Carbon capture and storage (CCS) technology has become one of the most cost‐effective and promising ways to achieve global climate change mitigation goals. The CO2 storage capacity in depleted oil and gas reservoirs is currently the safest and most economical option. The long‐term sealing of the cement–formation interface in CO2 storage wells (CSW) is essential to avoid CO2 leakage. The filter cake easily affects the interfacial sealing ability, which is a thin impermeable layer formed by drilling fluid residue or solid particles remaining on the borehole wall due to permeable formation. Filter cake removal is essential for favorable cementation and production efficiency. This study highlights the current developments and the main challenges for oil‐ and water‐based mud filter cake removal during the cementing and completion process. Moreover, research ideas and recommendations for various types of filter cake removal are proposed to provide a reference for future work. This information helps deepen understanding with respect to the different filter cake removal options available in the CCS industry and provides a knowledge base that can facilitate the improvement of the cementing quality and production efficiency of existing systems to combat battle CSW safety and production efficiency problems.

This paper introduces occurrence characteristics of coal bed methane in China, and analyses the influence of coal seam permeability on coal mine methane extraction. In addition, it presents the mechanism of increasing permeability by pressure relief. Lastly, the methane extraction technologies are discussed, and the applicable conditions of these technologies are analyzed. It is seen that choosing appropriate methane drainage technology, often in combination with several technologies including ground drilling, underground drilling, and pressure relief and permeability improving measures, is crucial for geological complex coal seam, especially low permeability soft coal seam.

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