Evolution and application of in-seam drilling for gas drainage

The presence of seam gas in the form of methane or carbon dioxide presents a hazard to underground coal mining operations.In-seam drilling has been undertaken for the past three decades for gas drainage to reduce the risk of gas outburst and lower the concentrations of seam gas in the underground ventilation.The drilling practices have reflected the standards of the times and have evolved with the development of technology and equipment and the needs to provide a safe mining environment underground.Early practice was to adapt equipment from other felds,with rotary drilling being the only form of drilling available.This form of drainage allowed various levels of gas drainage coverage but with changing emphasis,research and development within the coal industry has created specifc equipment,technology and practices to accurately place in-seam boreholes to provide effcient and effective gas drainage.Research into gas content determination established a standard for the process and safe levels for mining operations to continue.Surveying technology improved from the wire-line,single-shot Eastman survey instruments which was time-dependent on borehole depth to electronic instruments located in the drill string which transmitted accurate survey data to the drilling crew without time delays.This allowed improved directional control and increased drilling rates.Directional drilling technology has now been established as the industry standard to provide effective gas drainage drilling.Exploration was identifed as an additional beneft with directional drilling as it has the ability to provide exploration data from long boreholes.The ability of the technology to provide safe and reliable means to investigate the need for inrush protection and water drainage ahead of mining has been established.Directional drilling technology has now been introduced to the Chinese coal industry for gas drainage through a practice of auditing,design,supply,training and ongoing support.Experienced drilling crews can offer site specifc gas drainage drilling services utilising the latest equipment and technology.

The Discovery of Water Conduction in Karst Collapsed Column Caused by Fault Cutting:Evidence from Chronology,Exploration Data and Hydrochemical Test

The water conductivity of karst collapsed column is affected by multiple factors such as the characteristics of its own column filling,structure and mining disturbance.As a structural water-conducting channel,fault usually plays a controlling role in hydrogeological structure.During the process of mine water hazard prevention and control,it was discovered that the lithology composition,compaction and cementation degree and water physical properties of karst collapsed column fillings were all non-conducting water,but due to the influence of combined development faults,some exploration drill holes showed concentrated water outflow.Based on this,the scientific hypothesis was proposed that fault cutting leads to water conduction in karst collapsed columns.The study comprehensively used methods like chronology,exploration data analysis,and hydrochemical testing to analyze the chronological relationship between faults and karst collapsed columns,their spatial relationship,outlet point distribution and water chemical properties,and the impact of faults on the water-conductivity of karst collapsed columns,which proved the effect of fault cutting on changing water conductivity of karst collapsed column.The research showed that later fault cutting through karst collapsed columns turned the originally non-conductive karst collapsed columns into water-conductive collapsed columns at the fault plane,creating a longitudinally connected water-conducting channel.A new model of fault cutting karst collapsed column to change the original water conductivity of karst collapsed column was proposed.The research results can provide a theoretical basis for the prediction of the water conductivity of the karst collapsed column.According to whether the karst collapsed column was cut by the fault,it was predicted theoretically,so as to determine the key areas of water conductivity detection and prevention and control,and has broad application prospects under the background of source control of mine water disaster.

Sequence Stratigraphy Study of the Late Quaternary Activity of the Nankou-Sunhe Fault in Its Northern Segment,Beijing

A test drilling exploration was implemented across the northern segment of the Nankou-Sunhe fault in the Beijing plain,and a combined borehole section was built by sequence stratigraphy,lithologic facies analysis,magnetic susceptibilityand absolute chronology to investigate the episodic activities of the fault since 60 ka BP. The results show that the active stages of the fault are 60 ka to 47 ka BP,36 ka to 28 ka BP,and 16 ka BP to present. Other intervals are relatively stable. The average vertical slip rate is 0.35 mm/a from 60 ka to 37 ka BP,0 mm/a from 37 ka to 32 ka BP,0.78 mm/a from 32 ka to 12 ka BP,and 0.35 mm/a since 12 ka BP. Compared with the conventional analyses on lithology and sedimentary facies,the sequence stratigraphy method has certain advantages in the studies of borehole strata comparison and episodic activity of buried faults.

Late Quaternary Activity of the Central-North Segment of the Taihang Mountains Piedmont Fault Zone

The location and late Quaternary activity of the Central-North Segment of the Taihang Mountains Piedmont fault zone have been studied by shallow seismic survey and combined drill exploration.Our results show that the Baoding-Shijiazhuang fault and the Xushui fault were active in the late Pleistocene,but the south Xushui fault has been inactive since the late Pleistocene.The maximum magnitude of potential earthquake of the faults is 6.0.