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1.
During the calculation of the oil and gas resources of Western Siberia, especially in the sediments of the Tyumen Formation, the presence of thin nonreservoir clay intercalations must be accounted for. However, the resolution of standard geophysical methods that are used to identify productive sequences is insufficient, and the clay intercalations are included into the total thickness of reservoir rocks, which leads to considerable errors during resource assessment. The most efficient method for the estimation of clay mineral content in sedimentary rocks is the gamma method or gamma-ray well logging, which is typically used for this purpose. However, its application requires the knowledge of correlations between the abundance of clay minerals in the sediments; the contents of K, U, and Th; and total radioactivity. To solve this problem, four grain-size fractions (sand, coarse silt, fine silt, and clay) were separated from the sediments of the Tyumen Formation at the Lovin Field and were analyzed for naturally radioactive elements (NRE), total radioactivity, and mineral composition. The tendencies found in the distribution of NRE and total radioactivity in different grain-size fractions provided a methodical basis for the determination of clay mineral contents in the productive sediments of the Tyumen Formation at the Lovin Field using gamma-spectrometric data.  相似文献   

2.
【研究目的】不同页岩岩相的矿物组分、含气性和可压性等的差异,决定不同岩相的开发潜力不同,页岩岩相的划分及评价对找寻页岩气勘探开发甜点具有重要指导意义。【研究方法】基于钻井、岩心和分析测试资料,综合利用地质理论结合硅质矿物-黏土矿物-碳酸盐矿物含量三端元图解,对鄂西宜昌斜坡带上奥陶统五峰组—下志留统龙马溪组下段含气页岩岩相进行划分,结合有机碳含量、含气量、岩心镜下特征等划分优势岩相。优选有机质丰度、硅质矿物含量、黏土矿物含量3项指标与页岩含气量进行相关性分析,建立了五峰组—龙马溪组含气页岩优势岩相的分级标准。【研究结果】研究区优势岩相均为II类优势岩相,II1类（最优）优势岩相为S-2混合硅质页岩相和S-3含黏土硅质页岩相,位于龙马溪组一亚段和五峰组上段,厚6 m;II2类（次优）优势岩相为S硅质页岩相,位于五峰组下段,厚4 m。【结论】宜昌斜坡带和涪陵地区具有相似的岩相垂向演化序列,优势岩相均位于五峰组—龙马溪组一亚段,但同一岩相组合的页岩厚度和品质差异较大,发生在鲁丹阶早期的湘鄂西水下隆起和鲁丹阶晚期的水下隆起是造成宜昌地区优势岩相的厚度和品质均要差于涪陵地区的主要原因。创新点：建立五峰组—龙马溪组含气页岩优势岩相的分级标准,提出龙马溪组一亚段和五峰组是优势岩相发育层位。  相似文献   

3.
鄂尔多斯盆地延长组深水岩相发育特征及其石油地质意义   总被引：1，自引：0，他引：1  
鄂尔多斯盆地湖盆中部地区三叠系延长组长7油层组广泛发育深水沉积。沉积物的粒度、沉积结构与构造、有机地球化学等特征研究表明,深水沉积岩可划分为四种岩相类型,分别为油页岩岩相、暗色泥岩岩相、砂质泥岩与泥质砂岩岩相和砂岩岩相。其中,油页岩岩相有机碳含量高,有机质类型好,测井曲线具有高阻、高伽马、低电位和时差跳跃频繁等特征;暗色泥岩岩相具有富含有机质、中低阻、中高伽马、高密度和高时差等特征;砂质泥岩与泥质砂岩岩相具有中电阻、低伽马、高密度、时差跳跃频繁等特征,泥质含量 20~70%;砂岩岩相表现出低的电阻、时差和伽马、泥质含量小于20%的特征,并刻画了各种深水岩相的剖面发育特征。深水斜坡带和湖底平原区的岩相组合存在较大的差异。深水岩相对非常规油气资源意义重大,其中油页岩岩相和暗色泥岩岩相为盆地中生界主力烃源岩,深水砂岩岩相是盆地大规模致密油的重要储集体,砂质泥岩与泥质砂岩岩相、暗色泥岩岩相富含丰富的页岩油资源,也具有潜在经济价值。  相似文献   

