Quantitative characterization of deep-water gravity flow sand body in the Chang 73 submember in Huachi area, Ordos Basin: A case study of sandbodies encountered drilling of Y1-1 and Y2-1 horizontal wells

  • Xiujuan WANG , 1, 2, 3, 4 ,
  • Honggang XIN 2, 3 ,
  • Dangxing CHENG 2, 3 ,
  • Dongxia CHEN 1, 4 ,
  • Shutong LI 5, 6
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  • 1. College of Geosciences,China University of Petroleum (Beijing),Beijing 102249,China
  • 2. Research Institute of Exploration and Development,PetroChina Changqing Oilfield Company,Xi’an 710018,China
  • 3. National Engineering Laboratory for Exploration and Development of Low Permeability Oil and Gas Fields,Xi’an 710018,China
  • 4. National Key Laboratory of Petroleum Resources and Engineering,China University of Petroleum (Beijing),Beijing 102249,China
  • 5. Northwest Institute of Eco⁃Environment and Resources,Chinese Academy of Science,Lanzhou 730000,China
  • 6. Key Laboratory of Oil and Gas Resources Exploration and Evaluation in Gansu Province,Lanzhou 730000,China

Received date: 2024-01-16

  Revised date: 2024-04-15

  Online published: 2024-04-25

Supported by

The National Natural Science Foundation of China(41772142)

the Key Research and Development Program of Gansu Province(Industrial)(23YFGM0002)

the Science and Technology Major Project of CNPC(2023ZZ15)

the Science and Technology Plan of Gansu Province, China(22JRSRA045)

Abstract

The blocky powdery fine sand bodies deposited by deep-water gravity flow are the main “sweet spot” for shale oil exploration and development in the seventh member of Yanchang Formation (Chang 7 Member) in Ordos Basin. Quantitatively and accurately characterizing the scale and spatial distribution of powdery fine sand bodies, improving the drilling rate of horizontal well sandbodies, is crucial for the successful development of shale oil in this layer. Using core, logging, and imaging logging data from the Y1-1 and Y2-1 horizontal wells in the Huachi area, combined with 2D seismic data, the lithology, combination structure, thickness, width, and extension direction of the gravity flow sedimentary sandbody in the Chang 73 submember of the area were finely characterized, quantitatively characterizing the width to thickness ratio and scale of different types of sandbody groups. Research has shown that the lithology of the sandbody in the study area's Chang 73 submember is mainly composed of fine sandstone and siltstone, with quartz (36.6%-42.3%) and feldspar (32.6%-45.6%) as the main mineral components, and clay mineral content ranging from 12.2% to 18.6%. The thickness of a single stage (individual) sandbody is generally 0.6-5.0 m, with a width mostly less than 150 m, mainly distributed in the SW → NE direction; the structure of the sandbody group can be divided into three types: isolated type, interval stacking type, and continuous stacking type. Their width to thickness ratio is 95∶1 (isolated type), 344∶1 (interval stacking type), and 144∶1 (continuous stacking type), respectively. The length in the NE direction is 3 000-4 000 m. The lower part of the Chang 73 submember has good sedimentary continuity and a wide distribution range of thick sandbody groups (>5 m), while the middle and upper parts of the Chang 73 submember have poor sedimentary continuity and a small distribution range of thick sand body groups.

Cite this article

Xiujuan WANG , Honggang XIN , Dangxing CHENG , Dongxia CHEN , Shutong LI . Quantitative characterization of deep-water gravity flow sand body in the Chang 73 submember in Huachi area, Ordos Basin: A case study of sandbodies encountered drilling of Y1-1 and Y2-1 horizontal wells[J]. Natural Gas Geoscience, 2024 , 35(12) : 2142 -2154 . DOI: 10.11764/j.issn.1672-1926.2024.04.016

