苏里格大型致密砂岩气田储层结构与水平井提高采收率对策

在分析苏里格气田辫状河体系及储层结构特征的基础上,提出了剖面储量集中度的概念,建立了厚层块状型、垂向叠置泛连通型、分散局部连通型、分散孤立型4种砂体分布模式,探讨了不同储层结构下的水平井采出程度,提出了水平井提高采收率技术对策。研究结果表明,辫状河沉积体系复合有效砂体由于“阻流带”的存在,直井动用不完善,水平井能克服“阻流带”的影响,提高层内储量动用程度;但由于砂体多层状分散分布,水平井开发会导致纵向含气层系储量动用不充分,影响层间采出程度。对于剖面储量集中度高的厚层块状型、垂向叠置泛连通型储层,采用水平井整体开发,Ⅰ+Ⅱ类井比例达70%以上,可显著提高储量动用程度和采收率。对于剖面储量集中度低的分散局部连通型储层,采用直井井网开发后进行甜点式优选水平井井位加密部署,可提高采收率10%以上。     

PNN在煤田随钻测井岩性判识应用研究

介绍了PNN方法原理及其算法训练学习过程,详细阐述了网络识别岩性参数的选取、岩性识别模型的建立过程.通过对比研究PNN与其他6种岩性识别方法,分析相同条件下预测结果,得到不同识别方法的优劣性.经研究发现,PNN概率神经网络方法在生产应用中效果更佳、训练识别用时最短.利用人工智能神经网络对测井数据进行自动解释分析,可满足随钻测井时效性及快速解释处理的地质导向需求.     

Magnetic measurements in electrical prospecting by resistivity methods

The electrical resistivity and induced polarization (IP) methods are widely used in geological mapping, prospecting and exploration of mineral deposits, engineering geology, hydrogeology, archaeology, and geotechnical and environmental applications. Historically, these methods have formed the basis of the electrical prospecting technique. In these methods, a DC or low-frequency AC electrical current is introduced into the earth through a grounded transmitter line. The measured quantity is the electric field. However, if the earth’s resistivity or chargeability changes horizontally, this change gives rise to an anomalous magnetic field, which is studied by the magnetometric resistivity (MMR) and magnetic induced polarization (MIP) methods, respectively. Along with advantages, some shortcomings are inherent in the MMR and MIP techniques. Apparently, the main drawback of these methods is that the magnetic fields of both the transmitter line wire and ground electrodes on the surface are several orders of magnitude greater than the anomalous magnetic field response. This introduces a significant “noise” to magnetic-resistivity data. We investigate the potential of using a circular electric dipole (CED) in magnetometric resistivity techniques. It has been found that the application of a CED, instead of a conventional transmitter line, dramatically enhances the signal-to-noise ratio.     

Effect of 2D spatial variability on slope reliability: A simplified FORM analysis

To meet the high demand for reliability based design of slopes, we present in this paper a simplified HLRF(Hasofere Linde Rackwitze Fiessler) iterative algorithm for first-order reliability method(FORM). It is simply formulated in x-space and requires neither transformation of correlated random variables nor optimization tools. The solution can be easily improved by iteratively adjusting the step length. The algorithm is particularly useful to practicing engineers for geotechnical reliability analysis where standalone(deterministic) numerical packages are used. Based on the proposed algorithm and through direct perturbation analysis of random variables, we conducted a case study of earth slope reliability with complete consideration of soil uncertainty and spatial variability.     

Probabilistic stability analyses of undrained slopes by 3D random fields and finite element methods

A long slope consisting of spatially random soils is a common geographical feature. This paper examined the necessity of three-dimensional(3 D) analysis when dealing with slope with full randomness in soil properties. Although 3 D random finite element analysis can well reflect the spatial variability of soil properties, it is often time-consuming for probabilistic stability analysis. For this reason, we also examined the least advantageous(or most pessimistic) cross-section of the studied slope. The concept of"most pessimistic" refers to the minimal cross-sectional average of undrained shear strength. The selection of the most pessimistic section is achievable by simulating the undrained shear strength as a 3 D random field. Random finite element analysis results suggest that two-dimensional(2 D) plane strain analysis based the most pessimistic cross-section generally provides a more conservative result than the corresponding full 3 D analysis. The level of conservativeness is around 15% on average. This result may have engineering implications for slope design where computationally tractable 2 D analyses based on the procedure proposed in this study could ensure conservative results.     

