Multi-scale data joint inversion of minerals and porosity in altered igneous reservoirs—A case study in the South China Sea

There are abundant igneous gas reservoirs in the South China Sea with significant value of research,and lithology classification,mineral analysis and porosity inversion are important links in reservoir evaluation.However,affected by the diverse lithology,complicated mineral and widespread alteration,conventional logging lithology classification and mineral inversion become considerably difficult.At the same time,owing to the limitation of the wireline log response equation,the quantity and accuracy of minerals can hardly meet the exploration requirements of igneous formations.To overcome those issues,this study takes the South China Sea as an example,and combines multi-scale data such as micro rock slices,petrophysical experiments,wireline log and element cutting log to establish a set of joint inversion methods for minerals and porosity of altered igneous rocks.Specifically,we define the lithology and mineral characteristics through core slices and mineral data,and establish an igneous multi-mineral volumetric model.Then we determine element cutting log correction method based on core element data,and combine wireline log and corrected element cutting log to perform the lithology classification and joint inversion of minerals and porosity.However,it is always difficult to determine the elemental eigenvalues of different minerals in inversion.This paper uses multiple linear regression methods to solve this problem.Finally,an integrated inversion technique for altered igneous formations was developed.The results show that the corrected element cutting log are in good agreement with the core element data,and the mineral and porosity results obtained from the joint inversion based on the wireline log and corrected element cutting log are also in good agreement with the core data from X-ray diffraction.The results demonstrate that the inversion technique is applicable and this study provides a new direction for the mineral inversion research of altered igneous formations.

Elastic direct envelope inversion based on wave mode decomposition for multi-parameter reconstruction of strong-scattering media

The parameter reconstruction of strong-scattering media is a challenge for conventional full waveform inversion(FWI).Direct envelope inversion(DEI)is an effective method for large-scale and strongscattering structures imaging without the need of low-frequency seismic data.However,the current DEI methods are all based on the acoustic approximation.Whereas,in real cases,seismic records are the combined effects of the subsurface multi-parameters.Therefore,the study of DEI in elastic media is necessary for the accurate inversion of strong-scattering structures,such as salt domes.In this paper,we propose an elastic direct envelope inversion(EDEI)method based on wave mode decomposition.We define the objective function of EDEI using multi-component seismic data and derive its gradient formulation.To reduce the coupling effects of multi-parameters,we introduce the wave mode decomposition method into the gradient calculation of EDEI.The update of Vp is primarily the contributions of decomposed P-waves.Two approaches on Vs gradient calculation are proposed,i.e.using the petrophysical relation and wave mode decomposition method.Finally,we test the proposed method on a layered salt model and the SEG/EAGE salt model.The results show that the proposed EDEI method can reconstruct reliable large-scale Vp and Vs models of strong-scattering salt structures.The successive elastic FWI can obtain high-precision inversion results of the strong-scattering salt model.The proposed method also has a good anti-noise performance in the moderate noise level.

THE MULTI-PARAMETER INVERSION OF ELASTIC WAVE IN HALF-SPACE

The multi-parameter inverse scattering problem of elastic waveequation with single fre- quency is investigated within Bornapproximation. By use of a wideband measuring scheme in which bothtransmitters and receivers scan over the half-space surface, theformula of the scattering field of elastic wave is derived. Fourtypes of mode conversion of elastic wave(P→P, P→S, S→P, S→S)areseparated from the scattering field. These components containsufficient information for usto recon- struct the configuration ofthe density and Lame parameters of the medium.

Lithological Characterization and Its Application Based on Three-Dimensional Structure-Coupled Joint Inversion of Gravity and Magnetic Data

Incorporating structural-coupling constraint, known as the cross-gradients criterion, helps to improve the focussing trend in cross-plot of multiple physical properties. Based on this feature, a?post-processing technique is studied to characterize the lithological types of subsurface geological materials after joint inversion. A simple domain transform, which converts two kinds of participant physical properties into an artificial complex array, is adopted to extract anomalies manually from homogenous host rock. A synthetic example shows that structure-coupled joint inverted results tend to concentrate on the feature trends in the cross-plot, and the main geological targets are recovered well by a radius-azimuth plot. In a field data example, the lithological characterization?reveals that the main rock types interpreted in the study area agree with the geological information, thus demonstrating the feasibility of this technique.

