Characterisation of likelihood of gas hydrates occurrence in the South China Sea based on Bonferroni mean-based TOPSIS and fuzzy set theory     

《地学前缘(英文版)》2023,14(2):101513

The efficiency of gas hydrate production depends on the success of gas exploration and occurrence evaluation. The existing evaluation models are generally univariate and only applicable to certain geological settings. This study presents a holistic approach to evaluate the likelihood of gas hydrate occurrence by supplying an index for mapping gas hydrate levels with depth. The approach integrates a generalised TOPSIS method with the fuzzy set theory. An expedition of gas hydrate conducted in the Shenhu area of the South China Sea was adopted as a case study to assess the reliability of the proposed index. As a multivariate model, the proposed approach enables the capture of non-linearity associated with gas hydrates in its entirety. The magnitude of the strength of the influential factor varies substantially from one site to another across the Shenhu area. The results also show that no site achieves the highest likelihood ‘Level V’. These results are consistent with the gas saturation values obtained using Archie’s relationship. For example, at SH4 and SH7, the values of the likelihood index are the highest between 170–185 m and 150–165 m, respectively, and the observed saturation at these locations varies from 20% (SH4) to 43% (SH7). The proposed likelihood index yields a prominent ability to quantify the level of occurrence of gas hydrates with depth at different sites. It appears to be an efficient multicriteria system bound to improve the management of the gas production trial stage.  相似文献   

基于Ka波段云雷达的六盘山顶云特征分析     

田磊  桑建人  姚展予  常倬林  舒志亮  曹宁 《气象与环境学报》2021,37(2):84-90

利用宁夏六盘山气象站2017年9月至2018年8月的Ka波段云雷达观测资料,统计分析了六盘山顶不同云的出现频率及宏观特征。结果表明：六盘山顶云出现频率最高值在7月,为61%,最低值在12月,为26%;按云层数划分,六盘山顶出现的云主要以1层云、2层云及3层云为主,相对总云的月平均出现频率分别为68%—86%、14%—27%及0.4%—4.8%;按云底高度及云层厚度划分,六盘山顶低云、中云、高云及直展云相对总云的月平均出现频率分别为29%—53%、14%—58%、6%—22%及2%—20%。云底高度在冬春季节高于夏秋季节,云顶高度在夏秋季节高于冬春季节,云层厚度为1.6—3.6 km,年变化特征与云顶高度类似。整体来看,春、夏、秋季云厚在白天大于夜间,冬季云厚在夜间大于白天,其中夏、秋季云厚日变化特征较为明显。  相似文献   

阜新排山楼金矿金的赋存状态     

张耀华  谷振东  陈为民 《国土资源》1993,(2)

排山楼金矿赋存在蚀变糜棱岩带内,金矿化发生在三类矿石中。矿石组成成分相对简单,有用矿物为自然金和银金矿,金矿物具有成色高、粒度细的特点。其赋存形式有三种,即晶隙金、裂隙金和包体金。晶隙金兼有单体和群体两种,单体金多属中粒金和细粒金。呈不规则粒状,群体金由几粒至几十粒构成,其粒度相对偏小,在群体金附近均有黄铁矿产出。裂隙金主要以长条状、角粒状充填在黄铁矿的裂隙中,包体金则作为黄铁矿、次为黄铜矿的包体金。本矿床金矿石的金矿物以晶隙金、裂隙金为主,包体金次之,这种存在形式的金矿物对于金矿的选冶是有利的。  相似文献   

Ordovician conodonts of the Tarim Region, Xinjiang, China: Occurrence and use as paleoenvironment indicators     

Wang Zhi-hao  Qi Yu-ping  Stig M. Bergstrm 《Journal of Asian Earth Sciences》2007,29(5-6):832-843

