Genesis of green sandstone/mudstone from Middle Jurassic Zhiluo Formation in the Dongsheng Uranium Orefield, Ordos Basin and its enlightenment for uranium mineralization

The middle Jurassic Zhiluo Formation in the Dongsheng is comprised of a big set of green sandstone/mudstone with most of uranium orebodies occurring in close proximity to its footwall.By synthesizing field observations,region analysis,data collected from previous coal and uranium borehole,a regional north-south geological profile across the entire orefield is conducted.Experiments on sandstone/mudstone including rock mineral identification,clastic micromorphology and element geochemistry were carried out.Information from the geological profile indicates that green sandstone/mudstone is widely present in a stable horizon with clear boundaries to the country rock.Microscopic observations and geochemical data on sandstone/mudstone exhibit similar mineral composition with almost identical slightly flat,minor Eu enriched,Ce depleted chondrite-normalized REE patterns.Furthermore,the green clay membrane of the clasts has a complex composition containing chlorite/smectite,green smectite,chlorite,and green kaolinite,with elements including Fe,Mg,Si,and Al.These above results indicate that the green sandstone/mudstone underwent resemble sedimentary diagenetic processes as the country rock without transformation by large-scale regional fluid,while the existence of Fe2+-rich membrane is the main factor to the green sandstone/mudstone.Further concentration of the pre-enrichment uranium during diagenetic process led to the final formation for uranium deposits.The above studies are conducive to enrich the metallogenic mechanism of sandstone type uranium deposits and could provide certain reference for uranium exploration and deployment.

Insights into the Tectonic Fractures in the Yanchang Formation Interbedded Sandstone-Mudstone of the Ordos Basin Based on Core Data and Geomechanical Models

The distribution and intensity of tectonic fractures within geologic units are important to hydrocarbon exploration and development. Taken the Upper Triassic Yanchang Formation interbedded sandstone-mudstone in the Ordos Basin as an example, this study used the finite element method（FEM） based on geomechanical models to study the development of tectonic fractures. The results show that the sandstones tend to generate tectonic fractures more easily than mudstones with the same layer thickness, and the highest degree of tectonic fractures will be developed when the sandstone-mudstone thickness ratio is about 5.0. A possible explanation is proposed for the tectonic fracture development based on two important factors of rock brittleness and mechanical layer thickness. Generally, larger rock brittleness and thinner layer thickness will generate more tectonic fractures. In interbedded sandstone-mudstone formations, the rock brittleness increases with the increasing mechanical layer thickness, hence, these two factors will achieve a balance for the development of tectonic fractures when the sandstone-mudstone thickness ratio reaches a specific value, and the development degree of tectonic fractures is the highest at this value.

Understanding hydraulic fracture propagation behavior in tight sandstone–coal interbedded formations: an experimentalinvestigation

Whether hydraulic fractures could connect multiple gas zones in the vertical plane is the key to fracturing treatment to jointly exploit coalbed methane and tight sandstone gas through integrative hydraulic fracturing in tight sandstone–coal interbedded formations. Laboratory true triaxial hydraulic fracturing experiments were conducted on layered specimens with di erent combination types of natural sandstone and coal to simulate the propagation behavior of hydraulic fractures. The effects of the fracture initiation position, fracturing fluid viscosity and injection rate were discussed. The results showed that di erent fracture morphologies could be found. When initiating from coal seams, three patterns of fracture initiation and propagation were obtained:(1) The main hydraulic fracture initiated and propagated along the natural fractures and then diverged due to the effects of in situ stress and formed secondary fractures.(2) The hydraulic fracture initiated and propagated in the direction of the maximum horizontal stress.(3) Multiple fractures initiated and propagated at the same time. With the same fracturing fluid viscosity and injection rate, the hydraulic fractures initiating in sandstones had greater chances than those in coal seams to penetrate interfaces and enter neighboring layers. Excessively small or large fracturing fluid viscosity and injection rate would do harm to the vertical extension height of the induced fracture and improvement of the stimulated reservoir volume. Compared with operation parameters(fracturing fluid viscosity and injection rate), the natural weak planes in coals were considered to be the key factor that a ected the fracture propagation path. The experimental results would make some contributions to the development of tight sandstone–coal interbedded reservoirs.

