应用环境扫描电镜研究储集层砂岩样品润湿性的变化特征

环境扫描电镜是国际上根据科学研究的需要在常规扫描电镜的基础上发展起来的一项新技术 ,应用ESEM 2 0 2 0型环境扫描电镜常温环境台的功能 ,通过观察水蒸气在样品表面凝结速度的快慢和凝结水滴与样品表面的接触角大小来判断样品的润湿性。利用环境扫描电镜观察对比了较强亲油砂岩、较弱亲油砂岩及强亲水砂岩的润湿性特征 ,表明环境扫描电镜技术在微观尺度上用于研究样品润湿性具有迅速、直观等优点。图

含油气盆地露头砂岩样品定向流体包裹体薄片制作方法及其意义

制备高质量的定向流体包裹体薄片是从"构造-成岩"角度入手深入研究含油气盆地砂岩储层中构造裂缝属性的关键与前提。建立一种针对含油气盆地露头砂岩样品的定向流体包裹体薄片的制作方法。以有效保留露头砂岩样品的原始方向信息作为贯穿整个制片过程的主旨,体现在野外砂岩样品的定向采集、砂岩样品原始产状的恢复、样品切割方向的标定、首次切样、粘样以及在载玻片上标定样品的方向等多个制片环节中,以确保砂岩样品的方向信息在制作的流体包裹体薄片中得以准确呈现。结果表明:利用该方法制备的薄片兼有定向薄片和流体包裹体薄片的双重功能,不仅可为砂岩中流体包裹体岩相学观察的顺利进行提供保障,还可为样品中脉体和流体包裹体面的原始方位信息的准确恢复以及后续相关流体地球化学测试分析奠定强有力的薄片基础,以便为从"构造-成岩"角度入手深化认识砂岩储层中构造裂缝特征及其相关油气成藏过程的定量化研究提供服务。

砂岩铀矿地质样品中铀含量仲裁分析方法——同位素稀释电感耦合等离子体质谱法

本工作研究铀矿地质样品中铀含量仲裁分析方法——同位素稀释电感耦合等离子体质谱法。样品经混酸密闭消解溶矿，采用浓缩铀为稀释剂，使用高分辨电感耦合等离子体质谱测定铀同位素比值，进而计算样品中的铀含量。本方法具有明晰的计量溯源特性，铀的测量范围为1-10000μg/g，对于铀含量约为4μg/g的砂岩样品，相对扩展不确定度小于4.0%（扩展因子K=2.57），可满足砂岩铀矿地质样品中铀含量仲裁分析要求。

大南湖凹陷西山窑组层间氧化带砂岩岩石化学特征

本文主要利用砂岩样品(主要为岩芯样)的鉴定和分析测试资料，对区内层问氧化带岩石化学特征作初步研究。根据砂岩的物质组分，碎屑分选性、磨圆度等结构特征并对比蚀源区岩石，认为区内沉积物主要来自北部的南湖隆起、其次为南部的觉罗塔格山。通过对砂岩结构构造及填隙物含量、胶结类型的研究发现，砂岩的孔隙度、渗透率与体重关系密切，且与胶结物中碳酸盐含量高低及次生矿物种类、含量有关。统计与水成铀成矿关系密切的C有、CO2、Fe、S、U、Th及伴生元素的含量，发现区氧化带砂岩中上述元素含量比还原带低，而Fe^3+/Fe^2+氧化带比还原带高的特点。根据地浸砂岩铀矿的成矿条件，区内有机质含量较高，碳酸盐含量中等，部分地段或层位碳酸盐含量较低，Fe、S、U、Th及伴生元素的氧化、溶解、迁移、沉淀和富集符合水成铀矿的变化规律。

Experimental investigation on the energy evolution of dry and water-saturated red sandstones

