Confined pyrolysis of Tertiary lacustrine source rocks in the Western Qaidam Basin,Northwest China: Implications for generative potential and oil maturity evaluation

The parameter S₁ + S₂ (genetic potential) of Rock-Eval analysis is widely used as an evaluation of the genetic potential for the source rocks. Oligocene–Miocene saline lacustrine source rocks in the western Qaidam basin have low total organic C contents (TOC), most around 0.5% with a few exceptions >1.0%. Mineral matrix effects are substantial for source rocks with low TOC, resulting in relatively low S₁ and S₂ peaks. Based on the results of confined pyrolyses (sealed Au capsules) on 6 Oligocene–Miocene source rocks from the western Qaidam basin, with TOC ranging between 0.48% and 2.22%, the relationship between the S₁ + S₂ parameter and the maximum amount of extracted bitumen or saturated and aromatic hydrocarbons (SA) after the confined pyrolysis has been established as follows: bitumen (mg/g rock) = 1.4924 × (S₁ + S₂) + 0.3201 (r = 0.987), or SA (saturates + aromatics) (mg/g rock) = 0.7083 × (S₁ + S₂) + 0.4045 (r = 0.992). Based on these formulas, the amounts of hydrocarbons generated from source rocks can be reasonably estimated. The typical crude oils with low biomarker maturities in this region appear substantially different to the pyrolysates of these six rocks at 180–300 °C but comparable to the pyrolysates at 320 °C and higher temperatures based on molecular parameters. This result, in combination with the physical and gross compositions of the crude oils, suggests that the majority of these crude oils were generated from the source rocks during the main oil-generative stage, possibly at a maturity higher than R_o 0.74%.     

Spiky Fine Structure of Type III-like Radio Bursts in Absorption

An uncommon fine structure in the radio spectrum consisting of bursts in absorption was observed with the Chinese Solar Broadband Radiospectrometer (SBRS) in the frequency range of 2.6?–?3.8 GHz during an X3.4/4B flare on 13 December 2006 in active region NOAA 10930 (S05W33). Usual fine structures in emission such as spikes, zebra stripes, and drifting fibers were observed at the peak of every new flare brightening. Within an hour at the decay phase of the event we observed bursts consisting of spikes in absorption, which pulsated periodically in frequency. Their instantaneous frequency bandwidths were found to be in the 75 MHz range. Moreover, in the strongest Type III-like bursts in absorption, the spikes showed stripes of the zebra-pattern (ZP) that drifted to higher frequencies. All spikes had the duration as short as down to the limit of the instrument resolution of ≈8 ms. The TRACE 195 Å images indicate that the magnetic reconnection at this moment occurred in the western edge of the flare loop arcade. Taking into account the presence of the reverse-drifting bursts in emission, in the course of the restoration of the magnetic structures in the corona, the acceleration of the beams of fast particles must have occurred both upward and downward at different heights. The upward beams will be captured by the magnetic trap, where the loss-cone distribution of fast particles (responsible for the emission of continuum and ZP) were formed. An additional injection of fast particles will fill the loss-cone later, breaking the loss-cone distribution. Therefore, the generation of continuum will be quenched at these moments, which was evidenced by the formation of bursts in absorption.     

青藏高原东缘龙门山断裂带晚新生代构造地貌生长及水系响应

河流地貌对新构造活动具有非常敏感的响应,水系形态能够较好地记录构造活动方式,水系形态分析可以为研究新构造的演化过程提供有力的证据.位于青藏高原东缘的龙门山与四川盆地是青藏高原周边最陡的地形梯度带,沿高原东缘发育青农江、岷江、涪江和嘉陵汀等一系列斜交于龙门山断裂带的水系.利用卫星遥感图像和数字高程模型(DEM)数据提取构造地貌和水系特征,对龙门山构造带水系形念进行分析研究,发现龙门山南西段冲断带褶铍具有横向牛长的演化特征,逆冲褶皱带的构造演化影响青衣江和岷江水系的演化和重组,同时也控制着研究区晚新生代的沉积格局.受断裂带右旋走滑作用的影响,龙门山北东段水系表现出系统右旋错化特征,在北川县擂鼓镇至曲山镇一带涪江水系上游的重要支流一湔江出现3.8km的右旋错位,并导致湔江北川段出现河流袭夺和水系重组现象.根据涪江上游发生的5km和4km最大右旋错位及其涪江流域形成的最早沉积记录的年代大约为3Ma,估算映秀-北川断裂带和灌县-安县断裂带北东段上新世-第四纪以来的平均走滑速率分别为1.67mm/a和1.33mm/a,而龙门山断裂带北东段的长期走滑速率至少为3.0mm/a.本研究表明可以将水系形态作为研究区域构造变形的重要地貌标志,该方法同样适用于世界上其他构造活动变形地区.     

