Quantitative prediction of channel sand bodies based on seismic peak attributes in the frequency domain and its application

The boundary identification and quantitative thickness prediction of channel sand bodies are always difficult in seismic exploration.We present a new method for boundary identification and quantitative thickness prediction of channel sand bodies based on seismic peak attributes in the frequency domain.Using seismic forward modeling of a typical thin channel sand body,a new seismic attribute-the ratio of peak frequency to amplitude was constructed.Theoretical study demonstrated that seismic peak frequency is sensitive to the thickness of the channel sand bodies,while the amplitude attribute is sensitive to the strata lithology.The ratio of the two attributes can highlight the boundaries of the channel sand body.Moreover,the thickness of the thin channel sand bodies can be determined using the relationship between seismic peak frequency and thin layer thickness.Practical applications have demonstrated that the seismic peak frequency attribute can depict the horizontal distribution characteristics of channels very well.The ratio of peak frequency to amplitude attribute can improve the identification ability of channel sand body boundaries.Quantitative prediction and boundary identification of channel sand bodies with seismic peak attributes in the frequency domain are feasible.

Composite Sand Bodies Architecture of Deep-Water Turbidite Channels in the Niger Delta Basin

Deep-water turbidite channels have attracted much attention as a focused issue in petroleum exploration and development. Extensive studies have been performed on the architecture of turbidite channels, and most researches have focused on their geometric shapes, sedimentary processes and controlling factors. However, little attention has been paid to the distribution patterns, distribution laws and quantitative studies of composite sand bodies of turbidite channels. Taken one slope area of the Niger Delta Basin as an example, this study conducted a semi-quantitative to quantitative analysis on architecture of composite sand bodies of turbidite channels based on cores, well logging and seismic surveys. It is shown that turbidite channel systems can be classified as confined and unconfined channel systems. For confined channel systems, the vertical evolution process involves four stages. The sinuosity of a channel system is controlled by slope, with a negative power function relationship between them. When slope gradient reaches four degrees, the channel system is nearly straight. Based on the migration direction and migration amount of single channels within channel complexes, channel composite patterns can be divided into four classes（the lateral composite, en-echelon composite, swing composite and vertical composite） and several subclasses. Various channel composite patterns show specific distribution laws spatially. For meandering channel complexes at the middle-late evolution stage of confined channel systems, the lateral migration amongst single channels shows the features of integrity and succession. The sinuosity of single channels in the late period is greater than that in the early period, and cut-offs may occur locally when the sinuosity is larger than five degrees. This study provides a better understanding for the geological theory of deep-water sedimentary, and also improves exploitation benefits of this type of reservoirs.

Side lobes of wavelets impact identification of thin sand bodies

Recently, we found that side lobes of wavelets have a large impact on the identification of thin sand reservoirs when studying some gas fields in a basin in Northwest China. Reflections from the top of the H Formation, in which there are gas-bearing thin sand bodies, have the main wavelet lobe between two weak peak side lobes. The lower one always mixes with another peak reflected from the top of a thin sand reservoir. That makes it difficult to identify the sand reservoir. In order to solve this, many forward models were set up using typical well logs. 2D synthetic profiles were produced using Ricker wavelets to study the relationships between the effects of wavelet side lobes and thin sand position and frequency and between amplitude and the thin sand body. We developed the following conclusions： First, it is easier to identify thin sands in a shallower position. Second, a good way to tell sand body reflections from side lobes is by comparing profiles with different frequency windows. Third, it is helpful and effective to describe sand extent using amplitude attributes.

Braided river and distribution patterns of sand bodies of Jurassic Badaowan formation in Block T13 of Junggar basin

In order to determine the planar and volume distribution of sand bodies of the Jurassic Badaowan formation in Block T13 of Junggar basin,we used analysis of field outcrop and 3D seismic data,which play an essential role in areas of sparse well coverage.We describe sedimentary facies characteristics,sand body planforms,width and connectivity patterns of sand bodies,and vertical associations and successions by acoustic impedance inversion technology and sedimentological theory.Results of our study show braided fluvial strata deposits in the Jurassic Badaowan formation.Each sand body is approximately lenticular in shape.The width of each sand body falls in the range 100～800 m,with most between 200 and 400 m.The sand bodies vary in thickness from 4 to 13 m,with most below 9 m.The width/thickness ratios lie in the range 20～55.The connectivity of braided fluvial channel sand bodies is controlled by changes of accommodation space.One fining-upward sedimentary cycle of base-level rise is recognized in Badaowan formation,representing an upward rise of base level.The connectivity of sand bodies was found to be greatest in the early stage of base-level rise,becoming progressively worse with increasing base-level rise.

