Origin, hydrocarbon accumulation and oil-gas enrichment of fault-karst carbonate reservoirs: A case study of Ordovician carbonate reservoirs in South Tahe area of Halahatang oilfield, Tarim Basin

Based on comprehensive analysis of tectonic and fault evolution, core, well logging, seismic, drilling, and production data, the reservoir space characteristic, distribution, origin of fault-karst carbonate reservoir in Yueman block of South Tahe area, Halahatang oilfield, Tarim Basin, were studied systematically. And the regular pattern of hydrocarbon accumulation and enrichment was analyzed systematically based on development practice of the reservoirs. The results show that fault-karst carbonate reservoirs are distributed in the form of "body by body" discontinuously, heterogeneously and irregularly, which are controlled by the development of faults. Three formation models of fault-karst carbonate reservoirs, namely, the models controlled by the main deep-large fault, the secondary fault and the secondary internal fault, are built. The hydrocarbon accumulation and enrichment of fault-karst carbonate reservoirs is controlled by the spatiotemporal matching relation between hydrocarbon generation period and fault activity, and the size and segmentation of fault. The study results can effectively guide the well deployment and help the efficient development of fault-karst carbonate reservoirs of South Tahe area, Halahatang oilfield.

Experimental Simulation Study of the Dominant Enrichment Area of Terrestrial Organic Matter in the Shallow-Delta Sedimentary System of the Yacheng Formation in the Qiongdongnan Basin

Shallow-delta sedimentary systems receive both terrestrial and marine organic matter. As oil and gas exploration activities determine that the source rocks of the deep-water area of the Qiongdongnan Basin, northern South China Sea, are generally rich in and even dominated by terrestrial organic matter, this has led many researchers to examine the rules governing terrestrial organic matter enrichment in shallow-delta sea sedimentary systems. However, the deep burial of source rocks in deep-water areas and the relatively small amount of drilling undertaken have greatly restricted the study of these rules. In this study, the ‘forward modeling' research method was used to observe and analyze the deposition and preservation of terrestrial organic matter through flume experiments, where the depositional results were carefully depicted and sampled. The total organic carbon content of selected samples was measured and when combined with qualitative observations and quantitative comparison results, the dominant enrichment areas of terrestrial organic matter were identified. The experimental results show that the overbank parts of the delta front, the dune countercurrent surface, the low-lying parts, the delta front slope area and the shallow-prodelta sea area are where terrestrial organic matter is predominantly enriched. This provides an important basis and guidance for the prediction of the development areas of marine source rocks with terrestrial input in the deep-water areas of the Qiongdongnan Basin.

The enrichment characteristics and geological controlling factors of coalbed methane occurrence in Laochang area, Yunnan Province

The enriched characters of methane content in the main coal seam of Yunnan＇s Laochang coal mine was analyzed through combined with the geologic conditions of the research area： structure type, hydrogeology condition, coal reservoir＇s macerals, ash, water content, and so on. The geology factors of controlling gas in Laochang coal mine were illustrated; and the different geology models of controlling gas of geologic condition coupling were posed. Research shows that, in the region, the methane contents of the main coal seams decrease gradually from middle to all around it; the northeast and southeast is higher than the west. In the local area, the methane content of anticline axis is higher, and the gas content is reduced to both wings and plunging crown. On macroscopic view, the distribution of methane content in coal-beds was controlled by structural type. On microscopic view, the methane content in coal-beds is mainly involved in coal reservoir＇s macerals, ash content, and water content. The enriched characters of CBM in the research area are mainly the result of structure-hydrogeology-petrophysics coupling controls of CBM. On the basis of above analysis, according to the distribution character of methane content in coalbeds, the research area was divided into low gas area, middle gas area, and high gas area.

