Geochemical characteristics,generation,and evolution mechanism of coalbed methane in the south-western Ordos Basin,China

The south-western Ordos Basin is rich in low-middle rank coalbed methane(CBM)resources;while the geochemical characteristics and genetic mechanism of CBM are not clear.Herein,according to geological and geochemical test data from gas and coal seam water from CBM wells in Bingchang,Jiaoxun,Huangling,Yonglong,and Longdong minging areas,we systematically studied the geochemical characteristics,generation,and evolution mechanism of CBM in Jurassic Yan’an Formation in the south-western Ordos Basin.The results show that the CH4 content of whole gas is in the range of 42.01%-94.72%.The distribution ranges of theδ^(13)C-CH_(4)value is−87.2‰to−32.5‰,indicating diverse sources of thermogenic gas and biogenic gas.The microbial methane is mainly generated by a CO_(2)reduction pathway,with certain methyl-type fermentation spots.Theδ^(13)C-CH_(4)has a positive correlation with burial depth,indicating the obvious fractionation of CBM.The relationship between the genetic types and burial depth of the CBM reservoir indicates that the favorable depth of secondary biogenic gas is less than 660 m.The Late Cretaceous Yanshanian Movement led to the uplift of the Ordos Basin,and a large amount of thermogenic gas escaped from the edge of the basin.Since the Paleogene Period,the coal reservoir in the basin margin has received recharge from atmospheric precipitation,which is favorable for the formation of secondary biogenic methane.The deep area,generally under 1000 m,mainly contains residual thermogenic gas.The intermediate transition zone is mixed gas.Constrained by the tectonic background,the genetic types of CBM in different mining areas are controlled by the coupling of burial depth,coal rank,and hydrogeological conditions.The Binchang mining area contains biogenic gas,and the development of CBM has achieved initial success,indicating that similar blocks with biogenic gas formation conditions is key to the efficient development of CBM.The research results provide a scientific basis for searching for favorable exploration areas of CBM in the south-western Ordos Basin.

Pore structure evolution of lacustrine organic-rich shale from the second member of the Kongdian formation in the Cangdong Sag,Bohai Bay Basin,China

Pyrolysis experiments were conducted on lacustrine organic-rich shale from Cangdong Sag in Bohai Bay Basin,China,to investigate the impact of hydrocarbon generation on shale pore structure evolution.Thermal evolution is found to control the transformation of organic matter,hydrocarbon products characteristics,and pore structure changes.Furthermore,pore volume and specific surface area increase with increasing maturity.In low-mature stage,the retained oil content begins to increase,pore volumes show slight changes,and primary pores are occluded by the generated crude oil of high molecular weight and density.In the oil-window stage,the retained oil content rapidly increases and reaches maximum,and pore volumes gradually increase with increasing thermal maturity.At high mature stage,the retained oil content begins to decrease,and the pore volume increases considerably owing to the expulsion of liquid hydrocarbon.In over mature stage,natural gas content significantly increases and kerogen transforms to asphalt.Numerous organic pores are formed and the pore size gradually increases,resulting from the connection of organic pores caused the increasing thermal stress.This study lays a foundation for understanding variation of hydrocarbon products during the thermal evolution of lacustrine shales and its relationship with the evolution of shale reservoirs.

UEs Power Reduction Evolution with Adaptive Mechanism over LTE Wireless Networks

At present, the major drawback for mobile phones is the issue of power consumption. As one of the alternatives to decrease the power consumption of standard, power-hungry location-based services usually require the knowledge of how individual phone features consume power. A typical phone feature is that the applications related to multimedia streaming utilize more power while receiving, processing, and displaying the multimedia contents, thus contributing to the increased power consumption. There is a growing concern that current battery modules have limited capability in fulfilling the long-term energy need for the progress on the mobile phone because of increasing power consumption during multimedia streaming processes. Considering this, in this paper, we provide an offline meaning sleep-mode method to compute the minimum power consumption comparing with the power-on solution to save power by implementing energy rate adaptation(RA) mechanism based on mobile excess energy level purpose to save battery power use. Our simulation results show that our RA method preserves efficient power while achieving better throughput compared with the mechanism without rate adaptation(WRA).

