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1.
The Precambrian basement rocks of the Eastern Granite-Rhyolite Province(EGRP)in central Illinois(midcontinent region of North America)exhibit a complex history of early volcanism,granite emplacement,and intrusion of mafic rocks.A comprehensive suite of dedicated petrographic analyses,geophysical logs,and drill core from four basement-penetrating wells,two-dimensional and three-dimensional seismic reflection data,and U-Pb age data from the Illinois Basin–Decatur Project(IBDP)and Illinois Carbon Capture Storage(ICCS)Project site provide new constraints for interpreting the Precambrian basement of the Illinois Basin.These new data reveal the basement to be compositionally and structurally complex,having typical EGRP felsic volcanic rocks intruded by the first reported gabbro in the Precambrian basement in Illinois.Zircons(n?29)from rhyolite give a U-Pb weighted mean average age of 14679 Ma.Zircons(n?3)from a gabbro dike that intrudes the rhyolite yield a concordia age of 107312 Ma,which corresponds to Grenville-age extension and represents the first Grenville-age rock in Illinois and in the EGRP.A high-resolution three-dimensional seismic reflection volume,coincident with the four wells,provides a context for interpreting the petrological data and implies a high degree of heterogeneity for basement rocks at the IBDP–ICCS site,as also shown by the drill cores.The occurrence of Grenville-age gabbro is related to a prominent bowl-like structure observed on local two-dimensional seismic reflection profiles and the three-dimensional volume that is interpreted as a deep-seated mafic sill complex.Furthermore,heterogeneities such as the brecciated EGRP rhyolite and later gabbro intrusion observed in the basement lithology at the IBDP–ICCS may reflect previously unknown distal elements of the 1.1 Ga Midcontinent Rift in the EGRP and more likely Grenville-age extension.  相似文献   

2.
In the eastern part of the Indian shield,late PaleozoiceMesozoic sedimentary rocks of the Talchir Basin lie precisely along a contact of Neoproterozoic age between granulites of the Eastern Ghats Mobile Belt(EGMB)and amphibolite facies rocks of the Rengali Province.At present,the northern part of the basin experiences periodic seismicity by reactivation of faults located both within the basin,and in the Rengali Province to the north.Detailed gravity data collected across the basin show that Bouguer anomalies decrease from the EGMB(wt15 mGal),through the basin(w 10 mGal),into the Rengali Province(w 15 mGal).The data are consistent with the reportedly uncompensated nature of the EGMB,and indicate that the crust below the Rengali Province has a cratonic gravity signature.The contact between the two domains with distinct sub-surface structure,inferred from gravity data,coincides with the North Orissa Boundary Fault(NOBF)that defnes the northern boundary of the Talchir Basin.Post-Gondwana faults are also localized along the northern margin of the basin,and present-day seismic tremors also have epicenters close to the NOBF.This indicates that the NOBF was formed by reactivation of a Neoproterozoic terrane boundary,and continues to be susceptible to seismic activity even at the present-day.  相似文献   

3.
The Jiza' basin is located in the eastern part of Yemen, trending generally in the E–W direction. It is filled with Middle Jurassic to recent sediments, which increase in thickness approximately from 3,000 m to more than 9,000 m. In this study, block-35 of this sedimentary basin is selected to detect the major subsurface geological and structural features characterizing this basin and controlling its hydrocarbon potentials. To achieve these goals, the available detailed gravity and magnetic data, scale 1:100,000, were intensively subjected to different kinds of processing and interpretation steps. Also, the available seismic reflection sections and deep wells data were used to confirm the interpretation. The results indicated three average depth levels; 12.5, 2.4, and 0.65 km for the deep, intermediate, and shallow gravity sources and 5.1 and 0.65 km for the deep and shallow magnetic sources. Accordingly, the residual and regional anomaly maps were constructed. These maps revealed a number of high and low structures (horsts and grabens and half grabens), ranging in depth from 0.5 km to less than 4.5 km and trending mainly in the ENE, NW, and NE directions. However, the analytical signal for both gravity and magnetic data also showed locations, dimensions, and approximate depths of the shallow and near surface anomaly sources. The interpretation of the gravity and magnetic anomalies in the area indicated that the NW, NNW, ENE, and NE trends characterize the shallow to deep gravity anomaly sources; however, the NE, NW, and NNE trends characterize the magnetic anomaly sources, mainly the basement. Two-dimensional geologic models were also constructed for three long gravity anomaly profiles that confirmed and tied with the available deep wells data and previously interpreted seismic sections. These models show the basement surface and the overlying sedimentary section as well as the associated faults.  相似文献   

