Integrated geophysical methods for the characterisation of an archaeological site (Massenzio Basilica — Roman forum, Rome, Italy)

A geophysical study that involved different techniques was carried out with the aim to improve the knowledge of the archaeological site where the Basilica of Maxentius was founded and to discern individual covered structures (foundations).Vertical Electrical Sounding (VES), seismic refraction and Electrical Resistivity Tomography (ERT) studies were performed in the archaeological site. VES and seismic refraction allowed to characterise the main geological formations of the hill where the Basilica was built and to distinguish the concrete floor and backfilling. Electrical data were processed using different algorithms; their results were compared to appraise the inverted models' robustness.ERT inversion algorithms were used to delineate shape and size of a much more complex structure, that were originally expected from archaeological excavation plan. The results of the commercial program were used as a posteriori information to include them in the algorithm proposed by the authors; the sequential use of the programs defined a processing procedure.The integrated use of different geophysical techniques reduced a great deal the intrinsic ambiguities of each method. Direct explorations (boreholes and archaeological excavations) confirmed the geophysical results.     

新疆地下水资源开发利用现状及潜力分析

在分析研究开发利用现状的基础上,结合新疆地下水资源最新评价成果,对可开采量、超采区治理、潜力区开发布局等进行了系统研究,提出了地下水开发利用与保护的对策措施。特别强调了合理开发利用地下水资源,对于调解水资源供需矛盾、调控地下水位防治土壤次生盐碱化发生、提高水资源利用效率、保护生态环境的重要性。新疆2008年地下水开采量72.11亿m~3,远期随着水资源利用效率的提高和地下水转换补给量的减少,地下水可开采量宜控制在111亿m~3左右。总体看,地下水开发还有一定潜力,主要分布在南疆和外流河区。由于过去对地表水与地下水转化规律缺乏系统科学的研究,对大规模地下水开发缺乏及时的科学指导,上世纪80年代末部分地区开始出现地下水超采现象,吐哈盆地、天山北坡东中段、塔额盆地等地区已出现大面积的超采区,严重影响经济社会可持续发展和生态环境保护。     

利用微动勘察方法探测煤矿陷落柱

陷落柱是危害煤矿安全生产的主要因素之一,如何有效探测陷落柱是实现煤矿安全、高效生产的当务之急.本文首次将微动勘察方法应用于煤矿采区勘探,结果表明,该方法对陷落柱异常区反映敏感.在山西潞安漳村煤矿2002工作面测区已知陷落柱上,无论是单点反演获得的S波速度结构,还是微动视S波速度剖面,均能清晰显示陷落柱.微动剖面确定的陷落柱位置与巷道揭露位置一致,边界误差在10 m左右.微动勘察方法是探测陷落柱的一种行之有效的物探方法,由于其分辨率高、无需人工源、野外施工方法灵活便捷、不受施工场地限制等特点,对探测村庄覆盖区之下的煤层构造、圈定陷落柱等,具有得天独厚的技术优势和应用前景.     

综合地球物理方法在华南桂中海相残留盆地沉积相预测中的应用

沉积相研究是盆地隐蔽油气藏勘探中重要的研究内容之一,综合利用地球物理方法有效识别构造、岩性或沉积相差异是盆地隐蔽油气藏勘探的前提.本文基于重力、航磁、地震等综合地球物理资料,通过重磁异常正演剥离和剖面正反演拟合技术研究了华南桂中地区海相地层的密度分布特征,预测了岩相、沉积相的变化规律.研究发现,本区中、下泥盆统海相地层存在横向的岩性、岩相变化,研究区西北、东南部的台地相区重力异常高、岩石拟合密度值高;中部“X”型台地边缘相区重力异常杂乱、岩石拟合密度变化范围大;东部台沟相区重力异常低、岩石拟合密度值低.利用综合地球物理方法预测沉积相为盆地岩性圈闭油气藏和生物礁油气藏勘探提供了新的研究思路,研究成果已得到初步检验,但还有待进一步完善与实践.     

基于多元信息约束的隐伏矽卡岩型铁矿床的定位——以云南北衙金矿区红泥塘矿段为例

矽卡岩型矿床是云南北衙金多金属矿区的一种主要矿床类型,受岩体、构造及层位等控制,其有利找矿空间为中酸性岩体与碳酸盐岩的接触带.以岩石物性为纽带,实现目标地质体与地球物理场的转换,提取有效信息.接触带中低电阻率、岩体的低密度性、铁矿的高磁性和高极化率等都是矽卡型铁矿床的特有地球物理属性.通过地质地球物理等多元信息的层层约束,解析不同级次的成矿要素问题,实现对隐伏矽卡岩型铁矿床的定位,建立地球物理勘探模式,并在矿区外围开展方法有效性的验证,取得了良好的勘探效果,提出一套适应于北衙地区及类似成矿地质背景下的隐伏矽卡岩型铁矿床定位预测方法.     