A review of the distribution of different Ordovician conodont faunas in eight areas of the Tarim Region shows that these conodont faunas can be classified into the North China and South China types. The North China type is characterized by Aurilobodus leptosomatus, A. aurilobodus, A. simplex, Tangshanodus tanshanensis, Loxodus dissectus, Parasseratognathus paltodiformis, Microcoelodus symmetricus, Belodina compressa, B. confluens, Pseudobelodina dispansa, Yaoxianognathus yaoxianensis, and Taoqupognathus blandus. These were adapted to shallow, warm-water environments. The South China type is represented by the genera Amorphognathus, Baltoniodus, Cahabagnathus, Eoplacognathus, Lenodus, Microzarkodina, Oepikodus, Paroistodus, Paracordylodus, Periodon, Polonodus, and Pygodus, which were adapted to outer shelf, deeper, and colder water environments. Using the general pattern of conodont distribution, it is possible to interpret the various depositional environments and to reconstruct broad changes in palaeogeography of the Tarim Region during Ordovician time. In general, during Tremadocian to early Middle Ordovician time, most of the Tarim Region was a shallow semi-restricted platform that became deeper towards the north and east, with an open platform in Kalping and in the northern part of Taklimakan Desert. A slope and deep basin existed in the current Tianshan Mountains region. The Tarim sea was shallow during the Early Ordovician and became deeper during “Caradocian” (Sandbian and Early Katian) time, to become shallow again during “Ashgillian” (Late Katian) time, with the exception of part of central Taklimakan, which was a land area during “Caradocian” (Sandbian and Early Katian) time.  相似文献   

基于泊松分布的地震烈度发生概率模型   总被引：10，自引：1，他引：10  

高孟潭 《中国地震》1996,12(2):195-201

地震烈度发生概率和地震烈度超越概率都是衡量场地地震危险性的重要指标，地震烈度发生概率的计算民是人们比较关注的问题之定。本文根据目前工程地震和地震减灾研究中比较常用的Ｃｏｒｎｅｌｌ类地震活动性模型和反映地震时，空，强非均匀性的地震活动性模型，推导了场地地震烈度发生概率和计算表达式，通过计算实例，讨论了其与场地地震烈度极值概率（即超越概率差，通常被用来替代地震烈率发生概率）的差异，认为在一般情况下，两  相似文献   

银家沟硫铁矿床伴生金的赋存状态初步研究   总被引：1，自引：0，他引：1  

洛长义  张树林 《西北地质科学》1998,19(2):41-45

初步认为银家沟硫铁矿床的伴生金主要以自然金形式赋存于黄铁矿中,粒度0．5～23μ,是包体金和裂隙金状态产出,含金达96．07％～96．37％．  相似文献   

雪峰山中段含金剪切带型金矿脉产状特征及成因浅析     

曹进良 《湖南地质》2001,20(3):189-192,224

雪峰山中段铲子坪和大坪等金矿区目前发现的岩金矿脉均赋存于剪切带中，说明剪切作用本身也就是成矿作用。通过剪切作用过程中的应力分析，发现剪切带中金矿脉走向与剪切带走向的交角遵循一定的数学关系，从而提出二者交角的数学表达式，该数学表达式推算出的理论值与实测值可以相互对照。  相似文献   

六盘山东麓断裂的古地震研究   总被引：4，自引：0，他引：4  

向宏发  池田安隆 《中国地震》1999,15(1):74-81,91

野外详细调查和探开挖揭示,在六盘山东麓断裂的孙家庄－海子峡地段自距今４．６万年以来存在有６次古地震位借事件的地质形迷,它们分别发生在距今３５２５０,２０２５０,１４７５０,１２１５０,８５５０和４０００年前,各次事件的重复间隔依次是１５０００,５５００,２６００,３６００和４５５０年。按Ｍ－Ｄ经验关系,事件１,２约相当于８级地震的位错,其余各次事件约相当６．５－７．５级地震的位错。  相似文献   

用向量法求矿脉产状   总被引：1，自引：0，他引：1  

李海全  于丽霞 《矿产与地质》1999,13(5):312-316

对板状似板状的矿脉,依据控制顶板（或底板）三个点的坐标,求出其所在平面的方程,该平面与水平的交线和Ｘ轴夹角即矿脉走向,平面与水平的夹角即为矿脉倾角,文末给出实例及计算程序。  相似文献   

10年尺度地震烈度发生概率预测方法     

高孟潭 《中国地震》1995,11(4):310-314

本文提出了一种利用１０年尺度地震危险性（地震发生概率的空间分布）预测结果进行１０年尺度地震烈度发生概率估计的方法。并用此方法计算了全国２３１６个城镇不同地震烈度（Ⅵ－Ⅹ）的发生概率。该结果可以用于相应时间尺度的地震损失预测、地震保险和防灾规划等。该方法也适用于利用短期地震预报结果（以预测单元地震发生概率表示），进行场地地震强度发生概率预测。  相似文献