Effect of Sand Body Enrichment Under the Restriction of a Tectonic Transfer Zone: A Case Study on the Pinghu Formation in the Kongqueting Region on the Pinghu Slope

Results of long-term explorations in the Kongqueting region,located in an East China Sea depression,suggest that the strong fault activity during the sedimentary period of the Pinghu formation significantly influenced the development of the sedimentary system.However,the aggregation and enrichment of the sand body under a tectonic background has become a problem that requires an immediate solution.Considering research outcomes of previous studies,this study used three-dimensional seismic and logging data to identify Y-or H-type and the en echelon distribution patterns of the fault plane,as well as identify the locations wherein the fault growth index value is greater than 1 in the study region,indicating the tectonic background of the fault transfer zone in the region.Second,the development type of the fault transfer zone was studied,and the sand body enrichment site was identified based on seismic inversion data and the development position of the fault transfer point.This helps clarify the evolution of sedimentary facies of the Pinghu formation combined with the sedimentary environment of the braided-river delta.Finally,after summarizing the coupling relationship between the synsedimentary fault systems and the sand body enrichment patterns,three sand-control models were determined,namely,the flexural-parallel,the en echelon collinear,and the torsional-reformed superimposed transfer zones.The findings of this study lay a foundation for the subsequent search of tectonic lithologic oil and gas reservoirs.

Distribution of shallow water delta sand bodies and the genesis of thick layer sand bodies of the Triassic Yanchang Formation, Longdong Area, Ordos Basin

Based on the cores from 47 wells and logging data of 130 wells,the main types of sand bodies in the shallow water delta of the Chang 8_(2) sub-member in the Triassic Yanchang Formation,Longdong Area,Ordos Basin were comprehensively analyzed,the distribution characteristics of sand bodies more than 20 m thick were identified,and the genetic types of the thick sand bodies were sorted out.In this region,thick-bed sand bodies can be divided into two types according to the shape and position:type 1 is the sand body in wide strip and is distributed between the average high water mark and the average low water mark;type 2 is distributed on both sides of the average low water mark and is in irregular lump shape.Based on the principle of the volume distribution of sediments and the change rule of accommodation space,the genetic models of two types of thick-bed sand bodies in the Chang 8_(2) sub-member are superimposed distributary channel sand bodies in high accommodation space and superimposed composite sand bodies in low accommodation space.

Vertical structure and dominating factors of sand body during Late Triassic Chang 9 time of Yanchang Formation in Ordos Basin, NW China

Based on a synthetic geological study of drilling, well logging and core observations, two main genetic types of Chang 9sand body in Odors Basin were recognized, which included two effects, that is, delta environment and tractive current effects that lead to the development of mouth bar, distal bar, sheet sand and other sand bodies of subaerial and subaqueous distributary channel,natural levee, flood fan and delta front, and shore-shallow lake environment and lake flow transformation effects that result in the development of sandy beach bar, sheet sand and other sand bodies. Chang 9 sand body mainly developed five basic vertical structures, namely box shape, campaniform, infundibuliform, finger and dentoid. The vertical stacking patterns of multilayer sand body was complex, and the common shapes included box shape + box shape, campaniform + campaniform, campaniform + box shape, infundibuliform + infundibuliform, campaniform + infundibuliform, box shape + campaniform, box shape + infundibuliform,and finger + finger. Based on the analysis on major dominating factors of vertical structure of sand body, sedimentary environment,sedimentary facies and rise, fall and cycle of base level are identified as the major geological factors that control the vertical structure of single sand body as well as vertical stacking patterns and distribution of multistory sand bodies.