0 引言

鄂尔多斯盆地三叠系延长组7段(长7段)页岩油资源潜力巨大,勘探开发前景广阔1-2,估算页岩油可采资源量达(10~15)×108 t3-6。中国石油长庆油田分公司依据鄂尔多斯盆地长7段内重力流沉积砂岩与原地泥页岩的配置关系、砂地比及单砂体厚度等地质特征,将页岩油类型分为多期砂岩叠置型(Ⅰ类)、含砂岩夹层泥页岩型(Ⅱ类)和页理型(Ⅲ类)3种类型7-10。目前,长7段内Ⅰ类页岩油探明储量达11.5×108 t,并已成功规模开发,建成10亿吨级的庆城大油田7。另外,Ⅱ类页岩油也取得了重大勘探突破8。重力流沉积的细砂岩和粉砂岩是Ⅰ类和Ⅱ类页岩油的主要储层甜点811-12,水平井对“甜点”砂体的钻遇率是决定页岩油开发成效的关键812-13
大量的井资料对比表明,湖盆中央深水区内的长7段重力流砂体具有厚度不稳定、连续性差、空间分布规律性不强等特点13-16。区域内高精度三维地震覆盖范围十分有限,二维地震受黄土高原地貌的影响,品质较差、分辨率低,加之单砂体厚度多不足5 m。因此,利用地震资料识别和追踪长7段(特别是长73亚段)泥页岩内的薄层砂体存在较大困难9-101217-18。目前,长73亚段泥页岩内薄层砂体的发育规模主要利用测井资料进行刻画和预测,但这种预测无法精确地表征砂体的空间分布方向及规模,很难基于此而提高长7段Ⅱ类页岩油水平井甜点砂体的钻遇率。如何定量刻画并准确地追踪甜点砂体是鄂尔多斯盆地长7段Ⅰ类和Ⅱ类页岩油勘探开发的关键,更是难点。因此,亟需建立砂体厚度和宽度及延伸距离之间的定量关系,对深水重力流沉积砂体的空间展布做定量约束,以更加准确地确定出砂体分布范围及规模大小,进而为盆地长7段页岩油的勘探开发提供参考。
长期以来,对野外露头的解剖是刻画鄂尔多斯盆地内深湖区重力流沉积的薄层砂体空间展布的主要手段,基于此建立的砂体展布模式对页岩油勘探开发具有一定参考意义19-22,但是如何借助钻井、测井和精度有限的二维地震资料对盆地内重力流薄层砂体进行精细刻画仍未取得突破。随着鄂尔多斯盆地长7段湖相含砂岩夹层泥页岩型(Ⅱ类)页岩油勘探开发的不断深入,定量、准确地刻画薄层粉、细砂岩空间分布迫在眉睫。基于此,本文研究重点利用华池地区以延长组长73亚段为目的层位的Y1-1和Y2-1两口水平井的岩心、录井、成像测井等资料,对其钻遇砂体的类型、数量、厚度以及宽度进行定量统计,并精细刻画重力流沉积砂体结构类型和展布方向,定量表征不同结构类型砂体的垂向厚度和纵向的延伸长度,并分析了其宽厚比;在此基础上,建立了研究区长73亚段重力流砂体的空间分布。本文研究旨在为鄂尔多斯盆地长73亚段页岩油水平井的设计和部署以及页岩油的勘探开发提供理论指导,并为认识古代湖相重力流沉积体发育规模和形态提供具体的研究案例。

1 地质背景

鄂尔多斯盆地是中国第二大沉积盆地,面积约为25×104 km2,盆地边缘断裂褶皱较发育,而盆地内部构造则相对简单,地层平缓,倾角一般不足1°1323-25。本文着重研究的Y1-1、Y2-1水平井位于盆地中南部华池地区,属于伊陕斜坡构造单元(图1)。盆地三叠系延长组由新到老,可划分为长1至长10段共10个段,延长组记录了盆地内三叠纪湖盆从形成、发展、鼎盛到萎缩消亡的整个演化过程,其中长7段沉积期为湖盆鼎盛期,半深湖—深湖面积可达6.5×104 km2 [926-27。根据次一级沉积旋回、岩性组合及地层厚度,长7段自上而下分为长71、长72、长73 共3个亚段246913。长73亚段沉积期,华池地区处于湖盆中央深水区,主要以黑色富有机质泥页岩和重力流沉积为主。研究表明,区域内重力流沉积物主要分为滑动—滑塌沉积、砂质碎屑流沉积和浊流沉积3种类型13
图1 华池地区构造位置(a)及井位(b)

