保温水泥在中低温地热井中的应用及建议

中低温地热资源开采过程中井口水温较储层温度明显降低,资源浪费严重.本文提出在固井过程中引入保温水泥的方法,以期提升井口水温和地热资源利用效率.选用多层圆筒传热模型,模拟计算了保温水泥在不同使用条件下的保温效果.结果表明,保温水泥的使用能明显提高热水达到抽水泵的温度,且井径越大、井底温度越高、井深越大、使用开次越多,保温...     

煤系高岭石—醋酸钾复合体的热行为

用煤系高岭石与醋酸钾合成夹层复合体，并利用热分析（TA）、红外光谱（IR）和X射线衍射（XRD）等手段研究其热行为特征。夹层复合体在低于300℃左右的条件下相当稳定，当温度进一步升高，夹在高岭石层间的醋酸钾就会发生熔化，在此阶段脱羟基作用发生。复合体脱羟基所需的温度比纯高岭石发生同样作用所需的温度要低得多。红外光谱研究发现，高岭石复合体中不同性质羟基团的脱羟基作用的发生遵循着一个固定的顺序。     

Fluid evolution and thermal structure in the rapidly exhuming gneiss complex of Namche Barwa–Gyala Peri, eastern Himalayan syntaxis

High‐grade gneisses (amphibolite–granulite facies) of the Namche Barwa and Gyala Peri massifs, in the eastern Himalayan syntaxis, have been unroofed from metamorphic depths in the late Tertiary–Recent. Rapid exhumation (2–5 mm year^?1) has resulted in a pronounced shallow conductive thermal anomaly beneath the massifs and the intervening Tsangpo gorge. The position of the 300 °C isotherm has been estimated from fluid inclusions using CO₂–H₂O immiscibility phase equilibria to be between 2.5 and 6.2 km depth below surface. Hence, the near‐surface average thermal gradient exceeds 50 °C km^?1 beneath valleys, although the thermal gradient is relatively lower beneath the high mountains. The original metamorphic fluid in the gneisses was >90% CO₂. This fluid was displaced by incursion of brines from overlying marine sedimentary rocks that have since been largely removed by erosion. Brines can exceed 60 wt% dissolved salts, and include Ca, Na, K and Fe chlorides. These brines were remobilized during the earliest stages of uplift at >500 °C. During exhumation, incursion of abundant topography‐driven surface waters resulted in widespread fracture‐controlled hydrothermal activity and brine dilution down to the brittle–ductile transition. Boiling water was particularly common at shallow levels (<2.5 km) beneath the Yarlung Tsangpo valley, and numerous hot springs occur at the surface in this valley. Dry steam is not a major feature of the hydrothermal system in the eastern syntaxis (in contrast to the western syntaxis at Nanga Parbat), but some dry steam fluids may have developed locally.     

Conditions of contact metamorphism, Papoose Flat Pluton, eastern California, USA: implications for cooling and strain histories

Abstract Petrological study of highly strained carbonate and pelitic rocks within the contact aureole surrounding the western part of the Papoose Flat pluton yields thermal profiles (plots of metamorphic temperature versus distance) across the aureole that show temperature gradients which are relatively flat and narrow (<100m). The gradients occur close to the contact and indicate a slight decrease in temperature from 500–550°C at the pluton/wall rock contact to 450–500°C at the outer margin of the aureole. One thermal profile across low-strain metasedimentary rocks located in the southern part of the aureole shows that thermal effects from emplacement extend no further than 600 m from the contact. Coexistence of andalusite and cordierite in pelitic rocks of the aureole constrain pressures to <4 kbar. Thermal modelling using an analytical solution of the conductive heat flow equation for a rectangular-shaped pluton reproduces the observed thermal maxima and profile shape. Conductive rather than convective cooling also is supported by isotopic and field evidence for limited fluid flow along the strongly deformed margin of the pluton. Simple thermal models coupled with observed high-temperature deformation features and a measured 90% attenuation of stratigraphic units in the plastically deformed western part of the pluton's aureole indicate that strain rates may have been of the order of 10^-12s^-1. Evidence for episodic heating, such as two distinct generations of andalusite growth in pelites from the aureole, alternatively may indicate a longer heating event and, therefore, slower strain rates. Thermal models also indicate that parts of the pluton still may have been above the solidus during deformation of the pluton margin and aureole.     