腐植酸泥浆正交试验优化研究

腐植酸泥浆是非开挖钻进砂层、砾石、卵石以及破碎地层时常用的一种护壁浆液。针对常用的腐植酸泥浆的配方,设计了四因素三水平的正交试验,分析了泥浆性能受各组分影响的主次,然后进行配方优化。把NaCl作为一个正交试验因素,分析了NaCl不同加量对泥浆性能的影响。正交优化后的泥浆性能粘度较高,失水量较小,能较好的满足施工的要求。     

甘肃省地下水资源及其开发利用状况研究

甘肃省地处我国西北内陆,地下水资源匮乏,水资源供需矛盾突出,查明地下水资源大账显得十分必要。本文在全面收集和分析以往不同时期水文地质勘查及研究成果基础上,按不同水文地质单元、行政区划、地貌单元较系统地总结了各区地下水资源量,简要分析了开发利用状况。结果表明,甘肃省地下水天然补给资源量132.79×108m^3/a。其中,内陆河流域51.80×108m^3/a,黄河流域47.07×108m^3/a,长江流域33.91×108m^3/a;西部地区57.86×108m^3/a,东部地区20.97×108m^3/a,南部地区53.95×108m^3/a;山区80.98×108m^3/a,平原区51.80×108m^3/a。全省现有地下水开采机井约3.5×104眼,地下水开采量26.2×108m^3/a,地下水可开采资源量53.89×108m^3/a。西部地区开发利用程度较高,尤其是石羊河的民勤县地下水严重超采。东部和南部地区开发利用程度较低。     

贵州簸箕田金矿单矿物稀土元素和同位素地球化学特征

簸箕田金矿位于灰家堡背斜东头倾覆端,是灰家堡卡林型金矿田重要的组成部分。金矿床具有低温成矿特征,出现硅化、白云石化、黄铁矿化等围岩蚀变和特征的Au-As-Hg元素组合。成矿期方解石具有MREE富集和正Eu异常特点,显示矿热液是一种MREE相对富集以及具有正Eu异常的还原性流体,来源于深部或至少经历过对富含斜长石源区的水-岩反应。成矿期方解石的δ~(13)C为-6‰～-0.1‰,成矿期后方解石的δ~(13)C为0.2‰～3.2‰,显示成矿期碳来源于地幔碳和地层碳的混合,成矿期后碳主要来自于地层。矿床硫同位素变化于0.73‰～5.86‰,组成均一化较高,具有接近幔源硫的特征,反映了成矿物质可能主要来自于深源岩浆。总之我们推测成矿物质主要来源于深部,在燕山期区域构造作用下沿深大断裂上涌,当成矿流体运移至背斜核部时,由于成矿条件的聚变,金被快速富集沉淀,形成簸箕田金矿床。     

渤海湾西侧泥质海岸带全新世岸线的变化与海洋的影响

以渤海湾泥质海岸带为例,从形态和地层证据2个方面总结了全新世岸线变化与海洋作用对该地区海岸带发育的影响。中全新世以来千年级别的岸线变迁至少以6次停顿（形成贝壳堤和泥质岭地）和岸进的交替为特征。过去130年间10年级别的岸线变化分为4个阶段,显示了＂小冰期＂结束后随气温上升而发生的岸线自然蚀退是如何逐渐被人类活动（特别是2000年以来的围海造陆）所取代的。全新世海相沉积中发现的9个峰值期和晚全新世的7次风暴驱动事件,表明了研究区泥质海岸带增强的海洋影响。这些结果提供了一条经由地质背景认识现代泥质海岸带过程的途径。     

川东北元坝地区三叠系飞仙关组储层地质模型

依据对川东北元坝地区飞仙关组沉积岩石学特征、储集空间类型及物性分布特征的综合研究,对该地区的储层特征加以抽象和概念化,建立了飞仙关组储层地质模型。地质模型揭示元坝地区海相碳酸盐岩储层段均发育在台地边缘沉积区。其中,台地边缘浅滩最为发育,台地边缘斜坡次之,未见台地边缘生物礁。飞仙关组一段至二段下部为台地边缘斜坡沉积,二段上部至三段为台地边缘浅滩沉积。认为飞仙关组二段和三段的鲕滩沉积储集岩为下一阶段勘探开发的重点,其中飞仙关组二段孔隙—裂缝性储层的勘探开发潜力尤为巨大。     

渤海湾西岸细砂质潮间带的成因分析

根据在海河口南缘至独流减河岸段潮间带地区采集的36个表层和1个无扰动柱状沉积物样品的粒度分析结果,探讨了该岸段的粒度分布特征.结果表明:平面上(自南向北),该潮间带表层沉积物由粉砂质砂变为细砂,呈逐渐变粗、分选性变好的趋势;垂向上,潮间带表层45 cm以下主要为粉砂质砂和粘土质粉砂的互层沉积,向上,渐变为细砂或极细砂,显示向上变粗、分选性变好的趋势.这一向北、向上变粗、分选变好的总趋势,是近半个世纪以来因海河防潮闸的修建而使河流泥砂输运能力降低、近岸海洋影响增强的海河三角洲退化的现代过程的反映.     

应用模糊综合评判原理评价安全煤柱的留设

勘探阶段如何定量评价在厚度较大的新生界下采煤时,如何确定留设安全煤柱的水文工程地质条件,目前尚无完善的方法。以新郑矿区煤田地质勘探获取的水文地质及工程地质资料为例,选取新生界底部含水层、隔水层、风化带、煤层上覆岩组的水文地质及工程地质特征及区域地应力状态五个指标,采用模糊综合评判方法,对矿区留设安全煤柱的水文地质及工程地质条件进行综合评价。评价结果表明:研究区安全煤柱留设条件的优良级得分为48分,中等级得分为33分,较差级得分为19分,表明该矿二1煤层留设安全煤柱的水文地质及工程条件较好。研究结果可为矿区留设安全煤柱提供参考。