Toxic metal enrichment characteristics and sources of arid urban surface soil in Yinchuan City, China

To investigate the environmental quality of the urban surface soil in Yinchuan City, the capital of Ningxia Hui Autonomous Region （Ningxia）, China, we sampled surface soil and measured the concentrations of 8 toxic metals （Pb, Cr, Cu, Zn, Co, Bi, Ni and V） using X-ray fluorescence spectrometry. The enrichment characteristics and sources of these toxic metals in the soil were analyzed by the enrichment factor （EF） and multivariate statistical analysis. The results showed that the mean concentrations of these toxic metals in the soil samples were 25.0, 109.1, 16.8, 26.0, 37.2, 2.7, 25.3 and 59.9 mg/kg for Pb, Cr, Cu, Zn, Co, Bi, Ni and V, respectively, which were 1.2, 1.8, 0.8, 0.4, 3.2, 8.7, 0.7 and 0.8 times of the corresponding background values of Ningxia soil, respectively. The variations of Pb, Zn, Co, Bi and Ni concentrations in the surface soil of Yinchuan were larger than those of the other metals. Our results also showed that the toxic metals investigated in the soil had different enrichment levels. Both Co and Bi were significantly enriched, whereas Cr was only moderately enriched in the soil. There was a deficiency or minimal enrichment of the other toxic metals in the soil. Source analysis results based on the concentration, enrichment characteristics and multivariate statistical analysis indicated that Cr, V and Ni originated from a combination of fossil fuel combustion, traffic pollution and natural occurrence. Pb, Cu and Zn were predominantly derived from natural and traffic sources, while Co and Bi primarily originated from construction sources.

Rare earth elements-rich phase and enriching mechanism in sediments from CC area, the Pacific Ocean

Compared to North American shale composition (NASC), REE contents of sediments from the CC area in the Pacific Ocean are obviously high except that cerium has equal content to that of NASC. Three-valence rare earth elements were completely enriched in phosphate-phase and cerium in iron-phase. Rare earth elements in the sediments were originally derived from seawater. During lithi- genic and minerogenic processes of metalliferous nodules, three-valence rare earth elements in sediments mobilized and incorporated into sediments as authigenous biogenic-apatite, while cerium had change from Ce3+ to Ce4+ and directly precipitated from seawater and entered metalliferous nodules and caused Ce anomalies in REE pattern in sediments.

Coalbed Methane Enrichment Regularity and Major Control Factors in the Xishanyao Formation in the Western Part of the Southern Junggar Basin

There are abundant coal and coalbed methane(CBM)resources in the Xishanyao Formation in the western region of the southern Junggar Basin,and the prospects for CBM exploration and development are promising.To promote the exploration and development of the CBM resources of the Xishanyao Formation in this area,we studied previous coalfield survey data and CBM geological exploration data.Then,we analyzed the relationships between the gas content and methane concentration vs.coal seam thickness,burial depth,coal reservoir physical characteristics,hydrogeological conditions,and roof and floor lithology.In addition,we briefly discuss the main factors influencing CBM accumulation.First,we found that the coal strata of the Xishanyao Formation in the study area are relatively simple in structure,and the coal seam has a large thickness and burial depth,as well as moderately good roof and floor conditions.The hydrogeological conditions and coal reservoir physical characteristics are also conducive to the enrichment and a high yield of CBM.We believe that the preservation of CBM resources in the study area is mainly controlled by the structure,burial depth,and hydrogeological conditions.Furthermore,on the basis of the above results,the coal seam of the Xishanyao Formation in the synclinal shaft and buried at depths of 700-1000 m should be the first considered for development.

Measurement of Metallogenic Depth and Deep Second Enrichment Belt Forecasting in Jiaodong Gold Deposit

The depth is important for ore finding in Jiaodong gold deposit. However, many geologists are still discussing how to confirm the depth for the tectonic and metallogenesis formation. The authors of this paper propose a new method-the correction of metallogenic depth via its structure to calculate the depth. This method, based on the crust rock in a solid stress state, emphasizes the elastic pattern rather than the static fluid pattern. In addition, this method is more appropriate to the actual situation in the crust than the method of weight/special weight. The authors of this paper illustrating, with the Jiaodong gold deposit as an example, the metallogenic depth correction via structure conclude that the depth of the most deposits, lower than 4-6 km, is often 2.5 km. Therefore, the authors suggest that there exists a second enrichment belt and that ore resources are more potential at the belt of Jiaodong area. These results have been demonstrated by years of exploration.

