Base-Level Cycles and Episodic Coal Accumulation——Case Study of Dongsheng Coalfield in Ordos Basin

The advantage of high-resolution sequence stratigraphy, which takes base-levels as reference, is that it can be applied to continental depositional basins controlled by multiple factors and can effectively improve the accuracy and resolution of sequential stratigraphic analysis. Moreover, the principles of base-level cycles are also suitable for analyzing sequential stratigraphy in continental coal-bearing basins because of their accuracy in forecasting distribution of coal measures. By taking the Dongsheng coalfield in the Ordos basin as an example, the extensive application of base-level cycles in exploration and exploitation of coal is analyzed. The result shows that the Yan’an formation in the Dongsheng area is a long-term base-level cycle which is bordered by nonconformities and made up of five mid-term cycles and 13 short-term cycles. The long-term cycle and the mid-term cycles are obvious in comparison with a transverse profile. The episodic coal accumulation in the Mesozoic Ordos basin means that the deposition of primary matter (peat bogs) of coalification is discontinuous, periodical and cyclical in the evolution of the basin. The episodic accumulation of coal measures in the Yan’an stage is controlled by ascending-descending changes of a long-term cycle and middle-term cycles. Coal measures formed during the early and late periods of the long-term cycle are characterized by multiple layers, big cumulative thickness and poor continuity. Coal measures formed in the mid-term of the long cycle are dominated by good continuity, fewer layers and a small additive thickness, which is favorable for the accumulation of thick and continuous coal measures in the transition stage of mid term base-level cycles.

Geochemical characteristics of Dongsheng sandstone-type uranium deposit, Ordos Basin

Generally, sandstone-type uranium deposits can be divided into three zones according to their redox conditions: oxidized zone, ore zone and reduced zone. The Dongsheng uranium deposit belongs to this type. In order to study its geochemical characteristics, 11 samples were taken from the three zones of the Dongsheng uranium deposit. Five samples of them were collected from the oxidized zone, four samples from the ore zone and two samples from the reduced zone. These samples were analyzed using organic and inorganic geochemical methods. The results of GC traces and ICP-MASS indicate that the three zones show different organic and inorganic geochemical characteristics.

Geochemical Characteristics of REE in Jurassic Coal of Yan'an Formation from Dongsheng Coalfield

Concentrations of rare earth elements (REE) in Jurassic coal of YanAn Formation from Dongsheng coalfield located in the northeast of Ordos basin were determined by instrumental neutron activation analysis (INAA). Curves of distribution pattern of REE were drawn, and many geochemical parameters were calculated. The result shows that 1) The contents of REE in Jurassic coal with low ash and sulfur are lower than those of Carboniferous and Permian coal from the Basin of North China; 2) Inside the Dongsheng coalfield, coal from the north has higher contents of REE than that form the south because the north is near the area of source rock which is the main supplier of REE, while the south is far away from the area of source rocks; 3) Although Jurassic coal in Dongsheng is the low ash coal with less than 10%, the contents of REE are still proportional to ash yield of ash and SiO 2 contents. 4) Although the Jurassic coal in Dongsheng were deposited in oxidative continental environment of river lake, Eu depletion of REE in coal commonly exists, and positive abnormity of Ce dose not exist. This reflects the REE distribution pattern of REE in source rock of continental area; and 5) Compared with other rocks, coal shows extremely complexity of distribution pattern of REE, which is the result of continuous alteration and redistribution of matter in coal occurred in open basin system.