4.
内蒙古拉布达林盆地面积大、油气勘探程度很低.由于浅层广泛分布的火山岩的强反射屏蔽作用造成地震勘探对深层成像差,难以评价盆地油气勘探潜力.为了解决盆地主要目的层上库力组底界深度及沉积岩分布不清的问题,对盆地南部二维地震资料开展重力-地震联合反演解释.通过在GM-SYS重磁剖面解释软件中加载地震剖面,建立重力模型,利用地震浅层可靠解释成果做约束条件,消除上覆火山岩的重力干扰,减少了重力反演深层构造界面的多解性,成功地反演了盆地上库力组底界深度、沉积岩厚度,指出巴彦哈达断陷为有利勘探区,在此基础上估算出油气资源量.  相似文献   

5.
前人根据敦化盆地的地层的地层,认为该盆地下白垩统为河流—湖泊相碎屑岩。通过对新钻的敦参1井岩屑录井资料的分析、对16条二维地震资料的层位标定与追踪,以及对敦化盆地早白垩世盆地演化阶段的分析,得到了以下主要结论:1)敦化盆地下白垩统可能有两种分布形态,在盆地的主体部位,以浅变质岩形态存在,而在其他部位则以正常沉积岩形态零星存在;2)敦化盆地白垩系的分布规模不大,夹持于一个北北东向的狭窄长槽内;3)敦化盆地早白垩世处于裂谷盆地发展的初始张裂阶段;4)敦化盆地下白垩统不宜作为勘探目的层。  相似文献   

6.
四川盆地北部下三叠统飞仙关组层序地层分析   总被引:3,自引:1,他引:3  
为了探讨礁滩储集岩的分布规律,以层序地层学理论与方法系统研究了四川盆地北部下三叠统飞仙关组地层。通过露头、岩芯、测井、地震数据综合分析,识别出两个三级层序及四个准层序组,确定蒸发台地、局限台地、开阔台地、台地边缘滩、斜坡和盆地相六类沉积类型。层序划分及层序界面的确定,依据陆上暴露和向上变浅两个方面的识别标志。暴露界面表现为泥岩表面干裂,淡水选择性溶蚀、白云化现象,白云岩、石膏,伽玛曲线高值。向上变浅层序有向上变厚、变粗序列,向上变细、变泥、变红序列,向上γ值变低序列。对比发现高水位体系域后期发育台地边缘鲕滩和台地内鲕滩。广泛白云岩化作用的台地边缘鲕滩相,具有很好的孔渗性,成为最有利的储集层。对指导进一步的勘探与开发具有重要意义。  相似文献   

7.
Seismic attributes such as: amplitude envelope, instantaneous phase and cosine of instantaneous phase of 2D post-stack seismic data facilitates structural and stratigraphic interpretation of shallow marine offshore, Krishna-Godavari basin. Two seismic sections namely, X and Y oriented N-S passing through wells W-1 andW-2 respectively are considered for seismic attribute analysis and porosity prediction. The gamma ray log trend indicates deposition of cleaning upward sediment. Coarsening upward, clayey-silty-sandy bodies, making a series of about 50-60 m thickness, have been evidenced from the gamma ray log. An extensional structural style comprising growth faults is associated with the progradational style of deposition. Four seismic zones have been distinguished. These zones differ in amplitude, frequency and continuity of the reflectors. Channel sands of Cretaceous age of Raghavapuram shale are identified in well log, seismic section and its acoustic impedance section. Major stratigraphic horizons along with faults extending to basement are marked with the help of attribute analysis. Porosity is mapped from transformation of acoustic impedance. The shales/unconsolidated sediments measure a high porosity with low impedance and the more porous sands are in an intermediate range. The predicted impedance and porosity values may be erroneous beyond the drilled depth because of non availability of well log data for calibration.  相似文献   

8.
 Detailed hydrogeological studies in a granitic micro-watershed have been carried out to determine the extent, behavior, and characteristics of the aquifer. The study includes analysis of lithologs, drill time log, pumping tests, and slug tests. Realistic field conditions have been taken into account for characterizing the aquifer system. Slug tests were carried out to estimate aquifer parameters at the wells which could not sustain pumping. Received: 20 November 1997 · Accepted: 23 February 1998  相似文献   

