Geological characteristics and exploration breakthroughs of coal rock gas in Carboniferous Benxi Formation,Ordos Basin,NW China

To explore the geological characteristics and exploration potential of the Carboniferous Benxi Formation coal rock gas in the Ordos Basin,this paper presents a systematic research on the coal rock distribution,coal rock reservoirs,coal rock quality,and coal rock gas features,resources and enrichment.Coal rock gas is a high-quality resource distinct from coalbed methane,and it has unique features in terms of burial depth,gas source,reservoir,gas content,and carbon isotopic composition.The Benxi Formation coal rocks cover an area of 16×104km^(2),with thicknesses ranging from 2 m to 25 m,primarily consisting of bright and semi-bright coals with primitive structures and low volatile and ash contents,indicating a good coal quality.The medium-to-high rank coal rocks have the total organic carbon(TOC)content ranging from 33.49%to 86.11%,averaging75.16%.They have a high degree of thermal evolution(Roof 1.2%-2.8%),and a high gas-generating capacity.They also have high stable carbon isotopic values(δ13C1of-37.6‰to-16‰;δ13C2of-21.7‰to-14.3‰).Deep coal rocks develop matrix pores such as gas bubble pores,organic pores,and inorganic mineral pores,which,together with cleats and fractures,form good reservoir spaces.The coal rock reservoirs exhibit the porosity of 0.54%-10.67%(averaging 5.42%)and the permeability of(0.001-14.600)×10^(-3)μm^(2)(averaging 2.32×10^(-3)μm^(2)).Vertically,there are five types of coal rock gas accumulation and dissipation combinations,among which the coal rock-mudstone gas accumulation combination and the coal rock-limestone gas accumulation combination are the most important,with good sealing conditions and high peak values of total hydrocarbon in gas logging.A model of coal rock gas accumulation has been constructed,which includes widespread distribution of medium-to-high rank coal rocks continually generating gas,matrix pores and cleats/fractures in coal rocks acting as large-scale reservoir spaces,tight cap rocks providing sealing,source-reservoir integration,and five types of efficient enrichment patterns(lateral pinchout complex,lenses,low-amplitude structures,nose-like structures,and lithologically self-sealing).According to the geological characteristics of coal rock gas,the Benxi Formation is divided into 8 plays,and the estimated coal rock gas resources with a buried depth of more than 2000 m are more than 12.33×10^(12)m^(3).The above understandings guide the deployment of risk exploration.Two wells drilled accordingly obtained an industrial gas flow,driving the further deployment of exploratory and appraisal wells.Substantial breakthroughs have been achieved,with the possible reserves over a trillion cubic meters and the proved reserves over a hundred billion cubic meters,which is of great significance for the reserves increase and efficient development of natural gas in China.

Analysis on the Evolution of Dry and Wet Degree in Benxi Area in Recent 57 Years

[Objective] The research aimed to analyze the evolution situation of dry and wet degree in Benxi area in recent 57 years.[Method] By using the annual,quarterly and monthly temperature and precipitation data in Benxi area during 1953-2009,the interdecadal variations of temperature,precipitation,dry and wet index were analyzed.[Result] The annual average temperature in Benxi area displayed the obvious increase trend,and the linear trend rate was 0.29 ℃/10 a.But the precipitation showed the obvious decrease trend,and the linear trend rate was-29.01 mm/10 a.The dry and wet index showed the decrease trend,and the linear trend rate was-33.61 mm/10 a,which closely related to the rise of temperature and the decrease of precipitation after the 1980s.[Conclusion] It showed the warming-drying development trend in Benxi area.

