**Author details**

**4. Conclusions**

1. An ultralow surface tension could be obtained using OSSF. A 0.20 wt% OSSF solution can alter cores from water wetting to preferential gas wetting.

2. OSSF can remarkably decrease the water saturation and spontaneous imbibition rate of cores, resulting in a reduction in the cores' water blocking damage rate. In this case, the effect of cores' wettability alteration to water saturation

3. In the gas driven flow-back experiment, OSSF improved core permeability recovery. The remaining water saturation was also found to be low.

4. The main mechanism for improving core permeability includes the physical obstruction effect, surface tension reduction, and adsorption energy reduction, as well as the capillary force, adhesion, and shear stress of methane and

This work was supported by the National Major Science and Technology Project of China (Nos. 2016ZX05051, 2016ZX05052, and 2016ZX05030) and Research on

The authors declare that there is no conflict of interest regarding the publication

The supervisor, Jie Zhang, conducted the experimental work and analyzed the results of the research. All authors contributed to the analysis of results. Jie Zhang wrote the manuscript. Xu-Yang Yao contributed to experiment's design and analysis of the results. Bao-Jun Bai contributed to analysis and discussion of the results,

Qaidam's Excellent Drilling and Completion Technology (2016E-0109).

and the spontaneous imbibition rate is higher.

liquid on rock surfaces.

*21st Century Surface Science - a Handbook*

**Acknowledgements**

**Conflicts of interest**

**Author contributions**

reviewing, and editing of the manuscript.

of this paper.

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Jie Zhang1,3\*, Xu-Yang Yao2 , Bao-Jun Bai<sup>3</sup> and Wang Ren<sup>1</sup>

1 Drilling Fluids Research Department, CNPC Engineering Technology R&D Company Limited, Beijing, P.R. China

2 Petrochina Xin Jiang Oil Field Company, Karamay, P.R. China

3 Department of Petroleum Engineering, Missouri University of Science and Technology, Rolla, MO, USA

\*Address all correspondence to: zhangjiedri@cnpc.com.cn

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
