CBM Desorption Model and Stages Based on a Natural Desorption Experiment

Abstract

Coalbed methane (CBM) desorption modeling is critical for understanding CBM desorption mechanisms and objectively analyzing the production characteristics of CBM wells. According to the CBM natural desorption experimental data of 64 coal samples taken from the Qinshui Basin, we established a CBM desorption model, quantitatively identified the CBM desorption stages, and discussed the relationship between CBM desorption characteristics and well productivity. The results indicated a very significant functional relationship between the CBM natural desorption time and cumulative desorption quantity, which could be accurately described by the model V = a L t/(t + b L ). On the basis of this model and the numerical description of the desorption data, the CBM natural desorption process was divided into four stages: the desorption startup stage, desorption sensitive stage, desorption steady stage, and desorption decay stage. As indicated by analogical reasoning of the CBM well production process, the desorption startup stage corresponded to the drainage-based pressure drop stage, the desorption sensitive and steady stages corresponded to the steady production stage, and the desorption decay stage corresponded to the production declining stage. The CBM adsorption time exponentially decreased with the increase in the average CBM desorption rate and with the increase in the CBM gas content and vitrinite/inertinite ratio. Furthermore, within a certain range of desorption pressure, a high ratio between the adsorption time and gas content corresponded to the extension of the steady production stage of CBM wells, whereas higher or lower ratios were adverse to steady production.

Construction and Application of a Big Data System for Regional Lakes in Coalbed Methane Development

“…Taking CBM as an example, , this paper introduces the detailed application method of the data lake. The data lake still has broad application prospects in other fields of the petroleum industry, − and the reasons are as follows: − master data management module: With the deepening of the construction of the data lake, the petroleum exploration industry is gradually trying to use the advantages of the data lake to carry out data governance.…”

Characterization of Lower Paleozoic Water and Gas Distribution in Yan’an Gas Field, Ordos Basin

“…According to the nature of the basement, geological evolution history, and tectonic features, the Ordos Basin can be divided into six tectonic units: the Yimeng Uplift, the Yishan Slope, the Tianhuan ore-seeking depressions, the Jinshi Belt, the Western Marginal Fold Belt, and the Weibei Uplift. − The Yishan Slope was formed at the end of the early Bailian period. − It is the largest primary tectonic unit in the basin, 250 km wide from east to west and 400 km long from north to south. − The current tectonic feature is a large, gently dipping monocline that dips to the west, with an average dip of about 1° and a dip of less than 1°. , The Ordos Basin was uplifted as a whole at the end of the Ordovician in the Early Paleozoic and underwent hundreds of millions of years of weathering stripping and candle stripping without Silurian, Devonian, and Lower Carboniferous. , During this period, the weathering crustal solution candle stripping zones formed by exposed weathering and buried karst are of great significance for the formation of ancient weathered crustal gas reservoirs in the Lower Paleoproterozoic. − Feng et al studied the geochemical characteristics of natural gas in the Paleozoic era. Zhang et al conducted a systematic study on pore structures such as primary pores, secondary pores, and microcracks.…”

Study on Reservoir Characteristics and 3D Spatial Carving of Fault Solution Reservoirs Based on Geophysical Methods

“…The slip distance of intra-cratonic strike–slip faults usually does not exceed several kilometers and is also known as small-scale strike-slip faults. − This type of strike–slip fault is a widely developed local structure within the basin, with a complex three-dimensional geological structure. − Due to its small slip distance and the limitation of seismic data resolution, the activity characteristics of this type of fault are studied. − At present, there are two quantitative analysis methods for the horizontal slip distance of underground strike–slip faults: − ① using 3D seismic data to deeply slice and constrain the horizontal slip distance of strike–slip faults by the distance of ancient river channels, igneous rocks, and lithofacies boundaries that have been offset and ② quantitative analysis of strike–slip fault overlapping composite structures using the conservation of area method. − Based on the relevant structural types of strike–slip fault zones, it can be inferred that they were formed in a convergent or extensional tectonic background. If the main slip zone and adjacent structures are dominated by compressive structures, they are formed in a baroclinic stress environment. − If the structure is mainly tensile, it is formed in a diagonal tensile stress environment. The oblique compression deformation related to strike–slip faults presents a positive flower-shaped structure on the profile, while the oblique tension deformation presents a negative flower-shaped structure. − Strike-slip fault zones usually exhibit good segmentation.…”