Sedimentology and Paleoenvironmental Characteristics of Fine-grained Sediments in Coal-bearing Strata in the Eastern Ordos Basin:A Case Study of the Exploratory Well in the Zizhou Area

The continuously collected cores from the Permo-Carboniferous coal-bearing strata of the eastern Ordos Basin are essential for studying the hydrocarbon potential in this region.This study adopted sedimentological and geochemical methods to analyze the sedimentary environment,material composition,and geochemical characteristics of the coal-bearing strata.The differences in depositional and paleoclimatic conditions were compared;and the factors influencing the organic matter content of fine-grained sediments were explored.The depositional environment of the Benxi and Jinci formations was lagoon to tidal flat with weakly reduced waters with low salinity and dry-hot paleoclimatic conditions;while that of the Taiyuan Formation was a carbonate platform and shallow water delta front,where the water was highly reductive.The xerothermic climate alternated with the warm and humid climate.The period of maximum transgression in the Permo-Carboniferous has the highest water salinity.The Shanxi Formation was deposited in a shallow water delta front with a brackish and fresh water environment and alternative weak reductiveness.And the paleoclimate condition is dry-hot.The TOC content in fine-grained samples was averaging 1.52%.The main controlling mechanism of organic matter in this area was the input conditions according to the analysis on input and preservation of organic matter.

A New Understanding on South China Permian Coal-bearing Strata and Coal Accumulation Regularity

The Longtan Formation was originally thought to belong to the Late Permian, but this study reveals that the lower part of this formation belongs to the Middle Permian. The study proposes the corresponding chro-nostratigraphic boundary and new schemes for the correlation of geological sections. Based on these schemes a new understanding on the accumulation regularity of Permian coal measures in South China is reached.

SHRIMP dating of volcanic rock in the Zhangwu-Heishan area, West Liaoning province, China: Its relationship with coal-bearing strata

The Zhangwu-Heishan area is located to the east of the Fuxin-Yixian Basin and is mostly covered with volcanic rock. At various periods, different geologists had varying opinions about their age and periods of volcanic eruptions, especially on sequences between volcanic rock and main coal-bearing strata, which affect the direction of searching for coal, as well as prospecting the entire research area. During our study, we carried out detailed field investigations in this research area; observed and recorded the main repre- sentative outcrops of volcanic rock. We collected over 20 volcanic rock samples and tested the Sensitive High Resolution Ion Microprobe II (SHRIMP II) U-Pb isotope age of 11 samples. The age of our volcanic rock samples ranged between 56.0 ± 2.9 and 132.3 ± 2.3 Ma. After taking earlier investigations into con- sideration, we concluded that, except for a suite of paleogene olivine basalt, the volcanic rock in the Zhangwu-Heishan area is younger than the coal-bearing Shahai Formation. It is therefore most unlikely to find coal seams equivalent to those of the early Cretaceous Shahai Formation in Fuxin Basin below vol- canic rock.

Insights into lithium adsorption by coal-bearing strata kaolinite

The sharp increase in the demand for lithium(Li)for high-energy-storage battery materials due to its high specific energy and low negative chemical potential render Li a geopolitically significant resource.It is urgent to develop a low-cost,efficient method to improve lithium extraction.Herein,Li ion(Li+)adsorption in coal-bearing strata kaolinite(CSK)was studied.The effects of pre-activation acid leaching(meta-kaolinite/H2SO4,MK-HS)and dimethyl sulfoxide intercalation(coal-bearing strata kaolinite/dimethyl sulfoxide,CSK-DMSO)on the Li+adsorption capacity were studied under the same adsorption conditions.The results indicated that the adsorption was completed in 60 min under alkaline conditions(pH=8.5),a high solution concentration(400 mg/L),and a low dosage(1 g/100 mL);and the comprehensive adsorption capacity is MK-HS>CSK-DMSO>CSK.Furthermore,the DMSO intercalation caused the interlayer spacing of the CSK to increase,which provided more space for Li+to enter and increase the adsorption capacity.After thermal pre-activation and acid leaching,structural failure and lattice collapse resulted in the presence of more micropores in the MK-HS,which resulted in a 10-fold increase in its specific surface area and caused coordination bond changes(Al(VI)to Al(IV))and leaching of aluminum(Al)from the lattice.It is proposed that these structural changes greatly improve the activity of CSK so that Li+cannot only adsorb onto the surface and between the layers but can also enter the lattice defects,which results in the MK-HS having the best adsorption performance.Combined with the adsorption kinetics analysis,the adsorption methods of CSK and two modified materials include physical adsorption and chemical adsorption.In this study,the adsorption capacity of CSK and its modified products to Li were explored,providing a new option for the reuse of CSK and the extraction of Li.