9.
塔里木盆地二叠系划分对比与火山岩分布   总被引:2,自引:1,他引:2  
根据全盆地钻井与露头剖面对比和地震剖面追踪解释,探讨了塔里木盆地覆盖区二叠系岩石地层的划分对比。二叠系自下而上由一个自然伽玛曲线加积段、三个自然伽玛曲线退积段组成,加积段为南闸组、退积段分别为库普库兹曼组、开派雷兹克组和沙井子组。南闸组是塔里木盆地最后一次海侵形成的滨浅海灰岩泥岩薄互层为主的沉积。库普库兹曼组和开派雷兹克组是两个基性火山岩-酸性火山岩的旋回或基性火山岩-砂泥岩的旋回。沙井子组是一个与区域构造运动有关的冲积扇、辫状河-曲流河沉积的异旋回。二叠系火山岩在和田河、塔中西部和顺托果勒地区厚度较大,库普库兹曼组火山岩一般0~60m,开派雷兹克组火山岩一般0~200m,局部可超过400m。与库普库兹满组火山岩相比,开派雷兹克组火山岩分布范围由塔西南朝塔东北方向有所迁移。中西部的库普库兹曼组火山岩可能喷发于水下。火山通道多沿着古隆起上的断背斜、断鼻构造分布。火山岩可形成油气藏遮挡,或本身形成储层,但火山活动改造或不同程度地破坏了早期已有油气藏。  相似文献   

10.
The northern South China Sea margin has experienced a rifting stage and a post-rifting stage during the Cenozoic.In the rifting stage,the margin received lacustrine and shallow marine facies sediments.In the post-rifting thermal subsidence,the margin accumulated shallow marine facies and hemipelagic deposits,and the decpwater basins formed.Petroleum systems of deepwater setting have been imaged from seismic data and drill wells.Two kinds of source rocks including Paleogene lacustrine black shale and Oligocene-Early Miocene mudstone were developed in the deepwater basin of the South China Sea.The deepwater reservoirs are characterized by the deep sea channel fill,mass flow complexes and drowned reef carbonate platform.Profitable capping rocks on the top are mudstoues with huge thickness in the post-rifting stage.Meanwhile,the faults developed during the rifting stage provide a migration path favournble for the formation of reservoirs.The analysis of seismic and drilling data suggests that the joint structural and stratigraphic traps could form giant hydrocarbon fields and hydrocarbon reservoirs including syn-rifting graben subaqueous delta,decpwater submarine fan sandstone and reef carbonate reservoirs.  相似文献   

11.
Well log analysis provides the information on petrophysical properties of reservoir rock and its fluid content. The present study depicts interpretation of well log responses such as gamma ray, resistivity, density and neutron logs from six wells, namely W-1, W-2, W-9, W-12, W-13 and W-14 under the study area of Krishna-Godavari (K-G) basin. The logs have been used primarily for identification of lithology and hydrocarbon-bearing zones. The gamma ray log trend indicates deposition of cleaning upward sediment. Coarsening upward, clayey-silty-sandy bodies have been evidenced from the gamma ray log. Gas-bearing zones are characterised by low gamma ray, high deep resistivity and crossover between neutron and density logs. Total 14 numbers of hydrocarbon-bearing zones are identified from wells W-9, W-12, W-13 and W-14 using conventional log analysis. Crossplotting techniques are adopted for identification of lithology and fluid type using log responses. Crossplots, namely P-impedance vs. S-impedance, P-impedance vs. ratio of P-wave and S-wave velocities (Vp/Vs) and lambda-mu-rho (LMR), have been analysed to discriminate between lithology and fluid types. Vp/Vs vs. P-impedance crossplot is able to detect gas sand, brine sand and shale whereas P-impedance vs. S-impedance crossplot detects shale and sand trends only. LMR technique, i.e. λρ vs. μρ crossplot is able to discriminate gas sand, brine sand, carbonate and shale. The LMR crossplot improves the detectability and sensitivity of fluid types and carbonate lithology over other crossplotting techniques. Petrophysical parameters like volume of shale, effective porosity and water saturation in the hydrocarbon-bearing zones in these wells range from 5 to 37%, from 11 to 36 and from 10 to 50% respectively. The estimated petrophysical parameters and lithology are validated with limited core samples and cutting samples from five wells under the study area.  相似文献   