Comparison between several seismic inversion methods and their application in mountainous coal fields of western China

With the objective of establishing the necessary conditions for 3D seismic data from mountainous areas in western China, we compared the application results of wave impedance technology in the lithology and exploration of coal fields. First, we introduce principles and features of three kinds of inversion methods. i.e., Model-Based Inversion, Constrained Sparse Spike Inversion (CSSI) and Geology-Seismic Feature Inversion. Secondly, these inversion methods are contrasted in their application to 3D seismic data from some coalfields in western China. The main information provided by the research includes: improving the vertical resolution of coal deposit strata, inferring lateral variation of the lithology and predicting coal seams and their roof lithology. Finally, the comparison between the three methods shows that the model-based inversion has the higher resolution, while CSSI inversion has better waveform continuity. The geology-seismic feature inversion requires information from a large number of wells and many types of logging curves of good quality. All three methods can meet the requirements of seismic exploration for lithological exploration in coal fields.

Study of the Sensitive Properties of Marine Gas Hydrate Based on the Prestack Elastic Inversion

Using a bottom simulating reflector(BSR)on a seismic profile to identify marine gas hydrate is a traditional seismic exploration method.However,owing to the abundance differences between the gas hydrate and free gas in different regions,the BSR may be unremarkable on the seismic profile and invisible in certain cases.With the improvement of exploration precision,difficulty arises in meeting the requirements of distinguishing the abundance differences in the gas hydrate based on BSR.Hence,we studied other sensitive attributes to ascertain the existence of gas hydrate and its abundance variations,eventually improving the success rate of drilling and productivity.In this paper,we analyzed the contradiction between the seismic profile data and drilling sampling data from the Blake Ridge.We extracted different attributes and performed multi-parameter constraint analysis based on the prestack elastic wave impedance inversion.Then,we compared the analysis results with the drilling sampling data.Eventually,we determined five sensitive attributes that can better indicate the existence of gas hydrate and its abundance variations.This method overcomes the limitations of recognizing the gas hydrate methods based on BSR or single inversion attribute.Moreover,the conclusions can notably improve the identification accuracy of marine gas hydrate and provide excellent reference significance for the recognition of marine gas hydrate.Notably,the different geological features of reservoirs feature different sensitivities to the prestacking attributes when using the prestack elastic inversion in different areas.

煤矿精细地层模型反演技术研究

针对煤矿三维地质建模中煤层厚度及顶底板岩性准确刻画的难题,提出在传统“点”和“线”数据插值为主的三维地质建模技术基础上,加入三维地震数据作为约束,基于全局插值方法的径向基函数,用“点”和“线”数据对“体”数据精细解释层位进行校正,以校正后的精细地层框架为基础,基于地质统计学反演方法对煤系地层进行了岩性及厚度预测,分析了校正前与校正后地层框架为约束的反演结果准确性。研究结果表明,校正后的反演结果与实际资料的相对误差在5%以内,相较于未校正的反演结果,校正后的反演结果相对误差降低10%,校正后的结果与真实值之间误差控制在0.1 m以内,说明校正后的反演结果与实际水平钻孔结果吻合较好,能够精确刻画各岩性厚度及其空间展布情况。通过分析校正后的反演数据结果发现,地质岩性模型的精度得到极大提高,提高了钻孔间地层信息的准确度,在锦界煤矿取得了较好的应用效果。

针对岩性储层的定量地震波成像

油气地震勘探目标越来越复杂。碎屑岩储层、火山岩储层、碳酸盐岩储层、非常规储层都已成为油气勘探的目标。地震波成像技术由定性的、带限反射系数为成像目标转为定量的、宽带波阻抗为成像目标,这是面对复杂储层勘探时的必然选择。带限反射系数定性地刻画深度域三维空间地下介质几何结构;宽带波阻抗定量地描述深度域三维空间地下介质岩性变化。后者更适于复杂岩性储层的描述。无论是定性的带限反射系数为目标的地震波成像还是定量的宽带波阻抗为目标的地震波成像都是信息不足情形下的参数估计问题。无论叠前地震数据或是与待估计参数有关的先验信息,在复杂构造和(或)复杂岩性变化情形下,都不满足高精度成像的要求。在大数据和机器学习技术已经普及的情况下,定量的、信息融合理念下的地震波成像技术路线也是不可回避的。为此提出了一条针对岩性储层的定量地震波成像技术路线:特征波反演成像(characteristic wave inversion,CWI)+信息融合宽带波阻抗建模(wide band impedance modeling,WBIM)方法技术系列。本质上,它是将FWI宽带波阻抗反演分解成背景速度建模、背景密度建模、线性化的宽带反射系数估计这三个凸性更好的反问题进行求解。关键是我们并没有将宽带波阻抗估计提成一个非线性的反演问题来求解,而是转化成一个信息融合问题,把已有的、认为最好的背景速度建模、背景密度建模、线性化的宽带反射系数估计结果,通过提出和求解一个约束非线性优化问题,重构出宽带波阻抗模型。这样做完全避开了反演求解宽带波阻抗时的不稳定、不收敛问题,同时在此过程中还可以进一步引入其他先验信息,通过将这些先验信息合理地融入到当前已有的反演成像算法中,在信息融合这一步继续提升宽带阻抗建模的精度。这是不同于目前常规波阻抗反演的一种新的宽带波阻抗建模方法技术,建模结果稳定,地质含义更清楚。宽带波阻抗模型各波数带的信息来源清楚,低频(低波数)来自背景波阻抗,高频(高波数)来自高分辨带限反射系数成像。中频成分的补充依赖于背景速度建模和构造成像精度的提高,也依赖于带限反射系数成像包含更充分的低中频信息(期望的带限反射系数是Gauss型的反射系数)。首先分析了定量地震波成像的理论基础;在此基础上,针对面向岩性油藏的定量地震波成像问题提出了定量地震波成像的技术路线(CWI+WBIM);把宽带波阻抗分为低波数带、中波数段、高波数带和超高波数带,分析了不同波数带波阻抗成分(包括背景阻抗和四种类型的带限反射系数(脉冲型反射系数、Gauss型反射系数、期望子波型反射系数、Ricker子波型反射系数)对宽带波阻抗建模的影响,形成了宽带波阻抗建模的技术流程。指出了定量地震波成像的核心不在于低波数背景阻抗建模结果的定量化,而是宽带反射系数成像结果的定量化。实际数据情况下,定量的宽带反射系数的获取首先依赖于保真的地震成像,然后是保真成像结果的频带展宽,最后是用测井反射系数标定地震反射系数的量级。理论数据和实际数据的测试结果证明了所提出的针对岩性储层的定量地震波成像技术的可行性、有效性和实用性。