Fig.1 Regional tectonic sketch(a) and well location(b) of the Huachi area

2 砂体特征及其结构类型

2.1 砂体类型及特征

研究区长73亚段内储层砂体主要为细砂岩和粉砂岩。细砂岩以灰色块状为特征[图2(a)],为砂质碎屑流沉积13。矿物分析表明,其石英平均含量为36.6%,长石平均含量为45.6%,黏土矿物平均含量为12.2%[图2(c)]。粒度分析表明,细砂岩中细砂级(0.125~0.25 mm)颗粒占比为51.67%,极细砂(0.062 5~0.125 mm)颗粒占比为43.06%,粗粉砂(0.031 2~0.062 5 mm)颗粒占比为4.27%,其中C值为0.200 6 mm,M值为0.110 6 mm[图2(e)]。粉砂岩以灰色块状为主,部分发育平行层理、沙纹层理和水平层理,其主要为浊流沉积砂体13[(图2(b)];粉砂岩岩石成分主要由石英和长石组成,石英含量最高,平均含量为42.3%,长石平均含量为32.6%,黏土矿物含量平均为18.6%,黄铁矿为1.0%左右[图2(d)];从粒度分布参数统计中可知粉砂岩中,细砂(0.125~0.25 mm)颗粒占比为33.42%,极细砂(0.062 5~0.125 mm)颗粒占比为58.47%,粗粉砂(0.031 2~0.062 5 mm)颗粒占比为7.11%,其中C值为0.230 6 mm,M值为0.126 5 mm[图2(f)]。
图2 研究区长73亚段砂体类型及特征

(a)Y1-1井,长73亚段,2 030.39 m,细砂岩;(b)Y1-1井,长73亚段,2 054.23 m,粉砂岩; (c)Y1-1井,长73亚段,2 034.56 m,细砂岩;(d)Y1-1井,长73亚段,2 014.05 m,粉砂岩;(e)细砂岩粒度分布参数统计图;(f)粉砂岩粒度分布参数统计图

Fig.2 Types and characteristics of Chang 73 submember sand body in the study area

2.2 砂体组合结构

研究区长73亚段主要发育滑动—滑塌、砂质碎屑流、浊流3种沉积类型的重力流砂体13,不同沉积期的重力流砂体在空间上相互叠置形成不同组合类型的重力流砂体结构。利用Y1-1D导眼井以及Y1-1、Y2-1水平井的岩心、录井和测井等资料,将研究区内长73亚段深水重力流砂体的组合结构分为孤立型、间隔叠加型和连续叠加型3种(图3)。
图3 研究区长73亚段砂体结构类型及钻井响应特征

Fig.3 Structure type and drilling response characteristics of Chang 73 submember sand body in the study area

孤立型砂体以砂质碎屑流沉积的块状细砂岩为主,其底部常发育滑移变形的砂岩和泥岩混合沉积。测井曲线上,砂岩段的自然伽马(GR)和声波时差(AC)曲线表现为明显的单一“箱形”(图4)。该类单砂体的直井钻遇厚度一般为5 m左右,水平井上连续钻遇长度超过100 m。间隔叠加型砂体以浊流沉积的粉—细砂岩为主,发育沙纹、水平层理。单砂体间存在稳定的泥页岩,GR、AC曲线表现为“锯齿状”;直井上,钻遇单砂体厚度一般为2 m左右,水平井钻遇长度30~50 m。连续叠加型砂体为砂质碎屑流、滑塌和浊流混合沉积的细砂岩和粉砂岩,岩心可观察到砂脉注入和软沉积变形等沉积构造;测井上,GR、AC曲线整体表现为“齿化箱形”,单砂体厚度一般小于2 m,其在水平井段的延伸长度一般在60 m以上。
图4 研究区长73亚段砂体叠加类型及空间分布对比

Fig.4 Stacking type and spatial distribution of the Chang 73 submember sand body in the study area

在研究区SE方向的连井剖面上(图4),长73亚段下部主要以连续叠加型组合砂体为主。长73亚段沉积期,区域地震与火山活动频繁28,使得盆地西南陡坡带未固结的沉积物频繁发生失稳滑塌,形成浊流事件,并将砂质沉积物搬运到湖盆中央,形成连续叠加的砂体13;而长73亚段中、上部主要为间隔叠加型和孤立型砂体组合结构,这指示重力流事件频次降低,砂体之间存在泥页岩,这与长73中、晚期随着湖盆演化趋于稳定,周缘火山活动逐渐减弱相一致。在NE方向的连井剖面上,长73亚段砂体结构类型由连续叠加型组合砂体向孤立型砂体组合结构转变,但越往湖盆中心,砂体以连续叠加型组合砂体为主,并且砂体数量逐渐减少,而泥岩和页岩沉积厚度逐渐增大(图4)。

