Advances of supramolecular interaction systems for improved oil recovery (IOR).

Improved oil recovery (IOR) includes enhanced oil recovery (EOR) and other technologies (i.e. fracturing, water injection optimization, etc.), have become important methods to increase the oil/gas production in petroleum industry. However, conventional flooding systems always encounter the problems of low efficiency, high cost and complicated synthetic procedures for harsh reservoirs conditions. In recent decades, the supramolecular interactions are introduced into IOR processes to simplify the synthetic procedures, alter their structures and properties with bespoke functionalities and responsiveness suitable for different conditions. Herein, we primarily review the fundamentals of several supramolecular interactions, including hydrophobic association, hydrogen bond, electrostatic interaction, host-guest recognition, metal-ligand coordination and dynamic covalent bond from intrinsic principles and extrinsic functions. Then, the descriptions of supramolecular interactions in IOR processes from categories and advances are focused on the following variables: polymer, surfactant, surfactant/polymer (SP) complex for EOR and viscoelasticity surfactant (VES) for clean hydraulic fracturing aspects. Finally, the field applications, challenges and prospects for supramolecular interactions in IOR processes are involved and systematically addressed. The development of supramolecular interactions can open the way toward adaptive and evolutive IOR technology, a further step towards the cost-effective production of petroleum industry.

pH-Responsive aggregates transition from spherical micelles to WLMs induced by hydrotropes based on the dynamic imine bond.

In recent years, the use of dynamic chemical bonds to construct stimulus-responsive micelle systems has received increasing attention. However, current reports focus on the construction of dynamic covalent bond surfactants using dynamic chemical bonds, and the method of applying dynamic covalent bonds to hydrotropes has not been reported yet. In this study, a novel pH-responsive worm-like micelle system was constructed by mixing cetyltrimethylammonium bromide (CTAB), 4-hydroxybenzaldehyde (HB) and p-toluidine (MB) at the molar ratio of 60 mM : 40 mM : 40 mM. The formation mechanism of the dynamic covalent bond hydrotropes and the rheological behavior of the micelles were investigated via rheology, 1H-NMR spectroscopy and Cryo-TEM. The results show that as the pH increases, the viscosity of the solution first decreases and then increases rapidly. The microscopic aggregates in the solution transition from spherical micelles to worm-like micelles (WLMs), and the solution changes from a water-like fluid without viscosity to a gel system that can withstand its own weight. The transformation of the aggregates and their rheology can be attributed to the formation of MB-HB-, which is a type of hydrotrope with dynamic covalent bonds. Moreover, the transition from spherical micelles to worm-like micelles in this system is reversible.

The advances of organic chromium based polymer gels and their application in improved oil recovery.

In recent years, with the further development of old oilfields, in order to further improve the oil recovery, they must be conformance controlled. Among various types of conformance control methods, polymer gels composed of polymers and crosslinkers have attracted widespread attention because of their efficiency and low costs. Among them, organic chromium gels with their good formation adaptability and high stability have been fully developed in recent decades. This review introduces the different types of polymers and crosslinkers used in the preparation of organic chromium gels, and the mechanisms of affecting their performance are analyzed. On this basis, the organic chromium gels for different formation conditions are introduced, including nanoparticle-reinforced and compound organic chromium gels. At the same time, evaluation methods of organic chromium gels are introduced, while the focus is on the in-situ measurement method (mirco-rheology) of gel formation time developed in recent decades. Based on the currently developed organic chromium gel and the analysis of the development status in oilfields, future directions like the use of supramolecular organic chromium gel and shear organic chromium gel are suggested.