Cenozoic giant coal-bearing basin belt discovered in China's sea and its adjacent areas

Sea area is an important area of oil and gas exploration in China.It has been found that China's sea area mainly consists of coal type oil and gas,and the exploration of coal-bearing series source rocks has become an important part of oil and gas exploration there.Through years of comprehensive geological research in China's sea area,it has been revealed that it has undergone multiple occurrences of tectonic opening and closing movements in varying degrees in the Paleogene,forming 26 Cenozoic sedimentary basins of various types,such as active continental margin,passive continental margin,transitional continental margin and drift rift basins.In the present study,it is observed for the first time that coal type source rocks are mainly developed in 14 continental margin basins in China's sea area,revealing that a very large C-shaped coal-bearing basin group developed there in the Cenozoic.Next,based on the coupling analysis of paleoclimate,paleobotany,paleogeography and paleostructure,it is observed that there are five coal-forming periods in China's sea area,namely the Paleocene,Eocene,early Oligocene,late Oligocene and Miocene-Pliocene,and the coal-forming age is gradually new from north to south.It is also found that the coal seams in the sea area are mainly developed in three coal-forming environments in Cenozoic,namely delta,fan delta and tidal flat-lagoon.The coal seams developed in different environments are characterized by thin thickness,many layers and poor stability.However,the coal-bearing series source rocks in China's sea area have a wide distribution range,very high thickness and large amount,thus forming a material basis for the formation of rich coal type oil and gas.

DEPOSITS OF TIDAL SAND RIDGES IN THE COAL-BEARING STRATA OF MAYI DISTRICT, PANXIAN COUNTY, GUIZHOU PROVINCE

Tidal sand ridges are large-scale linear bottom configurations in a good many tidal seas. The modern tidal sand ridges in Jianggang area, the northern part of Jiangsu Province, China, have attracted the attention of geological circles because of the radial form and large scale. Berg, Brenner and Davies have reported that linear sand bodies of this kind were recognized within the Mesozoic strata of western America, but we have not seen any reports about the discovery of this kind of sediment from the ancient lithofacies analyses of China, especially in coal-bearing strata. Based on the study of sedimentary facies, this note describes the deposits of tidal sand ridges in the coal-bearing strata of China.

A NEW TYPE OF DISTRIBUTARY CHANNEL DEPOSITS IN COAL-BEARING STRATA OF NAYONG AREA, GUIZHOU PROVINCE

Considerable progresses in the sedimentologic studies of the anastomosing river models have been made in recent years. There are now many modern and ancient examples such as those described by Smith, Rust et al. Flores et al. But all examples are found in the alluvial plains and the intermontane basins. None is known reporting about the upper delta plain environment. However, this type of distributary channels

LA-ICP-MS zircon U-Pb dating of tuffites in the Sachakou Pb-Zn mining area, Karakorum, Xinjiang and its establishment of Early Triassic strata

1.Objective In the past decade,a group of medium to giant lead-zinc deposits,represented by Huoshaoyun,Sachakou,and Yuanbaoling,have been discovered in the Aksai Chin region of Karakoram,Xinjiang.They are all located in the Mesozoic carbonate and clastic rock formations.The Sachakou leadzinc mining area is adjacent to the northwest of the Huoshaoyun lead-zinc mining area and is in the same stratigraphic layer as Huoshaoyun.Although many scholars have been arguing about the type and age of Huoshaoyun lead-zinc mineralization,few scholars have paid attention to the classification of the ore-bearing strata in the area.The stratigraphy of the Lower Permian Shenxianwan Group to the Upper Cretaceous Tielongtan Group is exposed in the Sachakou area of Karakorum,Xinjiang,however,the Late Permian-Early Triassic stratigraphy is missing(Fig.1a).Due to the harsh natural conditions in the area and the low level of work,the stratigraphic delineation is not exhaustive,and the regional lithology is dominated by carbonates and clastic rocks,which makes it difficult to identify the age of the regional lithology and causes problems for the exploration and research of lead-zinc in the area.

