位移不连续模型在黏弹性节理刚度计算的应用

考虑节理质量对应力波传播的影响,运用波的位移位函数推导了谐波在厚黏弹性节理的透、反射系数计算公式,采用波形相关系数描述子波穿过黏弹性节理的波形变化,讨论具有一定厚度的黏弹性节理简化位移不连续模型的适用条件。设厚黏弹性节理模型和位移不连续模型的透射波波形相关系数为0.9时对应的节理厚度为临界厚度,岩体与节理的阻抗比对临界厚度的影响很小;临界厚度随子波中心频率增大呈负指数减小,入射角越大,临界厚度随中心频率减小得越慢。试验数据分析表明：当节理厚度为0.03 m时,采用位移不连续模型和厚黏弹性模型计算得到的节理力学参数非常接近,随节理厚度和子波中心频率增加,运用位移不连续模型的计算结果偏差越大,试验结果与理论分析是一致的。     

航海用DDM向非航海用转换时的整体偏差补偿方法

针对航海用数字水深模型（DDM）向非航海用转换这一问题,提出了一种用整体偏差值补偿来提高转换精度的方法。首先建立航海用DDM整体性偏差值与海底地形复杂因子、海图比例尺之间的关系;其次依据上述关系预先推算航海用DDM的整体偏差值;最后将整体偏差值补偿到转换前的航海用DDM的模型点上,以提高转换后的非航海用DDM精度。试验证明：①所提的方法可行,可提高转换后非航海用DDM的精度;②转换后非航海用DDM精度提高的程度与海底地形复杂因子和海图比例尺有关。     

三峡大坝运行后长江中下游流域气温与植被变化特征及原因分析

基于长江中下游流域120个气象站点1971-2015年日值气温数据,2006-2015年ERA-Interim土壤湿度再分析资料和2006-2015年MODIS卫星遥感植被指数产品MOD13A3,研究了在考虑全球变暖背景下,长江中下游流域春、夏、秋、冬4个季节平均气温在三峡大坝运行前后的变化,采用百分比阈值方法量化最高和最低气温并进行MK突变检验,并分析三峡大坝运行后的长江中下游流域四季土壤湿度和增强型植被指数（EVI）的变化。结果表明：长江中下游流域四季平均气温在三峡大坝运行以后出现明显变化,江南地区主要出现增温现象,江北地区主要出现降温现象;MK突变检验结果显示,江南地区的高温日和江北的低温日均在2006年左右发生突变,与三峡大坝完全运行的时间相符;长江中下游流域土壤湿度在三峡大坝运行后出现南湿北干的变化趋势;EVI在江南地区诸多区域出现显著增加趋势,其中冬季最突出（33.06%）,而江北地区诸多区域则出现显著减小趋势,其中夏季最明显（5.11%）,EVI与平均气温的空间变化在春、夏、冬3个季节显著相关。     

牛D1井复杂构造带绳索取心钻探工艺技术研究

复杂构造带的绳索取心钻探易发生井漏、井塌以及取心困难等难题,处理不当甚至可导致井眼报废。结合牛D1井实例,介绍了绳索取心钻探工艺在复杂地层所遇的施工难点,并分析诱发井漏、井塌以及取心困难的原因,指出常规防塌堵漏技术不能满足复杂构造带钻探施工原因,提出优选钻井液、优化钻具组合以及改进堵漏工艺等现场可操作的具体改进措施。总结的施工经验可为今后复杂构造带绳索取心钻探施工提供宝贵经验。     

塞内加尔盆地成藏组合划分与资源潜力评价

西非塞内加尔盆地是全球近期油气勘探最活跃的前缘盆地之一。基于盆地最新的油气藏数据和勘探成果,应用石油地质综合研究和含油气系统分析的方法,研究了塞内加尔盆地的油气分布规律和主控因素,以成藏组合为评价单元,评估了待发现油气可采资源量,并探讨了盆地油气资源潜力和未来的勘探领域。研究表明,盆地发育3套含油气系统,志留系含油气系统、盐下三叠系含油气系统和白垩系含油气系统,白垩系含油气系统是最重要的含油气系统。区域上,盆地的油气主要分布于毛里塔尼亚次盆和北部次盆;层系上,油气主要储集于上白垩统赛诺曼阶、下白垩统阿尔比阶和中新统;埋深上,盆地油气储量集中分布于1 500~2 000 m和2 000~2500 m。油气富集的主要控制因素是生储盖的有效配置、优质的储层和圈闭及盐活动。资源评价结果表明,塞内加尔盆地待发现石油、天然气和凝析油的可采资源量分别为1 5083×106 bbl、363 Tcf(万亿立方英尺)和3270×106 bbl,合计7 8879×106 boe油当量,最具勘探潜力的成藏组合是上白垩统赛诺曼阶成藏组合和下白垩统阿尔比阶成藏组合。     

Improvement of very soft ground by a high-efficiency vacuum preloading method: A case study

This paper describes a full-scale test on a very soft clay ground around 70,000?m², which is conducted in Huizhou of Guangdong Province, China, to present a new method of vacuum preloading method. A novel moisture separator was developed, which can automatically regulate the vacuum pressure variation by changing the volume of the gas inside it. A large quantity of water drained by the proposed moisture separators can be directly used as a surcharge loading, which would shorten the ground improvement time and save costs as well. Three levels of silt-prevention prefabricated vertical drains were used in the treating process to accelerate the consolidation. In addition, the vacuum preloading method also included an effective radial drainage device which would strengthen the dredged soft clay fill in a deep layer. In the in situ test, tens of piezometers and settlement plates were installed to measure the variations of excess pore water pressures and settlement of two stages of observation points at different positions in the ground. The results show that the largest average consolidation settlement was 314.1?cm and made a saving of more than 66% in power consumption compared with traditional method. It demonstrates that this adopted method is an efficient, cost-effective, and environmentally friendly method for improving sites with low bearing capacity and high compressibility soils.     