Origin of natural sulfur-metal chimney in the Tangyin hydrothermal field,Okinawa Trough: constraints from rare earth element and sulfur isotopic compositions

For the first time, we present the rare earth element (REE) and sulfur isotopic composition of hydrothermal precipitates recovered from the Tangyin hydrothermal field (THF), Okinawa Trough at a water depth of 1206 m. The natural sulfur samples exhibit the lowest ΣREE concentrations (ΣREE= 0.65×10^–6–4.580×10^–6) followed by metal sulfides (ΣREE=1.71×10^–6–11.63×10^–6). By contrast, the natural sulfur-sediment samples have maximum ΣREE concentrations (ΣREE=11.54×10^–6–33.06×10^–6), significantly lower than those of the volcanic and sediment samples. Nevertheless, the δEu, δCe, (La/Yb)_N, La/Sm, (Gd/Yb)_N and normalized patterns of the natural sulfur and metal sulfide show the most similarity to the sediment. Most hydrothermal precipitate samples are characterized by enrichments of LREE (LREE/HREE=10.09–24.53) and slightly negative Eu anomalies or no anomaly (δEu=0.48–0.99), which are different from the hydrothermal fluid from sediment-free mid-oceanic ridges and back-arc basins, but identical to the sulfides from the Jade hydrothermal field. The lower temperature and more oxidizing conditions produced by the mixing between seawater and hydrothermal fluids further attenuate the leaching ability of hydrothermal fluid, inducing lower REE concentrations for natural sulfur compared with metal sulfide; meanwhile, the negative Eu anomaly is also weakened or almost absent. The sulfur isotopic compositions of the natural sulfur (δ³⁴S=3.20‰–5.01‰, mean 4.23‰) and metal sulfide samples (δ³⁴S=0.82‰–0.89‰, mean 0.85‰) reveal that the sulfur of the chimney is sourced from magmatic degassing.     

黔东地区航磁特征与岩性构造填图

为了弄清黔东深覆盖地区的成矿地质背景,以2014年该区1:5万比例尺的直升机航磁资料为基础,结合地质、重力等资料,研究了该区不同岩浆岩、断裂构造的航磁特征,在综合分析的基础上,编制了该区的岩性构造图。通过分析对比,本次新圈定具有一定规模的隐伏岩体7处、蚀变岩15处,新圈定不同规模的断裂17条 。上述成果对黔东地区基础地质研究和找矿工作具有重要意义。     

重力方法在祁连山地区构造特征与岩体解释中的应用

依据地质、航磁等资料,结合实测岩石物性资料,以1∶250 000重力资料为基础对祁连山地区(张掖、刚察地区)进行综合研究。研究地质构造与地球物理特征,划分了大地构造单元,探讨了隐伏与半隐伏岩体分布。该区域经多年的重力工作,勘探面积已近3万多km²,根据重力资料研究布格重力场特征并进行分区; 对地质构造单元重新划分,对主要断裂进行探讨; 圈定隐伏与半隐伏岩体,推断其空间展布特征,并对其解释。结果表明: 祁连山地区地壳密度结构横向分区、纵向分层明显,布格重力异常场的分区特征与地质构造分区特征基本一致。结合2.5D重力剖面反演印证了新的推测结果,为综合地质、地球物理找矿提供参考。     

改进的无网格法及其在冻土区桩基温度场中的应用

采用带权正交基函数对传统的无网格法中的基函数进行了改进,避免了计算过程中可能出现的矩阵不可逆情况,而且编程容易实现且计算效率高。并将其应用到冻土区桩基包括了热传导和相变潜热的温度场中,同时考虑了混凝土水化热释放对桩周冻土的影响,将计算结果和有限元计算结果及现场实测数据进行了比较分析,从趋势和最大数值看都反映了实测曲线的趋势,又把不同深度处桩侧和不同桩径处温度随时间的变化规律计算结果和有限元计算结果做了对比,都验证了该方法的可行性和优越性。     

辽宁赛马碱性岩体异性石化学成分特征及其蚀变组合对碱性岩浆-热液演化的指示意义

辽宁赛马碱性岩体早年因产铀矿而闻名,该岩体主要由响岩、霞石正长岩和异霞正长岩组成,其中铀、锆和稀土等元素矿化主要集中于异霞正长岩岩浆阶段。异性石是异霞正长岩中特征的锆-稀土矿物,主要分为两期,晚期异性石表现出更加富集Nb、REE等高场强元素的特点。早期异性石经历了一系列的热液蚀变,根据蚀变强弱程度,蚀变矿物组合可分为:(1)异性石+钠锆石+霓石±钠沸石;(2)异性石+钠锆石+锆石+钠沸石±霓石;(3)异性石假晶,假晶主要由残余异性石+钠锆石+锆石+钠沸石+霓石+钾长石+铈硅磷灰石组成。相比于岩浆锆石,蚀变组合中次生锆石具有富Ca、Al、Fe的特点,与异性石本身化学成分和流体性质密切相关。通过对异性石及其蚀变组合的精细矿物学研究,我们得知假晶的形成可能是异性石"溶解-再沉淀"的结果,致使假晶形成的流体至少包括:(1)占主导的富Na(±K)、Al、F的自交代流体;(2)少量晚期富Ca流体。假晶中次生锆石和铈硅磷灰石的结晶说明了Zr和REE等高场强元素的热液活动性,自交代碱性流体和富Ca流体在此过程中起到"搬运"和"提纯"的作用,这对认识碱性岩稀有、稀土成矿机制具有重要的指示意义。