洪海沟矿床北西矿带头屯河组下段砂体非均质性特征与铀成矿关系

近年来由于在伊犁盆地南缘西端洪海沟矿床找矿勘查工作中取得了显著成效,特别是对新层位头屯河组的投入不断增加,落实了特大型规模铀矿床,因此深入研究矿床北西矿带成矿特征对于指导矿床外围勘查工作尤为重要。本次研究分别从砂体外部形态和内部结构两方面入手,对洪海沟矿床北西矿带头屯河组下段砂体厚度、砂地比、非渗透性岩石层数及累计厚度进行了数据统计,对矿床北西矿带头屯河组下段砂体非均质性进行了定量化表征,判断其与铀成矿关系,发现区内含矿砂体受河道沉积相带变化因素较为密切,砂体厚度在20~30 m,砂地比在40%~60%时,非渗透性岩石隔夹层层数为0~2层、累计厚度为0~3 m时,铀成矿几率最高,铀矿化多出现在砂岩粒度为粗粒的部位。本次研究成果对类似铀矿体的寻找以及矿体边界的确定有一定的指导作用。

基于沉积微相和测井参数的储层油水分布规律研究

准噶尔盆地腹部不同区域三工河组储层因埋深的巨大差异使其岩电特征显著差异化,复杂的岩电关系导致无法建立全区统一的含油性测井解释标准。针对上述问题,对研究区内22口取芯井砂组等时性对比和沉积微相及沉积砂体叠置样式分析,利用录井资料确定各等时性砂组的含油性特征;通过沙窝地和征沙村地区油水层的差异化电性特征分析,筛选储层流体敏感测井参数,识别出油水界面,分区域建立油水解释标准,研究其油水分布规律。研究表明,沙窝地地区属于“常规低阻油藏”,征沙村地区属“低对比度油藏”,储层油水分布总体具有“上油下水”、“高油低水”、“上干下油”等特征;垂向上具体表现为3种特征样式:①油水同层—(差油层)—水层—干层;②油水同层—干层差油层互层;③干层—高阻水层互层。油水层和油水界面的分布均表现出明显的相控及层控特征,并受微地貌影响。沙窝地地区油水界面多分布在四砂组,征沙村地区油水界面多分布在五砂组。油层、油水同层发育在四、五砂组的河上坝叠置砂体和河道弱冲刷叠置砂体中,含油水层和差油层发育在三、六砂组的河上坝叠置砂体和河道弱冲刷砂体中,水层和干层主要分布在一、二砂组的河道强冲刷砂体中。分析研究区的油水关系特征有利于为该区域进一步的油气勘探部署提供理论依据,也给区分差异埋藏区、深埋藏区的油藏研究提供参考价值。

静态流动单元划分方法研究

流动单元指一个受砂体及其内部因受边界限制、不连续薄隔挡层、各种沉积微相界面、小断层及渗流率差异等造成的渗流特征相同、水淹特征一致的储层单元。本文以渤海湾盆地某油田为例,综合考虑沉积环境、储层宏观特征、储层微观孔隙结构与流体流动特征等参数,对研究区储层进行流动单元识别与划分,通过参数优选后,选择与水淹程度相关性较好的岩相类型、泥质含量、渗透率、流动带指数与电阻率下降率作为识别参数,主要分为4类静态流动单元,不同类型流动单元具有不同的水淹特征,由于河道砂体整体呈现正韵律,在河道下部往往发育物性较好的Ⅰ类静态流动单元。

渤南低凸起东段明下段砂体差异发育特征及勘探意义

针对渤南低凸起东段明下段主力勘探层系砂体展布规律认识不清的问题,综合运用录井资料、测井资料、分析化验资料和地震资料等开展研究。结果表明:渤南低凸起东段明下段发育1个中期旋回(对应低位体系域、湖侵体系域和高位体系域)和5个短期旋回(对应划分了5个油层组),富砂储层主要发育在低位体系域中的Ⅴ油层组和高位体系域中的Ⅱ油层组。Ⅴ油层组砂体展布受东部物源体系的影响,主要发育河道型砂体和席状型砂体;Ⅱ油层组砂体分布受西部物源体系影响,主要发育河道型砂体、河口坝型砂体和席状型砂体。明下段Ⅴ油层组勘探重点区带在东北部,明下段Ⅱ油层组勘探重点区带在西北部。