四川乌依铅矿床成矿物质来源:硫、铅同位素和方铅矿稀土元素地球化学制约

四川布托县乌依铅矿床是川滇黔相邻区赋存于奥陶系大箐组地层中的典型密西西比河谷型矿床之一,其成矿物质来源仍不清楚。本文开展了方铅矿和石膏硫同位素及方铅矿稀土元素地球化学研究,获得方铅矿硫同位素δ~(34)S平均值为-4.04‰(n=31),石膏δ~(34)S平均值为29‰(n=15)。方铅矿稀土元素地球化学表明,轻稀土富集,重稀土明显亏损,稀土配分模式曲线大致向右倾,Eu正异常和Ce负异常。结合前人的硫、铅同位素数据,认为乌依铅矿床硫来源于细菌还原地层中硫酸盐所产生的硫,矿石铅来自上地壳,成矿物质来源为奥陶系大箐组,与峨眉山玄武岩无关。     

Evolution Mechanism and Rainfall Warning Criteria for Maijianwo Slope in Henan Province,China

In this study, two different research methods are applied to investigate the evolution mechanism and rainfall warning criteria for Maijianwo slope located in Henan Province, China. On the one hand, an indoor-model test is performed under artificial rainfall and based on similarity theory. A set of monitoring system is utilized to track the moisture content, deformation and cracks of critical points of the model during the test. On the other hand, the numerical simulation is carried out to provide an insight into the variation of unstable zone and factor of safety for the landslide with the increasing cumulative rainfall. Results indicate that the evolution process of Maijianwo slope is composed of three stages of initiating, accelerating and failure respectively, and stability of slope decreases gradually as cumulative rainfall increases. Based on the evolution mechanism of retrogressive landslide verified by both model test and numerical simulation, cracking time of critical positions on the slope prior to each stage were set as the initiating time of each stage and the cumulative rainfall associated with each initiating time (E₁ = 75 mm, E₂ = 180 mm) has been defined as the warning criteria for the Maijianwo slope. As the cumulative rainfall in Maijianwo slope reaches 75 and 180 mm, the landslide orange and red warning codes are issued, respectively. Otherwise, the slope is in a safe condition when the cumulative rainfall is less than 75 mm.     

Probability distribution method based on the triple porosity model to identify the fluid properties of the volcanic reservoir in the Wangfu fault depression by well log

Due to the powerful anisotropy of the physical properties of volcanic reservoirs, their component minerals and pore configuration are very complex, rendering fluid identification very difficult. This paper first computed the cementation exponent, which was based on triple porosity model, then used the varied matrix density and matrix neutron to compute the porosity, and finally combined with resistivity well log, and a P ^1/2 probability distribution curve was built. The fluid properties were predicted from the shape of the P ^1/2 probability distribution curve. Good results were achieved when these methods were used in the volcanic reservoir of the Wangfu fault depression, which indicated that these methods can be used in the fluid property identification of volcanic reservoirs and can also be referred to for other lithology reservoirs.     

Numerical simulation to quantify the leakage risk in a multi-layer aquifer system of pure brine recovery and CO<Subscript>2</Subscript>-enhanced brine recovery: a case study of potassium-rich brine recovery in Jianghan Basin of China

Deep brine recovery enhanced by supercritical CO₂ injection is proposed to be a win–win method for the enhancement of brine production and CO₂ storage capacity and security. However, the cross-flow through interlayers under different permeability conditions is not well investigated for a multi-layer aquifer system. In this work, a multi-layer aquifer system with different permeability conditions was built up to quantify the brine production yield and the leakage risk under both schemes of pure brine recovery and enhanced by supercritical CO₂. Numerical simulation results show that the permeability conditions of the interlayers have a significant effect on the brine production and the leakage risk as well as the regional pressure. Brine recovery enhanced by supercritical CO₂ injection can improve the brine production yield by a factor of 2–3.5 compared to the pure brine recovery. For the pure brine recovery, strong cross-flow through interlayers occurs due to the drastic and extensive pressure drop, even for the relative low permeability (k = 10^?20 m²) mudstone interlayers. Brine recovery enhanced by supercritical CO₂ can successfully manage the regional pressure and decrease the leakage risk, even for the relative high permeability (k = 10^?17 m²) mudstone interlayers. In addition, since the leakage of brine mainly occurs in the early stage of brine production, it is possible to minimize the leakage risk by gradually decreasing the brine production pressure at the early stage. Since the leakage of CO₂ occurs in the whole production period and is significantly influenced by the buoyancy force, it may be more effective by adopting horizontal wells and optimizing well placement to reduce the CO₂ leakage risk.