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1.
第四纪沉积物天然热释光测量方法技术研究——山东草桥油田研究实例 总被引：13，自引：0，他引：13
第四纪沉积物天然热释光测量是一种累积间接油气勘查新方法。文中给出了首次系统研究的成果 ,从数百个样品中总结出的适用油气勘探的预热线形升温、恒温最佳加热程序 ,升温速率以 β=6℃ /s为宜 ,恒温温度 40 0℃ ,40 0℃恒温时间为 12s。在沉积物辐射剂量响应及日光晒退实验数据的基础上 ,总结了样品采集、预处理及测量方法。通过对山东草桥油田第四纪沉积物天然热释光与游离气烃野外实测资料的分析 ,发现天然热释光异常与气烃异常完全吻合 ,在油水边界上方 ,热释光、甲烷、乙烷出现高值异常 ,油田上方是低值带 ,为串珠状异常模式。热释光最大值为 2 0 4.2 μGy ,平均值为 79.45μGy ,标准差为 3 4 .14 μGy ;甲烷浓度异常下限为 2 5μL/L ,乙烷浓度异常下限为 4.4μL/L。 相似文献
2.
南海西沙海槽S14站位的地球化学异常特征及其意义 总被引：22，自引：6，他引：16
西沙海槽具备良好的天然气水合物的形成条件,并已发现与其有关的地球物理标志--模拟海底反射层（BSR）。通过对西沙海槽S14大型活塞站位的孔隙水和沉积物样品进行化学组分、酸解烃和热释光等方面的分析测试,结果发现在海底之下4～5 m区间存在着较明显的高盐高烃异常,其中酸解烃中的甲烷、乙烷、丙烷含量及其热释光值均有所增高,孔隙水中的绝大部分离子及其盐度也存在着明显的升高,这一高盐高烃异常可能是下部与天然气水合物有关的孔隙流体沿着断层向上迁移所致。这些地球化学异常以及模拟海底反射层等地球物理标志显示该站位之下可能存在天然气水合物。 相似文献
3.
Detection and Evaluation of Gas Hydrates in the Eastern Nankai Trough by Geochemical and Geophysical Methods 总被引：2，自引：0，他引：2
Abstract: Interstitial waters extracted from the sediment cores from the exploration wells, “BH‐1” and “MITI Nankai Trough”, drilled ～60 km off Omaezaki Peninsula in the eastern Nankai Trough, were analyzed for the chloride and sulfate concentrations to examine the depth profiles and occurrence of subsurface gas hydrates. Cored intervals from the seafloor to 310 mbsf were divided into Unit 1 (～70 mbsf, predominated by mud), Unit 2 (70–150 mbsf, mud with thin ash beds), Unit 3 (150–250+ mbsf, mud with thin ash and sand), and Unit 4 (275–310 mbsf, predominated by mud). The baseline level for Cl “concentrations was 540 mM, whereas low chloride anomalies (103 to 223 mM) were identified at around 207 mbsf (zone A), 234–240 mbsf (zone B), and 258–265 mbsf (zone C) in Unit 3. Gas hydrate saturation (Sh %) of sediment pores was calculated to be 60 % (zone A) to 80 % (zones B and C) in sands whereas only a few percent in clay and silt. The total amount of gas hydrates in hydrate‐bearing sands was estimated to be 8 to 10 m3 of solid gas hydrate per m2, or 1.48 km3 CH4 per 1 km2. High saturation zones (A, B and C) were consistent with anomaly zones recognized in sonic and resistivity logs. 2D and high‐resolution seismic studies revealed two BSRs in the study area. Strong BSRs (BSR‐1) at ～263 mbsf were correlated to the boundary between gas hydrate‐bearing sands (zone C) and the shallower low velocity zone, while the lower BSRs (BSR‐2) at～289 mbsf corresponded to the top of the deeper low velocity zone of the sonic log. Tectonic uplift of the study area is thought to have caused the upward migration of BGHS. That is, BSR‐1 corresponds to the new BGHS and BSR‐2 to the old BGHS. Relic gas hydrates and free gas may survive in the interval between BSR‐1 and BSR‐2, and below BSR‐2, respectively. Direct measurements of the formation temperature for the top 170 m interval yield a geothermal gradient of ～4.3d?C/ 100 m. Extrapolation of this gradient down to the base of gas hydrate stability yields a theoretical BGHS at～230 mbsf, surprisingly ～35 m shallower than the base of gas hydrate‐bearing sands (zone C) and BSR‐1. As with the double BSRs, another tectonic uplift may explain the BGHS at unreasonably shallow depths. Alternatively, linear extrapolation of the geothermal gradient down to the hydrate‐bearing zones may not be appropriate if the gradient changes below the depths that were measured. Recognition of double BSRs (263 and 289 mbsf) and probable new BGHS (～230 mbsf) in the exploration wells implies that the BGHS has gradually migrated upward. Tectonically induced processes are thought to have enhanced dense and massive accumulation of gas hydrate deposits through effective methane recycling and condensation. To test the hypothetical models for the accumulation of gas hydrates in Nankai accretionary prism, we strongly propose to measure the equilibrium temperatures for the entire depth range down to the free gas zone below predicted BGHS and to reconstruct the water depths and uplift history of hydrate‐bearing area. 相似文献
4.