Analysis on Variation of Rainfall Trend and Agriculture Dryness in Benxi City of Liaoning Province

Linear regression,climate trend rate,integral humidity indicator and dry-wet index were adopted to analyze the precipitation change,drought or waterlogging frequency and occurrence period in Benxi of Liaoning.The results showed that in recent 55 years,the tendency rate of annual precipitation in Benxi was-30.749 mm/10 a,reducing 165 mm in trend;the precipitation tendency rate during the growing season of plants was-31.371/10 a,reducing 173 mm in trend.The climate type was changed from light flood 20 a ago to wet type.The satisfaction of agriculture-required water was above 150% and annual average precipitation surplus was 290 mm.Benxi was hit by the medium floods to heavy floods in 10 years,about once in five years.The occurrence period of mild drought was 5 a,about once in ten years.The drought in spring below the medium degree occurred twice in a decade while the waterlogging above the medium degree occurred once in a decade.The waterlogging in summer above the medium degree occurred once in two years.The waterlogging in autumn above the medium degree occurred twice in a decade while the drought below the medium degree occurred four times in a decade.The occurrence frequency of heavy waterlogging in July and August was 54.5%.May and September were the period of time with a strikingly higher prevalence in drought.

Analysis on the Variation Characteristics of Temperature and Precipitation in Benxi Area under the Background of Climate Warming

[Objective] The research aimed to study the variation characteristics of temperature and precipitation in Benxi area under the background of climate warming.[Method] Based on the monthly mean temperature and precipitation data of four routine meteorological stations in Benxi area from 1953 to 2010,by using linear tendency rate,linear regression equation,wavelet analysis,Mann-Kendall detection and so on,the variation characteristics of temperature and precipitation under the background of climate warming in the area were analyzed.[Result] The annual average temperature during 1953-2010 in Benxi area presented rise trend,and the linear tendency rate was 0.28 ℃/10 a.It was temperature increase trend in four seasons.The temperature rise rate in winter was the maximum and was the minimum in summer.The annual rainfall presented decrease trend,and the linear tendency rate was-18.16 mm/10 a.Except in spring,it was decrease trend in other seasons.Mann-Kendall mutation detection showed that the mutation of annual average temperature in Benxi area in recent 58 years appeared in 1986.There was no mutation phenomenon in summer.Spring mutation appeared in 1974,and autumn mutation appeared in 1987.Winter mutation was in 1981.The annual and seasonal precipitation didn’t have the mutation phenomenon.The wavelet analysis found that the annual average temperature had the periodic variations of 12-14,5-6 and 2 years in Benxi area in recent 58 years.The annual rainfall had the periodic fluctuations of 8-12,5-6 and 2 years.[Conclusion] The research provided the scientific basis for exploration and sustainable development of the climate resources in the mountain area.

Analysis on the Heavy Snow Weather Process in Benxi Area

[Objective] The aim was to study the formation and development of a heavy snow in Benxi area. [Method] Based on conventional meteorological data, the formation and development of a heavy snow in Benxi area from December 4th to 5th in 2009 were analyzed from the aspects of weather situation evolution and physical quantity field feature. [Result] The heavy snow was caused by upper trough and North China cyclone. In this process, there was upper level divergence and lower level convergence over Benxi area, and it was warm at low attitude and cold at high attitude; southwest jet at low attitude transported water vapor from Bohai Sea to eastern Liaoning, which provided good water vapor condition for snow, but it didn’t reach heavy snow due to inadequate ascending force. The development of Ural Mountains high ridge played an important role in the snow process and the strengthened high ridge moving northward was beneficial to the southward movement of cold air and deepening of upper trough. Analysis on physical quantity field could provide reference for predicting beginning and ending time and strength of heavy snow. [Conclusion] The study could provide basis for the forecast of heavy snow.

SUSTAINABLE DEVELOPMENT OF THE SERIOUSLY POLLUTED CITIES IN CHINA——Taking Benxi City as an Example

The environmental problems in the seriously polluted cities in China have been paid attention to by policy makers and foreign and domestic scholars. However, it is very difficult to improve the environmental quality fundamentally due to its complexity, for example the formation of the seriously deteriorated environment. It is considered that the terminal harnessing is an important way,but the spread of high level terminal treatment is restricted by the limit of funds and technological level. Therefore, the way for a sustainable development of the seriously polluted cities should be multiple sided, which is to correlate the operation of environmental protection with the operation of city construction. To achieve an identity of these opposites, measures should be taken during economic development and environmental protection in every developing stage. In this paper, the authors take Benxi City as a case study.

