Note on the evolution of a Miocene composite volcano in an extensional setting, Zârand Basin (Apuseni Mts., Romania)

Bontâu is a major eroded composite volcano filling the Miocene Zârand extensional basin, near the junction between the Codru-Moma and Highi?-Drocea Mountains, at the tectonic boundary between the South and North Apuseni Mountains. It is a quasi-symmetric structure (16–18 km in diameter) centered on an eroded vent area (9×4 km), buttressed to the south against Mesozoic ophiolites and sedimentary deposits of the South Apuseni Mountains. The volcano was built up in two sub-aerial phases (14–12.5 Ma and 11–10 Ma) from successive eruptions of andesite lava and pyroclastic rocks with a time-increasing volatile budget. The initial phase was dominated by emplacement of pyroxene andesite and resulted in scattered individual volcanic lava domes associated marginally with lava flows and/or pyroclastic block-and-ash flows. The second phase is characterized by amphibole-pyroxene andesite as a succession of pyroclastic eruptions (varying from strombolian to subplinian type) and extrusion of volcanic domes that resulted in the formation of a central vent area. Numerous debris flow deposits accumulated at the periphery of primary pyroclastic deposits. Several intrusive andesitic-dioritic bodies and associated hydrothermal and mineralization processes are known in the volcano vent complex area. Distal epiclastic deposits initially as gravity mass flows and then as alluvial volcaniclastic and terrestrial detritic and coal filled the basin around the volcano in its western and eastern part. Chemical analyses show that lavas are calc-alkaline andesites with SiO₂ ranging from 56–61%. The petrographical differences between the two stages are an increase in amphibole content at the expense of two pyroxenes (augite and hypersthene) in the second stage of eruption; CaO and MgO contents decrease with increasing SiO₂. In spite of a ～4 Ma evolution, the compositions of calc-alkaline lavas suggest similar fractionation processes. The extensional setting favored two pulses of short-lived magma chamber processes.     

树轮记录的贺兰山北部5—7月PDSI变化

利用采自贺兰山北部3个采样点的油松树轮样本,建立了区域树轮宽度年表。相关分析发现,5—7月的帕尔默干旱指数(PDSI)与区域树轮宽度差值年表(RES)具有良好的相关性。因此,利用RES重建贺兰山北部1759—2005年来5—7月的PDSI变化,重建方程的方差解释量达47.90%,且方程稳定。贺兰山北部5—7月的PDSI重建序列平均值为-0.41。重建结果揭示了20世纪20年代干旱事件和19世纪后期、20世纪中期两个显著湿润期的存在。     

塔克拉玛干地区近四十年来的干湿变化

本文利用塔克玛干,周围山区、及相邻地区的４８个气象站近４０年的降水资料,分析塔克拉玛干地区年与四季干湿变化的阶段与周期,与与周围山区及相邻地区进行相关性分析。     

Fluid Property Discrimination in Dolostone Reservoirs Using Well Logs

The Ordovician Majiagou Formation is one of the main gas-producing strata in the Ordos Basin,China.The identification of hydrocarbon-bearing intervals via conventional well logs is a challenging task.This study describes the litholog of Ma 5(Member 5 of Majiagou Formation)dolostones,and then analyzes the responses of various conventional well logs to the presences of natural gas.The lithology of the gas bearing layers is dominantly of the dolomicrite to fine to medium crystalline dolomite.Natural gas can be produced from the low resistivity layers,and the dry layers are characterized by high resistivities.Neutron-density crossovers are not sensitive to the presences of natural gas.In addition,there are no significant increases in sonic transit times in natural gas bearing layers.NMR(nuclear magnetic resonance)logs,DSI(Dipole Sonic Imager)logs and borehole image logs(XRMI)are introduced to discriminate the fluid property in Majiagou dolostone reservoirs.The gas bearing intervals have broad NMR T_2(transverse relaxation time)spectrum with tail distributions as well as large T_(2gm)(T_2 logarithmic mean values)values,and the T_2 spectrum commonly display polymodal behaviors.In contrast,the dry layers and water layers have low T_(2gm) values and very narrow T_2 spectrum without tails.The gas bearing layers are characterized by low V_p/V_s ratios,low Poisson’s ratios and low P-wave impedances,therefore the fluid property can be discriminated using DSI logs,and the interpretation results show good matches with the gas test data.The apparent formation water resistivity(AFWR)spectrum can be derived from XRMI image logs by using the Archie’s formula in the flushed zone.The gas bearing layers have broad apparent formation water resistivity spectrum and tail distributions compared with the dry and water layers,and also the interpretation results from the image logs exhibit good agreement with the gas test data.The fluid property in Majiagou dolostone reservoirs can be discriminated through NMR logs,DSI logs and borehole image logs.This study helps establish a predictable model for fluid property in dolostones,and have implications in dolostone reservoirs with similar geological backgrounds worldwide.     