天然气水合物是在高压、低温条件下由水分子和气体分子形成的笼形化合物,是21世纪一种具有巨大潜在开发价值的海洋新型能源矿产.其勘探、开发和利用的科学与技术是当前面临的重大课题.天然气水合物的地球物理识别标志包括似海底反射层、空白反射带、极性反转、垂直地震剖面（VSP）和全波形反演速率、AVO和VAMP'S结构、测井等;地球化学识别标志包括甲烷异常、表层沉积物中的H2S气体异常和大气中CO2含量异常等气体异常检测,沉积物中含水量异常、孔隙水离子浓度异常、同位素地球化学异常等流体地球化学标志,以及标志性矿物（标型矿物）及沉积物热释光分析等. 相似文献
5.
祁连山冻土区木里地区天然气水合物矿藏是迄今为止在中纬度带首次发现的水合物矿藏,为了研究中纬度带水合物地球化学勘查技术,选择木里矿区作为方法技术的试验区。试验指标内容有土壤顶空气、酸解烃、碳酸盐和甲烷碳同位素。研究表明:祁连山木里天然气水合物矿藏存在明显的近地表地球化学异常;由甲烷碳同位素和烃类组成判断地表油气化探异常为热解成因,指示该区天然气水合物成藏物质来源于油气和煤成气。进一步研究了中纬度带冻土区天然气水合物成藏模式,指出该区进行天然气水合物勘探的同时应进行石油和煤成气的综合勘探。 相似文献
6.
吸附烃(酸解烃和热释烃)技术在常规油气地球化学勘查中已显示出良好的应用效果。选择青海木里三露天进行土壤热释烃地球化学方法试验,通过对土壤样品热释烃特征值和地球化学异常分布特征的分析,显示研究区已知矿藏区上方存在良好的土壤热释烃地球化学环状异常,异常的空间展布受到地下矿藏的控制,二者具有良好的对应关系 。通过对研究区烃类甲烷碳同位素分析,指示土壤热释烃地球化学异常为热解成因,与天然气水合物具有相似的成因类型。试验结果表明,土壤热释烃技术适用于天然气水合物地球化学勘查,能够圈出水合物矿藏范围,可与其他水合物化探技术互相补充。 相似文献
7.
Abstract. For the purpose of development of methane hydrate, occurring in the deep marine subsurface, as a resource, the most important issue is to understand the methane hydrate system (generation, migration and accumulation) as well as to delineate the methane hydrate reservoir properties. We have applied the Amplitude Versus Offset (AVO) analysis to the seismic data acquired in the Nankai Trough, offshore Japan, in order to confirm the occurrence of gas just below the methane hydrate-bearing zone, assuming that gas will show a so-called Class-3 AVO response. Knowledge of the amount and occurrence of gas in the sediment below methane hydrate-bearing zone is one of the keys to understand the methane hydrate system.
