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.

Cyclic Characteristics of the Physical Properties of Key Strata in CBM Systems Controlled by Sequence Stratigraphy—An Example from the Gujiao Block

Multiple coal seams and interbedded rock assemblages formed in vertical progression due to the influence of multiple stages of sea level transgressions.Based on mercury injection experiment,low temperature liquid nitrogen experiment,porosity and permeability experiment and breakthrough pressure experiment,the vertical variation characteristics of coal-bearing strata in Gujiao block are explained in detail.The results of the mercury injection and low temperature liquid nitrogen experiments show that the pore structure characteristics fluctuate with increasing depth in the strata,with fewer micropores followed by transition pores.The BET specific surface area and average pore diameter of the Shanxi Formation are generally larger than those of the Taiyuan Formation.Due to the continuous cyclic sequence stratigraphy changes,the porosity,permeability,breakthrough pressure and breakthrough time of the samples show a certain cyclicity.Within the same sequence,the porosity is larger,and the permeability is smaller near the maximum flooding surface.Although the permeability of the sandstone samples is higher,the porosity is lower,and the breakthrough pressure and breakthrough times are greater.The strata in the study area formed in an oxidized environment that was affected by freshwater,and the pore structure of different lithologies is quite different.After the formation of sandstone,the intergranular pores generally underwent filling with secondary quartz,clay minerals and organic matter,resulting in low porosity and permeability.

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.

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

我国煤系锗镓资源前景及研究方向

2023年7月3日,商务部和海关总署发布公告称,决定自2023年8月1日起对镓、锗相关物项实施出口管制。我国锗镓资源储量和产量均居世界前列,但随着需求端的不断增长,锗镓资源的储量优势正在不断下降,因此,需要寻找新的锗镓资源储量,稳固我国的资源优势。在特定的地质作用下,煤系中可以高度富集镓、锗、稀土等战略性关键金属。在战略金属资源供应日趋紧张的大环境下,煤系战略性金属矿床能够成为战略性金属资源的重要来源。我国煤系锗富集异常点主要分布于海拉尔-二连盆地、鄂尔多斯盆地周缘、郯庐大断裂一带及滇西-滇中盆地等区域,其余地区煤系锗富集异常点均为零星分布。我国煤系镓主要富集在阴山南麓准格尔煤田和山西省北部石炭系-二叠系煤田,准东煤田侏罗系煤层中镓富集异常点出现成片分布情况,其余地区的不同成煤时代煤层中镓富集异常点零星分布,如四川盆地周边、重庆市南武矿区和南桐矿区、贵州省西南矿区二叠系煤层、山东省滕县煤田、河南省登封煤田石炭系煤层、宁夏回族自治区磁窑堡矿区侏罗系煤层等。煤系锗镓矿产成矿机理、提取工艺和综合勘探与综合开发利用的研究具有广泛前景,研究重点应该集中在资源成矿条件、成矿机制和成矿模式、多种金属协同提取工艺、勘查评价规范制定、综合勘查示范工作等方面。

鲁西地区石炭-二叠系锂锗镓含矿特征及综合利用远景

通过搜集以往地质资料进行统计分析,结合钻孔岩心取样情况,研究鲁西地区石炭-二叠纪煤系地层中锂锗镓的含矿特征,并结合开采利用现状,对鲁西地区石炭-二叠纪煤系地层锂锗镓的综合利用远景进行评价。通过分析研究,锂元素在铝土岩中较其他岩类富集,在煤层中较难达到综合利用价值;镓元素既可在铝土岩中富集,也可在煤层中富集,在淄博地区铝土矿中提交了伴生资源量;锗元素则主要在煤层中富集,在济宁-滕州煤田中具有综合利用价值。研究成果可为鲁西地区煤系中锂锗镓资源的勘查预测及其综合利用提供依据。

Formation mechanism of carbonate cemented zones adjacent to the top overpressured surface in the central Junggar Basin,NW China

Carbonate cemented zones are normally adjacent to the top overpressured surface in the central Junggar Basin,NW China.Stable carbon and oxygen isotopic compositions and petrological investigations of carbonate cements in the carbonate cemented zones indicate that:(1) carbonate cements are composed dominantly of ferrocalcite,ferroan dolomite,and ankerite;(2) carbonate cements are formed under a high temperature circumstance in the subsurface,and organic fluid migration has an important effect on the formation of them;and(3) carbon and oxygen ions in the carbonate cements migrate from the underlying overpressured system.This suggests that the occurrence of carbonate cemented zones in this region results from multiple phases of organic fluid expulsion out of the overpressure compartment through geological time.This study provides a plausible mechanism of the formation of carbonate cemented zones adjacent to the top overpressured surface in the clastic sedimentary basins,and has an important implication for understanding the internal correlation between the formation of carbonate cemented zones adjacent to top overpressured surface and geofluids expulsion out of overpressured system.

The Newly Discovered Yanchang Gas Field in the Ordos Basin, Central China

The Yanchang gas field is located in the Ordos Basin of central China to the southeast of the Yishan Slope, covers an exploration area of 2.6× 10~4 km^2 and has approximately 3.5× 10^（11） m^3 of gas reserves. The gas field is dominated by lithologic gas reservoirs but also has a few structural gas reservoirs. Sand bodies were deposited in the Carboniferous Benxi Formation around offshore barrier islands and in distributary channel fillings in the delta front of the P_1s_2 and P_1s_1 divisions of the Permian Shanxi Formation. The P_2h_8 division of the Shihezi Formation contains the main reservoirs. The depths of the reservoirs are between 1 970 and 3 500 m. The Yanchang gas field can be classified as a typical tight sandstone gas reservoir filed because its porosity is lower than 10% and permeability lower than 1 mD. The discovery and development of the Yanchang gas field has led to a great increase in total natural gas reserves in the Ordos Basin. Its exploration has improved methods of locating large gas fields in deep-water depositional environments in the south part of the basin.