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.

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.

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.

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.

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 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.

The Late Paleozoic Lithofacies Palaeogeography of the Benxi and Taiyuan Formation Controls Coal Accumulation in Yuzhou,Henan China

The significance of this paper is to understand the characteristics of Late Paleozoic depositional environment, lithofacies palaeogeography and its distribu- tion pattern in Henan Province,to resolve the issue of basic geological,exploration and prospecting services for the region.Yuzhou in Henan Province

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.

Constraints of palaeoenvironment on organic matter of Benxi Formation shale and discussion on enrichment mechanism under different facies

As a hydrocarbon-rich sedimentary basin in China,the Ordos Basin has enormous potential for shale gas resources.The shale of the Upper Carboniferous Benxi Formation is rich in organic matter,however,its palaeoenvironment and organic matter enrichment mode are yet to be revealed.In this study,the geochemical characteristics of the shale of the Benxi Formation in the east-central part of the Ordos Basin were analyzed to investigate its palaeoenvironment.At the same time,the organic matter enrichment modes in different sedimentary facies were compared and analyzed.The results indicate that:1)the shale of the Benxi Formation was mainly deposited on the continental margin and strong terrestrial clastic input;2)the deposition period of the Benxi Formation shale had a hot and humid climate with high palaeoproductivity and local volcanic hydrothermal fluid,and a high sedimentation rate with the strong stagnant environment.The bottom water was in dysoxic conditions and a semi-saline deposition environment;3)multiple factors,such as palaeoproductivity,volcanic hydrothermal,redox conditions,and palaeosalinity interact to influence the enrichment of shale organic matter in Benxi Formation;4)the organic matter enrichment modes of continental,marine-continental transitional,and marine shales can be classified into three types:“production mode”,“hybrid mode of preservation and production”,and“preservation mode”,respectively.This study provides a reference for the organic matter enrichment mode,shale gas formation conditions,and core area evaluation in these marine-continental transitional shales,and also offers new guidance for exploration ideas for shale gas in different sedimentary facies.

鄂尔多斯盆地石炭系本溪组煤岩气地质特征与勘探突破

通过对鄂尔多斯盆地石炭系本溪组煤岩分布、煤岩储层特征、煤质特征、煤岩气特征以及煤岩气资源和富集规律等方面开展系统研究,评价其勘探潜力。研究表明:①煤岩气是有别于煤层气的优质天然气资源,在埋深、气源、储层、含气性、碳同位素组成等方面具有独特特征;②本溪组煤岩分布面积达16×10^(4)km^(2),厚度2~25m,以原生结构的光亮和半亮煤为主,挥发分和灰分含量低,煤质好;③中高阶煤岩TOC值为33.49%~86.11%,平均值为75.16%,演化程度高(Ro为1.2%~2.8%),生气能力强,气体稳定碳同位素值高(δ^(13)C_(1)值为-37.6‰~-16.0‰,δ^(13)C_(2)值为-21.7‰~-14.3‰);④深层煤岩发育气孔、有机质孔和无机矿物孔等基质孔隙,与割理、裂缝共同构成良好储集空间,储层孔隙度为0.54%~10.67%,平均值为5.42%,渗透率为(0.001~14.600)×10^(-3)μm^(2),平均值为2.32×10^(-3)μm^(2);⑤纵向上发育5种煤岩气聚散组合,其中煤岩-泥岩聚气组合与煤岩-灰岩聚气组合最为重要,封闭条件好,录井全烃气测峰值高;⑥构建了广覆式分布的中高阶煤岩持续生气、煤岩基质孔和割理裂缝规模储集、源-储一体赋存、致密岩盖层密闭封堵的煤岩气富集模式,存在煤岩侧向尖灭体、透镜体、低幅度构造、鼻状构造和岩性自封闭5种高效聚气类型。⑦依据煤岩气地质特征评价划分出8个区带,估算埋深超过2000m的煤岩气资源量超过12.33×10^(12)m^(3)。上述认识指导风险勘探部署,两口井实施后分别获得工业气流,推动进一步部署预探井和评价井,获得规模突破,提交超万亿方预测储量和超千亿方探明储量,对中国天然气效益增储和高效开发具有重大意义。

辽宁本溪地区新太古代晚期钾质花岗岩的发现及其地质意义

辽宁本溪地区位于华北克拉通东部陆块东北部,区内广泛发育新太古代深成侵入岩和变质表壳岩,尚无钾质花岗岩的报道。钾质花岗岩的形成过程是早期陆壳发育成熟和稳定的重要标志,本次钾质花岗岩的发现对系统的研究华北克拉通早期陆壳的形成与演化具有重要的价值。本文对本溪地区马家沟的钾质花岗岩进行了岩石学、成岩年代学、岩石地球化学的研究,探讨了岩石成因和形成的构造背景。马家沟岩体为片麻状中细粒黑云母二长花岗岩。锆石U-Pb测年数据显示,岩石^(207)Pb/^(206)Pb加权平均年龄为(2490±21)Ma,形成于新太古代晚期。该岩体属弱过铝质、高钾钙碱性系列钾质岩石;主要富集高场强元素La、Zr、Th及大离子亲石元素K、Nd等元素,亏损P元素、高场强元素Nb和大离子亲石元素Sr、Ti等;REE曲线为右倾型,负Eu异常,属于S型花岗岩。研究区钾质花岗岩岩浆主要来源于地壳,是变质泥岩部分熔融的产物,形成于活动大陆边缘碰撞造山后的伸展环境,代表华北太古宙克拉通固结基底形成之前的最后一次岩浆活动,标志着在新太古代晚期本溪地区微陆块已拼贴完成,并与其他地区一起构成稳定的华北太古宙克拉通。