We have utilized the qualitative analysis of AVO methodology to delineate how gas is located below the BSR, which is thought to be the reflection event from the interface between the methane hydrate-bearing zone and the underlying gas-bearing zone. In the region of MITI Nankai Trough Well PSW-3, we observe two BSRs separated by 25 ms. After AVO modeling using well data, we applied AVO attribute analysis and attribute crossplot analysis to the seismic data. Finally we applied an offset-amplitude analysis to CMP gather data at specific locations to confirm the results of AVO attribute analysis. The AVO analysis shows that there is very little gas located in the underlying sediment below methane hydrate-bearing zone. This result supports the fact that we could not obtain any clear evidence of gas occurrence just below the methane hydrate-bearing zone in the Nankai Trough well drilling. 相似文献
We have utilized the qualitative analysis of AVO methodology to delineate how gas is located below the BSR, which is thought to be the reflection event from the interface between the methane hydrate-bearing zone and the underlying gas-bearing zone. In the region of MITI Nankai Trough Well PSW-3, we observe two BSRs separated by 25 ms. After AVO modeling using well data, we applied AVO attribute analysis and attribute crossplot analysis to the seismic data. Finally we applied an offset-amplitude analysis to CMP gather data at specific locations to confirm the results of AVO attribute analysis. The AVO analysis shows that there is very little gas located in the underlying sediment below methane hydrate-bearing zone. This result supports the fact that we could not obtain any clear evidence of gas occurrence just below the methane hydrate-bearing zone in the Nankai Trough well drilling. 相似文献
8.
中国近海天然气水合物的研究进展 总被引：40，自引：1，他引：40
南海、东海具有形成天然气水合物的良好动力学环境和丰富的烃类气体来源。根据卫星对海面增温异常的观测、底水气体地球化学、标志矿物和流体组成的研究表明 ,南海、东海海底存在强烈的烃流体活动和排气作用 ;南海南北陆坡区海底气体主要由CH4组成 ,前者多为微生物成因气 ,后者多为热解气 ;冲绳海槽热液沉积区的气体 ,主要为CO2 (86 % ) ,其次为CH4、H2 、H2 S(14 % ) ,分别来自岩浆流体及陆源有机质的降解 ,也属热解成因气。地震地球物理的研究主要集中于南海东北部、北部、南部陆坡区和冲绳海槽中南部 ,测线长度还很有限 ,虽然都有BSR标志的发现 ,但质量比较好 ,研究程度也比较高的还只有南海东北部主动陆缘和北部被动陆缘的一些海域。通过沉积物烃含量和热释光的研究 ,南海、东海共获得 6个地球化学异常区。在综合对比物化探、地热等项资料的基础上初步认为 :笔架南 (Ⅰ )、台西南—东沙 (Ⅱ )异常区是寻找水合物的最佳远景区 ;琼东南—西沙海槽(Ⅲ )、中建南—中业北 (Ⅳ )和冲绳海槽南部异常区是寻找水合物和常规油气藏的有利地区 ,但Ⅳ区更有利于寻找油气 ,其余 2区更有利于寻找水合物 ;南沙海域的研究程度总体上比较低 ,但在其中的南沙海槽 ,物化探异常标志均优 ,甲烷含量较其它地区高 2个数量级 相似文献
9.
海底水合物地球化学探测方法的试验研究 总被引：15，自引：5，他引：15
选择西沙海槽水合物潜在富集区作为已知区 ,利用陆上油气地球化学勘查方法 (酸解烃、热释烃、蚀变碳酸盐方法 )开展了试验性研究。通过对海底浅表层沉积物各项测试指标的分析 ,发现酸解烃方法效果好 ,而热释烃方法和蚀变碳酸盐方法的试验效果并不理想。同时还对海底浅表层沉积物酸解烃重新进行了释义 ,认为酸解烃方法适合于海底水合物的勘查 ,值得进一步推广 相似文献
10.
