In the heart of China’s energy sector, a groundbreaking study is set to redefine the landscape of coal-rock gas exploration and development. Led by Ze Deng from the PetroChina Research Institute of Petroleum Exploration & Development in Beijing, this research delves into the key controlling factors of coal-rock gas in the Benxi Formation of the Ordos Basin, offering a roadmap for more efficient and targeted resource extraction.
The Ordos Basin, a vast sedimentary basin in northern China, is known for its rich coal-rock gas resources. However, the lack of clarity on the key factors controlling gas content has been a significant hurdle in the exploration and development process. Deng’s study, published in the journal ‘Meitan kexue jishu’ (which translates to ‘Coal Science and Technology’), aims to change that.
The research systematically analyzes the geological conditions of coal-rock gas in the Benxi Formation, using a wealth of measured data, including gas content, coal rock and coal quality, coal geochemistry, and pore structure. The findings are profound and multifaceted. Deng explains, “We found that sedimentation, coal rank, and buried depth lay the overall pattern of gas content of coal.”
The study reveals that the sedimentary environment restricts the hydrocarbon material base, the original occurrence space of coal-rock gas, and the plane distribution of preservation conditions. The evolution of the coal-forming environment determines the longitudinal difference distribution of coal quality, creating longitudinal heterogeneity of gas content. Moreover, coal rank not only controls the gas generation intensity of coal but also affects the occurrence space and reservoir performance of coal-rock gas by influencing the pore structure. The adsorption performance of coal is strengthened with the increase of metamorphism.
The buried depth mainly affects the proportion of adsorbed gas and free gas. Below the critical depth, with the increase of burial depth, the proportion of free gas increases. However, the total gas volume decreases after the depth exceeds 3000 meters. Micro-amplitude structures play a role in local gas enrichment in the development and gentle slope zone.
Deng’s research identifies a north-south strip from Yulin to Yichuan as the coal-rock gas enrichment zone, with an average gas content of up to 23 cm3/g. This finding is a game-changer for the energy sector, offering a clear target for exploration and development efforts.
The study also constructs an evaluation system of coal-rock gas resource conditions, dividing the coal seams of the Benxi Formation in the basin into four categories and 13 communities. The class I area is mainly distributed in Yulin area, Daning-Jixian area, and Yanan area, while the class II area is mainly distributed in Wushenqi area.
The implications of this research are vast. By providing a clearer understanding of the key controlling factors of coal-rock gas, Deng’s work is expected to guide the orderly exploration and development of coal-rock gas in the Ordos Basin. This could lead to more efficient resource extraction, reduced costs, and a significant boost to China’s energy sector.
As the world continues to grapple with energy challenges, research like Deng’s offers a beacon of hope. By unlocking the secrets of coal-rock gas, we can pave the way for a more sustainable and energy-secure future. The study, published in ‘Meitan kexue jishu’, is a testament to the power of scientific inquiry and its potential to shape the future of the energy sector.