The stimulation history in offshore Brazil is undergoing into a deep transformation. The requirements of technology, before focused on sandstone reservoirs demand, are being expanded by the need for techniques to stimulate carbonate reservoirs, specially the pre-salt carbonates. In this scenario, a self-diverting acid system based on a viscoelastic surfactant (VES) technology was introduced for carbonate reservoir stimulation. The Self-Diverting VES (SD-VES) promotes viscosity development when the acid comes in contact with the carbonate formation. The mechanism of viscosity development is simple: In concentrated acid, the system presents low viscosity, which results in friction reduction while pumping; however, when the fluid reacts with the formation and the acid concentration decreases, the micelle spherical structures combine, transforming into rod-like micelles that convert to a 3-D structure, which increases the fluid viscosity. The high viscosity generates a temporary barrier across the high-injectivity zones, diverting the subsequent fluid to treat other reservoir zones. Generally the SD-VES is associated with several placement techniques that aid in achieving good treatment distribution through the entire producer interval. Regardless of the placement technique applied, the SD-VES is generally used as the main acid fluid and is bullheaded into the well. Because of its rheological behavior, the SD-VES is pumped as a single fluid during bullheading, aiming to achieve formation stimulation and good treatment distribution throuth the entire productive interval. Since the SD-VES was introduced in 2009 to treat carbonate reservoirs in offshore Brazil, more than 40 wells have been treated using the system in the various acid placement techniques presented in this paper. Three case histories are presented to better illustrate the different scenarios where the SD-VES was applied.

This paper reviews the past 50 years of the SPE Oilfield Chemistry Conference to understand how the event and papers published at it have evolved, what function does the conference serve today, and what future trends should the oilfield chemistry community anticipate and adapt towards. All the papers from the 26 conferences run by the SPE since 1973 have been collated and analyzed for data such as topic, keywords, authorship (and number of authors), number and type of organizations involved, and number of citations (to 2022 Q4). The data are plotted to enable analysis of the evolution of trends over time. In addition, professionals in the earlier, mid and later stages of their careers contribute their perspectives on the conference content and what benefits they derive from participation. Over the years the number of topics has expanded, as have the number and range of contributors. For example, in the first year of the conference (1973) there were 12 papers on 8 topics, written by 23 authors, averaging 2 authors per paper. In the most recent year (2021), there were 68 papers on 11 topics, with an average of 4.8 authors per paper. For a majority (7 out of 12) papers in 1973 the lead authors were from academia, with only one paper from an operator, whereas by 2021 there was a more balanced spread, with 37% papers led by universities/research institutes and the remainder well distributed amongst operators, service companies and chemical manufacturers. While the overall number of topics and papers has expanded over 50 years, some topics have appeared and then disappeared, and others have made a comeback. Indeed, for six conferences between 1977 and 1985, the word "geothermal" was included in the conference name, before being dropped again. In 1973, the paper contributed by an operating company was cited 8 times more than all the other 11 papers put together, whereas 85% of the citations at the following conference are associated with six university authored papers. Much has changed in the past half century, and yet some of the papers from the early years remain very relevant today, and will undoubtedly impact how we address future challenges. The oil and gas industry has been challenged to engage with the Energy Transition: we show that the technologies and information introduced at this conference are and will be at the forefront of the emerging energy production landscape.

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