Tracing of natural gas migration by light hydrocarbons:A case study of the Dongsheng gas field in the Ordos Basin,NW China

Based on the analysis of light hydrocarbon compositions of natural gas and regional comparison in combination with the chemical components and carbon isotopic compositions of methane,the indication of geochemical characteristics of light hydrocarbons on the migration features,dissolution and escape of natural gas from the Dongsheng gas field in the Ordos Basin is revealed,and the effect of migration on specific light hydrocarbon indexes is further discussed.The study indicates that,natural gas from the Lower Shihezi Formation(Pix)in the Dongsheng gas field displays higher iso-C5-7contents than n-C5-7contents,and the C6-7light hydrocarbons are composed of paraffins with extremely low aromatic contents(<0.4%),whereas the C7light hydrocarbons are dominated by methylcyclohexane,suggesting the characteristics of coal-derived gas with the influence by secondary alterations such as dissolution.The natural gas from the Dongsheng gas field has experienced free-phase migration from south to north and different degrees of dissolution after charging,and the gas in the Shiguhao area to the north of the Borjianghaizi fault has experienced apparent diffusion loss after accumulation.Long-distance migration in free phase results in the decrease of the relative contents of the methylcyclohexane in C7 light hydrocarbons and the toluene/n-heptane ratio,as well as the increase of the n-heptane/methylcyclohexane ratio and heptane values.The dissolution causes the increase of isoheptane values of the light hydrocarbons,whereas the diffusion loss of natural gas in the Shiguhao area results in the increase of n-C5-7contents compared to the iso-C5-7contents.

天然气运移轻烃地球化学示踪--以鄂尔多斯盆地东胜气田为例

基于天然气中轻烃化合物组成分析和区域性对比,结合组分和甲烷碳同位素组成特征,揭示轻烃地球化学特征对鄂尔多斯盆地东胜气田上古生界天然气运移和水溶及逸散等示踪作用,探讨运移作用对特定轻烃指标的关联效应。研究表明:①东胜气田二叠系下石盒子组天然气C5−7异构烷烃含量高于正构烷烃,C6−7轻烃组成呈链烷烃优势分布且芳香烃含量明显偏低(小于4.0%),C7轻烃主体呈甲基环己烷优势分布,整体表现出煤成气特征且受到了水溶等作用影响;②东胜气田天然气经历了自南向北的游离相运移,并在充注后发生不同程度的水溶作用,其中泊尔江海子断裂以北什股壕地区天然气在聚集后具有明显的散失;③长距离的游离相运移导致天然气C7轻烃中甲基环己烷相对含量和甲苯/正庚烷值降低、正庚烷/甲基环己烷值和庚烷值增大,水溶作用导致轻烃异庚烷值增大,天然气散失导致什股壕地区天然气中C5−7正构烷烃相对异构烷烃含量增加。

东胜煤田巴音陶勒盖勘查区煤层及聚煤环境分析

巴音陶勒盖勘查区位于东胜煤田北部,侏罗系中下统延安组为本区含煤地层,按沉积旋回和岩性组合特征,自上而下可划分为3个岩段4个煤组。以东胜煤田巴音陶勒盖勘查区资料为基础,对勘查区煤层和聚煤环境进行综合研究表明,区内沉积环境以河流—三角洲相为主,伴有滨湖、浅湖和滨湖—泥炭沼泽相,局部发育半深湖相—深湖相。煤层发育严格受沉积环境的控制,区内形成了可对比煤层11层、可采煤层7层。

东胜气田致密高含水气藏合采气井层间干扰影响因素

为了明确鄂尔多斯盆地北缘致密高含水气藏合采气井层间干扰及其影响因素,指导同类型气藏合采气井高效开发,以该盆地北缘东胜气田致密高含水气藏为研究对象,分析了储集层地质条件、储集层改造对合采井产层段贡献的影响,指出了该类合采气井层间干扰的主控因素。研究结果表明:(1)合采井各产层段贡献率主要受各产层段的孔隙度、渗透率及含气饱和度控制,其产层段孔隙度占主导地位;(2)储层压裂改造对于提高气井产量具有较大的作用,但对合采井各产层段的贡献率却很小;(3)对于致密高含水气藏而言,含气饱和度是合采井产层段贡献率及层间干扰的一个重要影响因子;(4)合采井各产层段之间的孔隙度级差、渗透率级差及含气饱和度级差直接影响着合采井层间干扰程度。结论认为:(1)合采井产层段的孔隙度越大、渗透性越好、含气饱和度越高,则产层段的产量贡献率越大;(2)合采井孔隙度、渗透率及含气饱和度3个参数的级差越大,层间干扰程度越大,当孔隙度级差大于1.248或渗透率级差大于2.69或含气饱和度级差大于1.22时,合采井层间干扰已经非常严重,亟需开展治理。