12.
近年来, 准噶尔盆地石炭系火山岩勘探屡获突破, 展现了火山岩储层良好的勘探前景。由于准噶尔盆地石炭系火山岩存在埋藏深度大, 受勘探手段和地球物理资料品质等因素的制约, 深层火山岩的识别与解释目前仍存在诸多困难和问题, 为油田地震勘探工作带来了极大困难。如何通过现有物探方法和技术提高深部火山岩的分辨、识别能力, 具有很强的理论和实际意义。由于特殊地质体在密度、磁化率或电阻率等物性组合方面存在特殊性, 因此可通过多方法综合物探技术对其进行综合识别、限定。本文在深入分析达巴松凸起钻井、物性资料的基础上, 利用重磁电异常信息模式判别技术, 预测了石炭系火山岩的平面展布, 缩小和锁定了深层火山岩地震勘探的有利靶区; 再以地震相分析、地震属性解释、构造制图及综合评价为主要技术手段, 对深层火山岩进行定量识别和预测, 落实和优选了深层火山岩有利勘探目标, 并取得了良好效果。总结了深层特殊地质体勘探的高精度地震资料采集和重磁电震(井)综合应用、联合反演解释等手段, 极大地提高了准噶尔盆地深层火成岩的勘探精度。  相似文献   

13.
Gosses Bluff, west of Alice Springs, Northern Territory, comprises a roughly circular rim of steeply dipping sandstone, locally overturned with downward facing folds, surrounding a topographically lower core of steeply dipping faulted sandstone, shale, and limestone. Abundant shattercones occur both in outcrop and to depths of 1,000 m. The structure lies on an’ anticlinal trend‐Structural, gravity, seismic and drill hole data indicate that the structure continues to some depth. Shattercones also occur outside the rim of Gosses Bluff. At a nearby prominence, Mt Pyroclast, they occur with peculiar breccias and devitrified glassy rocks, some of which may be of volcanic or impact fusion origin.

Gosses Bluff has previously been regarded as a diapir caused by salt intrusion. The evidence now available suggests that it is a crypto‐explosion structure, resulting either from deep‐seated explosive volcanic activity, or from meteorite impact, probably at some time during the Mesozoic Era.  相似文献   

14.
The Toolebuc Formation, which is a potentially important source of oil shale in the Eromanga Basin of NW Qld, exhibits a marked gamma‐ray response that has long beeen used as a stratigraphic marker. At Julia Creek, a large area of the Formation contains low‐grade oil shale that is accessible to mining. Detailed investigation, by gamma‐ray spectrometry and neutron activation analysis, of drill core samples from this deposit and from the type section of the Toolebuc Formation at Boulia (BMR Boulia 3A stratigraphic drill hole) show that the Toolebuc gamma‐ray anomaly in the northern Eromanga Basin is due to the presence of uranium. Analyses for organic carbon and phosphorus show that the uranium is associated primarily with organic matter in the oil shales and with phosphatic skeletal fish debris in the accompanying coquinites.

Drill core samples from Tibooburra, N.S.W. were also analysed (BMR Urisino‐1 stratigraphic drill hole) to investigate whether the gamma‐ray anomalies observed in the Bulloo Embayment on the southern margin of the Eromanga Basin (possibly correlative with the Toolebuc Formation) might also be indicative of oil shale. The results show that the much weaker anomaly at this locality is due principally to potassium and reflects the presence of an argillaceous siltstone within glauconitic sandstones.  相似文献   

15.
Tertiary reservoir represented by Jeribe, Anah, Azkand, and Azkand/Ibrahim formations has been studied from reservoir characterization point of view in Khabbaz Oil Field/Northern Iraq. Examined thin sections prepared from core rock samples which are selected from the wells Kz-8 and Kz-9 revealed the existence of different microfacies in which are varies types of porosity such as interparticle, intraparticle, moldic, vuggy, and fractures have been noticed. In addition to these different types of diagenetic features are represented mainly by cementation, dolomitization, recrystallization, and dissolution. The available log data for the wells Kz-11, Kz-14, and Kz-16 have been used in characterizing the reservoir properties of the studied formations. The detected lithologies from porosity logs showed domination of limestone, dolomitic limestone, and dolomites in addition to few thin beds of anhydrites in Jeribe Formation and thin beds of sand dominated lithologies in Azkand Formation. Clay content has been calculated from gamma ray log along the studied sections and appeared to be mostly of dispersed clay type as shown from density-neutron porosity crossplot of Thomas-Stieber. Correction from the effect of clay content has been done for all the measured sonic, density, and neutron porosities. The available porosity and permeability values which are measured from core tests in the well Kz-9 for the formations of Jeribe, Anah, and Azkand have been adapted to formalize the best equation for calculating permeability in the other studied wells which have no core test measurements but only log data (Kz-11, Kz-14, and Kz-16 wells). Depending on porosity, permeability, and shale content, the studied sections have been subdivided into seven reservoir units in the wells Kz-11 and Kz-16, and for eight reservoir units in the well Kz-14.  相似文献   

