# Synthesis and Property Analysis of a High-Temperature-Resistant Polymeric Surfactant and Its Promoting Effect on Kerogen Pyrolysis Evaluated via Molecular Dynamics Simulation

## TL;DR

This paper introduces a high-temperature-resistant surfactant that improves oil recovery from shale by promoting kerogen breakdown and oil desorption.

## Contribution

A novel polymeric surfactant with high thermal stability is synthesized and shown to enhance kerogen pyrolysis and oil desorption.

## Key findings

- The surfactant has a main degradation temperature above 300°C and reduces water surface tension to below 25 mN·m−1.
- It changes shale contact angles from 127.96° to 57.59°, promoting a water-wet state and reducing oil saturation by half.
- PS promotes kerogen breakdown into smaller molecules like methane and shale oil, with reactions primarily occurring at the kerogen-surfactant interface.

## Abstract

Surfactants can be utilized to improve oil recovery by changing the performance of reservoirs in rock pores. Kerogen is the primary organic matter in shale; however, high temperatures will affect the overall performance of this surfactant, resulting in a decrease in its activity or even failure. The effect of surfactants on kerogen pyrolysis has rarely been researched. Therefore, this study synthesized a polymeric surfactant (PS) with high temperature resistance and investigated its effect on kerogen pyrolysis under the friction of drill bits or pipes via molecular dynamics. The infrared spectra and thermogravimetric and molecular weight curves of the PS were researched, along with its surface tension, contact angle, and oil saturation measurements. The results showed that PS had a low molecular weight, with an MW value of 124,634, and good thermal stability, with a main degradation temperature of more than 300 °C. It could drop the surface tension of water to less than 25 mN·m−1 at 25–150 °C, and the use of slats enhanced its surface activity. The PS also changed the contact angles from 127.96° to 57.59° on the surface of shale cores and reversed to a water-wet state. Additionally, PS reduced the saturated oil content of the shale core by half and promoted oil desorption, indicating a good cleaning effect on the shale oil reservoir. The kerogen molecules gradually broke down into smaller molecules and produced the final products, including methane and shale oil. The main reaction area in the system was the interface between kerogen and the surfactant, and the small molecules produced on the interface diffused to both ends. The kinetics of the reaction were controlled by two processes, namely, the step-by-step cleavage process of macromolecules and the side chain cleavage to produce smaller molecules in advance. PS could not only desorb oil in the core but also promote the pyrolysis of kerogen, suggesting that it has good potential for application in shale oil exploration and development.