开发不受沼泽微生物影响的地球化学勘查技术是提高中纬度冻土区天然气水合物探井预测成功率的重要课题之一。选择在祁连山聚乎更天然气水合物已知区进行土壤热释光勘查技术实验。实验区为高寒沼泽景观,面积150 km2,采样密度2点/km2,采样深度60 cm,采集土壤样品300件,应用热释光测量仪对土壤样品进行了热释光分析。实验结果表明,天然气水合物矿藏上方出现天然热释光高值异常,与烃类异常浓度范围一致,为顶部异常模式。结合地质和地球化学勘查成果对异常进行了综合解释,认为祁连山聚乎更地区天然气热释光异常与天然气水合物矿藏关系密切,源于深部水合物矿藏。研究对天然气水合物的进一步调查具有重要的参考价值。 相似文献
11.
西沙海槽研究区天然气水合物地球化学勘探及成藏模式研究 总被引：10，自引：0，他引：10
依据ODP204航次1250C站位钻井样品酸解烃数据结果,以及作者在南海西沙海槽研究区天然气水合物地球化学现场勘查中得到的多种烃类指标数据、异常点上微量甲烷碳同位素数值等资料,对海洋水合物地球化学勘探的依据和研究区气态烃异常特征、气体成因、天然气水合物成藏模式等相关问题进行了研究探讨。结果表明:气态烃指标地球化学异常主要分布在工区北部斜坡地带,并与BSR等地震标志及深部断裂关系密切;西沙海槽研究区海底沉积物气态烃甲烷以热解成因为主,但也有混合成因;推测该区天然气水合物为断层渗滤综合成藏模式。研究成果比较合理地解释了BSR分布和海底沉积物甲烷局部异常并非完全一致的原因;评价预测了该区天然气水合物有利勘探目标。成果为该区天然气水合物勘探、天然气水合物成因机制研究和天然气水合物远景预测,提供了地球化学方面的证据。 相似文献
12.
根据祁连山木里地区已知天然气水合物上方不同期次近地表土壤地球化学勘查重复性试验,对土壤酸解烃、顶空气、荧光光谱、碳酸盐等指标方法的稳定性及异常重现性问题进行研究和探讨。结果表明,各项化探指标不同期次含量最大值等特征值虽然存在一定程度的差异,但是其数据波动特征和数据结构是相对一致的。顶空气甲烷、酸解烃、荧光光谱和碳酸盐方法指标前后两次测量结果均具有较高的相关性,配对T-检验显示顶空气轻烃、酸解烃和碳酸盐指标数据变化差异不显著,从统计学上看其指标数据具有较好的稳定性。顶空气甲烷、酸解烃、荧光光谱等指标地球化学异常在研究区已知天然气水合物矿区上方具有相似的空间分布特征,说明其化探指标异常空间上具有良好的稳定性和重现性;但是顶空气重烃异常模式、碳酸盐异常强度的变化,反映其具有重现性,但异常稳定性相对较差。这为地球化学勘查在陆域冻土区天然气水合物勘查中发挥作用提供了较好的基础。 相似文献
13.
14.
南海琼东南盆地气态烃地球化学特征及天然气水合物资源远景预测 总被引：2，自引：1，他引：2
天然气水合物研究覆盖了地球物理学、地球化学和地质学等多门学科,其中勘查地球化学方法可以从海底介质中直接获得与天然气水合物有关的地球化学信息,圈定水合物异常区域。近些年来大量的研究工作和陆续发现的地球物理和地球化学证据显示,南海北部海域是我国勘查天然气水合物最有潜力的区域之一。依据广州海洋地质调查局2005年第4航次获得的南海琼东南盆地沉积物酸解烃测试结果和高异常段位同位素分析数据,探讨了琼东南盆地气态烃地球化学分布特征和异常成因。结合西沙海槽已有的勘探资料和水合物成藏地质条件,分析南海北部西沙海槽—琼东南地区与天然气水合物有关的地球化学异常特征,并对水合物成藏远景进行了预测。研究成果为南海北部天然气水合物勘探提供地球化学证据。 相似文献
15.
