琼东南盆地华光凹陷天然气水合物成藏条件及有利区带预测

分析了琼东南盆地华光凹陷天然气水合物稳定条件、气源供给来源、运移通道类型等成藏条件,指出了研究区天然气水合物的勘探方向并建立了天然气水合物的成藏模式。华光凹陷浅部沉积层的温度、压力条件满足天然气水合物形成的要求,生物成因甲烷水合物稳定带最大厚度约320m,热成因天然气水合物稳定带最大厚度约为345m。气源岩主要分布在凹陷西部地区的断陷期层序中,具有早、晚两期生烃且以晚期为主的特征,有利于热解成因气在水合物稳定带内的聚集成藏。晚中新世以来快速沉降的巨厚半深海细粒沉积物为生物成因气的形成提供了物质基础。泥底辟与其伴生断裂及多边形断层等构成了天然气水合物成藏的主要流体运移体系。华光凹陷靠近(1)号断裂的西部地区是有利的勘探方向。晚中新世以来的快速沉降使得渐新世成熟—过熟烃源岩大量生气或裂解,而且由于欠压实作用形成的地层超压为含气流体的运移提供了强大的动力。热解天然气和生物气沿着泥底辟和多边形断层等构成的输导网络向上垂向运移至水合物稳定带,形成天然气水合物,其中深水浊流水道是寻找高饱和度水合物的有利目标体。     

琼东南盆地深水区天然气水合物稳定域分布特征与预测

天然气水合物的形成与温度和压力密切相关,低温高压稳定域直接决定了水合物的分布特征及展布规模。根据波诺马列夫经验公式,依据琼东南盆地水合物稳定域形成的关键参数（天然气组分、地温梯度及水深等）,计算了琼东南盆地深水区水合物稳定域厚度,并初步分析了水合物稳定域分布特征。研究表明：水深（压力）越大、地温梯度越小,水合物稳定域厚度越大,当研究区水深达334.1 m时,深水海底浅层即具备了形成甲烷水合物稳定域条件;同时,水合物稳定域分布整体上具有南北薄、中间厚,自西向东逐渐变厚的趋势,主体厚度分布介于200～300 m,最大厚度可达400 m。     

琼东南盆地深水区上新世以来天然气水合物稳定域时空迁移及其分布特征

琼东南盆地深水区天然气水合物富集条件优越,具有巨大的勘探开发前景。基于近年来新获取的海洋地质地球物理关键参数,反演了琼东南盆地深水区上新世（约5 Ma）以来的天然气水合物稳定域迁移过程。研究表明：琼东南盆地现今天然气水合物稳定域主要存在于水深>600 m的海底,约在水深1 800～2 400 m处水合物稳定域厚度达到最大值,约190 m;冰期海平面下降导致水合物稳定域向深海平原迁移,而陆坡-深海平原转换带的水合物稳定域厚度则相对于现今减薄约80 m;岩浆热事件导致深海平原水合物稳定域厚度减薄约50 m,天然气水合物随之分解后释放大量气体导致多边形断层形成。     

天然气水合物稳定带顶底界线及厚度预测

天然气水合物稳定带顶底界线和厚度以及分布范围预测是天然气水合物资源评价的基础，对了解天然气水合物的成藏规律和指导天然气水合物的勘探开发具有重要的指导意义，因此，准确预测天然气水合稳定带顶底界线和厚度非常重要。     

海底天然气水合物稳定带厚度的影响因素

天然气水合物在未来能源、环境及海洋地质灾害等方面有重要意义,是当前研究的热点。海底沉积物中含有大量的天然气水合物资源。天然气水合物稳定带厚度可用于水合物资源量的预测,在水合物资源评估中有重要意义。研究了不同因素对海底天然气水合物稳定带厚度的影响,结果表明:海水深度、地温梯度、孔隙水盐度及组成和气体组分对水合物稳定带厚度的影响不同。水合物稳定带厚度随着海水深度的增加而增大,与地温梯度呈指数递减关系;随着孔隙水盐度的增加水合物稳定带厚度减小并呈良好的线性关系,不同盐类对水合物稳定带厚度的影响程度不同;混合气体中的C2H6、CO2及H2S会使水合物稳定带厚度增加,而N2使水合物稳定带厚度减小,并且含量越大对稳定带厚度的影响越明显。     

