Ran Bi
Senior Reservoir Engineer
Research Institute of Petroleum Exploration and Development, PetroChina
China
Participates in
TECHNICAL PROGRAMME | Primary Energy Supply
Opportunities for Oil & Gas Supply Growth - Shales, Oil Sands, New Basins Other Unconventionals
Forum 02 | Hall 5 Digital Poster Plaza 1
13
October
12:30
14:30
UTC+3
The growing demand for natural gas in China has driven a shift in supply over the past decade — from predominantly conventional sources to an increasing share of unconventional reservoirs. Commercial-scale Coalbed Methane (CBM) production was primarily extracted from Qinshui basin, targeting the shallow CBM deposits with very low single-well gas rates. By 2019, the exploration and development of deep CBM (depth greater than 1500m) in the Ordos Basin has been deciphered with the cost-effective scheme. Investments and activities have surged into the area to exploit the CBM resources and turned the production online. This comprehensive study examines the geological, engineering and management variations influencing the outcome by comparing key performance metrics from Ordos, San-Juan Basin and Queensland.
In this study, we first evaluate the formation characteristics that influence production performance, including reservoir pressure, in-situ stress, gas content, adsorption-desorption behavior, and brittleness. As coal seams extend to greater depths, the controlling factors become increasingly complex, exerting significant influence on properties that are closely linked to gas productivity. For example, coal seams located within zones of restricted water retention may exhibit higher gas saturation, while the orientation and density of butt and face cleats can impact permeability and fracability. In addition to geological variability, engineering designs and management strategies are also examined to address the unique challenges of deep CBM development. This paper provides a detailed comparison of key performance metrics across major CBM basins worldwide.
Overall, the study indicates that mid-to-high-rank coals in the Ordos Basin generally exhibit lower permeability but possess higher or comparable gas content relative to those in the San Juan and Queensland. Well completion practices also vary across these basins. In the Ordos Basin, the majority of wells are hydraulically fractured horizontal wells, whereas in the San Juan basin and Queensland, open-hole cavity vertical wells or directional wells targeting thicker coal seams are commonly employed. This comparative analysis highlights three key findings: 1) Production profiles differ between the Ordos Basin and the other two basins, with water production declining rapidly after gas production reaches a plateau. 2) Higher initial gas rates are largely driven by elevated free gas content (exceeding 20%). 3) Implementation of a controlled drawdown strategy can improve well EUR by 10–20%.
In this study, we first evaluate the formation characteristics that influence production performance, including reservoir pressure, in-situ stress, gas content, adsorption-desorption behavior, and brittleness. As coal seams extend to greater depths, the controlling factors become increasingly complex, exerting significant influence on properties that are closely linked to gas productivity. For example, coal seams located within zones of restricted water retention may exhibit higher gas saturation, while the orientation and density of butt and face cleats can impact permeability and fracability. In addition to geological variability, engineering designs and management strategies are also examined to address the unique challenges of deep CBM development. This paper provides a detailed comparison of key performance metrics across major CBM basins worldwide.
Overall, the study indicates that mid-to-high-rank coals in the Ordos Basin generally exhibit lower permeability but possess higher or comparable gas content relative to those in the San Juan and Queensland. Well completion practices also vary across these basins. In the Ordos Basin, the majority of wells are hydraulically fractured horizontal wells, whereas in the San Juan basin and Queensland, open-hole cavity vertical wells or directional wells targeting thicker coal seams are commonly employed. This comparative analysis highlights three key findings: 1) Production profiles differ between the Ordos Basin and the other two basins, with water production declining rapidly after gas production reaches a plateau. 2) Higher initial gas rates are largely driven by elevated free gas content (exceeding 20%). 3) Implementation of a controlled drawdown strategy can improve well EUR by 10–20%.