4.
由于自然伽马能谱测井(NGS)的放射性元素U、Th、K的含量与粘土矿物有着密切的关系,所以可利用NGS定性或定量确定油气储层粘土矿物含量。阐述了自然伽马能谱测井资料在确定粘土矿物含量中的地质依据,建立了研究地层粘土矿物含量的计算模型。由研究油田的NGS测井资料计算并对比了粘土矿物的含量,最终得到很好的效果。  相似文献   

5.
滇黔北坳陷五峰组-龙马溪组下段页岩岩相与沉积环境   总被引：1，自引：0，他引：1  
滇黔北坳陷为南方海相地层的有利研究区域,发育多套海相页岩。上奥陶统五峰组与下志留统龙马溪组地层,尤其是五峰组-龙马溪组下段页岩作为优质烃源岩而备受重视。通过岩芯观察、薄片鉴定、X衍射分析及微量元素地球化学指标判识,对其进行页岩岩相划分与沉积环境分析。结果显示:滇黔北坳陷五峰组-龙马溪组下段地层共划分出六种页岩岩相:硅质页岩、黏土质页岩、钙质页岩、黏土质硅质混合页岩、黏土质钙质混合页岩、钙质硅质混合页岩,其中硅质页岩和黏土质页岩的TOC含量明显高于其余四种岩相。V/（V+Ni）、V/Cr、Ni/Co和U/Th指标指示五峰组-龙马溪组下段总体处于低能、滞留、局限条件,与深水陆棚环境匹配,Mo元素含量与四川盆地均值相当。五峰早期与龙马溪早期海侵的发生形成了以深水陆棚占主导的沉积格局,低能、滞留、局限的厌氧环境与快速海侵是有机质富集与保存的重要条件。  相似文献   

6.
The aim of the study is to assess the natural background radiation in and around Rameswaram Island. In this context, samples were collected to measure the gamma radiations of 238U, 232Th, and 40K using NaI(Tl) detector-based gamma ray spectrometer. The average activity concentrations of 238U, 232Th, and 40K are noted to be well below the world average values. The calculated absorbed dose rate, radium equivalent activity, and hazard index values were below the prescribed limit. The grain size of the sediment was analyzed following Trefethen’s nomenclature, and its correlation with the natural background radioactivity was studied. The sample that contained clay show elevated activity of 40K. The percentage of heavy minerals shows concomitant variation in natural radioactivity, especially in the activity of 238U and 232Th.  相似文献   

7.
柴北缘石炭系克鲁克组发育了一套厚层富有机质细粒沉积岩,是研究区页岩气勘探的主力层系。克鲁克组泥页岩形成于陆表海沉积环境,与深海富硅质泥页岩和湖相富碳酸盐泥页岩具有显著差异,目前研究程度相对较低,因此对其开展岩相与沉积环境研究具有十分重要的沉积学与油气地质学意义。通过野外露头和岩心观察,薄片鉴定、X射线衍射分析等技术,以区分标志明显、易于识别为主要原则,综合矿物组成、沉积构造、化石组合及其他混入物等因素,将柴北缘石炭系克鲁克组泥页岩划分出10种主要岩相类型,分别指示不同的沉积微环境。其中,煤岩、水平层理碳质黏土岩、透镜状层理粉砂质黏土岩、波状层理黏土质粉砂岩、脉状层理粉砂岩均属于潮坪沉积;富含菱铁矿结核的块状黏土岩为潟湖沉积;块状泥灰岩和块状生屑灰岩属碳酸盐台地沉积;而含介壳粉砂型泥岩和介壳型泥岩则属于潟湖与局限台地之间的过渡沉积,具有原地混积的特点。由于陆表海平缓的古坡脚,致使区内沉积体系受短期海平面升降变化影响显著,随滨线快速迁移,不同沉积环境的泥页岩在垂向上频繁叠置,交互出现,可总结出3种主要的岩相组合类型,分别形成于局限台地相潟湖相潮坪相组合,局限台地相潟湖相组合和局限台地相生物碎屑浅滩相组合。在泥页岩的岩相类型、特征、沉积环境及垂向演化序列研究的基础上,最终建立了陆表海泥页岩沉积模式。  相似文献   