琼东南盆地深水区东区凹陷带结构构造及其演化特征

琼东南盆地深水区东区凹陷带,即松南—宝岛—长昌凹陷,位于琼东南盆地中央坳陷东端。在大量地震资料解释的基础上,对38条主要断层进行了详细分析。获得以下认识:(1)琼东南盆地深水区东区凹陷带平面上表现为近EW向展布的平行四边形,剖面结构表现为自西向东由半地堑—不对称的地堑—半地堑有规律变化。(2)琼东南盆地深水区东区凹陷带断裂系统可划分控制凹陷边界断层、控制洼陷沉积中心断层和调节性断层3类。(3)琼东南盆地深水区东区凹陷带古近纪时期受到太平洋板块俯冲和南海海盆扩张的双重影响,构造应力场发生NW—SE→SN转变。构造演化可划分为3个阶段:~32 Ma,应力场以区域性NW—SE向伸展为主,断裂系统以NE—SW向为主,控制凹陷边界;32~26 Ma,以南海海盆近SN向拉张应力场为主,断裂系统以NWW—SEE向为主,断层活动控制凹陷沉积中心;26~ Ma,区域性伸展与南海海盆扩张应力均逐渐减弱,NE—SW向和NWW—SEE向断裂继承性发育。(4)琼东南盆地深水区东区凹陷带内部主要断层在渐新统崖城组和陵水组沉积时期活动速率快,地形高差大、沉积水体深、沉积厚度大,控制了崖城组和陵水组的大规模沉积,有利于烃源岩的发育。圈闭以受断层控制的断鼻和断块为主,长昌主洼凹中隆起带发育2个最为理想的构造圈闭。     

琼东南盆地气烟囱构造特点及其与天然气水合物的关系

气烟囱是由于天然气(或流体)垂向运移在地震剖面上形成的异常反射,是气藏超压、构造低应力和泥页岩封隔层综合作用而形成。气烟囱在形成过程中携带大量富含甲烷气的流体向上运移到天然气水合物稳定带,其形成之后仍可作为后期活动的油气向上运移的特殊通道。在中中新世后,气烟囱是琼东南盆地气体向上运移的通道。地震识别出的似海底反射(BSR)分布区存在大量的气烟囱构造,通过速度、泥岩含量、流体势等属性参数及钻井资料,判断该烟囱构造为有机成因的泥底辟型烟囱构造。     

AVO反演在琼东南海域天然气水合物识别中的应用

为了更好地研究天然气水合物展布形态和赋存情况,利用AVO反演技术对琼东南海域天然气水合物进行了识别。首先通过对不同地层模型下天然气水合物和游离气的AVO属性特征进行了正演模拟分析,获得了天然气水合物AVO属性的响应特征。研究表明,天然气水合物饱和度不同时,其BSR处AVO属性特征也不同。当天然气水合物饱和度较高时,BSR处的AVO属性特征为：截距为负值,梯度为正值,截距×梯度为负值,流体因子为负值;当饱和度较低时,受游离气的影响,其BSR的AVO属性特征为：截距为负值,梯度为负值,截距×梯度为正值,流体因子为负值且幅值较大。鉴此,根据正演分析结果,重点对琼东南海域地震资料进行了天然气水合物AVO属性异常分析,判识确定该区具有高饱和度水合物的AVO属性特征,其天然气水合物勘探潜力大。     

琼东南盆地块体搬运体系对天然气水合物形成的控制作用

琼东南盆地深水区中新世以来构造运动不活跃,自中新世以来沉积物厚度达5 000～9 000 m,Ya35-1-2井显示更新世地层沉积物主要以泥质与砂泥互层的细粒沉积物为主,深部流体垂向运移通道不发育.高分辨率地震资料和3D地震资料表明,琼东南盆地的上新世及其以上地层存在大量气烟囱和块体搬运体系.气烟囱为深部流体垂向运移提...     