Geochemistry of Late Triassic pelitic rocks in the NE part of Songpan-Ganzi Basin,western China:Implications for source weathering,provenance and tectonic setting

Major, trace and rare earth element （REE） concentrations of Late Triassic sediments （fine- grained sandstones and mudstones） from Hongcan Well 1 in the NE part of the Songpan-Ganzi Basin, western China, are used to reveal weathering, provenance and tectonic setting of inferred source areas. The Chemical Index of Alteration （CIA） reflects a low to moderate degree of chemical weathering in a cool and somewhat dry climate, and an A-CN-K plot suggests an older upper continental crust prove- nance dominated by felsic to intermediate igneous rocks of average tonalite composition. Based on the various geochemical tectonic setting discrimination diagrams, the Late Triassic sediments are inferred to have been deposited in a back-arc basin situated between an active continental margin （the Kunlun- Qinling Fold Belt） and a continental island arc （the Yidun Island Arc）. The Triassic sediments in the study area underwent a rapid erosion and burial in a proximal slope-basin environment by the petrographic data,while the published flow directions of Triassic turbidites in the Aba-Zoige region was not supported Yidun volcanic arc source. Therefore, we suggest that the Kunlun-Qinling terrane is most likely to have supplied source materials to the northeast part of the Songpan-Ganzi Basin during the Late Triassic.

Typology of Landslides, Investigation and Monitoring in Flysch Deposits in Albania

The development of infrastructure, energy and tourism in recent years in Albania has brought the necessity of geotechnical studies to a higher technical level. Most of these buildings （hydropower, motorway, pipeline） are built in mountainous areas with complicated geological conditions. The most complicated obstacles seem to be huge landslides, especially for those situated on flysch deposits. Most of the huge landslides were innate and active by the end of Pleistocene; however, some of them, especially those in flysch areas, are activated due to recent changes of climate and intensive man activities. Examples of re-activation of old landslides are encountered on Qukes-Qafe Pllo^e road, on Devoll river valley which are being built several hydropower and on Poli^an-Potom area where a gas line is built. These landslides are under design investigations using field and laboratory methods like drilling, inclinometers and piezometers measurement, geophysical probing, rock and soil testing. All slopes with flysch rocks in Albania have low stability because of the presence of active landslides. In any case they should be studied using advanced geotechnical methods and monitored for tong time in order to take the right protective measures.

干湿循环与加载先后顺序对砂泥岩混合料压缩特性的影响

为研究干湿循环与加载先后顺序对砂泥岩混合料压缩特性的影响,针对不同干湿循环次数、浸水时间和水温处置下的砂泥岩混合料,开展先干湿循环后加载、先加载后干湿循环的单向压缩试验。结果表明,两种试验方法所得砂泥岩混合料压缩量均随干湿循环次数增加、浸水时间增长、水温增高而增大;压缩量与干湿循环次数呈对数关系、与浸水时间呈幂函数关系、与水温呈线性关系,并推导出相应的压缩量计算公式;试验结果及理论分析均得出先干湿循环后加载的压缩量大于先加载后干湿循环的压缩量。

塔河油田T1-5H井泵送桥塞分段加砂压裂工艺

针对塔河油田泵送桥塞分段加砂压裂施工中存在泵送桥塞工具串易遇阻遇卡,缺乏相配的井下工具,含硫化氢、井控风险较高等问题,以T1-5H井为例,提出了井下工具泵送模拟技术,提高工具串在复合套管中的通过性;形成了人工井底地质深度回归结合连续油管探底的高精度校深方法,保证首段射孔位置精确;采用大通径全封堵桥塞,解决高压气井组下生产管柱的难题。应用表明,T1-5H井泵送桥塞分段加砂压裂完井工艺4段5簇,注入地层总液量3210.7 m^(3),累计产能提高2401.6 t,有效提高了储层动用程度。该工艺为西北工区砂泥岩薄互储层改造提供经验借鉴,为实现超深石炭系储层大规模开发奠定了技术基础。

重型绞吸挖泥船挖掘砂岩混泥岩施工工艺优化

针对重型绞吸船挖掘砂岩混泥岩的复杂工况,以钦州港东航道扩建工程为例,开展“天鲲号”绞吸船挖掘与输送砂岩混泥岩土质的施工工艺研究。通过7G与8G 6臂绞刀的对比试验,综合比较不同绞刀型号的生产效率及刀齿损耗,对挖泥机具进行比选;通过对绞吸船施工时进尺、切厚等关键施工参数的分析优化,结合砂岩混泥岩的土质特性,确定了最佳挖掘施工工艺;通过对泥泵性能的分析计算,确定了绞吸船输送的最佳控制浓度;从挖掘、输送2方面进行施工工艺优化,总结了重型绞吸船挖掘砂岩混泥岩的施工技术。研究成果可为类似工况的绞吸船施工提供参考。