Research on diagenesis of the sandstone-type uranium deposits in Dongsheng area, Ordos Basin

Synthetic methods of thin section petrography, scanning electron microscope, electron microprobe, energy spectrum analysis, cathodoluminescence, isotopic analysis and temperature measuring for fluid inclusions were used in analyzing sandstone samples collected from the Zhiluo Formation in order to fully understand the diagenesis evolution and the mineralizing response as well as the genesis of the uranium-bearing sandstone in Dongsheng area. The result shows that (1) the sandstone include lithic silicarenite, feldspathic litharenite and litharenite; (2) the authigenic minerals include clay minerals, carbonate minerals, siliceous and ferric minerals; (3) the physical property of sandstone is obviously controlled by diagenesis; and (4) the sandstone with favorable physical property is propitious to migration and storage of ore-forming fluid, and finally, forming the ore deposit. The sandstone of the Zhiluo Formation had undergone the early diagenetic stage (periods A and B) and the epidiagenetic stage. The evolution of diagenetic environment is in the order of acidic oxidation, alkalescent deoxidization, acidity to transitional environment of oxidation-deoxidization and acidity-alkalescence. The uranium exists in forms of pre-enrichment uranyl ion, active uranyl ion, dispersive adsorptive uranium and uranium mineral, respectively. In addition, the authors also hold that the formation of the sandstone-type uranium is not only related to the oxidation-deoxidization environment, but also closely related to the acidic-alkaline transitional environment, which are propitious to uranium mineralization in sandstone.

The first extra-large helium-rich gas field identified in a tight sandstone of the Dongsheng Gas Field,Ordos Basin,China

Helium gas is a scarce but important strategic resource,which is usually associated with natural gas.Presently,only one extra-large helium-rich gas field has been found in China:the Hetianhe Gas Field in the Tarim Basin.This paper reports a new example,the Dongsheng Gas Field(DGF)in the Ordos Basin.In this study,92 natural gas samples from the DGF were analyzed for helium content and isotope composition using isotope mass spectrometry.The natural gas samples were found to have an average helium content of 0.133%,with 65(70.7%)of the samples having a helium content of 0.1%or more.Based on the proven natural gas reserves of the DGF,the proven geological helium reserves were calculated to be 1.96×10^(8)m^(3),suggesting that it represents the first extra-large helium-rich natural gas reservoir to be hosted in tight sandstone in China.The ^(3)He/^(4)He ratios of 5 natural gas samples from the DGF are within the range of 3.03×10^(−8)–3.44×10^(−8).Therefore,the helium in the gas field is thought to be of typical crustal origin and to have formed in the granitic basement that is rich in uranium and thorium.The accumulation of helium-rich natural gas was controlled by regional tectonic activities.Activity along the fault connecting the reservoir with the basement caused release of the helium gas,which entered the overlying strata along the fault and accumulated with conventional hydrocarbon gas.Based on the structural background and the distribution of helium source rocks in the Ordos Basin,the main helium source rocks with high exploration potential are located in deep strata within the north and middle parts of the basin.

鄂尔多斯盆地北部下二叠统山西组2段储层特征及影响因素——以东胜气田A井区为例

为了进一步明确鄂尔多斯盆地北部东胜气田A井区二叠系下统山西组2段储层特征及影响因素,采用粒度分析、薄片鉴定、压汞试验、物性测试等技术手段及方法,对储层的岩石学及物性特征、储集空间类型与孔隙结构特征进行定性和定量分析,并从沉积作用和成岩作用两个方面探讨影响储层物性的主要因素。研究结果表明:①A井区山西组2段为辫状河三角洲平原沉积,储集层岩性为中—粗粒岩屑石英砂岩和石英砂岩,填隙物为泥质杂基和胶结物,主要发育碳酸盐胶结、黏土矿物胶结和硅质胶结。②储层属于特低孔隙、特低渗透率型,孔隙类型以粒间溶孔、粒内溶孔为主,伴有少量剩余粒间孔和微裂缝;孔隙以细孔为主,喉道主要为中—小喉,孔喉组合关系为细孔-中小喉。③储层物性受沉积作用和成岩作用双重控制,储层物性与岩石粒度呈显著正相关,位于分流河道上的心滩为最有利沉积微相。④破坏性成岩作用(机械压实和胶结作用)是降低储层孔隙度的主要因素,建设性成岩作用(溶蚀作用和裂缝作用)则可显著改善砂岩的孔渗性能。