琼东南盆地深水区流体势分析及其对天然气水合物成藏的意义

针对深水区缺乏钻井资料的情况,从可以广泛获取的叠加速度出发建立了一套计算地下流体势(气势)的方法,并以此对琼东南盆地深水区进行了实例分析,以此来获得天然气运移和水合物成藏的有益信息。盆地广泛发育断裂、底辟构造,影响着水合物的分布。BSR发育区与气体势场强度的汇聚区域有着较好的对应关系,水合物根据成因可分为两类:一类是以浅部地层生物成因气为主,另一类是以深部热成因气为主。大部分断层对应于相对低势区,反映断层的开启性,可以作为气体运移的通道,其上部发育深部热成因气为主的水合物藏。在构造隆起附近发育的底辟具有相对高气势的特征,这类底辟携带大量的深部热成因气运移至浅部,为水合物的形成提供充足的气源,在其附近剖面上常具有BSR的显示。     

琼东南盆地南部早中新世碳酸盐岩台地的地震解释

The southern uplift of the Qiongdongnan Basin is a deepwater area in which no wells have beens drilled. The Miocene-Quaternary strata in the Xisha Islands, which are located 40–100 km to the south, are composed of carbonate reef formations. Paleotectonic and paleogeographic analyses of the basin suggest that the southern uplift experienced favorable geological conditions for the development of carbonate reefs during the Miocene.The high-impedance carbonates have high amplitudes and low frequencies on seismic profiles. The reefs are distributed on paleotectonic highs and are thicker than the contemporaneous formations. A forward model of the variation in carbonate thickness based on lithological and velocity information from wells in nearby regions can simulate the seismic response of carbonates with different thicknesses. We identified several important controlling points for determining the thickness of carbonates from seismic profiles, including the pinchout point,the λ/4 thickness point, and the λ/2 thickness point. We depict a carbonate thickness map in the deepwater area of the southern Qiongdongnan Basin based on this model. The carbonate thickness map, the paleotectonic and paleogeographic background, and the seismic response characteristics of reefs suggest that the carbonates that developed on the southern uplift of the Qiongdongnan Basin during the Miocene were mainly an isolated carbonate platform peninsula and ramp deposits. It consisted of gentle ramp platform, steep slope platform,platform depression, gravity flow, and reef bank facies.     

南海北部大陆边缘天然气水合物稳定带厚度的地热学研究

The exploration of unconventional and/or new energy resources has become the focus of energy research worldwide,given the shortage of fossil fuels.As a potential energy resource,gas hydrate exists only in the environment of high pressure and low temperature,mainly distributing in the sediments of the seafloor in the continental margins and the permafrost zones in land.The accurate determination of the thickness of gas hydrate stability zone is essential yet challenging in the assessment of the exploitation potential.The majority of previous studies obtain this thickness by detecting the bottom simulating reflectors(BSRs) layer on the seismic profiles.The phase equilibrium between gas hydrate stable state with its temperature and pressure provides an opportunity to derive the thickness with the geothermal method.Based on the latest geothermal dataset,we calculated the thickness of the gas hydrate stability zone(GHSZ) in the north continental margin of the South China Sea.Our results indicate that the thicknesses of gas hydrate stability zone vary greatly in different areas of the northern margin of the South China Sea.The thickness mainly concentrates on 200–300 m and distributes in the southwestern and eastern areas with belt-like shape.We further confirmed a certain relationship between the GHSZ thickness and factors such as heat flow and water depth.The thickness of gas hydrate stability zone is found to be large where the heat flow is relatively low.The GHSZ thickness increases with the increase of the water depth,but it tends to stay steady when the water depth deeper than 3 000 m.The findings would improve the assessment of gas hydrate resource potential in the South China Sea.     