华北东部晚古生代过渡相煤系地层低阻成因、控制因素与地质意义

华北东部晚古生代过渡相煤系地层中低阻层发育,明确其成因类型、控制因素以及地质意义,可以充分揭示其中所包含的地质信息,对于相关层系油气资源评价和勘探部署具有积极意义。本文以华北东部太原组和山西组中低阻层为研究对象,综合运用岩心、薄片、扫描电镜、碳氧同位素和测录井资料,围绕其成因类型、控制因素和地质意义开展研究。结果表明:华北东部晚古生代过渡相煤系低阻层主要发育在太1段和山2段,成因类型包括砂泥岩薄互层、高束缚水体积和发育导电矿物,沉积作用和成岩作用控制了低阻的形成;太1段低阻的成因为砂泥岩薄互层和高束缚水体积,潮汐作用导致的潮汐成因层理和微细孔隙发育促进了障壁海岸背景下太1段低阻的形成,山2段低阻的成因为菱铁矿的密集发育,稳定的覆水还原环境和沉积有机物的成岩演化共同控制了三角洲背景下山2段低阻的形成;太1段的低阻和高毛细管束缚水体积指示着潮坪沉积,说明太原组自下而上为一个海退的过程,是对早二叠世早期冈瓦纳冰川迅速扩张和全球海平面快速下降的响应,山2段的低阻和高光电吸收截面指数指示着三角洲前缘沉积,说明山西组由一期三角洲沉积组成。

A区块砂泥岩薄互层气藏改建储气库的可行性研究

随着大庆油田原油、伴生气产量逐年递减,冬夏季供气不平衡的矛盾日益突出,在无法满足季节调峰需求时,需压减工业用气。因此,从满足冬季下游用户的用气需求、合理利用有限的油气资源和保护环境等角度出发,建设储气库势在必行。根据大庆油田库址筛选标准,优选出A区块进行库址规划,与大庆油田已建储气库相配合,联合保障大庆及周边地区用气季节调峰。A区块属于砂泥岩薄互层气藏,从地质特征、气藏开采特征等方面分析改建储气库的可行性,详细评价建库的地质条件和气藏条件,并设计库容参数和两套井位部署方案,建立数值模型进行优选对比。结果表明,A区块砂泥岩薄互层气藏具备建库的可行性。

湖北省三峡库区砂泥岩互层岩体劣化特征与劣化机理分析

受水位周期性变动影响,三峡库区地质环境产生复杂变化,尤其是对碎屑岩岸坡砂泥岩互层岩体劣化的影响显著。本文通过对湖北省三峡库区碎屑岩岸坡砂泥岩互层岩体进行现场调查,结合现场测试与室内试验成果,对比分析碎屑岩砂泥岩互层岩体两种结构单元的劣化差异,结合岸坡互层岩体的劣化现状,分析砂泥岩互层结构的岸坡岩体劣化变形过程,揭示砂泥岩互层岩体的劣化机理及其对岸坡致灾发展的影响,为后期合理进行岸坡岩体劣化评价及防治提供理论支撑。

南宁地区红层泥岩膨胀性对工程的影响分析

通过分析南宁地区红层泥岩在干湿交替环境下表现出的膨胀性,对比分析风化前后泥岩层膨胀性变化,依托南宁轨道交通工程,选取古近系、白垩系等不同时代的弱风化红层泥岩、风化层作为研究对象,对南宁地区红层泥岩及风化物膨胀性对基坑、边坡、道路工程的稳定性和安全性影响进行研究。

基于示踪剂监测的水平井高泥质含量段压裂可行性分析

针对研究区块储层非均质性强,水平段泥岩钻遇率高,影响水平井产能发挥的问题,开展示踪剂产能监测试验研究。选取YQ8井三段泥质含量较高压裂段作为试验段,两段砂岩储层段作为对比段,随压裂液加入气相、液相示踪剂,在地面取样分析,获取各压裂段产气、产水相关信息,获得泥质含量较高水平段压后产气贡献率分别为36.6%、39.8%、0.1%,表明水平段泥质含量较高时,压后仍具有产能贡献,甚至高于部分测井响应特征较好分段,需要加深对泥质含量较高分段的厚度、应力差等因素研究,优化压裂施工参数。研究证明水平井高泥质含量段的压裂可行性,以及示踪剂监测技术评价水平井分段压裂效果的可行性。

泥岩夹砂岩地层隧道底鼓原因分析及整治技术

某高铁隧道全长10649 m,洞身穿越白垩系下统泥岩、泥岩夹砂岩地层。2014年至2016年,隧道进口端泥岩夹砂岩局部段落隧底出现不同程度上拱、无砟轨道道床板与隧道仰拱填充之间离缝等问题,根据病害情况及工期要求,先后采取仰拱返工、钻孔灌注桩(锚杆)加固和离缝注浆封闭等措施进行了整治;2016年整治完成后,局部段落隧底上拱仍在缓慢持续发展。根据补充钻探、取样试验结果,分析为隧底长期积水使泥岩浸泡软化、吸水膨胀,层状软岩蠕变、水平构造应力和隧道结构薄弱等因素所致。结合前期整治情况,利用线路检修时机,采取拆换仰拱、调整仰拱曲率、底部增设钢架等措施进行了整治。2020年整治完成后,轨检小车连续监测结果显示轨道几何状态良好,达到了预期效果。