Prediction of Coal Seam Methane Enriched Areas Using Seismic Data

All coal mine disasters are dynamic geological phenomenon and affected by many factors. However, locating the enriched areas of CSM (coal seam methane) may be the precondition for the successful prediction of such disasters. Traditional methods of investigating CSM enriched areas use limited data and only consider a few important factors. Their success rate is low and cannot meet practical needs. In this paper, an alternative method is proposed. The proce- dure is given as follows: 1) fracture attributes derived from azimuth variations of P-wave data in coal seams and wall rocks can be extracted; 2) AVO attributes, such as the intercept P and gradient G parameters can be extracted from different azimuths from 3D seismic data; 3) seismic cubes can be inverted and the relative attributes of imped- ance cubes can be extracted; 4) using a GIS platform, multi-source information can be obtained and analyzed; these include fracture attributes of coal seams and wall rocks, the thickness of coal seams, the distribution of faults and structures, the depth of coal seams, the inclination and exposure of coal seams and the coal rank. Through this processing procedure, methane enriched areas can be systematically detected.

Effect of Soil Selenium on Nutritional Quality of Vegetables in the Selenium-enriched Areas of Qinghai Plateau

In order to improve the added value of the main vegetable products in Qinghai Province,we researched the effect of soil selenium content on vegetable quality in selenium-enriched area of Qinghai. Through the analysis of Qinghai selenium-enriched soil selenium content and5 kinds of main vegetables corresponds to the total selenium,part of the mineral elements and soluble sugar and VC content,the effects of soil selenium levels on selenium absorption and nourishment quality of vegetables were researched. The results showed that he Qinghai selenium-enriched soil selenium content in the range of 100. 00-563. 00 μg/kg,among them,the soil samples with sufficient selenium and rich selenium accounted for 76. 53% and 18. 88%,respectively. Soil selenium content of garlic sampling area was relatively high,and soil selenium content of sugar beet sampling area was relatively low. Vegetable selenium content was in the range of 11. 00-340. 94 μg/kg,the average content of total selenium content of garlic was up to 170. 40 μg/kg,and the average content of the total selenium content of radish is 73. 00 μg/kg.90. 63% of the vegetables in the region reached the level of sufficient selenium,and 70. 31% reached the level of selenium enrichment. The average content of Ca and Mg was higher than the national average. There was no significant correlation between selenium content of soil and vegetable and nutritional quality.

Geological Factors Controlling the Accumulation and High Yield of Marine-Facies Shale Gas: Case Study of the Wufeng-Longmaxi Formation in the Dingshan Area of Southeast Sichuan, China

The main geological factors controlling the accumulation and yield of marine-facies shale gas reservoirs are the focus of the current shale gas exploration and development research.In this study,the Wufeng-Longmaxi Formation in the Dingshan area of southeast Sichuan was investigated.Shale cores underwent laboratory testing,which included the evaluation of total organic carbon(TOC),vitrinite reflectance(Ro),whole-rock X-ray diffraction(XRD),pore permeability,and imaging through field emission scanning electron microscopy(FE-SEM).Based on the results of natural gamma ray spectrum logging,conventional logging,imaging logging,and seismic coherence properties,the exploration and development potential of shale gas in the Dingshan area have been discussed comprehensively.The results showed that(1)layer No.4(WF2-LM4)of the Wufeng-Longmaxi Formation has a Th/U ratio<2 and a Th/K ratio of 3.5–12.Graptolites and pyrite are relatively abundant in the shale core,indicating sub-high-energy and low-energy marine-facies anoxic reducing environments.(2)The organic matter is mainly I-type kerogen with a small amount of II1-type kerogen.There is a good correlation among TOC,Ro,gas content,and brittle minerals;the fracturing property(brittleness)is 57.3%.Organic and inorganic pores are moderately developed.A higher pressure coefficient is correlated with the increase in porosity and the decrease in permeability.(3)The DY1 well of the shale gas reservoir was affected by natural defects and important latestage double destructive effects,and it is poorly preserved.The DY2 well is located far from the Qiyueshan Fault.Large faults are absent,and upward fractures in the Longmaxi Formation are poorly developed.The well is affected by low tectonic deformation intensity,and it is well preserved.(4)The Dingshan area is located at the junction of the two sedimentary centers of Jiaoshiba and Changning.The thickness of the high-quality shale interval(WF2-LM4)is relatively small,which may be an important reason for the unstable production of shale gas thus far.Based on the systematic analysis of the geological factors controlling high-yield shale gas enrichment in the Dingshan area,and the comparative analysis with the surrounding typical exploration areas,the geological understanding of marine shale gas enrichment in southern China has been improved.Therefore,this study can provide a useful reference for shale gas exploration and further development.