In order to investigate the effect of water content on the energy evolution of red sandstone, the axial loading–unloading experiments on dry and water-saturated sandstone samples were conducted, and the distribution and evolution of elastic energy and dissipated energy within the rock were measured.The results show that the saturation process from dry to fully-saturated states reduces the strength, rigidity and brittleness of the rock by 30.2%, 25.5% and 16.7%, respectively. The water-saturated sample has larger irreversible deformation in the pre-peak stage and smaller stress drop in the post-peak stage.The saturation process decreases the accumulation energy limit by 38.9%, but increases the dissipated energy and residual elastic energy density, thus greatly reducing the magnitude and rate of energy release. The water-saturated sample has lower conversion efficiency to elastic energy by 3% in the prepeak region; moreover, the elastic energy ratio falls with a smaller range in the post-peak stage.Therefore, saturation process can greatly reduce the risk of dynamic disaster, and heterogeneous water content can lead to dynamic disaster possibly on the other hand.

Mechanical behavior and failure analysis of brittle sandstone specimens containing combined flaws under uniaxial compression

Based on the axial stress-axial strain curves,the effect of fissure angle on the strength and deformation behavior of sandstone specimens containing combined flaws is analyzed.The mechanical parameters of sandstone specimens containing combined flaws are all lower than that of intact specimen,but the reduction extent is distinctly related to the fissure angle.The results of sandstone specimens containing combined flaws are obtained by the acoustic emission,which can be used to monitor the crack initiation and propagation.The ultimate failure mode and crack coalescence behavior are evaluated for brittle sandstone specimens containing combined flaws.Nine different crack types are identified on the basis of their geometry and crack coalescence mechanism(tensile crack,hole collapse,far-field crack and surface spalling)for combined flaws.The photographic monitoring was also adopted for uniaxial compression test in order to confirm the sequence of crack coalescence in brittle sandstone specimens containing combined flaws,which recorded the real-time crack coalescence process during entire deformation.According to the monitored results,the effect of crack coalescence process on the strength and deformation behavior is investigated based on a detailed analysis for brittle sandstone specimens containing combined flaws by using digital photogrammetry.

Triaxial mechanical creep behavior of sandstone

Based on laboratory results of time-dependent mechanical behavior tests,we investigated short-term and mechanical creep behavior of sandstone,observed in conventional triaxial compression experiments at room temperature,using a servo-controlled rheology testing machine.Given our short-term experimental test results,we confirmed deviatoric creep stress levels of sandstone.Multiple deviatoric stress levels were applied in steps to each sample.Each deviatoric stress level before the final failed deviatoric stress was maintained for 48 h or longer.Time-dependent variations of axial strains of sandstone samples are discussed and evaluated.During the creep tests,complete tertiary creep curves of sandstone were observed under failed deviatoric stress levels with different confining pressures.Slices of coal in sandstone samples can lead to distinct tertiary creep deformation failure.

Experimental investigation on the relevance of mechanical properties and porosity of sandstone after hydrochemical erosion

Under the effect of chemical etching,the macroscopic mechanical properties,mesoscopic structure,mineral content,and porosity of rocks undergo significant changes,which can lead to the geological disasters; thus,an understanding of changes in the microscopic and macroscopic structure of rocks after chemical etching is crucial.In this study,uniaxial mechanical tests and nuclear magnetic resonance(NMR) spectroscopy were carried out on sandstone samples that had been previously subjected to chemical erosion under different p H values.The aim was to study changes in properties and mechanical characteristics,including deformation and strength characteristics,of the rock,and microscopic pore variation characteristics,and to perform preliminary studies of the chemical corrosion mechanism.Results show that different chemical solutions have a significant influence on the uniaxial compressive strength,the axial strain corresponding to the peak axial stress,elastic modulus,etc.With the passage of time,porosity increases gradually with exposure to different chemical solutions,and exposure to chemical solutions results in large changes in the NMR T2 curve and T2 spectrum area.Sandstone exposed to different chemical solutions exhibits different corrosion mechanisms; the root cause is the change of mineral.

