https://orcid.org/0000-0003-4157-5508
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ABSTRACT
(Ultra-) deep oil and gas reservoirs are the focus of attention in oil and gas exploration and development, with the characteristics of (ultra-) high temperature. There are problems such as fast acid-rock reaction rate and severe corrosion. Compared with ubiquitous acid systems (e.g. HCl, gelling acid, foam acid, etc.), self-generating acids achieve slow acidification and low corrosion by adding a reaction process, that is, controls the dissociation rate of H+. Therefore, self-generating acid was systematically investigated to provide a reference base for researchers interested in high temperature reservoirs acidizing stimulation. According to the type of product, it is subdivided into self-generating hydrochloric acid, self-generating organic acid, self-generating hydrofluoric acid and composite self-generating acid, and reviewed them specifically. However, existing research mainly focuses on the system development, lacking systematic literature reports on acidogenic mechanism. And it has not formed a set of systematic evaluation criteria. After investigation, it is considered that self-generating acid acidogenic mechanism includes nucleophilic substitution reaction and hydrolysis reaction. The authors suggest that factors such as acidogenic capacity, retarded performance and corrosion inhibition performance should be considered to evaluate self-generating acid systems, and more detailed evaluation indicators need to be further studied. After comparing and analyzing application conditions, results have shown composite self-generating acid has superior performance (applicable temperature up to 200°C, acidogenic capacity up to 4.8 mol/L) and accord with the likely future development trends in oil and gas resource exploitation. Thus, great efforts should be made to improve and optimize the performance of composite self-generating acid.
Acknowledgments
This work was supported by the Science and Technology Cooperation Project of the CNPC-SWPU Innovation Alliance (2020CX0105).
Disclosure statement
No potential conflict of interest was reported by the author(s).
Nomenclature
| HCl | = | hydrochloric acid |
| CH2O | = | formaldehyde |
| NH4Cl | = | ammonium chloride |
| CCl4 | = | carbon tetrachloride |
| HMTA | = | hexamethylenetetramine |
| (CH2)N4 | = | hexamethylenetetramine |
| CaCO3 | = | calcium carbonate |
| HCOOH | = | formic acid |
| CH3OH | = | methanol |
| HCOOCH3 | = | formic acid methyl ester |
| HCOONH4 | = | ammonium formate |
| AlCl3 | = | aluminum chloride |
| HF | = | hydrofluoric acid |
| HBF4 | = | borofluoric acid |
| NH4F | = | ammonium fluoride |
| NH4BF4 | = | ammonium borofluoride |
| CNPC | = | China National Petroleum Corporation |
| SWPU | = | Southwest Petroleum University |
Additional information
Funding
Notes on contributors
Juan Du
Juan Du is an associate professor and and master’s supervisor of the Petroleum Department of Southwest Petroleum University. She has been engaged in scientific research and teaching in oil and gas field stimulation and transformation technology, oilfield chemistry, and oil and gas production engineering for a long time. Her research direction is the mechanism and basic research of oil and gas reservoir stimulation and transformation, the development and evaluation of fracturing fluid and acid system, and the design and software development of fracturing and acidizing.
Yaoshun Yuan
Yaoshun Yuan is a master’s degree candidate at Southwest Petroleum University. The research direclion is focused on the theory and technology of oil and gas field stimulation, fracturing, acidification and diverting agent.
Pingli Liu
Pingli Liu is a professor and doctoral supervisor of the Petroleum Department of Southwest Petroleum University. He has been engaged in scientific research and teaching of oil and gas field stimulation and reconstruction technology and oil and gas production engineering for a long time. His research direction is acid fracturing of complex lithologic reservoir, matrix acidizing and acid fracturing of sandstone reservoir, stimulation and reconstruction of special lithologic reservoir and stimulation and injection of offshore oilfield.
Qiang Wang
Qiang Wang received his master degree of Southwest Petroleum University majoring in petroleum and natural gas engineering. His research interests include offshore reservoir stimulation, stimulating offshore loose sandstone.
Jinming Liu
Jinming Liu is currently pursuing a Ph.D. degree in petroleum engineering under the guidance of Dr. Pingli Liu from the School of Petroleum Engineering, Southwest Petroleum University, Chengdu, Sichuan, China. He completed his bachelor of Offshore Oil and Gas Engineering from Southwest Petroleum University in June 2019. His research interests include reservoir stimulation, acid fracturing technology for deep high-temperature carbonate, retarded acid system.
Qisheng Huang
Qisheng Huang is a master’s degree candidate of Southwest Petroleum University. His research direction is acid fracturing of complex lithologic reservoir, matrix acidizing and acid fracturing of sandstone reservoir, particle technology optimization research and particle transport fluid mechanics.