琼东南盆地深水区烃源岩生烃动力学及生气模式

In order to investigate the hydrocarbon generation process and gas potentials of source rocks in deepwater area of the Qiongdongnan Basin, kinetic parameters of gas generation(activation energy distribution and frequency factor) of the Yacheng Formation source rocks(coal and neritic mudstones) was determined by thermal simulation experiments in the closed system and the specific KINETICS Software. The results show that the activation energy(Ea) distribution of C1–C5 generation ranges from 50 to 74 kcal/mol with a frequency factor of 2.4×1015 s–1 for the neritic mudstone and the Ea distribution of C1–C5 generation ranges from 49 to 73 kcal/mol with a frequency factor of 8.92×1013 s–1 for the coal. On the basis of these kinetic parameters and combined with the data of sedimentary burial and paleothermal histories, the gas generation model of the Yacheng Formation source rocks closer to geological condition was worked out, indicating its main gas generation stage at Ro(vitrinite reflectance) of 1.25%–2.8%. Meanwhile, the gas generation process of the source rocks of different structural locations(central part, southern slope and south low uplift) in the Lingshui Sag was simulated. Among them, the gas generation of the Yacheng Formation source rocks in the central part and the southern slope of the sag entered the main gas window at 10 and 5 Ma respectively and the peak gas generation in the southern slope occurred at 3 Ma. The very late peak gas generation and the relatively large gas potential indices(GPI:20×108–60×108 m3/km2) would provide favorable conditions for the accumulation of large natural gas reserves in the deepwater area.     

琼东南盆地深水区中央峡谷油气指标的多重分形性分析

不同形态的多重分形频谱可用于含油气远景评价和油气分布规律的研究,本文运用多重分形矩方法对中央峡谷体系已钻井获得的2 684个数据13项油气指标的多重分形谱函数形态特征进行了研究。结果表明,琼东南盆地深水区中具有较强多重分形特征的指标,具有多重分形谱函数宽而连续的特征,成一右偏弧形状;而其他指标则显示较弱或单一分形特征。将这一结果与常用的统计方法因子分析结果做对比,结果表明,通过多重分形分析对这几项油气指标的分组结果与常规的统计分析结果基本吻合。为更进一步探究这几种主要油气指标在油气指示中的权重,采用主成分分析法对这几种指标进行分析,结果表明在琼东南盆地深水区,异丁烷、正丁烷、异戊烷为圈定油气远景区的重要指标。     

琼东南盆地陵水凹陷海底周期阶坎底形的特征及成因

海底周期阶坎底形一直是海洋地质关注的热点.本文基于285 km2三维地震资料对琼东南盆地海底周期阶坎底形几何构型(波长、波高、迎流面长度、背流面长度、迎流面夹角和背流面夹角)及形成机理进行了分析.研究区位于上陆坡(2°～14°),发育一条NE-SW水道,宽6.5 km,深35 m.水道内外均发育周期阶坎,剖面上具有波状...     

Reservoir characterization of gas hydrate in the Northwestern part of the Ulleung Basin,East Sea

An analysis of 3D seismic data from the northwestern part of the Ulleung Basin, East Sea, revealed that the gas hydrate stability zone (GHSZ) consists of five seismic units separated by regional reflectors. An anticline is present that documents activity of many faults. The seismic indicators of gas hydrate occurrence included bottom simulating reflector (BSR) and acoustic blanking in the gas hydrate occurrence zone (GHOZ). By the analysis of the seismic characteristics and the gradient of the sedimentary strata, the GHOZ was divided into four classes: (1) dipping strata upon strong BSR, (2) dipping strata below strong BSR, (3) parallel strata with acoustic blanking, and (4) parallel strata below weak BSR. Seismic attributes such as reflection strength and instantaneous frequency were computed along the GHOZ. Low reflection strength and high instantaneous frequency were identified above the BSR, indicating the occurrence of gas hydrate. A remarkably high reflection strength and low instantaneous frequency indicated the presence of free gas below the BSR. Considering the distribution of the gas hydrate and free gas, two gas migration processes are suggested: (1) stratigraphic migration through the dipping, permeable strata and (2) structural migration from below the GHSZ along faults.     

南海琼东南盆地新生代构造层序研究

基于南海琼东南盆地到目前为止还没有一个统一的构造层序划分方案的问题,在前人研究工作基础上,通过大量的二维地震构造层序闭合解释,从地震不整合面和构造发育特征识别出发,对新生代主要构造层序进行详细解剖。进一步结合对南海北部琼东南盆地新生代二维地震数据的精细综合分析,重新厘定了其新生代构造层序,并进行了构造层序的识别和划分。结果表明：按古构造运动面可将盆地充填序列划分为上、中、下三个构造层序,分别对应于盆地演化的三个阶段性。着重论述了三个构造层序的结构特征、叠加构造样式、构造层序发育特征、层序分布特征、沉积体系类型和盆地断裂演化序列之间的关系等,以期为今后的研究奠定基础。     