东胜致密低渗产水气藏水平井一点法产能模型研究

为进一步提升气藏产能预测的精度,针对东胜气田锦30井区作了水平井产能模型研究。借鉴Giger、Joshi、Borisov、陈元千等人提出的油藏水平井产能公式推导过程,并遵循渗流规律建立了气藏水平井产能公式;基于气相渗透率与含水率的拟合关系分析水气比对气井流入动态曲线的影响规律,发现不同水气比条件下的无因次流入动态曲线重合且为直线,但无阻流量受水气比的影响较大;提出产水气井无因次无阻流量新理念,建立了无因次无阻流量与水气比的关系式,进而在此基础上推导出一点法产能预测模型。

压裂示踪剂监测技术在东胜气田M井应用分析

为了准确评价东胜气田M井储层压裂改造效果,采用在压裂过程中加注微量元素,通过检测不同时段返排液中各种示踪剂的种类及含量,分析该井不同压裂段气、水产出能力与储层物性、压裂参数的关系,以此评价储层各压裂段改造效果,分析影响改造效果的主要原因。选取两相示踪剂对M井各段产出贡献占比实现有效测量,结果表明,各压裂段产气贡献与储层物性、含气性存在着一定的相关性,与压裂工艺参数的相关性并不明显,水平段钻遇的储层物性、含气性越好,产气贡献越大,产出越好。该研究成果为提升该区同类储层压裂改造的针对性和有效性提供技术支撑。

东胜气田A井区二叠系下石盒子组高含水气藏地质建模

为了精细描述致密高含水气藏可供开发调整的有利区、明确储集层参数的空间展布特征,以鄂尔多斯盆地东胜气田A井区二叠系下石盒子组气藏为研究对象,分析了适合高含水气藏的建模方法,综合岩心、测井、钻井等资料,借助Petrel软件建立了该区下石盒子组气藏三维地质模型。研究结果表明:①研究区整体上为北东高、南西低的宽缓单斜,区内发育两条正断层、小型鼻状隆起以及背斜构造;②盒1段河道及复合心滩规模较大,呈“砂包泥”状,盒2+3段河道及心滩规模相对较小,呈“泥包砂”状,研究区泥岩夹层占比为50%,粉砂岩夹层和致密层夹层占比为30%;③所建模型数据与实际钻井情况较为相符,能够快速高效地计算研究区天然气地质储量,计算出A井区下石盒子组气藏天然气地质储量为341.16×10^(8) m^(3)。结论认为:①利用精细水平井单层划分成果细化地层微构造可以建立全区精细构造模型;②建立水平井构型控制的沉积微相模型及隔夹层模型能有效提高物性参数模型的准确度和有效性;③沉积微相、岩石相、断层等主控因素约束的水平井气藏属性参数建模能有效提高物性参数模型的准确度和有效性,在致密高含水气藏“多、薄、窄、密、强、杂”型的储层空间中适用性好。

Lipids of sulfate-reducing bacteria and sulfur-oxidizing bacteria found in the Dongsheng uranium deposit