南沙海槽的构造和沉积受控于南海的构造运动和加里曼丹西北大陆边缘的演化,具有适于天然气水合物形成的物源基础、温压条件、输导系统和储藏场所。似海底反射层(BSR)出现在水深650~2 800 m、海底下65~350 m深的晚中新世沉积物中,与褶皱、逆冲推覆构造及穹窿构造有关;沉积物中的甲烷含量和孔隙水的SO24-含量表现出异常变化特征,硫酸盐-甲烷界面(SMI)深度仅为8~11 m;表层沉积的自生石膏和黄铁矿的成岩环境与甲烷流体排溢引起的厌氧甲烷氧化(AOM)有关,这些地球物理和地球化学指标均指示南沙海槽发育天然气水合物。研究表明,南沙海槽沉积物的甲烷以二氧化碳还原型微生物成因为主,少量为混合气,海槽东南部可能是最有潜力的天然气水合物远景区。 相似文献
16.
《地学前缘(英文版)》2022,13(2):101345
The mechanism of slope failure associated with overpressure that is caused by hydrocarbon migration and accumulation remains unclear. High-resolution seismic data and gas hydrate drilling data collected from the Shenhu gas hydrate field (site SH5) offer a valuable opportunity to study the relations between submarine slope failure and hydrocarbon accumulation and flow that is associated with a ～2 km-diameter gas chimney developed beneath site SH5 where none gas hydrates had been recovered by drilling and sampling despite the presence of distinct bottom simulating reflectors (BSRs) and favorable gas hydrate indication. The mechanism of submarine slope failure resulted from buoyancy extrusion and seepage-derived deformation which were caused by overpressure from a ～1100 m-high gas column in a gas chimney was studied via numerical simulation. The ～9.55 MPa overpressure caused by hydrocarbons that migrated through the gas chimney and then accumulated beneath subsurface gas hydrate-bearing impermeable sediments. This may have resulted in a submarine slope failure, which disequilibrated the gas hydrate-bearing zone and completely decomposed the gas hydrate once precipitated at site SH5. Before the gas hydrate decomposition, the largely impermeable sediments overlying the gas chimney may have undergone a major upward deformation due to the buoyancy extrusion of the overpressure in the gas chimney, and slope failure was initiated from plastic strain of the sediments and reduced internal strength. Slope failure subsequently resulted in partial gas hydrate decomposition and sediment permeability increase. The pressurized gas in the gas chimney may have diffused into the overlying sediments controlled by seepage-derived deformation, causing an effective stress reduction at the base of the sediments and significant plastic deformation. This may have formed a new cycle of submarine slope failure and finally the total gas hydrate dissociation. The modeling results of buoyancy extrusion and seepage-derived deformation of the overpressure in the gas chimney would provide new understanding in the development of submarine slope failure and the link between slope failure and gas hydrate accumulation and dissociation. 相似文献
17.
A review of the geochemistry of methane in natural gas hydrate 总被引：7，自引：0，他引：7
Keith A. Kvenvolden 《Organic Geochemistry》1995,23(11-12)
The largest accumulations on Earth of natural gas are in the form of gas hydrate, found mainly offshore in outer continental margin sediment and, to a lesser extent, in polar regions commonly associated with permafrost. Measurements of hydrocarbon gas compositions and of carbon-isotopic compositions of methane from natural gas hydrate samples, collected in subaquatic settings from around the world, suggest that methane guest molecules in the water clathrate structures are mainly derived by the microbial reduction of CO2 from sedimentary organic matter. Typically, these hydrocarbon gases are composed of > 99% methane, with carbon-isotopic compositions (δ13CPDB) ranging from − 57 to − 73‰. In only two regions, the Gulf of Mexico and the Caspian Sea, has mainly thermogenic methane been found in gas hydrate. There, hydrocarbon gases have methane contents ranging from 21 to 97%, with δ13C values ranging from − 29 to − 57‰. At a few locations, where the gas hydrate contains a mixture of microbial and thermal methane, microbial methane is always dominant. Continental gas hydrate, identified in Alaska and Russia, also has hydrocarbon gases composed of > 99% methane, with carbon-isotopic compositions ranging from − 41 to − 49‰. These gas hydrate deposits also contain a mixture of microbial and thermal methane, with thermal methane likely to be dominant. Published by Elsevier Science Ltd 相似文献
18.