3 砂体展布方向

本文研究利用TBEI过钻头电成像测井、TBDI过钻头声波测井以及岩屑录井资料,对Y1-1、Y2-1水平井钻遇砂体进行了精细的识别和追踪。Y1-1D导眼井岩心观察表明甜点砂体(T砂体)为典型的砂质碎屑流沉积,Y1-1、Y2-1两水平井钻遇T砂体的垂向有效厚度分别为6.16 m、6.69 m。钻井显示,Y1-1井水平井于斜深2 218 m处初次钻遇T砂体,于2 339 m时钻井轨迹以大角度(井轨迹与砂体顶面的夹角>45°)穿出该砂体,对应井斜角为90.55°。与Y1-1井相距200 m的Y2-1水平井于斜深2 277 m处初次钻遇T砂体,并在2 488 m大角度切出T砂体,对应井斜角89.66°(图5),两口水平井钻井轨迹均与T砂体大角度切出,说明T砂体在钻进方向上形成了尖灭。
图5 Y1-1、Y2-1水平井长73亚段砂体对比

Fig.5 Comparison of Chang 73 submember and body in Y1-1 and Y2-1 horizontal wells

Y1-1水平井2 500~2 900 m段和Y2-1水平井2 600~3 000 m段的录井、自然伽马成像特征十分相似,且均对应Y1-1D导眼井2 031~2 037 m,因而为同一砂体(即T砂体)。这也指示T砂体在两水平井间200 m的范围内,稳定延伸(图5)。另外,在两口水平井钻遇的其他5套砂体也有很好的对应关系。因此,我们认为研究区内重力流砂体在垂直水平井钻进方向上(SW→NE向)延伸性好。与之相反,在水平井钻进方向(SE→NW向)上,砂体延续性差、被泥页岩频繁间断。
对过Y1-1D导眼井的二维地震剖面分析表明,长7段泥页岩在二维地震剖面上表现为强反射特征,且长7段 TT7层的反射强弱与长72和长73亚段的砂泥比有关,砂岩越发育、砂泥比越高,TT7层反射越弱、振幅能量越低(表1)。
表1 长72+3亚段砂岩发育程度与对应的TT7层地震反射特征

Table 1 The development of Chang 72+3 submember sandstone and the seismic reflection of TT7

井号 长72+3泥厚/m 长72+3砂厚/m 砂泥比 波形特征 振幅能量
C80 55.1 16.1 0.292 中强波峰 19 365
S179 35.2 14 0.398 中弱波峰 14 559
W114 21.7 12.4 0.571 弱波峰 10 620
S178 20.2 23.1 1.15 弱波峰 9 210
研究区位于盆地内构造平缓的伊陕斜坡上,延长组地层倾角小(<1°),因此,整体上地震反射面基本水平(图6)。过 W114 井的 SW→NE 走向地震剖面,TT7反射层连续性好,反射面平直,整体为中—低振幅能量,指示地层岩性较为稳定、砂岩发育好[图6(a)];近Y1-1D导眼井的 SW→NE 走向地震剖面,TT7反射层连续性好、反射面平直,在Y1-1 水平井轨迹投影初始段为中—低振幅能量,而中后段则为中—高振幅能量,指示SW→NE方向上地层砂泥比增加,砂岩累计厚度变大[图6(b)];Y1-1井西部的SE→NW 走向地震剖面,TT7反射层整体连续性好、反射面整体平直,局部存在弱的起伏,以中—高振幅能量为主,指示地层岩性相对稳定、砂岩厚度薄[图6(c)];Y1-1井东部的SE→NW 走向地震剖面,TT7反射层受重力流砂体干扰,表现为低振幅能量,连续性较差,反射面起伏大,指示地层岩性变化大、砂岩厚度大[图6(d)]。
图6 Y1-1水平井组的地震剖面特征(剖面位置见图1(b))

(a)过 W114 井的 SW→NE 走向地震剖面; (b)近Y1-1D导眼井的 SW→NE 走向地震剖面;(c)Y1-1 井西部的 SE→NW 走向地震剖面;(d) Y1-1井东部的 SE→NW 走向地震剖面。注:地震剖面位置见图1(b),红色曲线为Y1-1水平井轨迹投影,箭头所指为TT7反射层

Fig.6 Seismic reflection profiles in the Y1-1 horizontal well group(the profile position is shown in Fig.1(b))