印度克里希纳-戈达瓦里盆地天然气水合物饱和度特征

印度国家天然气水合物计划(NGHP01)于2016年实施第1次钻探,证实了天然气水合物在印度大陆边缘的广泛分布。选择位于克里希纳-戈达瓦里盆地(KG盆地)的NGHP01-07D和NGHP01-15A钻孔,基于测井数据和岩心样品估算天然气水合物饱和度,分析天然气水合物赋存状态并探讨其形成机制。基于各向同性介质模型利用电阻率和声波测井计算NGHP01-15A钻孔的天然气水合物饱和度为0. 2%～33. 0%,平均值为9. 6%,在NGHP01-07D钻孔利用电阻率计算获得的天然气水合物饱和度高于岩心氯离子异常和气体释放获得的结果,但是基于各向同性岩石物理模型利用声波测井计算的天然气水合物饱和度与岩心结果一致,平均值为5. 0%。前人研究认为NGHP01-10D钻孔中天然气水合物以相对较高饱和度富集在高角度裂隙中。结合前人研究结果推断在克里希纳-戈达瓦里盆地存在3种不同的天然气水合物储层,即泥岩中砂质夹层各向同性储层、泥质/粉砂质高角度低连通性的低饱和度裂隙储层和泥岩中高角度高连通性的高饱和度裂隙储层,并提出对应的3种天然气水合物储层模型。     

琼东南盆地深水区第四系乐东组层序地层学特征及其水合物勘探启示

琼东南盆地深水区第四系乐东组是南海北部已证实的天然气水合物主要勘探层系。近年来,其层序地层格架、构成特征以及对天然气水合物稳定域及运聚成藏的控制影响作用等科学问题引发了广泛关注。为了厘清乐东组层序地层格架、构成特征及其展布规律,基于层序地层学理论,结合研究区高分辨率地震资料,建立了乐东组精细层序地层格架及层序样式。依据典型的地震接触关系识别了乐东组复合层序界面T20、T14和T0,同时划分确定了乐东组下段6套三级层序（LDSQ1-6）和上段8套三级层序（LDSQ7-14）。在三级层序内部还进一步识别出初始海泛面、最大海泛面以及最大海退面,在三级层序中进一步划分出低位体系域（LST）、海侵体系域（TST）、高位体系域（HST）和下降体系域（FFST）。研究表明,1.8 Ma以来,红河物源体系沉积物供给充足,乐东组下段陆架边缘体系进积和加积组分厚度大,层序样式主要为H型层序;0.9～0.8 Ma至今,地层以进积叠置样式为主,且峡谷发育频次增大,低位体系域组分占比增大,主要发育L-H型层序。笔者结合国内外相似区域的沉积相模式,明确了层序格架约束下的沉积相发育类型及时空演化特征,为该区域天然气水合物储层预测提供了地质依据。     

琼东南盆地深水区崖城组生成天然气的化学动力学及其应用

The natural gas generation process is simulated by heating source rocks of the Yacheng Formation, including the onshore-offshore mudstone and coal with kerogens of Type II_2-III in the Qiongdongnan Basin. The aim is to quantify the natural gas generation from the Yacheng Formation and to evaluate the geological prediction and kinetic parameters using an optimization procedure based on the basin modeling of the shallow-water area. For this, the hydrocarbons produced have been grouped into four classes(C_1, C_2, C_3 and C_(4-6)). The results show that the onset temperature of methane generation is predicted to occur at 110℃ during the thermal history of sediments since 5.3 Ma by using data extrapolation. The hydrocarbon potential for ethane, propane and heavy gaseous hydrocarbons(C_(4-6)) is found to be almost exhausted at geological temperature of 200℃ when the transformation ratio(TR) is over 0.8, but for which methane is determined to be about 0.5 in the shallow-water area. In contrast, the end temperature of the methane generation in the deep-water area was over 300℃ with a TR over 0.8. It plays an important role in the natural gas exploration of the deep-water basin and other basins in the broad ocean areas of China. Therefore, the natural gas exploration for the deep-water area in the Qiongdongnan Basin shall first aim at the structural traps in the Ledong, Lingshui and Beijiao sags, and in the forward direction of the structure around the sags, and then gradually develop toward the non-structural trap in the deep-water area basin of the broad ocean areas of China.