A hybrid near-field/far-field thermal discharge model for coastal areas

A hybrid technique has been used to simulate the dispersion of heat from surface discharges in coastal areas. Characteristics of the near field thermal dispersion are described by the CORMIX3 model. A two-dimensional harmonic finite element hydrodynamic model (TEA) and a Eulerian–Lagrangian transport model (ELA) are applied for the far-field computation. A Gaussian puff algorithm in ELA, which represents the near field plume as a series of patches, is used to link the two regimes. The computed results are compared to available field measurements. Very reasonable agreement is observed.     

Detecting climate change effects on forest ecosystems in Southwestern Romania using Landsat TM NDVI data

Nowadays, Southwestern Romania faces a large-scale aridization of the climate, revealed by the rise of temperatures and the decline of the amount of precipitations, with negative effects visible, among others, in the desiccation of forest vegetation. The present study means to identify the changes that occurred, quality-wise, in the past two decades （1990-2011） in forest vegetation in Southwestern Romania, and to establish the link between those changes and extant thermal stress in the region, whose particular features are high average annual and seasonal temperatures. In order to capture the evolution in time of cli- mate aridization, a first step consisted in using climate data, the temperature and precipitation parameters from three weather stations; these parameters were analyzed both individually and as aridity indexes （De Martonne and UNEP）. In order to quantify the changes in forest vegetation, NDVI indexes were used and analyzed, starting off from Landsat satellite images, acquired at three distinct moments in time, 1990, 2000 and 2011. In order to identify the link between the changes of NDVI index values and regional thermal stress, a yardstick of climate changes, statistical correlations were established between the peak values of average annual temperatures, represented in space, and negative changes in the NDVI index, as revealed by the change-detection analysis. The results obtained indicated there is an obvious （statistically significant） connection between thermal stress and the desiccation （degradation） of forest species in the analyzed area, with false acacia （Robinia Pseudoacacia） the main species to be impacted.     

中国煤层气资源控制程度及可靠性分析

查明深部煤层气成因和地球化学特征对其勘探开发具有重要意义,以鄂尔多斯盆地东缘临兴−神府区块深部煤层参数井解吸气为研究对象,系统测试了二叠系下统太原组8+9号煤层气体成分、含量和碳同位素等,结合热演化程度、含气性、煤层埋深、地质构造和水文地质条件等,分析深部煤层气地球化学特征及影响因素。结果表明,煤层气主要成分包括CH₄、CO₂ 、N₂ 、 乙烷、 丙烷 、异丁烷、 正丁烷、 异戊烷和 正戊烷,其中CH₄含量最高,体积分数在75.98%~96.20%,平均86.49%;其他含量较高的为乙烷(平均5.97%)、CO₂ (平均5.18%)及丙烷 (平均1.24%),气体成分含量与浅部煤层气区块无明显差异。煤层气δ¹³C₁(CH₄)分布在−51.9‰~−38.2‰,平均−42.84‰;δ¹³C_CO2分布在−8.6‰~−0.63‰,平均−4.66‰;δ¹³C₂分布在−27.36‰~−18.70‰,平均−25.27‰;δ¹³C₃分布在−25.96‰~−14.69‰,平均−22.93‰,且煤层气主要为热成因气体;δ¹³C₁(CH₄)较浅部小,δ¹³C_CO2较浅部大。在平面上,从临兴地区东南向西北δ¹³C₁呈增大趋势。从石炭纪起直到三叠纪末,研究区一直处于沉降状态;中侏罗世和早白垩世为主要生烃期,中侏罗世生烃持续时间较长,平均生烃速率较小,生烃产率一般;早白垩世生烃速率较大,生烃产率增加值较高,生气强度达到历史最大,是主要的生烃期。受气体分馏作用、储层孔裂隙发育特征、储层压力以及煤层顶底板密封性的控制,δ¹³C₁随着镜质体最大反射率(R_max)、含气量和埋深的增加而增加;在向斜核部区、断层应力集中区和褶皱两翼发育区的δ¹³C₁值相对较大;在断层应力释放区和背斜核部δ¹³C₁相对较大,这表明该区域的煤层气封存条件较差,不利于煤层气富集;受地下水溶解的影响,在水动力条件较强的地区δ¹³C₁值较小;在弱流体动力学或滞流区δ¹³C₁没有明显的变轻趋势。综合煤层气地球化学指标认为,临兴和神府地区东南部煤层气富集,且前者更有利,这对后期煤层气选区布井提供参考。

     

