The method of improving the cementing quality of the interface in deep coalbed gas well through the wetting reversal technique

ABSTRACT

Coalbed methane, also known as coalbed methane gas, is a natural gas formed by the biogeochemical and pyrolysis processes during the formation and evolution of coal and stored in coal seams. Compared with conventional coalbed methane, deep coalbed methane has a rich resource and is an important substitute for natural gas increase, storage, and production. During the process of coalbed methane extraction, the inability of coal rock to bond well with cement slurry leads to a decrease in the quality of cementing, which has become one of the main problems affecting the extraction of deep coalbed methane. To address this issue, this paper first analyzes the microstructure of the coal rock-cement interface to reveal the mechanism of strengthening the coal rock-cement interface bonding. Then, using the wettability of coal rock as an evaluation index and the surfactant wetting modification method, the paper modified the surface of coal rock to enhance its hydrophilicity, optimized the suitable coal rock wetting modification agent, and finally evaluated the enhancement effect of the coal rock wetting modification agent on the quality of the coal rock-cement interface bonding through interface bonding experiments. The research results indicate that the hydrophobicity of coal rock surface is the main reason for the poor bonding between coal rock and cement. The three primary surfactants can improve the water wettability of coal and rock surfaces by 41.57%–52.95%, among which AES surfactant has the best improvement effect. After soaking in 0.5% AES solution at 85°C for 8 min, the hydrophilicity of coal rock can be increased by 72.3%. There are no obvious cracks between the coal rock-cement interface, and the bonding quality of the coal rock-cement interface has increased 2.69 times. Coal rock surface wetting modification can effectively enhance the interface bonding effect, which is conducive to improving the quality of cementing of deep coalbed methane.

KEYWORDS:

• Deep coalbed methane
• coal rock wettability
• wettability alteration method
• surface active agent
• interface bonding quality
• cementing quality

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

Conceptualization, S.F. and J.Z.; methodology, J.Z.; validation, C.Z., W.S. and Y.Y.; formal analysis, Y.Y.; investigation, W.S.; resources, F.F.; writing – original draft preparation, C.Z.; writing – review and editing, C.Z.; visualization, Y.Z.; supervision, K.Z.; project administration, K.Z.; funding acquisition, K.Z. All authors have read and agreed to the published version of the manuscript.

Additional information

Funding

This research was funded by Heilongjiang Provincial Natural Science Foundation of China [No. LH2022E026].

Notes on contributors

Jianwei Zhang

Jianwei Zhang Associate Professor of Northeast Petroleum University, M.S. Supervisor, is engaged in the research of drilling fluid cement slurry oilfield chemistry and cementing technology. E-mail: [email protected]

Chaoqi Zhang

Chaoqi Zhang a master’s degree student at Northeast Petroleum University, is engaged in drilling fluid working fluid performance evaluation and cementing water mud performance rating research. E-mail: [email protected]

Sen Fan

Sen Fan Associate Professor of Northeast Petroleum University, M.S. Supervisor, is engaged in research and teaching in the direction of oil and gas well engineering. E-mail: [email protected]

Kuanliang Zhu

Kuanliang Zhu President of the Drilling and Production Technology Research Institute of PetroChina Jidong Oilfield Branch. E-mail: [email protected]

Yan Zhou

Yan Zhou Vice President of Drilling and Production Technology Research Institute of PetroChina Jidong Oilfield Branch. E-mail: [email protected]

Fuping Feng

Fuping Feng Professor of Northeast Petroleum University, Ph.D. in oil and gas engineering, Northeast Petroleum University, is engaged in the research of failure mechanisms and evaluation of wellbore integrity. E-mail: [email protected]

Wei Song

Wei Song a researcher at Drilling and Production Technology Research Institute of PetroChina Jidong Oilfield Branch. E-mail: [email protected]

Yan Yang

Yan Yang a researcher at Drilling and Production Technology Research Institute of PetroChina Jidong Oilfield Branch. E-mail: [email protected]