磁性层状介质的CSAMT电场分量响应特征

在传统的勘探电磁学理论中,往往把岩层磁导率近似看成空气中的磁导率,从而得到简化后的电磁场响应式,主要用于指导非磁性介质情况下的电磁探测.本文开展了磁性介质的电磁响应理论、数值模拟和特征分析等研究,以便实现对磁性矿体的电磁精细探测.首先推导出磁性层情况下的电磁响应表达式;然后,计算了几种典型磁性介质地质断面的响应曲线,并对其响应特征进行了分析;研究结果表明:当磁性层位于地表时,当表层相对磁导率μr1.2,磁性层对电磁测深曲线具体明显的影响;当岩层为中间层时,只要μr1.2,对H型、A型曲线中段会有影响.对H型曲线,主要表现在使极小值处的曲线抬高、变宽,以致使曲线形态发生变化;当磁性层处于最后一层时,不论岩层的磁导率是多少,对各类二、三层曲线来讲,不会影响曲线的形态,只是使渐近线前第一个极值点的位置右移,极值点至渐近线之间的线段变得较为陡峭.     

高密度电法在乌鲁木齐西山断裂探测中的应用

西山断裂是乌鲁木齐河以西一条颇具规模的断裂构造,控制着西山岭南麓,断裂从永光煤矿到红光山南长约37 km。断裂形成于中更新世期间,但整条断裂的形成过程可能并非同步,具有西老东新的特点,最新活动时代为晚更新世中晚期,为逆冲运动性质,断面北倾。该断裂在四道岔附近主断层及发育的一部分次级断层被第四系覆盖,研究该隐伏段对于以后城市土层合理利用和断层基本特征判断具有一定意义。目前高密度电法是探测隐伏断层的一种重要的物探方法,通过高密度电法对乌鲁木齐西山断裂隐伏段的探测,确定该断层隐伏段的位置及地层构造形态,为西山断裂深入研究提供一定依据。     

城镇有限场地条件下的物探找水试验

为在城区强干扰环境、有限场地条件下进行物探方法找水,特利用等值反磁通瞬变电磁法,在湖南郴州市某城镇进行了野外试验。在地表调查和周边人文环境基础上,常规电测深等找水有效手段在城镇区域难以施工,面对这个难题利用等值反磁通瞬变电磁法进行试验,其利用对偶中心耦合装置消除了收发线圈感应耦合来消除干扰。首先根据地质信息设计了近似南北向的4条剖面,然后进行了发射频率试验并进行单点连续探测,最后利用探测结果绘制了多测道曲线和二维模拟断面等值线图并设计了钻孔。钻探验证结果表明:等值反磁通瞬变电磁法在强干扰、场地受限的城镇区域找水效果较好,是一种值得推广的新方法。     

Prospective prediction and exploration situation of marine Mesozoic-Paleozoic oil and gas in the South Yellow Sea

The South Yellow Sea Basin is a large sedimentary basin superimposed by the Mesozoic-Paleozoic marine sedimentary basin and the Mesozoic-Cenozoic terrestrial sedimentary basin, where no oil and gas fields have been discovered after exploration for 58 years. After the failure of oil and gas exploration in terrestrial basins, the exploration target of the South Yellow Sea Basin turned to the marine Mesozoic-Paleozoic strata. After more than ten years’ investigation and research, a lot of achievements have been obtained. The latest exploration obtained effective seismic reflection data of deep marine facies by the application of seismic exploration technology characterized by high coverage, abundant low-frequency components and strong energy source for the deep South Yellow Sea Basin. In addition, some wells drilled the Middle-Upper Paleozoic strata, with obvious oil and gas shows discovered in some horizons. The recent petroleum geological research on the South Yellow Sea Basin shows that the structure zoning of the marine residual basin has been redetermined, the basin structure has been defined, and 3 seismic reflection marker layers are traceable and correlatable in the residual thick Middle-Paleozoic strata below the continental Meso-Cenozoic strata in the South Yellow Sea Basin. Based on these, the seismic sequence of the marine sedimentary strata was established. According to the avaliable oil and gas exploration and research, the marine Mesozoic-Paleozoic oil and gas prospects of the South Yellow Sea were predicted as follows. (1) The South Yellow Sea Basin has the same sedimentary formation and evolution history during the sedimentary period of the Middle-Paleozoic marine basin with the Sichuan Basin. (2) There are 3 regional high-quality source rocks. (3) The carbonate and clastic reservoirs are developed in the Mesozoic-Paleozoic strata. (4) The three source-reservoir-cap assemblages are relatively intact. (5) The Laoshan Uplift is a prospect area for the Lower Paleozoic oil and gas, and the Wunansha Uplift is one for the marine Upper Paleozoic oil and gas. (6) The Gaoshi stable zone in the Laoshan Uplift is a favorable zone. (7) The marine Mesozoic-Paleozoic strata in the South Yellow Sea Basin has the geological conditions required to form large oil and gas fields, with remarkable oil and gas resources prospect. An urgent problem to be addressed now within the South Yellow Sea Basin is to drill parametric wells for the Lower Paleozoic strata as the target, to establish the complete stratigraphic sequence since the Paleozoic period, to obtain resource evaluation parameters, and to realize the strategic discovery and achieve breakthrough in oil and gas exploration understanding.©2019 China Geology Editorial Office.