Despite the development of alternative energy sources, oil and gas still remain the predominant energy sources in most countries in the world. Due to gradual hydrocarbon reserve depletion and the existing downward trend in the production level, there is a need to search for methods and technical approaches to level off the falling rates. Chemically enhanced oil recovery methods (EOR) by surfactant solution injections are one of the possible approaches for addressing this issue in already developed fields. Most often, surfactants are injected together with polymers or alkalis. These technologies are called surfactant–polymer (SP) and alkali–surfactant–polymer (ASP) flooding. Basically, SP and ASP have been distributed in China and Canada. In this article, in addition to these countries, we paid attention to the results of pilot and full-scale tests of SP and ASP in Russia, Hungary, and Oman. This study was a comprehensive overview of laboratory and field tests of surfactant solutions used for oil displacement in SP and ASP technologies. The first part of the article discussed the physical fundamentals of the interaction of oil with surfactants. The second part presented the main chemical reagents used to increase oil recovery. In the third part, we described the main facilities used for the preparation and injection of surfactants. Further, the results of field tests of SP and ASP in the abovementioned countries were considered. In the discussion part, based on the considered results, the main issues and uncertainties were identified, based on which some recommendations were proposed for improving the process of preparation and injection of surfactants to increase oil recovery. In particular, we identified an area of additional laboratory and scientifically practical research. The outcomes of this work will provide a clearer picture of SP and ASP, as well as information about their limitations, current challenges, and potential paths forward for the development of these technologies from an economic and technological point of view.

The article is devoted to the issue of a low sweep efficiency in the heterogeneous terrigenous reservoirs containing remaining oil. Water plugging operations that redirect the injection fluid flows into unswept zones, are one approach to enhancing the oil recovery in these reservoirs. The commonly used chemical reagents in these treatments are acrylate polymer solutions. The polymer solutions must reach the target water-saturated zones and form a strong gel barrier there. Furthermore, the polymer compositions should have a low initial viscosity to provide a good injectivity and penetration ability. Therefore, the methods of adjusting the gelation time are necessary. There are numerous studies in modern scientific society devoted to the study of water-plugging polymer compositions. However, aspects, such as the effect of the hydrogen index on gelation, have received insufficient attention. In this paper, we describe the features of the developed polymer composition, based on a hydrolyzed polymer of acrylonitrile with a controlled gelation time for the chemically enhanced oil recovery. The component composition and the concentration levels were selected, based on the alterations in the hydrogen index of the polymer solution. It was scientifically proven that by adhering to a neutral hydrogen index, it is possible to improve the properties of the polymer composition. Moreover, using a model of a heterogeneous reservoir, it was confirmed that the proposed polymer composition achieves selective plugging. As a result of the polymer gel treatment, the water cut decreased by 4% and the displacement coefficient of oil increased by 20%, in comparison with the effect of the original composition without a gel-time modifier.

This paper presents a review of modern methods and technologies for extracting high- (HVO) and extra-high-viscous oil (EHVO). Special attention is given to thermal, physico-chemical, and combined enhanced oil recovery (EOR) methods based on the synergistic effect of these approaches. Theoretical aspects of these technologies, their applicability limits, and their practical implementation are considered. The article describes the main complicating factors in the extraction of HVO and EHVO using the reviewed methods, one of which is the high water cut in well production. We analyse the mechanisms of water production in HVO and EHVO fields. The paper highlights the experience of developing HVO and EHVO fields, primarily in Russia, and examines laboratory and field studies, ongoing projects, and future prospects. The authors of this paper have analysed the available literature and have provided further recommendations for studying these technologies. We hope that this work will be useful to all those interested in the challenges of oil production.

В данной статье представлены результаты исследования седиментационной устойчивости полимер-дисперсных систем (ПДС) на основе полимеров акрилового ряда и отхода химической промышленности, разрабатываемых для регулирования фильтрационных потоков в неоднородных терригенных коллекторах и повышения коэффициента охвата заводнением. Целью работы является определение наиболее стабильной во времени полимер-дисперсной системы. В рамках экспериментов выполнены следующие задачи: перевод техногенного отхода в нетоксичный вид и измельчение до порошкообразного состояния; приготовление водных растворов полимеров акрилового ряда различных молекулярных масс и ионных зарядов; визуальный контроль приготовленных полимер-дисперсных систем на протяжении 24 часов видеофиксацией; анализ полученных результатов. По результатам эксперимента установлено, что наибольшей седиментационной устойчивостью обладают полимер-дисперсные системы на основе анионных полимеров с большей молекулярной массой. Однако раствор на основе полимера DP-9 с высокой молекулярной массой седиментационно нестабилен. Таким образом, седиментационная устойчивость зависит от совокупности свойств используемого полимера, а именно его молекулярной массы, типа и плотности заряда молекул. This paper presents the results of the study of sedimentation stability of polymer-dispersed systems (PDS) based on acrylamide and chemical industry waste, developed to regulate filtration flows in heterogeneous terrigenous reservoirs and increase waterflood coverage ratio. The aim of the work is to determine the most stable polymer-disperse system in time. Within the framework of the experiments the following tasks were performed: conversion of technogenic waste into non-toxic form and grinding to powdery state; preparation of aqueous solutions of acrylic polymers of different molecular weights and ionic charges; visual control of the prepared polymer-disperse systems during 24 hours by video recording; analysis of the obtained results. From the experimental results, it was found that polymer-dispersed systems based on anionic polymers with higher molecular weight have the highest sedimentation stability. However, the solution based on DP-9 polymer with high molecular weight is not sedimentation stable. Thus, the sedimentation stability depends on the set of properties of the polymer used, namely its molecular weight, type and charge density of molecules.