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Based on water chemistry analyses of five batches of water product samples from eight coalbed methane (CBM) wells of the Songhe well group in the western Guizhou province in 2017, the single-factor index method, the Nemerow index method and the health risk assessment method were used to evaluate the environmental effects of the water product. The results show that the water co-product of the Songhe well group was characterized mainly by high Na+ and Cl− concentrations, alkalinity, high total dissolved solids and Na–Cl water types. The concentrations of carcinogens (i.e., As, Cd and Cr) were low, but the non-carcinogen Ba was enriched abnormally. The single-factor index method and the Nemerow index method were used to evaluate the water co-product from the eight CBM wells, and the results show a serious pollution level of up to grade 5. The ions Na+, Cl− and Ba2+ were the main sources of pollution. The pollution is more serious in the deeper part than in the shallow part of the well group. The health risk evaluation method was used to calculate the health risk index of carcinogenic factors (i.e., As, Cr, Cd) and non-carcinogenic factors (i.e., Pd, Fe, Cu, Zn, Mn, Hg, F, Ba). The results show that the spatial distribution regularity of these metals in the well group is weak. There were mainly two CBM wells with slight risk throughout the year. With increase in drainage time, the risk gradually decreased, but in the rainy season, the risk index increased abnormally to medium risk.

A critical examination of Hubbert’s model proves that it does not account for several factors that have significantly influenced the production of petroleum and other fossil fuels. The effect of these factors comes into the price of the fossil fuels, and the latter has a significant influence on the demand and rate of production of energy resources as well as on the long-term rate of production growth at both the regional and global levels. Based on several observations of historical production data, a simple mathematical model is constructed and presented in this paper for the lifetime of a fossil fuel resource. The recent data of global petroleum and natural gas production show that a very important period in the life of energy resources is a period when the demand of these resources increases almost linearly. The linear part of the production curve makes the entire lifetime production of the resource asymmetric. Information on the total available quantity of a resource at any time and of the average slope during this linear period yields an estimate of the timescale, T 2, when peak production is reached and depletion follows. The total available quantity of the energy resource is laden with significant uncertainty, which propagates in the estimates of the timescale of the peak production in any resource model. The time asymmetry of the current model leads to a delay of the timescale, when the onset of the resource production commences (e.g., peak oil). However, the rate of the resource production decline is significantly higher than that predicted by other models that use a symmetrical curve-fitting method.

Coal mining and coalbed methane (CBM) development in Western Guizhou are hampered by the tectonically deformed coal (TDC). In this article, the support vector machine algorithm was used to train and establish coal body structure detection models based on logging and seismic data, and the coal body structure distribution in the Dahebian block was predicted. The fivefold cross-validation prediction accuracy for identifying coal body structure using logging data is 96.46%. The coefficient of determination of fivefold cross-validation for predicting coal body structure thickness using seismic data is generally greater than 0.99. The coal body structure distributions in the No.1, 4, and 7 coal seams are similar, containing about 2–3 layers, and are dominated by cataclastic coal. The primary undeformed coal is usually found in the inter-fault area, whereas the cataclastic and granulated coals are mostly developed along the fault. The No.11 coal seam generally has more than 5 layers of coal body structures, mainly granulated coal. The primary undeformed coal is primarily distributed along the fault, and the granulated coal is widespread and not restricted to the fault area. The No.11 coal seam contains the most CBM resources, with more than half stored in TDC. The CBM resources in the No.1, 4, and 7 coal seams are mostly stored in cataclastic and granulated coal. The cumulative gas production is adversely associated with the proportion of TDC, and the increase in the gas production rate of wells with a high proportion of TDC is relatively slow. When releasing stress through protective layer mining, the No.11 coal seam is suitable as the protected layer. The utilization of horizontal well cavity completion for stress relief is an appropriate approach for CBM development in the No.11 coal seam dominated by thick granulated coal. This study has significant theoretical guidance and engineering reference significance for coal mining and CBM development in the study area and areas with similar demands.