An intelligent automatic correlation method of oilbearing strata based on pattern constraints:An example of accretionary stratigraphy of Shishen 100 block in Shinan Oilfield of Bohai Bay Basin,East China

Aiming at the problem that the data-driven automatic correlation methods which are difficult to adapt to the automatic correlation of oil-bearing strata with large changes in lateral sedimentary facies and strata thickness,an intelligent automatic correlation method of oil-bearing strata based on pattern constraints is formed.We propose to introduce knowledge-driven in automatic correlation of oil-bearing strata,constraining the correlation process by stratigraphic sedimentary patterns and improving the similarity measuring machine and conditional constraint dynamic time warping algorithm to automate the correlation of marker layers and the interfaces of each stratum.The application in Shishen 100 block in the Shinan Oilfield of the Bohai Bay Basin shows that the coincidence rate of the marker layers identified by this method is over 95.00%,and the average coincidence rate of identified oil-bearing strata reaches 90.02% compared to artificial correlation results,which is about 17 percentage points higher than that of the existing automatic correlation methods.The accuracy of the automatic correlation of oil-bearing strata has been effectively improved.

冲击载荷下叠合岩层巷道围岩的应力演化数值模拟研究——基于岩层运动并行计算系统StrataKing

煤系地层属于典型的层状沉积岩层,这在传统连续介质模型中不能被较好反映。为了探究冲击载荷下叠合岩层巷道围岩的应力演化规律,采用以拉格朗日元与离散元耦合连续-非连续方法为基础发展的岩层运动并行计算系统StrataKing,基于理想化模型分析了巷道上表面附近应力波的叠加。阐明了应力波叠加导致顶板开裂机理,并且探讨了冲击载荷幅值的影响规律。研究发现:在原始压应力波传至巷道上表面附近测点后,该测点的最大主应力刚开始呈下降-上升-下降的变化趋势,这是由原始压、拉应力波不同时刻的叠加不同导致的;由于次级应力波的波长较原始应力波的小,次级压、拉应力波的单独作用更明显,它们的叠加使巷道上表面附近测点能产生更低和更高的最大主应力,甚至导致顶板开裂;冲击载荷幅值越大,近似阶梯增长阶段中拉裂纹平均发展速度越快,巷道围岩最终开裂范围越大,巷道围岩平衡越困难。

Geochemical Characteristics and Sedimentary Control of Pinghu Formation(Eocene)Coal-bearing Source Rocks in Xihu Depression,East China Sea Basin

Coal-bearing source rocks of the Pinghu Formation in the Xihu Depression comprise an important material basis of oil and gas resources in the East China Sea Basin.Based on drilling core observation results combined with the analysis and test results of macerals,trace/rare earth elements,and rock pyrolysis,the geochemical characteristics and sedimentary control of coal-bearing source rocks formation are discussed in a high-frequency sequence framework.The results indicate that the macerals composition of the coal-bearing source rocks of the Eocene Pinghu Formation in the Xihu Depression is dominated by vitrinite,with low-medium abundance of exinite and almost no inertinite.The coals and carbonaceous mudstones display higher amounts of total organic carbon(TOC)(14.90%-65.10%),S1+S2(39.24-136.52 mg/g),and IH(191-310 HC/g TOC)respectively,as compared to the mudstones.Organic matter is plotted in typeⅢkerogens and partially in typeⅡ;it is mainly in the low maturity stage.The trace elements results imply that the samples were deposited in a weakly reducing to weakly oxidizing environment and were occasionally affected by seawater.The coal-bearing source rocks were deposited in a relatively oxygen-containing environment.The coal-bearing source rocks development is jointly controlled by the coal accumulation environment,the water conditions affected by ocean currents in offshore basins in China,oxidation-reduction cycles of aqueous media and paleoclimate evolution in a high-frequency sequence framework.

Dual Control of Depositional Facies on Uranium Mineralization in Coal-bearing Series： Examples from the Tuanyushan Area of the Northern Qaidam Basin, NW China