Acceleration Phase of Coronal Mass Ejections: I. Temporal and Spatial Scales

We study kinematics of 22 coronal mass ejections (CMEs) whose motion was traced from the gradual pre-acceleration phase up to the post-acceleration stage. The peak accelerations in the studied sample range from 40, up to 7000 m s⁻², and are inversely proportional to the acceleration phase duration and the height range involved. Accelerations and velocities are, on average, larger in CMEs launched from a compact source region. The acceleration phase duration is proportional to the source region dimensions; i.e., compact CMEs are accelerated more impulsively. Such behavior is interpreted as a consequence of stronger Lorentz force and shorter Alfvén time scales involved in compact CMEs (with stronger magnetic field and larger Alfvén speed being involved at lower heights). CMEs with larger accelerations and velocities are on average wider, whereas the widths are not related to the source region dimensions. Such behavior is explained in terms of the field pile-up ahead of the erupting structure, which is more effective in the case of a strongly accelerated structure.     

钻孔应变观测影响因素的数值模拟分析

利用有限元数值模拟方法,研究在非均匀地应力作用下,钻孔开挖前后区域应力场的变化特征,并探讨钻孔开挖后岩石、水泥、探头的弹性模量、泊松比及水泥的厚度与膨胀系数的变化对分量应变及面应变观测的影响。研究结果表明：钻孔开挖造成区域应力场扰动的范围大概为1.5倍孔径。在“探头 水泥环 围岩”系统中,各参数的变化对应变观测的影响程度不同,但分量应变对外界载荷的响应趋势基本一致。在均匀地应力作用下,水泥厚度对应变的影响与水泥的弹性模量有关,且随着水泥膨胀系数的增加,面应变存在减小的趋势。     

火山岩、白云岩储层基质孔隙度计算方法分析(英文)

火山岩、风化壳白云岩等缝洞储层基质孔隙度计算是测井评价亟需解决的难题之一.本文首先将全直径流纹岩声波实验公式(2005年,李宁)与国内外常用的基质孔隙度计算公式进行了细致的对比;进而就该公式在中基性火山岩、风化壳白云岩等缝洞储层中的适用性进行了深入讨论,并以岩心分析资料为基础,详细给出了该公式与其它公式在计算上述储层基质孔隙度时的误筹分布.误差统计结果表明该公式具有更高的精度.通过中国东部和西部三家油田70口井的实际应用验证,在孔隙度从1.5%到15%范围内,该公式不仅适用于酸性火山岩储层,而且适用于中基性火山岩、风化壳白云岩等缝洞储层基质孔隙度的评价.同时,该公式能够最大限度地减小扩径、岩石蚀变等复杂地质条件对计算结果的影响,实用性更强.     

新龙站近48年气温、降水量变化特征分析

新龙县位于青藏高原向四川盆地过渡面上,平均海拔3500m,研究新龙站的气候变化,对揭示青藏高原的气候有一定的参考价值。本文对新龙站1960~2007年气温和降水量资料进行了统计分析。结果显示:新龙站近48年平均气温略有上升的趋势,近10年处在一个较高的水平;冬季气温有上升趋势,夏季气温变化基本平稳;年平均气温有显著的15年左右的周期变化。降水量变化略有增加的趋势,无显著的年际和年代际变化特征,近年来强降水出现的频率增大。      

利用TDR100系统原位监测深厚包气带水热动态

利用标定后的TDR100系统原位监测太行山前深厚包气带（30.3 m）的土壤水热动态,根据2011、2012年2 a的监测结果,真实准确透析全剖面土壤水热运移规律。结果表明：厚度大、非均质并受控于多重外界条件的深厚包气带的水热运移,必然是相对滞后的复杂往复运动,水分补给滞后时间为2~3个月;粗颗粒层是良好的输水通道,而细颗粒层（如黏土层）才是决定入渗能力的关键层,对土壤体积含水量变化影响可达15%;浅层水热运移取决于降水蒸发和地表温度,5.0 m以下中深层水热运移常态取决于岩性和地下水位,而强降水入渗和人类活动产生瞬态关键效应。     

致密砂岩气层压裂产能及等级预测方法

致密砂岩储层孔隙度小、渗透率低、含气饱和度低,基本上没有自然产能,需要进行压裂,因此进行压裂产能的预测很有必要。笔者研究了鄂尔多斯盆地苏里格东部地区盒8段致密砂岩气层的压裂产能及等级预测。利用反映储层流动性质的测井参数(电阻率、自然伽马、声波时差、中子、密度)与反应压裂施工情况的压裂施工参数(单位厚度砂体积、砂比、砂质量浓度、单位厚度排量、单位厚度入井总液量),选择数学统计方法神经网络法进行致密砂岩气层压裂产能等级预测。分析比较Elman神经网络、支持向量回归(SVR)、广义回归神经网络(GRNN)3个神经网络预测致密砂岩气层压裂产能模型的网络结构参数、回判及预测精度以及运行耗费时间。结果表明:3个模型中,GRNN网络参数只有1个,回判和预测精度最高,运行时间小于1 s。因此,选择GRNN模型预测致密砂岩气层压裂产能,并用于苏里格东部地区致密砂岩气层压裂产能的等级预测。等级预测准确率达到90%。