鄂尔多斯盆地东北部神木地区本溪组煤系致密砂岩储层特征

由于致密砂岩储层发育影响因素复杂,导致对储层进行合理、定量分类通常较困难。运用铸体薄片、扫描电镜、黏土矿物X-射线衍射、高压压汞、核磁共振等资料,对鄂尔多斯盆地东北部神木地区石炭系本溪组煤系致密砂岩气储层特征进行研究,采用储层综合指数(CEI)建立储层定量分类标准,预测有利储层。结果表明:神木地区本溪组主要发育石英砂岩和岩屑石英砂岩,填隙物主要为高岭石、绿泥石、铁白云石和铁方解石等胶结物;孔隙类型以原生粒间孔隙和高岭石晶间孔隙为主,微裂隙和岩屑粒内溶孔次之,主要发育粗孔-中喉型和细孔-小喉型孔隙结构;区内压实压溶作用和胶结作用普遍,石英及岩屑粒内溶蚀作用发育,储层普遍进入中成岩B期阶段。神木地区本溪组发育Ⅰ类(CEI>0.6)、Ⅱ类(0.4<CEI<0.6)和Ⅲ类(CEI<0.4)储层,Ⅰ类和Ⅱ类为有利储层,Ⅰ类储层分布范围相比Ⅱ类储层较小,但两者纵向上均以本1段最为发育,平面上多分布在水下分支河道和砂坪微相中。

鄂尔多斯盆地上古生界煤岩气成藏地质条件及勘探方向

为了进一步提高鄂尔多斯盆地煤岩气勘探开发效益,综合钻井、录井和分析测试等资料,从盆地尺度上系统地研究了上古生界煤系地层聚煤环境、煤质特征、储层物性和含气性,分析了盆地煤岩气成藏条件,总结了煤岩气勘探开发关键技术,评估了盆地煤岩气资源,并指出了煤岩气的勘探方向。研究结果表明:①盆地石炭纪本溪期海陆交互相沉积与二叠纪山西期陆相三角洲沉积发育形成广泛分布的煤岩,热演化程度较高,镜质组含量高,生烃规模大。②盆地深层煤质优良,以光亮煤和半亮煤为主,煤体结构良好,以原生结构煤为主,固定碳含量高,挥发分和灰分产率低。③煤岩储层发育储集空间包括气孔、植物组织孔和无机矿物质孔,割理和裂隙发育,平均孔隙度为4.80%,平均渗透率为2.35 mD,属于致密储层;煤岩平均含气量为22.53 m^(3)/t,其中游离气平均含量为5.65 m^(3)/t,占总含气量的25.08%。④煤岩与上覆不同岩性形成了煤岩-泥岩、煤岩-石灰岩和煤岩-砂岩3种储盖组合,控制了游离气富集分布,提出了“源储一体、持续生烃、盖层封堵”的煤岩气成藏模式。⑤在煤岩气勘探实践中形成了地震地质综合建模、水平井钻完井、压裂改造和限压排采等一系列配套工程技术。⑥盆地本溪组8号煤岩和山西组5号煤岩埋深1500 m以深煤岩叠合总面积16.70×104 km^(2),估算煤岩气总资源量23.47×10^(12) m^(3)。其中8号煤岩分布面积10.63×104 km^(2),煤岩气资源量17.43×10^(12) m^(3);5号煤岩分布面积6.06×104 km^(2),煤岩气资源量6.04×10^(12) m^(3)。结论认为:①鄂尔多斯盆地煤岩气地质条件优越,资源潜力巨大,勘探配套技术已基本形成,煤岩气勘探开发前景良好;②神木周边、榆林周边、乌审旗周边、米脂北、佳县、绥德、吴堡、大宁-吉县等区带8号煤岩,神木-伊金霍洛旗、榆林-佳县、乌审旗北、横山-子洲等区带5号煤岩是近期煤岩气的重点勘探方向。

鄂尔多斯盆地含铝岩系天然气成藏主控因素与勘探启示

基于野外露头、岩心、录井、测井、试气及分析化验等资料,采用天然气成藏与铝土岩成矿一体化研究方法,分析鄂尔多斯盆地含铝岩系有效储层发育控制因素、煤系烃源岩与含铝岩系的源储配置关系,构建天然气成藏模式,对煤下含铝岩系天然气勘探潜力进行评价。研究表明:(1)鄂尔多斯盆地含铝岩系的有效储层主要为一水硬铝石含量超过75%,具有多孔状残余豆鲕、碎屑结构的蜂窝状铝土岩,溶蚀孔为主要储集空间;(2)铝土岩储层形成模式为夷平化作用提供含铝岩系发育的物质基础、岩溶古地貌控制含铝岩系发育、陆表淋滤作用改善储集性能;(3)晚石炭世—早二叠世,受湿热气候环境和海平面变化控制,古陆或古岛边缘的相对低洼带发育典型的煤-铝-铁三段式地层结构;(4)煤系烃源岩广覆式生烃,天然气在煤下含铝岩系储层富集,为源下成藏;(5)中国华北陆块的上石炭统—下二叠统含铝岩系气藏呈透镜状点群式聚集,勘探潜力大,有望成为华北克拉通上古生界重要的天然气勘探新领域。