novel aliphatic non-ionic surfactants. This paper introduces some new non-aromatic non-ionic surfactants to form an emulsified acid for HP/HT wells where the conventional acidizing systems face some shortcomings. The type and quality of the emulsified acid was assessed through conductivity measurements and drop test. Thermal stability of the system was monitored as a function of time through the use of pressure tubes and a preheated oil bath at 300 °F (150 °C). The viscosity of the emulsified acid was tested as a function of shear rate (0.1–1000 s−1). The microscopy study was used to investigate the droplets size and shape of the emulsified acid that was formed. Coreflood study was conducted to determine the performance of the newly developed stable emulsified acid in creating wormholes and reaching break through. Inductively Coupled Plasma (ICP) was used to determine dissolved cations. Superior stimulation results were achieved at 300 °F with the newly developed emulsified acid system. This study will assist in developing a more cost-effective and efficient design of acid treatments through introducing the development of a new and effective aliphatic non-ionic surfactants, which lead to the formation of a stable emulsified acid. This new emulsified acid system efficiently stimulates HP/HT carbonate reservoirs.