U-bearing sandstones from the Dongsheng deposit in Ordos Basin contain abundant C15-C18 fatty acids. The fatty acids may have been derived from modern and ancient organisms including organisms from the intervals of U mineralization. A certain amount of i15:0, a15:0, a17:0 fatty acids coexist with small amounts of i17:1ω7c and 10me16:0, characteristic biomarkers of Desulfovibrio and Desulfobacter sp., respectively. This indicates the existence of sulfate-reducing bacteria (SRB) in the sandstones. The presence of sulfur-oxidizing bacteria (SOB), such as Beggiatoa and Thioploca, is indicated by significant amounts of 16:1ω7c and 18:1ω7c fatty acids. The existence of the SRB in the deposit, as inferred from the fatty acids, is consistent with results from fossilized microorganisms and isotopic compositions of ore-stage pyrite. This suggests that the environment may have been favorable for the SRB to grow since ore formation (9.8-22 Ma). The bacteria may have degraded hydrocarbons directly, or indirectly utilized hydrocarbons degraded by oxic microbes in the deposits. This process may have produced 12C-rich calcite and prominent baseline humps of unresolved complex mixtures (UCM), and 25-demethylated hopanes and tricyclic terpanes. The existence of sulfur-oxidizing bacteria and sulfate-reducing bacteria in the deposit may have resulted in bacterial sulfate reduction to sulfide, re-oxidization of the sulfide to sulfate and subsequent reduction of the sulfate to sulfide. This assertion is supported by ore-stage pyrite with δ34S values as low as-39.2‰, and the lightest sulfate (about 11‰) measured during the Phanerozoic, a difference of more than 46‰.

渝东南南川地区东胜构造带常压页岩气勘探开发实践

渝东南南川地区东胜构造带位于四川盆地东南缘的盆缘过渡带,经历多期构造改造,具有构造复杂、保存条件复杂、地应力场复杂的典型地质特征,导致常压页岩气单井产量差异较大。为提高东胜复杂构造带常压页岩气单井产量、实现效益开发,通过开展地震资料目标处理、构造特征分析、成藏富集规律研究及生产动态分析等,以及加强基础研究和勘探开发实践,明确了东胜复杂构造带实现常压页岩气效益开发的四项关键技术对策:①提高浅层速度模型精度,提升构造解释准确度;②优化井网部署,提高井控储量;③地质工程一体化,钻定导协同导向提高甜点钻遇率;④建立分区差异化压裂方案,提高裂缝复杂度。东胜常压页岩气效益开发关键技术对策为复杂构造带常压页岩气的效益开发提供了技术支撑,同时也可为盆缘其他类似地区的勘探开发提供借鉴。

阴-非体系高温泡排剂HDHP的研究及应用——以四川盆地东胜页岩气井为例

四川盆地东胜区块页岩气井储层垂深大(最大4300 m)、地层温度高(最高140℃)、钙镁离子质量浓度高(最高2.8×10^(-3)kg/L),导致返排液量过低,泡排剂效果不佳。针对此问题,在室内选取脂肪醇聚氧乙烯醚硫酸钠(AES)、含氟己基乙醇聚氧乙烯醚(FT)、改性硅油树脂聚醚(FM)和金属螯合剂(EDTA-2Na)为原料,制得阴-非体系高温泡排剂HDHP。通过正交试验,研究了AES、FT和FM不同配比对发泡、稳泡性能的影响,从而确定HDHP的最佳配比。通过室内实验评价HDHP的泡沫综合性能,表明高温泡排剂HDHP具有良好的抗温性和抗钙镁离子能力。在东胜区块3口井的试验过程中,平均单井产气量提高了30%。研究结果表明,阴-非体系高温泡排剂HDHP适用于东胜区块超深页岩气井泡沫排采工艺,具有良好的应用前景。

煤炭矿区排矸场表层土壤重金属污染研究

采用填埋覆土的方式对煤矸石进行处理,在沉陷区沟壑地带分层充填矸石,使沟地变为平地,对环境保护有重要意义。神府东胜煤田的大多数煤矿现已基本采用填埋覆土的方式对煤矸石进行处理。以神府东胜煤田中某排矸场为研究对象,分析了排矸场表层土壤(地表及-1 m处)中As、Cd、Cr、Cu、Mn、Ni、Pb和Zn含量的空间分布特征及土壤中重金属的赋存形态。研究表明,排矸场中As、Cd、Cr、Cu、Pb、Zn含量超过该地区的土壤背景值,对当地的土壤环境造成了一定的污染;排矸场土壤中As、Cd、Cr、Cu、Mn、Ni、Pb在-1 m处的含量高于表层土壤,并且排矸场中-1 m处土壤的8种重金属元素的含量都高于对照区土壤重金属含量;排矸场中Cd、Cr、Cu、Ni残渣态占比最大,As可氧化态占比最大,Mn、Zn、Pb可交换态和可还原态占比较大,Mn、Zn、Pb以更不稳定的形态存在,对生态环境影响较大。