8.
中东T油田灰岩储层自然伽马能谱测井的应用   总被引：1，自引：0，他引：1  
中东地区T油田主力含油储层受高放射性物质影响,导致利用常规自然伽马测井资料无法合理求取泥质含量。同时,由于岩芯分析资料较少,确定各主力含油储层的黏土类型就显得比较困难。针对这些问题,笔者基于自然伽马能谱测井中铀、钍、钾与地层中黏土矿物的密切关系,利用无铀伽马测井资料对泥质含量进行了合理计算,参考斯仑贝谢理论交会图版,利用钍与钾交会图法确定了黏土类型,通过制作钍与铀比值的直方图对沉积环境进行了研究,取得了较好的应用效果,为油田后期的开发提供了更加可靠的资料支持。  相似文献   

9.
Spectral gamma ray (SGR) logs are used as stratigraphic tools in correlation, sequence stratigraphy and most recently, in clastic successions as a proxy for changes in hinterland palaeoweathering. In this study we analyse the spectral gamma ray signal recorded in two boreholes that penetrated the carbonate and evaporate‐dominated Permian–Triassic boundary (PTB) in the South Pars Gasfield (offshore Iran, Persian Gulf) in an attempt to analyse palaeoenvironmental changes from the upper Permian (Upper Dalan Formation) and lower Triassic (Lower Kangan Formation). The results are compared to lithological changes, total organic carbon (TOC) contents and published stable isotope ( δ 18O, δ 13C) results. This work is the first to consider palaeoclimatic effects on SGR logs from a carbonate/evaporate succession. While Th/U ratios compare well to isotope data (and thus a change to less arid hinterland climates from the Late Permian to the Early Triassic), Th/K ratios do not, suggesting a control not related to hinterland weathering. Furthermore, elevated Th/U ratios in the Early Triassic could reflect a global drawdown in U, rather than a more humid episode in the sediment hinterlands, with coincident changes in TOC. Previous work that used spectral gamma ray data in siliciclastic successions as a palaeoclimate proxy may not apply in carbonate/evaporate sedimentary rocks. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

10.
以松辽盆地三肇凹陷松页油3井青山口组一段泥页岩为例,对其沉积构造、有机质丰度及矿物组成等岩石学特征关系进行研究.结果表明,三肇凹陷青一段泥页岩发育块状构造和纹层状构造两种沉积构造;TOC含量介于0.50%~6.82%,平均值为3.16%,S1+S2介于2.01×10-3~49.41×10-3,平均值为23.02×10-3,总体为好-最好的烃源岩;矿物组成以长英质矿物为主,黏土矿物次之,碳酸盐矿物、黄铁矿含量较低.基于岩石学特征研究,按照"有机质丰度-岩石沉积构造-矿物组成"分类标准,将青山口组一段划分为9类岩相,其中高有机质纹层状长英质泥页岩岩相具有较好的生烃潜力,是三肇凹陷页岩油勘探的最有利的岩相类型.  相似文献   