综合4条二维地震剖面分析认为,在SW→NE 方向的TT7反射层整体为中—低振幅能量,连续性好,反射面平直,指示地层岩性较为稳定;而在SE→NW 走向TT7反射层表现为低振幅能量,连续性较差,反射面起伏大,指示地层岩性变化快。这与上文水平井钻井显示一致,即重力流砂体沿SW→NE方向连续性好,厚度稳定。

4 砂体发育规模定量表征

4.1 砂体宽厚比定量表征

研究区Y1-1、Y2-1两口水平井的导眼井为Y1-1D,两水平井间距为200 m,钻进方位均为345°。其中Y1-1水平井从着陆点2 218 m起,水平段总位移1 667 m,Y2-1水平井从入窗点2 340 m起,水平段总位移1 800 m(图7)。Y1-1、Y2-1水平井段井斜角为87°~91°,因此两口水平井钻遇砂体的长度近似等于砂体宽度。基于此,本文研究利用NeoScope伽马成像和PD Orbit的近钻头方位伽马测量工具进行砂体的识别和追踪,结合TBEI过钻头电成像测井、TBDI过钻头声波测井以及岩屑录井,对两口水平井钻遇砂体的宽度进行了定量刻画。综合解释结果来看,Y1-1井钻遇细砂岩31段,粉砂岩7段,泥页岩28段,细砂岩、粉砂岩、泥页岩钻遇长度占比分别为47.76%、10.45%、41.79%,其中累计钻遇粉—细砂岩956 m,泥页岩711 m813;Y2-1井钻遇细砂岩26段,粉砂岩10段,泥页岩26段,细砂岩、粉砂岩、泥页岩钻遇长度占比分别为41.94%、16.12%、41.94%,累计钻遇粉—细砂岩727 m,泥页岩1 073 m813。研究表明,单砂体厚度为0.25~6.69 m,平均为1.05 m;细砂岩的砂体宽度最大宽度为500 m,一般细砂岩类型的单砂体宽度在20~140 m范围,而粉细砂岩薄层单砂体的宽度一般为5~20 m;单砂体宽度在80~140 m范围内的砂体连续叠加后其累计宽度可达200~310 m,20~105 m单砂体宽度范围的6期单砂体间隔叠加累计宽度可达205~260 m(图7)。
图7 Y1-1、Y2-1水平井砂体的识别及定量刻画

Fig.7 Quantitative characterization of sand bodies in \Y1-1 and Y2-1 horizontal wells

本文研究选取了Y1-1、Y2-1水平井上钻井、测井、录井反映最好的61个单砂体,统计其宽度与厚度结果显示,单砂体宽度为2~133 m,平均为27.48 m,单砂体厚度为0.25~6.69 m,平均为1.05 m,单砂体平均宽厚比为26∶1。砂体宽度和厚度相关性分析发现,二者幂函数相关性好,决定系数R 2为0.58[图8(a)],关系式为:y(宽度)=0.095 9x(厚度)0.686 4
图8 Y1-1、Y2-1水平井长73亚段砂体宽度与厚度相关性分析

Fig.8 Correlation analysis between width and thickness of Chang 73 submember sand bodies in Y1-1 and Y2-1 horizontal wells

按照砂体结构,将Y1-1、Y2-1水平井上的61个单砂体归为22套叠加砂体,统计叠加砂体钻遇长度与厚度结果显示,孤立型砂体宽度为4~121 m,平均为42.33 m,砂体厚度为0.02~6.69 m,平均为2.30 m,单砂体平均宽厚比为95∶1;间隔叠加型砂体宽度为44~286 m,平均为130.33 m,砂体厚度为0.08~2.45 m,平均为1.01 m,单砂体平均宽厚比为344∶1;连续叠加型砂体宽度为12~146 m,平均为67.90 m,砂体厚度为0.08~1.58 m,平均为0.56 m,单砂体平均宽厚比为144∶1。对砂体平均叠加宽度和平均叠加厚度相关性分析发现,二者之间幂函数相关性依然最好:孤立型y=0.001 2x 1.863 9R 2=0.86;间隔叠加型y=0.001 1x 1.330 2R 2=0.32;连续叠加型y=0.011 1x 0.911 5R 2=0.70(表2)。钻遇叠加砂体平均宽度与平均厚度的比分别为:孤立型95∶1;间隔叠加型344∶1;连续叠加型144∶1[表2图8(b)—图8(d)]。
表2 Y1-1、Y2-1水平井长73亚段砂体宽度与厚度统计