半干旱地区矿区生态系统土壤保持功能评价——以神府-东胜矿区为例

[目的]评价2000—2020年神府—东胜矿区生态系统土壤保持功能变化情况,探讨矿区生态系统功能现状和存在问题,总结半干旱地区生产建设项目集中区生态功能提升途径,为半干旱地区生产建设项目区生态和经济协调发展提供借鉴。[方法]采用中国土壤流失方程(CSLE)和风力侵蚀模型,基于栅格像元计算不同时期(2000,2010和2020年)神府—东胜矿区土壤保持量,评价不同土地利用类型、不同植被覆盖度、不同矿井土壤保持量的时空变化。[结果]①神府—东胜矿区潜在土壤侵蚀量为3.76×10^(6) t/a,矿区生态系统土壤保持量由2000年的2.30×10^(6) t增长到2010年的3.17×10^(6) t,矿区生态系统减少风蚀量作用显著增加。②2000—2020年,矿区耕地、沙地和裸土地面积持续减少,园林草地面积持续增加。园林草地土壤保持量由1.18×10^(6) t/a增加到2.78×10^(6) t/a。③矿区植被由低覆盖度向中高覆盖度转变。2020年,中覆盖度和中高覆盖度林地土壤保持量占矿区生态系统土壤保持总量的67.12%。④治理程度不同的矿井土壤保持量均明显提高。[结论]2000—2020年,神府—东胜矿区土壤保持功能显著提升。半干旱地区生产建设项目可以通过实施有效的生态措施,改善生产、生活环境,探索生态经济实现路径,实现经济发展和生态改善双赢。

半矮杆耐密型大豆品种东生89高产栽培技术分析

东生89是中国科学院东北地理与农业生态研究所与黑龙江省农业科学院牡丹江分院于2019年通过辐射育种选育而成的半矮杆耐密型大豆新品种。2022年在黑龙江省海伦市长发镇种植东生89百亩示范田,平均产量为3839.90 kg/hm^(2)。该品种产量高、综合性状优良,生产应用前景广阔。文章通过对半矮杆耐密型大豆品种东生89高产栽培技术进行分析,结果表明,选用半矮杆耐密型大豆品种、建立群体理想株型结构,构建合理耕层、采用110 cm垄上3行宽窄行栽培模式,实行“两减一增”及精耕细管措施可使该品种获得高产。

东胜煤田西北缘延安组沉积特征及成煤沉积环境

基于钻井岩心、测井资料,以及煤岩煤质等实验测试资料,采用沉积学、煤地质学、层序地层学及岩相古地理学等理论方法,研究了东胜煤田西北缘延安组的沉积特征、成煤沉积环境及聚煤规律。研究区共识别出15种岩相,两种岩相组合类型。根据岩相组合所代表的沉积环境,识别出了曲流河、辫状河两种主要沉积体系,煤层主要形成于河漫的泥炭沼泽环境。通过分析研究区主采煤层显微煤岩组分特征,发现各煤层显微组分中主要为镜质组,其次是惰质组,壳质组及无机物含量最少,显微煤岩类型为微镜惰煤。通过分析煤的灰分、硫分,研究区的煤质类型以低灰煤、低硫煤为主。由镜惰比分析可以看出,研究区延安组成煤环境为潮湿—弱覆水环境和极潮湿—覆水环境。通过TPI-GI坐标图,识别出研究区存在两种煤相类型,即干燥森林沼泽相以及潮湿森林沼泽相。