The Albian to Santonian Colorado Group in the heavy oil area of Cold Lake, east-central Alberta represents a relatively condensed section of shale-dominated sedimentation within the Western Interior Sea. These shales form the cap rock to the underlying Clearwater and Grand Rapids formations that are exploited for bitumen extraction. Two cores covering the entire Colorado Group provide a unique opportunity for establishment of a stratigraphic reference in an area that has received attention only for its heavy oil-bearing Mannville Group. Based on sedimentology, geochemistry, micropaleontology, nannofossils, and wireline log data, the Colorado Group was subdivided into the Joli Fou, Viking, Westgate, Fish Scales, Belle Fourche, Second White Specks, and Niobrara formations. The Niobrara Formation was subdivided further into the Verger Member, informal Cold Lake member, and First White Specks Member. Because of this region’s small accommodation space and distance to sources of coarse clastic sediment, disconformities are indicated lithologically by bioclastic layers and missing biozones. Foraminiferal subzones revealed two erosional boundaries associated with the Viking Formation. Faunal and floral evidence coupled with wireline log correlations suggest that the Middle to Upper Turonian Carlile Formation, as described from southeastern Alberta, is missing. That extends the Middle Turonian to Coniacian unconformity, as recognized in central Saskatchewan, westwards into Alberta.

The content and distribution of unfrozen water in coal affect directly its pore structure and macroscopic mechanical properties. It is key to break through the theory of cryogenic mining technology to study the ice–water phase transition process of frozen coal. Taking bituminous coal in Yuan Zhuang, China, as the research object, this paper studied pore thawing characteristics of coal frozen by liquid nitrogen through nuclear magnetic resonance technology. The experimental results demonstrate that the unfrozen water content was exponentially related to temperatures. In the early thawing stage of the coal sample, the thawing speed of micropore was the fastest. The cumulative porosity has a linear relationship with the cumulative pore-throat distribution, and an exponential relationship with the unfrozen water content. According to the analysis of thermodynamics, pore water with high pressure and small aperture has low freezing point, causing the micropore structure was first generated with thawing. In general, during the thawing process of bituminous coal frozen by liquid nitrogen, there are more micropores and strong connectivity, which contain less ice and water. There are less mesopores and macropores, while the connectivity in the early thawing stage is poor, but the content of ice and water in that is large.

The liquid nitrogen (LN2) cyclic fracturing technology offers a novel approach to rockburst prevention. To study the effectiveness and feasibility of LN2 cyclic fracturing to reduce coal bursting liability, LN2 cyclic fracturing, ultrasonic velocimetry tests, and uniaxial compression experiments were carried out. Changes in P-wave velocity, porosity, and bursting liability indices, namely, dynamic fracture duration time (DFDT), uniaxial compressive strength (UCS), bursting energy index (BEI), and elastic strain energy index (ESEI), were studied. Moreover, acoustic emission (AE) and failure characteristics of coal were analyzed. Finally, the mechanism of strength weakening for reducing burst liability by LN2 cyclic fracturing is discussed. The results showed that LN2 cyclic fracturing can effectively cause the deterioration of coal samples, resulting in decrease of P-wave velocity by 25.92% and increase of porosity from 1.42 to 9.1%. After LN2 cyclic treatment, the bursting liability of coal samples was lowered considerably; coal DFDT rose significantly, whereas the post-peak phase of load-time curves dropped in a stepped pattern. After four times of LN2 fracturing, the UCS and BEI of coal samples decreased by 73.5% and 83.2%, respectively, and the ESEI declined from 2.85 to 1.06. The coal DFDT increased rapidly with decrease in P-wave velocity, while the UCS, BEI, and ESEI correlated positively with P-wave velocity. The AE activities of various LN2 cycle coal samples can be classified into fracture compaction stage, fracture steady growth stage, fracture unstable growth stage, and post-peak stage. Moreover, the cumulative AE energy declined with increase in LN2 cycles, while the proportion of post-peak AE energy increased in cycles. The failure mode of coal samples transformed from dynamic failure to static failure after four LN2 fracturing cycles.