川中地区金秋气田侏罗系沙一段有利含气区预测

针对金秋气田沙溪庙组一段(沙一段)河道砂体普遍致密化、物性差且非均质性强的问题,通过正演模拟优选多种叠前属性,运用三维透视和人工智能反演开展砂体边界、储层和含气性预测,优选致密气开发有利区。结果表明:沙一段Ⅲ、Ⅳ砂组河道最发育,河道集中在西部近物源区,向东宽度明显变窄,Ⅱ砂组和Ⅴ砂组次之,Ⅰ砂组河道数量最少。沙一段储层受分流河道控制明显,Ⅲ砂组和Ⅳ砂组储层厚度普遍大于8 m,呈连片状集中分布在西部JQ8井区,或呈条带状局限分布于东部JQ5H井区,Ⅱ砂组和Ⅴ砂组储层厚度为6~8 m,分别位于西部JQ8井区河道交汇处和东部JQ5H井区分流河道内部。通过人工智能有监督的学习,预测各砂组有利含气区,Ⅲ和Ⅳ砂组含气饱和度高,气藏集中分布在JQ8、JQ5H井区河道交汇处,Ⅱ砂组气藏呈窄条状分布在JQ8和JQ5H井区河道发育区,Ⅴ砂组则局限分布在QL7和JH5井区分流河道内。Ⅲ、Ⅳ砂组河道和储层厚度大,含气饱和度高,是致密气开发重点目的层。研究成果可以为川中地区金秋气田沙一段致密气高效开发提供地质依据。

THE SEEPAGE CHARACTERISTICS OF HETEROGENEOUS BODY WITH DIFFERENT SPREADING SOLUTION MODES AND ITS APPLICATIONS

As the dump was a typically heterogeneous body, the seepage was different with varied spreading solution modes. The phenomenon of lamination that occured in the site was simulated using three layers in an indoor experiment, and the seepage effect comparison experiment of the inside spreading solution model and the top spreading solution model have been carried out. In the inside spreading solution mode, the phreatic planar flew without infiltration and the parallel layer motion model was used to calculate the seepage coefficient and equivalent seepage coefficient of each state respectively. In the top spreading solution model, the phreatic planar flew with an even infiltration on the surface, and the vertical layer motion model was adopted to calculate the above coefficient. The results showed that the seepage coefficient of the inside model was larger than the top model in the heterogeneous body, The ratio of them was between 1.42 and 3.07. On the basis of these results, the following new technologies were discussed： installing a few small diameter mechanical pore sand piles with every lamination in the using dump; drilling some holes one-off in the unused dump. These two methods could changed the top spreading solution into the inside model, thus the seepage in the dump was improved.

Measurement of elastic modulus and evaluation of viscoelasticity of foundry green sand

Elastic modulus is an important physical parameter of molding sand; it is closely connected with molding sand’s properties. Based on theories of rheology and molding sand microdeformation, elastic modulus of molding sand was measured and investigated using the intelligent molding sand multi-property tester developed by ourselves. The measuring principle was introduced. Effects of bentonite percentage and compactibility of the molding sand were experimentally studied. Furthermore, the essential viscoelastic nature of green sand was analyzed. It is considered that viscoelastic deformation of molding sand consists mainly of that of Kelvin Body of clay membrane, and elastic modulus of molding sand depends mainly on that of Kelvin Body which is the elastic component of clay membrane between sands. Elastic modulus can be adopted as one of the property parameters, and can be employed to evaluate the viscoelastic properties of molding sand.

鄂尔多斯盆地本溪组碎屑障壁海岸砂体微相南北变化

在延长探区近1500口钻井资料的基础上,进行大量岩心和薄片观察以及砂厚和砂地比统计,探究鄂尔多斯盆地本溪组的砂体微相类型、平面形态和分布的沿岸变化及其控制因素。结果表明,延长气田本溪组总体均为中小潮差环境下的陆源碎屑障壁海岸沉积,但南部的甘泉—富县地区波浪作用较弱,形成了典型的障壁砂坝和障壁后沉积。北部延安—靖边南地区波浪作用较强,形成了改造障壁、浅滩和下切谷充填潮道3种主要微相砂体。障壁砂体呈平行岸线的带状或串珠状排列,近源和近岸分布;浅滩砂体呈多个分散的卵圆形远源远岸分布;潮道带砂体充填则受控于古地貌凹槽。该研究结果对延长气田和类似环境的储层识别和评价具有重要的指导意义。

CSAMT在松辽盆地梅里斯地区铀矿勘查中的应用

上白垩统四方台组是松辽盆地北部铀矿找矿的主要层位之一,其铀矿化主要受控于上白垩纪曲流河三角洲沉积体系,工业铀矿体主要在底部砂岩层富集,多呈板状、透镜状,矿体规模与砂体规模、层数等密切相关,砂体规模越大,矿化层越多,矿体规模越大,反之则规模越小。但是上白垩统四方台组底部砂体在松辽盆地西部超覆带内梅里斯地区发育情况尚不明确。以可控源音频大地电磁测深(CSAMT)为手段,利用Occam算法反演得到研究区电阻率断面,结合研究区内各地层岩石电阻率特征,分析了研究区内盖层结构,尤其是找矿目的层上白垩统四方台组的空间分布特征,同时还推断了基底起伏特征以及断裂走向、倾向及其延深情况。研究结果显示:研究区内四方台组河流相砂体主要分布于研究区的东南部,多呈透镜状,整体表现为自南东向北西呈逐渐尖灭的特征,厚度一般不超过180 m。研究成果为钻探工程的部署提供了依据。