Impact of coal mining on groundwater of Luohe Formation in Binchang mining area

Groundwater of Luohe Formation is the main water source for industrial and agricultural and residential use in Binchang mining area,which is one of the key elements to water conservation coal mining.However,few studies are available to document the enrichment characteristics and influence of underground coal mining on groundwater for the Luohe Formation.This study evaluates the changes of groundwater levels and spring flow caused by mining activities to explore the influence mechanism of coal mining on groundwater by comparatively analysing existing mining data and survey data combined with a series of mapping methods.The results show that the aquifer of Luohe Formation are gradually thinning south-eastwards,disappeared at the mining boundary.In the vertical direction,the lithological structure is distinct,due to alternative sedimentation of meandering river facies and braided river facies.According to the yielding property,the aquifer is divided into three sections,namely,strong water-rich section,medium water-rich section,and weak water-rich section,which are located in northwest and central part,southwest,and the rest part of the mining area,respectively.Mining of Tingnan Coal Mine since 2004 has caused a 3.16 to 194.87 meters drop in groundwater level of Luohe Formation.Until 2015,70.10%of the mining area undergoes a groundwater level drop larger than 10.00 meters.Another influence of underground mining is that the total flow from 34 springs in 8 southern coal mines of the area has decreased by 286.48 L/s with a rate of decrease at 46.95%from 2007 to 2017.The areas that groundwater level falls or spring flow declines are manly located in the mine gob areas.Results also indicate that the ratio of the height of water conducted fracture zone to the mining height in Binchang mining area is between 16.85 and 27.92.This may increase ground water flow in vertical direction,causing a water level in the aquifer system to drop and ultimately decreasing the flow from the springs.The research results will provide data and theoretical support for the protection of groundwater resources and water conservation coal mining of Luohe Formation in Binchang mining area.

Monte-Carlo Method for Coalbed Methane Resource Assessment in Key Coal Mining Areas of China

Monte-Carlo method is used for estimating coalbed methane （CBM） resources in key coal mining areas of China. Monte-Carlo method is shown to be superior to the traditional volumetric method with constant parameters in the calculation of CBM resources. The focus of the article is to introduce the main algorithm and the realization of functions estimated by Monte-Carlo method, including selection of parameters, determination of distribution function, generation of pseudo-random numbers, and evaluation of the parameters corresponding to pseudo-random numbers. A specified software on the basis of Monte-Carlo method is developed using Visual C＋＋ for the assessment of the CBM resources. A case study shows that calculation results using Monte-Carlo method have smaller error range in comparison with those using volumetric method.