Table 2 Statistics of width and thickness of Chang 73 submember sand bodies in Y1-1 and Y2-1 horizontal wells

类型 平均宽度/m 平均厚度/m 平均宽厚比 关系式 R 2
单砂体 27.48 1.05 26∶1 y=0.095 9x 0.686 4 0.58
孤立型砂体 42.33 2.30 95∶1 y=0.001 2x 1.863 9 0.86
间隔叠加砂体 130.33 1.01 344∶1 y=0.001 1x 1.330 2 0.32
连续叠加砂体 67.90 0.56 144∶1 y=0.011 1x 0.911 5 0.70

4.2 砂体空间分布定量表征

根据单砂体宽厚比、砂体结构、叠加砂体累计宽度与厚度比,对研究区长73亚段砂体空间展布进行了刻画。根据研究区NW方向和NE方向连井剖面,长73亚段单砂体井间可对比性差,但其相互叠加后可在井间进行较好的对比。NW方向上,单砂体延伸距离一般小于井间距,单砂体井间对比性差,砂体叠加后其宽度大幅度增加,方可在井间进行对比[图9(a)]。NE方向上,单砂体延伸距离长,一般超过井间距,最长3 000~4 000 m,叠加砂体的延伸长度可达5 000 m[图9(b)]。长73早期砂体单砂体沉积厚度薄,但其在纵向、横向上连续叠加,因而各井上砂体均有显示,进而增加了砂体的连片性;长73中—晚期砂体沉积频次变低,单砂沉积变厚,砂体间隔叠加或者相互孤立,砂体连片性变差。
图9 华池地区长73亚段砂体垂物源方向(a)和顺物源方向(b)连井剖面

Fig.9 Vertical source direction(a) and along provenance direction(b) of well connection profile diagram of Chang 73 submember sand bodies in Huachi area

基于以上单砂体、叠加砂体宽度和延伸长度定量分析结果,精细刻画了研究区长73亚段砂体平面展布(图10)。长73早期重力流沉积频次高,砂体主要为间隔型和连续叠加型为主的组合类型,砂体叠加后有效地增加了砂体在横向和纵向的分布范围,同时,局部砂体的叠加厚度增大,主砂体厚度可达5~7 m。长73中期,重力流沉积频次变低,砂体以孤立型和间隔型叠加砂体为主,砂体整体上以NE方向呈坨状展布,叠加面积整体上减小,叠加累计厚度小,以1~3 m为主;长73晚期以孤立型砂体为主,砂体在横向和纵向的分布均受到限制,砂体累计厚度多小于3 m。
图10 研究区长73亚段沉积早、中、晚期砂体厚度平面展布

Fig.10 Plan layout of early, middle and late sedimentation stages sand body thickness of Chang 73 submember in the study area

5 结论

(1)研究区长73亚段重力流沉积砂体岩性以细砂岩和粉砂岩为主,细砂岩岩石成分石英含量为36.6%,长石含量为45.6%,黏土矿物含量为12.2%,细砂岩中细砂级颗粒占比51.67%,极细砂占比43.06%,粗粉砂颗粒占比4.27%;粉砂岩岩石成分石英含量为42.3%,长石为32.6%,黏土矿物含量为18.6%,黄铁矿为1.0%,粉砂岩中,细砂颗粒占比33.42%,极细砂颗粒占比58.47%,粗粉砂颗粒占比7.11%;砂体组合结构可划分为孤立型、间隔叠加型及连续叠加型3种类型。
--引用第三方内容--

(2)研究区长73亚段重力流砂体展布方向为SW→NE向,单砂体厚度为0.25~6.69 m,平均为1.05 m;细砂岩单砂体宽度为20~140 m,粉细砂岩薄层单砂体的宽度一般为5~20 m;连续叠加型砂体累计宽度可达200~310 m,间隔叠加型砂体累计宽度可达205~260 m。

(3)研究区长73亚段砂体在SE→NW方向上单砂体宽厚比为1∶46;叠加后砂体的厚度和宽度均增大,叠加型砂体宽厚比分别为95∶1(孤立型)、344∶1(间隔叠加型)、144∶1(连续叠加型),延伸距离为3 000~4 000 m。
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Outlines

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