11.
《Applied Geochemistry》2005,20(3):611-625
This paper presents new data on the baseline concentrations of U, Th and K in 2389 stream sediments over the whole Campania region. These data, based on systematic sampling and analysis, are compared with those obtained by gamma-ray spectrometry surveys.Variations in the U, Th and K concentration in the surficial environment of the Campania region appear to be related to bedrock lithology. Generally, high U, Th and K values in stream sediments correspond well with the occurrence of volcanic rocks in the central-western part of the region, whereas low values are found in areas characterized by silico-clastic and carbonate deposits, occurring mostly in the southern and eastern part of the region. Gamma-ray spectrometry maps show a similar pattern, although the distribution of the highest radioactivity levels define more restricted areas than the ones resulting from mapping stream sediment geochemistry. Particularly high 40K radioactivity levels delimit all the known eruptive centers (Roccamonfina, Campi Flegrei and Somma–Vesuvius), including the fissural sources of Campania Ignimbrites, much better than U and Th radioactivity. One of the concerns for human health in the Campania region is the total gamma radiation and Rn potential related mostly to alkaline volcanics of the Neapolitan volcanological province. In particular, geothermal activity occurring in all the Campanian volcanic areas represents a potential hazard for Rn gas.  相似文献   

12.
Using trace elements to reconstruct paleoenvironment is a current hot topic in geochemistry. Through analytical tests of oil yield, ash yield, calorific value, total sulfur, major elements, trace elements, and X-ray diffraction, the quality, mineral content, occurrence mode of elements, and paleoenvironment of the Zhangjiatan oil shale of the Triassic Yanchang Formation in the southern Ordos Basin were studied. The analyses revealed relatively high oil yield (average 6.63%) and medium quality. The mineral content in the oil shale was mainly clay minerals, quartz, feldspar, and pyrite; an illite–smectite mixed layer comprised the major proportion of clay minerals. Compared with marine oil shale in China, the Zhangjiatan oil shale had higher contents of quartz, feldspar, and clay minerals, and lower calcite content. Silica was mainly in quartz and Fe was associated with organic matter, which is different from marine oil shale. The form of calcium varied. Cluster analyses indicated that Fe, Cu, U, V, Zn, As, Cs, Cd, Mo, Ga, Pb, Co, Ni, Cr, Sc, P, and Mn are associated with organic matter while Ca, Na, Sr, Ba, Si, Zr, K, Al, B, Mg, and Ti are mostly terrigenous. Sr/Cu, Ba/Al, V/(V + Ni), U/Th, AU, and δU of oil shale samples suggest the paleoclimate was warm and humid, paleoproductivity of the lake was relatively high during deposition of the shale—which mainly occurred in fresh water—and the paleo-redox condition was dominated by reducing conditions. Fe/Ti ratios of the oil shale samples suggest clear hydrothermal influence in the eastern portion of the study area and less conspicuous hydrothermal influence in the western portion.  相似文献   

13.
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14.
The main geological factors controlling the accumulation and yield of marine-facies shale gas reservoirs are the focus of the current shale gas exploration and development research. In this study, the Wufeng-Longmaxi Formation in the Dingshan area of southeast Sichuan was investigated. Shale cores underwent laboratory testing, which included the evaluation of total organic carbon(TOC), vitrinite reflectance(Ro), whole-rock X-ray diffraction(XRD), pore permeability,and imaging through field emission scanning electron microscopy(FE-SEM). Based on the results of natural gamma ray spectrum logging, conventional logging, imaging logging, and seismic coherence properties, the exploration and development potential of shale gas in the Dingshan area have been discussed comprehensively. The results showed that(1)layer No. 4(WF2-LM4) of the Wufeng-Longmaxi Formation has a Th/U ratio 2 and a Th/K ratio of 3.5–12. Graptolites and pyrite are relatively abundant in the shale core, indicating sub-high-energy and low-energy marine-facies anoxic reducing environments.(2) The organic matter is mainly I-type kerogen with a small amount of II1-type kerogen. There is a good correlation among TOC, Ro, gas content, and brittle minerals; the fracturing property(brittleness) is 57.3%. Organic and inorganic pores are moderately developed. A higher pressure coefficient is correlated with the increase in porosity and the decrease in permeability.(3) The DY1 well of the shale gas reservoir was affected by natural defects and important latestage double destructive effects, and it is poorly preserved. The DY2 well is located far from the Qiyueshan Fault. Large faults are absent, and upward fractures in the Longmaxi Formation are poorly developed. The well is affected by low tectonic deformation intensity, and it is well preserved.(4) The Dingshan area is located at the junction of the two sedimentary centers of Jiaoshiba and Changning. The thickness of the high-quality shale interval(WF2-LM4) is relatively small, which may be an important reason for the unstable production of shale gas thus far. Based on the systematic analysis of the geological factors controlling high-yield shale gas enrichment in the Dingshan area, and the comparative analysis with the surrounding typical exploration areas, the geological understanding of marine shale gas enrichment in southern China has been improved. Therefore, this study can provide a useful reference for shale gas exploration and further development.  相似文献   