Characteristics of PM_(2.5) in rural areas of southern Jiangsu Province, China

To understand pollution level and possible sources of atmospheric fine particulates in rural areas of southern Jiangsu Province of China, samples of PM2.5 were collected and analyzed in Xueyan Town and Taihu Lake Station over three seasons from July 2002 to January 2003. The mass concentrations of PM2.5 and 14 principal component elements were obtained. The results showed that pollution of PM2.5 was serious and the concentration levels of S, Zn, Pb and As were similar to city. There are different seasonal distribution laws of pollutant elements in PM2.5 between two sampling sites, probably due to contribution of local sources, medium or long distance transportation of fine particulates and complicated meteorological conditions. The enrichment levels of S, Zn, Pb, As, K were high, reflecting the influence of anthropogenic activities. Particularly enrichment level of S was much higher in summer, which was probably related to meteorological condition. The result of principal components analysis showed major sources of PM2.5 included crustal resuspension, coal burning, metal processing industry or waste incineration, vehicular emission, which suggests anthropogenic activities is of important influence on PM2.5 in rural areas of southern Jiangsu Province.

Geochemical Baseline and Trace Metal Pollution of Soil in Panzhihua Mining Area

A total of 31 topsoil samples were systematically collected from the Panzhihua mining area including steel smelting, coal mining, urban and rural districts. A normalization procedure was adopted to establish the environmental geochemical baseline models for this area. By using the above baseline models, the regional geochemical baseline values of As, Cr, Cu, Ni, Pb and Zn were determined. On the basis of the baselines, the enrichment factors were used to analyze the mechanism of trace metal pollution in topsoil from anthropogenic sources, and the results showed that the serious trace metal pollution is caused by human activities in coal mine, iron mine, smelting factory, tailing dam and other industrial districts in the Panzhihua area.

Geothermal occurrence analysis of Dongying Formation in Tanggu area of Tianjin

Based on introducing geological structure of Tanggu area, the authors analyzed the sedimentary environment of Paleogene Dongying Formation, and further analyzed its geothermal occurrence. The studied area spans two grade IV tectonic units which are Beitang depression and Banqiao depression. The studied area is mainly located in the Tanggu nose-like structure which is the secondary structure of Beitang depression. Its existence affects the sedimentary distribution of the part strata of Paleogene. The depositions of Dongying Ⅲ （ SQEd3 ） and Dongying Ⅱ （ SQEd2 ） are mainly delta front facies and lake sand bars which are propitious to the geothermal fluid enrichment. The favorable enrichment region of geothermal fluid is located in south Hetou- Tanggu. Most of Dongying Ⅰ （ SQEd1 ） changes into swamp plain deposition, only the northeast part of this area is the distributary riverway facies with developed sand layers. There is the favorable enrichment region of geothermal fluid. The hydraulic connection is weak among the geothermal reservoirs of Dongying Formation and its overlying Guantao and Minghuazhen formations. The underlying Shahejie Formation geothermal reservoir pro- vides a steady stream of fluid supply and ground pressure protection for Dongying Formation geothermal reservoir.

川东红星地区二叠系茅口组页岩气勘探突破及富集主控因素

四川盆地二叠系页岩气具有良好的成藏条件和勘探潜力,继二叠系吴家坪组获得勘探突破后,将低勘探程度层系——茅口组“高灰”页岩气作为重要的勘探接替方向。利用HYM-1等井的岩心、测录井和分析化验资料,系统开展茅口组页岩气藏条件与富集特征的研究,认为茅口组四段一亚段页岩具有高碳、高灰、高孔隙度、高含气性、高杨氏模量、薄储层、多夹层的“五高一薄一多”的典型地质特征;与五峰组—龙马溪组等页岩相比,茅四段页岩碳酸盐矿物含量更高、黏土矿物含量更低,储集空间类型以有机质孔为主,无机孔较少,孔隙度平均4.27%,整体表现为高孔隙度;茅四段一亚段平均含气量为4.96m^(3)/t,具备较高的含气量。综合分析认为,富藻高碳页岩的发育、良好的储集能力和保存条件,以及页岩储层的可压裂性,是茅四段页岩气富集高产的主控因素。

Construction of Chaihu Selenium Industrial Demonstration Area in Zhongxiang City of Hubei Province

In order to develop selenium industry in Jianghan Basin,Hubei Provincial Party Committee decided to build Chaihu selenium industrial demonstration area in Zhongxiang City.This paper introduced general situation of Chaihu Town,analyzed countermeasures for construction of selenium industrial demonstration area in depth,and finally came up with 12 constructive and pertinent recommendations.