A major breakthrough in geological survey of coal measure gas in Southern Sichuan, China

1.Objectives Southern Sichuan is located in Xuyong-Junlian superimposed fold belt in the southern margin of Sichuan Foreland Basin,with an area of about 15000 km^2.The coal measures of Upper Permian Xuanwei Formation and Longtan Formation are characterized by mudstone,clayey mudstone,fine sandstone,siltstone,and coal seams interbedded.The coal seams and carbonaceous mudstone have good hydrocarbon generation potential.The coal measure“three gas”includes coalbed methane(CBM),coal shale gas and coal measure tight sandstone gas coexist.There was a breakthrough in the CBM survey in Junlian,Gulin,and other areas in Southern Sichuan(Yin ZS et al.,2019).But it lacks a comprehensive and systematic evaluation of coal measure gas resource potential.

卸荷蠕变条件下软硬相接岩层非协调变形规律研究

软硬相接岩层在长时间跨度内的蠕变变形可能极为不协调,这对开挖工程安全稳定造成严重威胁。对某水电站引水隧洞同一开挖断面内砂质泥岩和泥质砂岩两种软硬相差较大的岩石进行卸荷条件下的蠕变试验和数值模拟,结果表明:在卸围压条件下,试样侧向蠕变变形较轴向发展更为迅速,呈现出显著的侧向扩容;初始围压水平较高时,试样卸荷蠕变破坏的侧向扩容效应更加显著;泥质砂岩在稳态蠕变阶段变形速率比砂质泥岩更慢,蠕变破坏时的应变值均比砂质泥岩蠕变破坏时的应变值要小,征兆性更弱。基于Burgers模型,引入损伤变量,建立带损伤的蠕变本构模型,模型曲线较好地描述了岩石破坏偏应力水平之前的线性蠕变特征和破坏偏应力水平下的非线性加速蠕变特征;软硬相接岩层蠕变数值模拟表明,蠕变变形初期,软硬相接点变形差别幅度不大,随着时间增长,在交接面处发生层间错动,对围岩整体稳定十分不利,工程实践中应予以足够关注。

基于FL-XGBoost算法的砂泥岩识别方法——以胜利油田牛庄地区为例

砂泥岩识别任务通常基于测井曲线,依据经验公式、实地岩心取样、交会图和聚类分析等传统方法实现,但这些方法难以充分利用测井曲线所包含的砂泥岩特征,且精度低、效率低,人为影响因素大。为此,以测井和录井资料为基础,综合砂泥岩识别的关键技术难点,对测井参数进行敏感性分析,以选取适当的影响因素,通过多项预处理操作构建完整的训练数据集,并根据测井标签稀疏性的特点,引入Focal Loss函数,提出FL-XGBoost模型,进而开展胜利油田牛庄地区砂泥岩识别。研究结果表明,采用FL-XGBoost算法的砂泥岩识别模型对研究区砂泥岩识别的准确率达到了0.827。通过5种公开分类数据集设计对比实验,证明FL-XGBoost算法在识别分类领域上具有强泛化能力。

薄互层致密砂岩水力压裂裂缝扩展特征研究

薄互层致密砂岩储层由于其砂泥叠置沉积,纵向非均质性强的特点,在水力压裂施工中,裂缝难以垂向扩展,有效沟通储层,明确薄互层水力裂缝垂向扩展规律对薄互层致密砂岩的开发具有重要意义。针对鄂尔多斯盆地临兴区块下石盒子组薄互层致密砂岩储层,通过建立薄互层致密砂岩地层裂缝扩展模型,研究了储隔层间应力差、储隔层厚度、岩石力学性质等地质因素和压裂液黏度、施工排量等工程因素对水力压裂裂缝扩展的影响,并通过现场井压裂效果和微震检测数据验证了模型的可靠性与准确性。研究结果表明:储隔层间应力差和储隔层厚度是影响水力裂缝穿层扩展最主要的地质因素,当应力差大于4 MPa时,裂缝垂向扩展受到抑制;弹性模量大的隔层有利于裂缝垂向扩展;泊松比对裂缝垂向扩展几乎没有影响;压裂液黏度对裂缝垂向扩展影响较小;泵注排量对裂缝垂向扩展有促进作用,但当排量增加到一定程度后,裂缝扩展放缓,对于不同的应力差,存在不同的最优排量。因此,对于薄互层致密砂岩水力压裂,低储隔层厚度、低储隔层应力差、高弹性模量和高注入排量能有效促进裂缝垂向扩展。研究成果可为该类储层水力压裂施工设计提供一定理论依据。

干湿作用对砂泥岩混合料压缩特性的影响

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