我国陆区地壳生热率分布与壳幔热流特征研究

壳幔热流配分代表了一个地区的深部热量来源与最基础的地热背景,为区域地热资源的形成提供了重要的约束条件.本文依托CRUST1.0模型与地质资料,将中国陆区在平面上划分为19个构造区,在垂向上将这些区域从第四系沉积物至上地幔的地层划分为8个圈层,确定了这些圈层的分布范围和厚度.在全国范围内实测放射性生热率数据664组,收集地壳放射性生热率及U、Th、K元素含量数据约1000组,系统地完成了上述区域各圈层的放射性生热率填图,统计得出我国陆区上、中、下地壳生热率的平均值分别为1.31 μW·m^-3、0.57 μW·m^-3与0.22 μW·m^-3.在此基础上,结合最新的全国大地热流测量数据（1503组）完成了我国陆区地壳-地幔热流分布的研究.研究结果表明,我国陆区q_c/q_m>1的面积占80.1%、q_c/q_m>1.2的面积占65.8%.除我国东部、中部的一些盆地之外,在我国陆区大部分地区,地壳均为大地热流的最主要热源.地壳各圈层中,基底层至中地壳为地壳的主要的产热区域,贡献了平均约50%的大地热流值.本文以面积加权计算得我国陆区地壳热流平均值为39.1 mW·m^-2,其中青藏高原最高、东南沿海次之,两者分别得益于较大的地壳厚度与较高的基岩地层生热率.我国陆区地幔热流平均值为29.7 mW·m^-2,与全球地幔热流平均值接近,其中东部沿海地区、环鄂尔多斯地区、藏滇地热带分布区较高.地壳热流、地幔热流的高值区与我国的主要地热资源分布区均具有较好的一致性.

     

长三角地区城市用地扩展及城乡热环境的特征分析

利用1993年和2004年长三角地区的卫星遥感资料,分析了该地区的3个主要区域南京、上海、苏锡常及其周边的土地利用类型变化,定量地评价城市用地扩展程度.结合2004年地表温度(LST)卫星资料,揭示了城乡LST空间分布特征及其差异.结果表明:上海、苏锡常和南京11a期间城市建设用地动态度K分别为204.0%、354.3%和99.2%,苏锡常城市扩展程度最快;不同土地覆盖类型的LST不同,城市用地LST最高,其次作物地,林地最低;城乡之间平均地表温差具有季节变化,冬季最大,而秋季最小.     

Study on the geochemical correlation of crude oils of Palaeocene and Jurassic ages from the Potowar Indus Basin in northern Pakistan

This study deals with a detailed geochemical characterization of three crude oils from the Upper Indus Basin, Punjab, Pakistan. The samples were obtained from three productive oil fields of the Datta Formation (Jurassic), Lochhart (Palaeocene) and the Dhak Pass zone (Palaeocene). The GC parameters for and the bulk properties of Datta Formation oils are essentially coincident with those of the oils from the Dhak Pass Formation in the Upper Indus Basin, Pakistan and the oils likely originate from a marine source rock. In contrast, the Lockhart Formation oils show different behaviors and seem to be originated from dirty carbonate rocks although all three crude oils are mature, being of non-biodegraded and somewhat mixed organic matter origin. Low Pr/Ph values and high C₃₅ homohopane index for the Lockhart Formation oils suggest a source of anoxic environment with low Eh while oils from the Datta Formation and Dhak Pass Formation showed different trends, i.e., lower values of C₃₅ homohopane index indicating different depositional environment than oil from the Lockhart Formation. All three crude oils from the Upper Indus Basin are mature for the hopane ratios, i.e., Ts/Ts+Tm, C₃₂22S/(S+R) and C₃₀ αβ/(αβ+βα) and sterane ratios, i.e., C₂₉22S/(S+R) and C₂₉ββ/(ββ+αα) but oils from the Lockhart Formation seem to be less mature than those from the Palaeocene and Datta Formation according to plots like API° vs. homohopane Index, Pr/Ph vs. sterane. The relative composition of 5α(H), 14β(H), 17β(H)-24-ethylecholestanes and the C₂₉20S/20S+20R index, indicate that all three crude oils are equally mature, which makes it unlikely with respect to the above said plots. This difference is may be due to the migratory chromatography which alters the concentrations of sterane and hoapnes and hence gives different results. These oils do not exhibit UCM and have complete n-alkane profiles indicating non-biodegradation.