Height growth of Korean pine plantation sapling in Benxi, Liaoning Province, China

The height growth of Korean pine plantation was investigated for different ages of saplings in Benxi city of the eastern Liaoning, China. The sapling and seedling age were determined by branch annuals. Results show that the mean height of third- to eight-year Korean pines ranges from 13.31 cm to 111.73 cm and only 19.4% of the saplings reached the height above 130 cm. The height （Y） of eight-year-old Korean pine increases linearly with the increment of ground stem （x） （Y=3.1x＋35.15）. The relation between height and age can be described by an exponential equation. The second year after planting of the Korean pine is considered as the key period of Korean pine growth really adapting to the local environment; plantation management should be strengthened in this year. The Korean pine seedlings need two years to adapt to the local environment, thus early care and management should be taken in the second year.

New Discovery of Molar Tooth Structures in the Kangjia Formation at Benxi,Liaoning and its Significance

Objective The Jilin-Liaoning area has widely spread Meso- and Neoproterozoic sediments and is always a focused area for researching Precambrian geology. Previous study has achieved a series of results about Neoproterozoic stratigraphy in this area, but the lack of precise geochronological data and signs of stratigraphic correlation has resulted in the long controversial stratigraphic age and regional correlation. During recent years,

Analysis of relationship between economic growth and environment in Benxi Shiqiaozi Development Zone

How to express and assess the coordination between environmental system and economic system is one crucial problem for the studies on regional sustainable development.The present study applies environmental supporting capacity (ESC) to evaluate the comparative coordination of economic development plans in a case study in Shiqiaozi Development Zone.The analysis conclusion showed the method is practicable.A new method for judging the efficiency of utilization of environmental system is also discussed in this paper.

Climate Change Tendency in Benxi City, Liaoning Province in Recent 60 Years

Based on data of temperature and precipitation in Benxi City from 1951 to 2010, variation characteristics and abrupt changes of the climate in Benxi City during recent 60 years were analyzed using linear trend and Mann-Kendall method. The results showed that annual average tem- perature in Benxi City showed an upward trend in recent 60 years, with the linear tendency rate of 0.12 ℃/10 a; average temperature in each season also showed an increasing trend, and the increase was the greatest in winter, followed by spring, autumn and summer. Annual precipitation showed a decreasing trend, as well as average precipitation in summer, autumn and winter. According to the variation characteristics of temperature and precipitation in Benxi, the climate tended to be warming and drying over the past 60 years; the temperature and precipitation had significant periodic and seasonal variations.

Establishment of Geographic Information Database of Benxi City and Its Application in Analysis of Climatic Resources

Based on 1:50 000 basic geographic information data,the digital elevation,longitude,latitude,slope,aspect and all kinds of terrain databases of Benxi City (China) were established with Arcgis 9.2 software.Township boundary database was established by digitizing map,and the township information was amended according to the reality.Taking the elaborate simulation of spatial distribution of annual mean temperature as an example,the paper reports the application of the geographic information database in analysis of climatic resources.

Analysis on Change Characteristics of Sunshine in Benxi Mountainous Area in Recent 57 Years

[Objective] This study aimed to analyze the change characteristics of sunshine hours in Benxi mountainous area in recent 57 years.[Method] Based on the data of monthly sunshine hours,total cloudiness,vapor pressure and ≥0.1 mm precipitation days from Caohekou weather station during 1954-2010,by using linear tendency,Mann-Kendall method and wavelet analysis,the change characteristics of sunshine hours in Benxi mountainous area in recent 57 years were analyzed,as well as the possible climatic factors resulting in the decrease of sunshine hours.[Result] In recent 57 years,except for the slight increase of sunshine hours in winter,annual sunshine hours and sunshine hours in other seasons showed significantly decreasing trend,and annual sunshine hours varied abruptly in 1971.In addition,total cloudiness,vapor pressure and ≥0.1 mm precipitation days affected sunshine hours obviously,but sunshine hours didn’t simply increase as the reduction of total cloudiness and ≥0.1 mm precipitation days,which showed that the influencing factors of sunshine hours were complex.[Conclusion] The research could provide scientific references for the reasonable utilization of light energy,adjustment of agricultural industrial structure and sustainable development of agricultural economy in mountainous areas.