15.
The radioactivity is dependent on the isotope and their concentration in the mineral such as potassium (K), uranium (U) and thorium (Th). In this paper the presence of a 3 to 5 m thick uranium and thorium bearing sediment of Cenozoic age is reported above Goru Formation of Jaisalmer basin. Gamma ray log response of Well-1 which falls under the study area has marked with very high GR (gamma ray) readings ranging from 350-1488 API coupled with high uranium and thorium content from spectral gamma ray log ranging from 92-178 ppm and 60-80 ppm respectively at the depth of 50 m from ground surface (-110m above MSL). Further studies are required to delineate the lateral thickness variation for mining purpose which may be a radioactive source.  相似文献   

16.
The Ramnad sub-basin is one of the most explored for hydrocarbons in Cauvery basin. A number of exploratory wells have been drilled to delineate hydrocarbon bearing horizons. Nannilam Formation of Santonian–Campanian age hosts considerable thickness of reservoir facies. The reservoir facies is mainly clastics such as sandstone and siltstone with lot of clay content. In addition to normal logs, the NGS (Natural Gamma Ray Spectrometry) logs are widely employed to estimate sediment composition and broad depositional environment of reservoir facies. The present study employs and analyses NGS logs of four well sections from Kanjirangudi area of Ramnad sub-basin to determine the clay mineral composition and depositional environment of Nannilam Formation. Thorium (Th), potassium (K) and uranium (U) concentrations and their interrelationships reveal that montmorillonite, illite and kaolinite are the dominant clay minerals. The clay mineral composition suggests that the sediments of the Nannilam Formation were derived from a provenance of acid igneous rocks during warm, humid and tropical conditions. Also, the ratios of Th/K indicate a deep open marine condition under which the sediments of the Nannilam Formation were deposited. These results would aid a better understanding and characterization of reservoir facies in the sub-basin.  相似文献   

17.
新甘交界北山地区早二叠世红柳河群的建立   总被引：1，自引：0，他引：1  
经1:5万区域地质调查研究,北山地区原红柳河组规模巨大,岩性、岩相差异明显,按岩石地层划分原则,应进一步分组.原红柳河组内部有4套岩性、岩相差异较大的岩石组合,以3次砾岩事件和1次火山岩事件为标志,代表了4个不同的沉积阶段,与之对应出现了4个重要的沉积(不整合)界面.依据这4个界面对早二叠世红柳河组进行了重新划分,即下二叠统河西组(P1h)、红柳村组(P1hl)、芦苇井组(P1l)和红柳井组(P1hj).在河西组采集到大量的腕足、苔藓虫等海相动物化石,在芦苇井组第二岩性段含炭粉砂岩中获孢粉化石组合,其时代属于二叠纪.本区新建的4个组实际上是由一个规模较大的老组再分组的结果.按岩石地层单位修定的要求,建议原红柳河组上升为群.  相似文献   