The uranium deposits in the Tuanyushan area of northern Qaidam Basin commonly occur in coal-bearing series. To decipher the U-enrichment mechanism and controlling factors in this area, a database of 72 drill cores, including 56 well-logs and 3 sampling wells, was examined for sedimentology and geochemistry in relation to uranium concentrations. The results show that coal-bearing series can influence uranium mineralization from two aspects, i.e., spatial distribution and dynamic control. Five types of uranium-bearing rocks are recognized, mainly occurring in the braided river and braided delta sedimentary facies, among which sandstones near the coals are the most important. The lithological associations of sandstone-type uranium deposits can be classified into three subtypes, termed as U-coal type, coal-U-coal type, and coal-U type, respectively. The coal and fine siliciclastic rocks in the coal- bearing series confined the U-rich fluid flow and uranium accumulation in the sandstone near them. Thus, the coal-bearing series can provide good accommodations for uranium mineralization. Coals and organic matters in the coal-bearing series may have served as reducing agents and absorbing barriers. Methane is deemed to be the main acidolysis hydrocarbon in the U-bearing beds, which shows a positive correlation with U-content in the sandstones in the coal-bearing series. Additionally, the 613C in the carbonate cements of the U-bearing sandstones indicates that the organic matters, associated with the coal around the sandstones, were involved in the carbonation, one important component of alteration in the Tuanyushan area. Recognition of the dual control of coal-bearing series on the uranium mineralization is significant for the development of coal circular economy, environmental protection during coal utilization and the security of national rare metal resources.

Identification methods of coal-bearing source rocks for Yacheng Formation in the western deepwater area of South China Sea

Owing to the fact that the coal-beds are with the characteristics of multi-beds, thin single-bed, rapid lateral changes and deep burial, coal-bearing source rocks are difficult to be identified and predicted, especially in the lower exploration deepwater area. In this paper, a new integrative process utilizing geology and geophysics is proposed for better predicting the distribution of coal-bearing source rocks. Coal-beds were identified by the logging responses of“three higher, three lower, and one expand”and carbargilite were recognized by the characteristics of“four higher and one lower”. Based on the above logical decision, coal-beds and carbargilite can be distinguished automatically by cluster analysis of logging curves in verticality. Within the constraints of well-seismic calibration, the coal-beds group also can be detected in horizontality by the integrated representation of“negative phase, higher Q, lower impedance and lower frequency”within the seismic data. However, the distribution of coal-bearing source rocks utilizing geophysical methodology may do not conform to the geological rules of coal accumulation. And then the main geological controlling factors of coal accumulation are comprehensively analyzed as follows：（1） Paleotopography and tectonic subsidence determine the planar range of terrestrial-marine transitional facies markedly;（2） The relative sea level changes affect the accommodation space and shoreline migration, and limit the vertical range of coal-beds. More specifically, the relationship between the accommodation creation rate and the peat accumulation rate is a fundamental control on coal accumulation. The thickest and most widespread coals form where those two factors reached a state of balance;（3） The supply of autochthonous clasts and the distance between deposition places and paleovegetation accumulated area are the critical factor to form abundant coal, which means that if deposition area is close to paleouplift, there would be sufficient organic matters to form abundant source rocks. The results show that the integrated methods can significantly improve prediction accuracy of coal-bearing source rocks, which is suitable for early exploration of western deepwater area of South China Sea.

Distribution of Selected Critical Elements in the Carboniferous Coal-bearing Series of the Upper Silesian and Lublin Coal Basins(Poland)

The distribution of selected critical elements in the sedimentary rocks of the Carboniferous coal-bearing series within the Polish Coal Basins is presented.Critical elements such as Be,Mg,Si,P,Sc,V,Co,Y,Nb,In,Sb,La,Ce,Hf,Ta,W,Bi were analysed using inductively-coupled plasma mass spectrometry(ICP/MS).Concentrations of elements such as Sb,Bi,In and,to a slightly lesser extent,Nb,as well as Sc,show average concentrations higher than those from the upper continental crust.The average concentrations of elements like Hf,Mg,P,Y,La,and Ce are slightly lower than in the upper continental crust.Other elements,such as Be,Co,Si,Ta,W and V have average concentrations that are similar,but slightly enriched or slightly depleted,relative to the upper continental crust.The research showed enrichment of some critical elements in the analysed samples,but not high enough that extraction would be economically viable.Statistical methods,which include correlation coefficients between elements and cluster analysis,reveal a strong positive correlation between elements like Be,Bi,Nb,Sc,Ta,W and V.Very high,almost total,positive correlation is also noted between La and Ce.