贵州普克金矿区黄铁矿和方解石地球化学特征及地质意义

贵州普克金矿区位于我国著名的滇-黔-桂“金三角”地区泥堡大型金矿西南方向的外围区域,与泥堡金矿处于相同的大地构造环境,地层特征、构造样式基本相同,成矿地质条件良好,对其开展成矿流体性质和物质来源研究,有助于理解普克矿区金的成矿作用,并为下一步找矿勘探提供新的参考。本文在对普克金矿区地表发育的(褐铁矿化)黄铁矿-方解石脉进行野外地质调查的基础上,开展矿物学、方解石稀土元素以及黄铁矿电子探针与微区原位LA-ICP-MS分析,结果显示普克金矿区内大部分方解石脉显示出与泥堡金矿床不含矿方解石脉相似的稀土元素配分特征,少数方解石样品显示出与黔西南卡林型金矿成矿期方解石稀土元素一样的中稀土元素富集和Eu正异常特征。该类方解石脉中的黄铁矿Au元素含量高出平均地壳丰度及沉积成因黄铁矿中Au的含量几个数量级,且Au在黄铁矿中以Au+离子形式存在,表明这些黄铁矿形成于金成矿期的热液环境。含金方解石出现中稀土元素富集模式和Eu正异常特征,表明金成矿流体系还原性质。由于地壳抬升剥蚀的影响,普克金矿区内中稀土元素富集、Eu正异常的方解石脉在地表的露头较少,也可能与普克金矿有利成矿地层层位(二叠系峨眉山玄武岩组)埋深较大、能运移到现今地表层位(三叠系永宁镇组)的成矿热液相对较少有关,指示深部有较好的金成矿潜力。

中国东西部陆相页岩油地质特征差异性分析及其对富集规律影响——以胜利探区为例

以胜利探区为例,系统对比研究了中国东西部陆相湖盆页岩油地质特征差异性及其对富集规律的影响。济阳坳陷沙四段上亚段—沙三段下亚段在古地貌、古气候、古水体介质等因素共同控制下,富有机质纹层状碳酸盐页岩大规模分布,富有机质黏土纹层成烃与富碳酸盐纹层成储协同演化为游离烃规模富集提供了有利条件。准噶尔盆地西北缘哈山地区风城组强裂陷作用导致强烈火山活动,在火山喷发物质与古气候共同影响下,富有机质纹层状含碱长英页岩相大规模分布,且成烃成储演化过程中形成较多的长英质矿物,并伴生大量的基质溶蚀孔和晶间孔,为页岩油富集奠定了重要基础。哈山地区在多期逆冲推覆过程中,准原地系统持续生烃、油多气少和相对较好的保存条件以及构造覆压、生烃增压作用产生的异常高压为页岩油高产提供了必要条件。准噶尔盆地东南缘(准东南)芦草沟组在海迹湖咸水环境下,受火山凝灰质与微生物作用影响,形成了富有机质纹层状页岩相夹贫有机质层状白云岩相的主要岩相组合类型。博格达山周缘山前构造带芦草沟组富有机质页岩均进入成熟演化阶段,胜利探区构造相对稳定区具备页岩油勘探前景。

煤矿采动稳定区煤层气开发区块经济评价技术

针对我国煤矿采动稳定区煤层气开发区块评价技术缺乏,难以有效指导经济开发应用这一问题,基于煤层气开发效果与综合效益,分析了采动稳定区煤层气开发区块评价关键参数,构建了考虑技术进步等动态影响因素的煤层气开发区块经济评价指标体系,采用层次分析方法获得了各单项指标的相对权重,并提出了开发区块最大隶属原则经济评价方法。应用试验表明,该经济评价方法可为煤矿采动稳定区煤层气开发决策提供可靠指导。