On the scientific exploitation of high-rank CBM resources

摘要

After over 10 years' development of coalbed methane (CBM) industry in China, two industrial bases have been built, i.e., the Qinshui Basin and the Ordos Basin. However, the biggest problem that restricts the high-efficiency development of CBM industry in China is that average single-well gas production rate is low. At present, the production of high-rank CBM accounts for more than 90% of total CBM production in China. In the future, the exploitation field of high-rank CBM resources will focus on the deep and medium reservoirs. The complex CBM occurrence and flow conditions (e.g. different tectonic field, stress field and fracture field) bring great challenges to the adaptability of existing engineering technologies to geological conditions. In this regard, this paper takes the research and practice of high-rank CBM technologies in the Qinshui Basin of PetroChina Huabei Oilfield Company as an example to analyze the “four low” (low effective reserve producing ratio, low remaining producible reserves, low single-well gas production rate and low exploitation profit) CBM exploitation phenomena and discuss the essence of CBM exploitation dialectically. And the following research results were obtained. First, current major problems in CBM exploitation include CBM reserve recoverability, geological difference, engineering technological adaptability and scientific drainage gas recovery. Second, the only way for scientific CBM exploitation is to break through the key bottlenecks under existing technical conditions, including control technology for reserve development, regional selection technology for economic productivity construction, engineering technology suitable for geological characteristics and top-level design technology for scheme preparation. Third, the exploitation practice achievements of high-rank CBM in the Mabidong Block and medium-rank CBM in the Dacheng uplift are realized by breaking the traditional geological cognitions and breaking through the restricted idea that the CBM below 800?m is not suitable to be developed. And it is demonstrated that burial depth is not the limitation condition to determine if CBM can be exploited and medium and deep reservoirs are not the forbidden areas of CBM exploitation.