18.
The clastic sediments of the Murree Formation of Miocene age are exposed in Jhelum valley areas of Azad Jammu and Kashmir Pakistan. Field observations revealed the cyclic deposition in the Murree Formation. The sandstone, siltstone, and shale constitute a single cycle within the formation. This single unit is divided into five different lithofacies which constitute the Bouma sequence in the Murree Formation. The Murree Formation shows faulted contacts with Panjal Formation and Nagri Formation in the study area. The modal mineralogy data obtained from the petrography of sandstone indicates that sandstone is litharenite and lithic greywacke. The mineralogical and textural data suggests that sandstone is compositionally mature and poorly to moderately sorted. The dominantly angular to sub angular quartz grains show nearness of the source area. Fractured and sutured quartz grain reveals tectonodiagentic changes that occurred in Murree Formation. The sandstone experienced diagenetic changes. The pressure solution and cementation reduced the primary porosity of sandstone. However, alteration of feldspar and fractures in grains have produced secondary porosity. The X-ray diffraction (XRD) of the shale samples indicates that shale of the Murree Formation is argillaceous and dominated by illite clay mineral. The illite crystallinity values indicate very low grade metamorphism of Murree Formation in core of Hazara Kashmir Syntaxis. The petrographic data suggests that the provenance of sandstone is recycled orogen. Quartz is of igneous and metamorphic origin. Feldspar (albite and microcline) composition suggests its derivation from acidic igneous rocks. The rock fragments of volcanics, slate, phyllite, and schist suggest igneous and metamorphic provenance. The petrographic data suggests that at the time of deposition of Murree Formation, igneous and low grade metamorphic rocks were exposed. However, presence of some clasts of carbonates indicates that sedimentary rocks were also exposed in the source region. The quartz content and clay minerals in the shale revealed that source region was igneous and metamorphic rocks. Cyclic deposition, lithofacies, and various sedimentary structures like cross bedding, ripple marks, and calcite concretions suggest that deposition of Murree Formation occurred in fluviatile environment by meandering river system having decreasing turbidity current.  相似文献   

19.
The depositional facies and environments were unraveling by studying 21 subsurface sections from ten oilfields in the central and southern Iraq and a large number of thin sections of the Nahr Umr (siliciclastic deposit) Formation (Albian). This formation is mainly composed of sandstone interlaminated with minor siltstone and shale, with occurrence of thin limestone beds. Nahr Umr Formation is subdivided into three lithostratigraphic units of variable thicknesses on the basis of lithological variations and log characters. Mineralogically and texturally, mature quartz arenite and sandstones are the common type of the Nahr Umr Formation. The sandstones are cemented by silica and calcite material and have had a complex digenetic history. Compaction, dissolution, and replacements are the main diagenetic processes. Prodelta, distal bar, distributary mouth bar, distributary channel, over bank, and tidal channel are the main depositional environments recognized for the Nahr Umr Formation, within the studied wells. This formation was deposited in shallow marine and fluvial–deltaic environments and exhibit progradational succession of facies. Eight sedimentary facies that have been identified in the Nahr Umr Formation include claystone lithofacies, claystone siltstone lithofacies, lenticular-bedded sandstone–mudstone lithofacies, wavy-bedded sandstone–mudstone lithofacies, flaser-bedded sandstone–mudstone lithofacies, parallel and cross lamination sandstone lithofacies, trough cross-bedded sandstone lithofacies, and planar cross-bedded sandstone lithofacies. The depositional model of the Nahr Umr Formation environment was built based on the lithofacies association concepts.  相似文献   

20.
中国大陆科学钻探主孔自然放射性测井及其解释   总被引：3，自引：0，他引：3  
为了认识江苏东海超高压变质带上地壳岩石自然放射性的垂向分布特征, 榴辉岩退变质程度对放射性元素浓度的影响, 以及放射性产热率对地温梯度的影响, 利用中国大陆科学钻探(CCSD) 主孔100~5000m自然放射性测井(自然伽马和自然伽马能谱) 资料统计了CCSD主孔各类岩石的自然放射性强度和铀、钍、钾元素的浓度, 计算出产热率曲线.自然伽马, 铀、钍、钾浓度和产热率从蛇纹岩到榴辉岩、角闪岩、副片麻岩、正片麻岩依次增大.随着榴辉岩退变质程度的增强, 其铀、钍、钾元素的浓度值逐渐增大.CCSD主孔自然放射性的垂向分布特征主要受岩性控制, 自然放射性随深度增加有增强趋势.产热率与自然伽马测井值之间有很好的线性关系, 在高放射性岩层的上部, 地温梯度会出现较强扰动和低值异常.   相似文献   

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