鄂尔多斯盆地大牛地气田二叠系山西组砂体叠置模式及油气开发意义

河流相砂体储层构型对致密砂岩中相对优质储层的分布规律和天然气开发具有重要意义。通过野外地质剖面和钻井岩心观察,结合测井、录井和岩心分析测试资料,对鄂尔多斯盆地大牛地气田大12井区二叠系山西组致密砂岩的砂体构型要素、叠置模式及油气开发意义进行了研究。研究结果表明:(1)鄂尔多斯盆地大牛地气田大12井区二叠系山西组发育六级复合辫流带和五级单一辫流带,其中单一辫流带包括河床(分流河道)和河漫共2个四级构型单元,河道内单个心滩沉积包含有三级增生体和落淤层;(2)辫状河三角洲平原五级单一辫流带中的四级泛滥平原沉积较辫状河河漫沉积更加发育,辫状河心滩沉积中落淤层欠发育;(3)山西组上部山2-2亚段辫状河单一辫流带内砂体呈“河道-心滩”连续沉积,泥质不发育,砂体叠置程度高(多呈复合式叠置)、连通性好,优质储层多;(4)山西组中下部山1段和山2-1亚段三角洲平原沉积中,西部河道连片性好,砂体以复合式和侧拼式叠置样式为主,连通性和生产效果均较好,东部砂体多为孤立式和侧接式,砂体钻遇率低,单井产量差。

泌阳凹陷下二门地区生长断层控砂作用研究

泌阳凹陷下二门地区油气资源丰富,油藏类型以断层-岩性油气藏为主,断裂特征与砂体展布的配置关系是该区油气勘探的主控因素。笔者综合3D地震、钻测井、岩心资料,以古近系核桃园组三段Ⅳ油组1小层(Eh3Ⅳ1)为例,通过精细构造解析、断层活动性定量分析和砂体展布特征刻画,从构造活动-沉积响应的角度分析生长断层对辫状河三角洲砂体展布的控制作用。结果表明,下二门地区主要发育一系列SW-NE转近E-W走向的北倾生长正断层,剖面形态呈阶梯状断层组合,各条断层沿走向活动性差异明显。研究区主要发育侯庄辫状河三角洲前缘亚相和前三角洲亚相,平面上来自北部的水下分流河道砂体在断层转换带或同一断层活动性较弱部位易通过,而在活动性较强部位受到限制或转向。垂向上,通过活动性较弱区域砂体垂向连续叠置、加厚发育,通过活动性较强区域砂体垂向间歇分散、减薄发育。该研究可为东部断陷盆地低序级生长断层发育区砂体展布规律认识和断层-岩性油气藏勘探开发提供一定借鉴。

准噶尔盆地齐古组浅水河控三角洲沉积特征及模式探讨

准噶尔盆地腹部A区上侏罗统齐古组是近年来油气勘探的热点地区,多口钻井获得了高产油气流,展示了较大的油气资源潜力。针对齐古组浅水三角洲前缘沉积体系有利砂体分布控制因素及模式不清等问题,综合岩心、测井、地震、重矿物及微量元素等资料,对研究区齐古组浅水河控三角洲沉积特征展开研究。研究表明:浅水河控三角洲形成于多物源供给、水体较浅且频繁震荡、水动力中等的沉积环境,砂体类型以河坝复合体为主,岩石普遍为氧化色。根据砾石层厚度、粒径、层理规模等将河坝复合体划分为主水道+残余河口坝、分支水道+残余河口坝、残余河口坝为主3类。其中,分支水道+残余河口坝、残余河口坝为主的河坝复合体为有利砂体,其分布主要受控于基准面变化、河道供源与古地貌、河流与波浪作用影响。有利砂体纵向上分布在基准面上升的中期;平面上分布在与主水道距离适中的斜坡区和平台区。该研究成果深化了浅水河控三角洲沉积特征研究,可为下一步优选区带提供依据,也可为类似区块提供借鉴。