16.
通过采用地表地质调查、钻孔岩心编录、地球物理测井、二维地震等多种技术手段,综合运用岩石地层、测井曲线、二维地震和钻井资料标定相结合的研究方法,将以辽法地1井、秀D1井为代表的义县组划分为4个岩性段,即:一段(K1y1)基性火山岩段,二段(K1y2)火山岩夹沉积-火山碎屑岩段,三段(K1y3)沉积岩段,四段(K1y4)酸性火山岩段.4个岩性段和界面在露头、钻井岩心、测井曲线、地震等资料上的特征明显.重、磁、电剖面联合反演综合解释推断及井震标定后的地震反射特征均表明下白垩统义县组4个岩性段在空间上具有一定的展布特征和分布规律.  相似文献   

17.
银根—额济纳旗盆地是中国西部的一个中新生代沉积盆地,盆地地层有多种不同的划分。近几年来,盆地经历了详细的石油勘探和地质调查。在地震和钻井勘探过程中,于下白垩统发现了一套新的地层单元,这套地层的古生物、电性、岩性、物理特征及地震层序与上覆和下伏地层有很大差别。这套新地层位于下白垩统上部,定名为银根组(K1y),银根组中部有良好储层,上部泥岩可作为区域性盖层,与下部烃源岩构成良好的生储盖组合,有一定的勘探意义。  相似文献   

18.
丽水—椒江凹陷位于东海陆架盆地西南部,是在中生代残留盆地基础上发育起来的新生代具有典型东断西超特点的断陷,是油气勘探的新区域。区域地质条件复杂、构造叠加、沉积厚度大,地震勘探无法获得较好的反射数据,因此采用面积广、深度大的重磁数据结合地震数据来描述基底构造和火成岩岩性特征,通过重磁数据的阶跃边界识别技术划分区域断裂。丽水—椒江凹陷内断裂呈北东向分布,控制凹陷的形状,且断裂作用使凹陷形成多个小型次凹,断陷特征明显。中—新生代火成岩具有较高的重磁异常,结合质量较好的地震剖面来获得地层、火成岩及岩性分布特征,并建立了多联通域地层的计算公式。区域内中—古生界较为发育,但凹陷内中—新生代火成岩侵入较少,不会对于油气构造造成大的破坏,因此该凹陷具有良好的油气前景。  相似文献   

19.
Modelling of gravity and airborne magnetic data integrated with seismic studies suggest that the linear gravity and magnetic anomalies associated with Moyar Bhavani Shear Zone (MBSZ) and Palghat Cauvery Shear Zone (PCSZ) are caused by high density and high susceptibility rocks in upper crust which may represent mafic lower crustal rocks. This along with thick crust (44–45 km) under the Southern Granulite Terrain (SGT) indicates collision of Dharwar craton towards north and SGT towards south with N–S directed compression during 2.6–2.5 Ga. This collision may be related to contemporary collision northwards between Eastern Madagascar–Western Dharwar Craton (WDC) and Eastern Dharwar Craton (EDC). Arcuate shaped N and S-verging thrusts, MBSZ-Mettur Shear and PCSZ-Gangavalli Shear, respectively across Cauvery Shear zone system (CSZ) in SGT also suggest that the WDC, EDC and SGT might have collided almost simultaneously during 2.6–2.5 Ga due to NW–SE directed compressional forces with CSZ as central core complex in plate tectonics paradigm preserving rocks of oceanic affinity. Gravity anomalies of schist belts of WDC suggest marginal and intra arc basin setting.The gravity highs of EGFB along east coast of India and regional gravity low over East Antarctica are attributed to thrusted high-density lower crustal/upper mantle rocks at a depth of 5–6 km along W-verging thrust, which is supported by high seismic velocity and crustal thickening, respectively. It may represent a collision zone at about 1.0 Ga between India and East Antarctica. Paired gravity anomalies in the central part of Sri Lanka related to high density intrusives under western margin of Highland Complex and crustal thickening (40 km) along eastern margin of Highland Complex with several arc type magmatic rocks of about 1.0 Ga in Vijayan Complex towards the east may represent collision between them with W-verging thrust as in case of EGFB. The gravity high of Sri Lanka in the central part falls in line with that of EGFB, in case it is fitted in Gulf of Mannar and may represent the extension of this orogeny in Sri Lanka.  相似文献   

20.
《China Geology》2019,2(1):67-84
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.  相似文献   

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