To look for gas hydrate, 22 multi-channel and 3 single-channel seismic lines on the East China Sea (ECS) shelf slope and at the bottom of the Okinawa Trough were examined. It was found that there was indeed bottom simulating reflector (BSR) occurrence, but it is very rare. Besides several BSRs, a gas seepage was also found. As shown by the data, both the BSR and gas seepage are all related with local geological structures, such as mud diapir, anticline, and fault-controlled graben-like structure. However, similar structural "anomalies" are quite common in the tectonically very active Okinawa Trough region, but very few of them have developed BSR or gas seepage. The article points out that the main reason is probably the low concentration of organic carbon of the sediment in this area. It was speculated that the rare occurrence of gas hydrates in this region is governed by structure-controlled fluid flow. Numerous faults and fractures form a network of high-permeability channels in the sediment and highly fractured igneous basement to allow fluid circulation and ventilation. Fluid flow in this tectonic environment is driven primarily by thermal buoyancy and takes place on a wide range of spatial scales. The fluid flow may play two roles to facilitate hydrate formation:to help gather enough methane into a small area and to modulate the thermal regime. 相似文献
19.
Abstract. The Nankai Trough parallels the Japanese Island, where extensive BSRs have been interpreted from seismic reflection records. High resolution seismic surveys and drilling site-survey wells conducted by the MTI in 1997, 2001 and 2002 have revealed subsurface gas hydrate at a depth of about 290 mbsf (1235 mbsl) in the easternmost part of Nankai Trough. The MITI Nankai Trough wells were drilled in late 1999 and early 2000 to provide physical evidence for the existence of gas hydrate. During field operations, continuous LWD and wire-line well log data were obtained and numerous gas hydrate-bearing cores were recovered. Subsequence sedimentologic and geochemical analyses performed on the cores revealed important geologic controls on the formation and preservation of natural gas hydrate. This knowledge is crucial to predicting the location of other hydrate deposits and their eventual energy resource. Pore-space gas hydrates reside in sandy sediments from 205 to 268 mbsf mostly filling intergranular porosity. Pore waters chloride anomalies, core temperature depression and core observations on visible gas hydrates confirm the presence of pore-space hydrates within moderate to thick sand layers. Gas hydrate-bearing sandy strata typically were 10 cm to a meter thick. Gas hydrate saturations are typically between 60 and 90 % throughout most of the hydrate-dominant sand layers, which are estimated by well log analyses as well as pore water chloride anomalies.
It is necessary for evaluating subfurface fluid dlow behavious to know both porosity and permeability of gas hydrate-bearing sand to evaluate subsurface fluid flow behaviors. Sediment porosities and pore-size distributions were obtained by mercury porosimetry, which indicate that porosities of gas hydrate-bearing sandy strata are approximately 40 %. According to grain size distribution curves, gas hydrate is dominant in fine- to very fine-grained sandy strata. 相似文献
It is necessary for evaluating subfurface fluid dlow behavious to know both porosity and permeability of gas hydrate-bearing sand to evaluate subsurface fluid flow behaviors. Sediment porosities and pore-size distributions were obtained by mercury porosimetry, which indicate that porosities of gas hydrate-bearing sandy strata are approximately 40 %. According to grain size distribution curves, gas hydrate is dominant in fine- to very fine-grained sandy strata. 相似文献
20.
海上气态烃快速测试与西沙海槽天然气水合物资源勘查 总被引：15，自引：6，他引：15
西沙海槽具有适合天然气水合物形成和赋存的地形地貌及地质条件 ,是中国海洋天然气水合物资源勘查的远景区。为配合中国首次天然气水合物资源的调查研究 ,在该区进行了海底表层沉积物甲烷、乙烷等气态烃快速现场测试。研究发现 ,海底沉积物随着埋深的增加气态烃含量具有增高的趋势 ;最佳取样深度应在埋深 1～ 4m处 ;海底沉积物甲烷高含量异常区域主要分布在B33周围、A0 9—A11周围、B17—A0 2周围和B0 1—B0 3周围等区域。西沙海槽北部陆坡比槽底及南部斜坡具有更好的甲烷异常显示。该研究成果为以后该区天然气水合物资源的重点勘查提供了科学依据 相似文献