Chronoframe of Archaean in Anshan-Benxi Area,Liaoning Province,China

The Anshan- Benxi area is one of the important places of the Precambrian in the North China craton, in which a lot of old geological bodies were found, including the Baijiafen mylontized granitic gneiss of 3.8 Ga ,the Chentaigou gneissic granite of 33 Ga and the supracrustal rocks and associated granites of relatively younger ages .Based on the age data and other geological information obtained in recent yeais, mis paper establishes fourfold-divison scheme of the Archaean in the Anshan-Benxi area .The time boundaries are 2.5,2.8,3.2 and 3.6 Ga, corresponding to those recommended by the International Sub-commission on Precambrian Stratigraphy . This paper also discusses some questions related to the crustal evolution of the early history, and indicates that it is possible to find out more residual crustal materials of older than 2.8 Ga.

Tidally Induced Water Temperature Change in Artesian Wells

Water temperature observation in wells,as a precursor observation project in China,aims to capture stress-strain information during the preparation of earthquakes. The study of the water temperature tidal effect has important significance,for water temperature tidal effect is both a reflection of stress-strain in crust and an interference factor of precursor observations. With a view of thermal conditions in artesian wells,the paper holds that there are two mechanisms for interpreting tidally induced water temperature changes in artesian wells. Namely,thermal conduction mechanisms and thermal convection mechanism. The paper then derives the quantitative relationship between water temperature and tidal volumetric strain changes in an ideal artesian well. Finally,the water temperature tidal effect in the Benxi artesian well is analyzed. The results show that the water temperature tidal effect in Benxi well is the result of joint action of thermal conduction mechanism and thermal convection mechanism,in which thermal conduction mechanism plays a leading role.

Main controlling factors and exploration enlightenment of aluminous rock series gas reservoirs in Ordos Basin,NW China

Based on the data of outcrop,core,logging,gas testing,and experiments,the natural gas accumulation and aluminous rock mineralization integrated research was adopted to analyze the controlling factors of aluminous rock series effective reservoirs in the Ordos Basin,NW China,as well as the configuration of coal-measure source rocks and aluminous rock series reservoirs.A natural gas accumulation model was constructed to evaluate the gas exploration potential of aluminous rock series under coal seam in the basin.The effective reservoirs of aluminous rock series in the Ordos Basin are composed of honeycomb-shaped bauxites with porous residual pisolitic and detrital structures,with the diasporite content of greater than 80%and dissolved pores as the main storage space.The bauxite reservoirs are formed under a model that planation controls the material supply,karst paleogeomorphology controls diagenesis,and land surface leaching improves reservoir quality.The hot humid climate and sea level changes in the Late Carboniferous–Early Permian dominated the development of a typical coal-aluminum-iron three-stage stratigraphic structure.The natural gas generated by the extensive hydrocarbon generation of coal-measure source rocks was accumulated in aluminous rock series under the coal seam,indicating a model of hydrocarbon accumulation under the source.During the Upper Carboniferous–Lower Permian,the relatively low-lying area on the edge of an ancient land or island in the North China landmass was developed.The gas reservoirs of aluminous rock series,which are clustered at multiple points in lenticular shape,are important new natural gas exploration fields with great potential in the Upper Paleozoic of North China Craton.

本溪自流井水位与水温同震变化关系研究

利用本溪自流井水位及水温对苏门答腊Ms8.7大震的同震响应资料,通过分析水位变化与水温变化的相互关系和研究区的井-含水层系统结构,建立了不同层位地下水混合的物理模型,并根据水位变化数据模拟出水温变化曲线,同时也揭示了同类型观测井水位与水温对远场大震的同震响应机理。