Creep failure mode and criterion of Xiangjiaba sandstone

Based on the results of conventional triaxial compression tests and triaxial compression creep tests on Xiangjiaba sandstone,the failure modes in short-term tests and creep tests,fractography of sandstone after creep failure,short-term and creep failure criterion are analyzed.In the short-term tests and creep tests,the sandstone samples fail in a mix mode consisting of shear failure in a single main plane and tensile failure.Confining pressure can restrict brittle failure and enhance the ductility of sandstone.In the creep tests,brittle fracture is reduced and plastic deformation can fully be developed compared to the condition of short-term tests.And the shear fracture surfaces are flat and they are covered by small particles as a result of friction.When confining pressure increases,particle size decreases while the degree of friction on shear plane increases.On the tensile failure plane,the tensile trace and direction of tearing could be clearly observed.There are obvious tearing steps on the tensile failure plane and tearing laminated structure on the front edge of tearing fracture.The same criterion can be used for the short-term and creep behavior,and the fitting effect using the MOGI criterion is better than the DRUCKER PRAGER criterion.The cohesion and friction angle calculated by the MOGI criterion are in good accordance with those calculated by the MOHR COULOMB criterion.

快速测定高硅存在下的二氧化钛

本文介绍了高硅存在下二氧化钛的快速测定。此法操作简单，测试周期短，结果准确、可行，完全能满足地质工作的一般需要。

江汉油田解决岩心岩屑保存难题

针对岩心、岩屑难以保存的问题，江汉油田研究院经过反复试验，终于摸索出一套简易的“岩心套装保存”技术，攻克了岩心、岩屑的保存难题。 由于岩心、岩屑易腐蚀、易挥发，盐和钙芒硝，暴露在空气中极易潮解、响样品质量。尤其是盐间非砂岩样品含有较多的变质，传统的裸露保存方式容易影响样品质量。

碎屑矿物组成的区域变化对西墨西哥湾深层-超深层下中新统砂岩储层物性的影响

未来在墨西哥湾中新统下段砂岩的勘探将越来越聚焦在埋深大于4．5km的地层，而对于那些深一超深层岩层来说，储层物性是一个关键风险因素。本研究的目的是了解西墨西哥湾中新统下段砂岩储层物性的变化。为此，我们用取自深度在0．9～7．2km之间地层样品的岩相和岩石物性数据，分析了五个地区碎屑矿物组成、成岩过程、储层物性的区域性变化，这五个地区是1）路易斯安那；2）上得克萨斯海岸；3）下得克萨斯海岸；4）墨西哥布尔戈斯盆地；5）墨西哥韦拉克鲁斯盆地。在研究区内矿物组成变化非常明显。路易斯安那近海下中新统砂岩的平均矿物组成为石英：86％；长石=12％；岩石碎屑=2％（Q86F12R2）。往南，随着源区内火山岩和碳酸盐岩的出现，长石与岩屑含量增加。在从得克萨斯近海采集的样品中，上得克萨斯海岸岩样的矿物组成为Q67F24R9，及至下得克萨斯海岸，为Q58F24R19。墨西哥北部陆上布尔戈斯盆地中新统下段砂岩的平均矿物组成为Q64F22R23，而取自墨西哥南部韦拉克鲁斯盆地砂岩样品的岩屑比例最高，达Q33F12R55。路易斯安那地区富含石英的下中新统砂岩的主要成岩事件有机械压实作用和石英胶结物沉淀。往南，伴随岩石碎屑含量持续增加，压实造成的孔隙度损失增大。南部方解石胶结物丰富，储层物性明显下降。在中等埋深，路易斯安那的富石英砂岩储层物性最好，而在得克萨斯和墨西哥，因岩屑含量增加，储层物性下降。在所有深度和温度下，相较下得克萨斯和墨西哥的岩层，路易斯安那和上得克萨斯岩层的孔隙度要高些，但地层深度〉5km、温度〉175℃时，孔隙度差异变小。西墨西哥湾从路易斯安那到墨西哥中新统中、下段的变化趋势可作为一个典型例证，来阐述作为一个成岩作用和储层物性控制因素碎屑矿物学变化的重要性。