The purpose of this paper is to study that, the relationship of reservoir liquid level pressure between the combined mining layers, the relationship of production pressure difference between the combined mining layers, and the relationship of gas-seeking time between the combined mining layers during the combined production of multi-layer coalbed methane reservoirs. To this end, this paper takes multi-layer independent coalbed methane reservoirs as the research object. Starting from the reservoir forming characteristics and coalbed methane production mechanism, based on the expression of downhole pressure expression of coalbed methane wells, the relationship expression of reservoir liquid level pressure between the combined mining layers was derived. Furthermore, the relational expression of production pressure difference between the combined mining layers and the relational expression of gas-seeking time between the combined mining layers were derived. The following conclusions are drawn through analysis. Due to the existence of the layer spacing, there is a certain difference in the reservoir liquid level pressure between the upper and lower reservoirs when the lower reservoir is bare. After the lower reservoir is exposed, the reservoir liquid level pressure at the reservoir between the upper and lower reservoirs is equal. The production pressure difference between layers and the gas-seeking time between layers are not necessary to be equal. And the size of the difference is related to the reservoir layer difference, interlayer spacing, and whether the reservoir is exposed. In addition, the difference in gas-seeking time between layers is also affected by the gas well production pressure difference. The research results provide a theoretical basis for the development of the drainage system of the coalbed methane combined production well and the selection of simulation experiment methods for combined production of coalbed methane reservoirs with multiple reservoirs.
Cite this article
Ying-shuang SHI, Bing LIANG, Lu XUE, Wei-ji SUN, Qing-chun WANG, Zhi-heng CHENG. Analysis on production characteristics of coalbed methane multi-layer production wells[J]. Natural Gas Geoscience, 2020, 31(8): 1161-1167. DOI: 10.11764/j.issn.1672-1926.2020.04.027
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