Exploring link generation in a temporal evolution network for human mobility

The prevalence of mobile devices has spurred human mobility to be applied in mobile networking and communications by using network science, in which the temporal evolution of a network topology is of great importance for protocol design and performance analysis. This paper focuses on link generation in a temporal evolution network. Based on observations revealing the strong correlation between the connection patterns of different time periods, a link generation potential based on historical connections is proposed in this paper, aiming to provide a method for making topological predictions with less randomness. Using MIT Reality dataset, an evaluation of the accuracy of the proposed method was conducted. The experimental results demonstrate the proposal's adequacy in terms of its accuracy.

Polarization evolution of vector beams generated by q-plates

The polarization evolution of vector beams(VBs) generated by q-plates is investigated theoretically and experimentally.An analytical model is developed for the VB created by a general quarter-wave q-plate based on vector diffraction theory.It is found that the polarization distribution of VBs varies with position and the value q.In particular,for the incidence of circular polarization,the exit vector vortex beam has polarization states that cover the whole surface of the Poincarésphere,thereby constituting a full Poincarébeam.For the incidence of linear polarization,the VB is not cylindrical but specularly symmetric,and exhibits an azimuthal spin splitting.These results are in sharp contrast with those derived by the commonly used model,i.e.,regarding the incident light as a plane wave.By implementing q-plates with dielectric metasurfaces,further experiments validate the theoretical results.

Successive formation of secondary pores via feldspar dissolution in deeply buried feldspar-rich clastic reservoirs in typical petroliferous basins and its petroleum geological significance

Clastic rock reservoirs in petroliferous basins are generally rich in feldspars. Feldspar dissolution has developed widely in clastic reservoirs, and the resulting secondary pores are crucial in deeply buried reservoirs. Based on a study of the diagenesis of clastic reservoirs in the Bohai Bay Basin, Tarim Basin, and Pearl River Mouth Basin and physical and numerical simulation experiments of fluid-rock interactions, this paper proposed a successive formation model of secondary pores via feldspar dissolution in deeply buried clastic reservoirs, considering the global research progresses in feldspar dissolution in clastic rocks. Feldspar dissolution can occur from shallow open systems to deep-ultra deep closed systems in petroliferous basins, resulting in the successive formation of secondary pores at different diagenetic stages. The successive mechanism includes three aspects. The first aspect is the succession of corrosive fluids that dissolve minerals. Meteoric freshwater dominates at the Earth’s surface and the early diagenetic A stage. Subsequently, organic acids and COformed via kerogen maturation dominate at the early diagenetic B stage to the middle diagenetic stage. COand organic acids formed via hydrocarbon oxidation in hydrocarbon reservoirs dominate at the middle diagenetic B stage to the late diagenetic stage. The second aspect is the successive formation processes of secondary pores via feldspar dissolution. Large-scale feldspar secondary pores identified in deep reservoirs include secondary pores formed at shallow-medium depths that are subsequently preserved into deep layers, as well as secondary pores formed at deep depths. Existing secondary pores in deeply buried reservoirs are the superposition of successively feldspar dissolution caused by different acids at different stages. The third aspect is a successive change in the feldspar alteration pathways and porosity enhancement/preservation effect. Open to semi-open diagenetic systems are developed from the Earth’s surface to the early diagenetic stage, and feldspar dissolution forms enhanced secondary pores. Nearly closed to closed diagenetic systems develop in the middle to late diagenetic stages, and feldspar dissolution forms redistributional secondary pores. The associated cementation causes compression resistance of the rock, which is favorable for the preservation of secondary pores in deep layers. These new insights extend the formation window of secondary pores in petroliferous basins from the traditional acid-oil generation window to a high-temperature gas generation window after hydrocarbon charging. The proposed model explains the genesis of deep-ultra deep high-quality reservoirs with low-permeability, medium-porosity and dominating feldspar secondary pores, which is significant for hydrocarbon exploration in deep to ultra-deep layers.