自流井水温固体潮效应及其应变响应能力

井水温度观测是一项重要的地震前兆观测手段,旨在捕捉地震孕育过程中的应力-应变信息。水温固体潮效应作为地壳应力-应变信息的真实反映和地震前兆观测的干扰因素,具有重要的研究意义。本文首先依据对自流井中热状态的分析,认为自流井水温固体潮效应可能主要存在两种机制,即热传导机制和热对流机制;据此,推导出热传导机制中水温与固体潮体应变变化的定量关系;最后以流量相对较大的本溪自流井为例进行分析。结果表明,本溪井水温固体潮效应是热传导机制和热对流机制共同作用的结果,其中,热传导机制起主要作用。

Source-to-sink of Late carboniferous Ordos Basin: Constraints on crustal accretion margins converting to orogenic belts bounding the North China Block

The Upper Carboniferous Benxi Formation of the Ordos Basin is the lowest strata overlying Middle Ordovician above the major ca.150-Myr sedimentary gap that characterizes the entire North China Block(NCB).We apply an integrated analysis of stratigraphy,petrography,and U-Pb dates and Hf isotopes on detrital zircons to investigate its provenance and relationships to the progressive collisions that formed the Xing’an-Mongolia Orogenic Belt to the north and the Qinling Orogenic Belt to the south.The results show that,in addition to regional patterns of siliciclastic influx from these new uplifted sources,the Benxi Formation is composed of two sequences corresponding to long-term glacial-interglacial cycles during the Moscovian to lower Gzhelian stages which drove global changes of eustatic sea level and weathering.The spatio-temporal distribution of sediment isopachs and facies indicate there were two sediment-infilling pulses,during which the southern and the northern Ordos Basin developed tidal-reworked deltas.The age spectra from detrital zircons,trace element patterns and εNd(t)values reveal that the siliciclastics forming the southern delta was sourced in the Qinling Orogenic Belt,whereas the northern delta was derived from the Xing’an-Mongolia Orogenic Belt.The source-to-sink evolution of this Upper Paleozoic system records the progressive development of orogenic belts and uplifts forming on the southern and northern margins of the NCB prior to its collisions with the South China and the Siberian plates,respectively.

Late Carboniferous-Early Permian Volcanic Event Deposits and Stratigraphic Correlation in Shandong Province and Its Adjacent Regions

Deposits of 10 volcanic events of 6 stages have been discovered by the authors after detailed field and lab studies of the Benxi and Taiyuan Formations in Shandong Province and its adjacent regions. They show certain temporal-spatial distribution characteristics. Volcanic fragments were probably derived from two different volcanic sources north and south of the North China Platform, while the magma of the two volcanic sources was probably derived from the lower crust. A new stratigraphic correlation scheme is put forward for the Benxi and Taiyuan Formations in this region on the basis of previous biostratigraphic work with the regionally widespread volcanic event layers as the marker bed for the isochronous stratigraphic correlation on a super-regional scale and in conjunction with the maximum transgressive event layers.

Non-seismic geophysical analysis of potential geothermal resources in the Longgang Block,Northeast China

Although geothermal energy has many clear advantages,including its sustainability and environmentally friendly nature,research into potential geothermal resources across the Longgang Block,Northeast China,has been limited.Here we present the first analysis of the potential geothermal resources in this region that employs joint geological and non-seismic geophysical methods to identify target areas that may be economically viable.We acquire and analyze high-precision gravity,magnetic,and magnetotelluric sounding data,which are constrained using the petrophysical parameters of outcropping rocks across the Longgang Block,to conduct a comprehensive evaluation of the region’s deep geological structures and their geothermal resources potential,with a focus on identifying faults,rock masses,and thermal storage structures.We find that Archean granitic gneiss and Mesozoic rock masses in the deeper section of the Longgang Block possess weak gravity anomalies and high resistivities.We also identify thermal storage structures near these deeper geological units based on their extremely low resistivities.The data are used to infer the dip and depth of known or hidden faults,to constrain the spatial distribution of intrusive rock masses,and to determine the spatial distribution of subsurface thermal storage structures.The potential of the target areas for geothermal resources exploitation is divided into three grades based on contact depths between faults and thermal storage structures,and the scale of their thermal storage structures.Our results suggest that a joint non-seismic geophysical approach can be effective in locating and evaluating geothermal resources in complex geological settings.