Evaluation and prediction of earth pressure balance shield performance in complex rock strata:A case study in Dalian,China

This research explores the potential for the evaluation and prediction of earth pressure balance shield performance based on a gray system model.The research focuses on a shield tunnel excavated for Metro Line 2 in Dalian,China.Due to the large error between the initial geological exploration data and real strata,the project construction is extremely difficult.In view of the current situation regarding the project,a quantitative method for evaluating the tunneling efficiency was proposed using cutterhead rotation(R),advance speed(S),total thrust(F)and torque(T).A total of 80 datasets with three input parameters and one output variable(F or T)were collected from this project,and a prediction framework based gray system model was established.Based on the prediction model,five prediction schemes were set up.Through error analysis,the optimal prediction scheme was obtained from the five schemes.The parametric investigation performed indicates that the relationships between F and the three input variables in the gray system model harmonize with the theoretical explanation.The case shows that the shield tunneling performance and efficiency are improved by the tunneling parameter prediction model based on the gray system model.

岩层运动并行计算系统StrataKing及应用

为了克服国外串行商业软件的功能有限、计算规模小和计算效率低的问题,历时10余年,自主研发了拉格朗日元与离散元耦合的岩层运动GPU并行计算系统StrataKing。介绍了Strata-King的计算流程、基本原理和功能,各计算模块均在GPU上执行。通过模拟三点弯梁的开裂过程,检验了StrataKing的正确性。在静水压力条件下,当单元数目较多时,巷道围岩的裂纹以更加弯曲、柔美而非突兀、生硬状向围岩深部发展,这与塑性力学中圆环形的各处均破坏的塑性区有所不同。在采动条件下,工作面煤壁超前支承压力和水平应力均具有峰值,后者与岩层之间的黏结作用有关,这与基于连续介质假定的厚壁筒径向应力特征有所不同。由此,StrataKing的大规模计算能力、丰富的功能和行业鲜明特色得到了进一步呈现。

Strata应力吸收层在旧路改造中的应用

在江西省南昌县芳湖路改造工程中,为最大程度减少罩面后产生的反射裂缝病害,采用了Strata应力吸收层+沥青混凝土的加铺改造技术。通过对加铺方案的甄选比对,材料性能分析及施工措施,验证了该材料在防反射裂缝性能方面较其他加铺技术有更大的优势,为其广泛应用提供了参考依据。

Numerical modeling of destress blasting for strata separation

Destress blasting(DB)implemented along the perimeter of safety pillars is a special application of destressing in coal longwall mining.The goal is to separate relatively more deformed mined areas from safety pillars,such as shaft pillars or cross-cut pillars,to reduce the transfer of high stresses to the protective pillar.This case study aims to numerically simulate selected destress blasts in the Czech part of the Upper Silesian Coal Basin and examine its impact on stress transfer to the safety pillar area.To separate the area between the protective pillar and the longwall(LW),two fans of five 93-mm blast holes(length of 93e100 m)were drilled from the gate roads into the overburden strata.Each set of blast holes was fired separately in two stages without time delay.The explosive charge(gelatin-type of explosive)of each stage is 3450 kg.The two DB stages were fired when the longwall face was approximately 158 m and 152 m away from the blast.A 3D mine-wide model is built and validated with in situ stress measured with hydrofracturing.Mining and destressing in three 5-m thick coal seams are simulated in the region.Numerical modeling of DB is successfully conducted using a rock fragmentation factor a of 0.05 and a stress reduction/dissipation factor β of 0.95.Buffering of transfer of additional stress from the mining area into the safety pillar is evaluated by comparison of yielding volume before and after DB.It is shown that yielding volume drops after DB by nearly 80%in the area of the destressing panel and near the safety shaft pillar.

Field and numerical modelling on the stability of underground strata in longwall workings

The longwall method is one of the feasible and efficient underground mining methods for greater depth of workings.Recently,Singareni Collieries Company Limited(SCCL),the largest coal-producing government company in the Southern part of India,has deployed a high capacity(2×1152T capacity)power support system in its Adriyala Longwall Project(ALP)at a depth of 375 m.There was a concern about the stability of the longwall workings and the protective pillars.Thus,research work was carried out with the geotechnical instruments and numerical modelling tools to analyze the stability while retreating the longwall panels.The outcomes revealed that the convergence in the gate roads increased with the longwall face advancement and the area of exposure.The pressure of the powered support legs on the dip side was less than the rise side legs,which implies a stable roof condition over the longwall face.An abutment zone was identified ahead of the line of extraction up to 10e25 m and presumed from the Factor of Safety(FoS)criterion that within this zone,the longwall pillar possibly will be of better stability at every stage of extraction.The results obtained from this study would be helpful for the mining engineers to understand the behaviour of underground strata in longwall workings.