松辽盆地梨树断陷基底岩性的重磁震联合解释

由于梨树断陷基底结构复杂,且地震深层资料品质常受影响,通过重磁震联合研究基底岩性分布对进一步评价该地区勘探潜力具有重要意义。在收集前人资料基础上,笔者等重新测定了部分样品的岩石物性。通过对研究区重磁资料进行重震结合剥皮及延拓等去浅部效应,利用小波分析和趋势分析等去深部影响,得到了基底剩余异常,并结合地震、钻井等资料联合解译了剩余异常,从而深化了对梨树断陷基底岩性的认识,预测了基底不同岩性的分布特征。梨树断陷基底岩性可分为如下几类:花岗岩、变余砂砾岩、板岩、千枚岩等浅变质岩,石英岩、石英片岩等中变质岩,片麻岩等深变质岩,灰岩以及火山岩。本次研究分类更加详细,与钻孔资料吻合较好。

机器深度学习技术在致密砂岩储层预测中的应用——以川西坳陷新场须家河组为例

川西坳陷新场须家河组二段致密砂岩储层具有非均质性强、储层薄等特点。前期直接通过地震属性和反演技术转换得到的岩性和物性结果受个人认识和解释精度的限制,其解释结果常常无法满足气藏精细开发需求。针对上述问题,以叠前岩性和物性敏感参数作为学习标本,将叠前反演技术与机器深度学习技术相结合,利用机器深度学习算法构建解释模型,最终实现砂岩厚度和储层量化预测。该方法有效提高储层预测分辨率、预测精度,其预测结果为沉积微相研究、成藏分析及井位部署等提供了有效的支撑,在新场须家河组二段气藏开发中取得较好的应用效果,为岩性和储层量化预测提供了新思路,对其他气田气藏开发起到良好的借鉴作用。

安第斯构造岩性油藏储层预测技术及应用

安第斯T区块位于奥连特盆地东部斜坡带,主要发育为低幅度构造—岩性复合油藏,具有储层薄、横向变化快和成藏规律复杂的特点,这些特点导致储层油水关系复杂以及井位优选难度大。常规的储层预测技术无法满足开发阶段同时预测储层分布范围和明确储层物性和含油性的生产需求,这对地球物理技术提出了极高的要求,因此亟需开展储层精细预测工作,预测储层展布、物性及含油性情况,为优选有利区带及勘探部署提供技术支撑。

滨里海盆地东缘石炭系盐下碳酸盐岩油气藏成藏规律与勘探技术

根据地震、钻井及薄片等资料,采用地震波阻抗储层反演技术,对滨里海盆地东缘石炭系盐下碳酸盐岩储层特征、油气成藏规律进行了研究,并指出了下一步风险勘探方向。研究结果表明:①滨里海盆地东缘石炭系盐下碳酸盐岩储层可分为灰岩类、云岩类、云灰岩/灰云岩类、硅化硅质岩类等,储层孔隙度为4%~12%,渗透率通常小于1 mD,属于低—中孔、低渗孔洞-孔隙型储层。②研究区阿克若尔构造带主要发育岩性油气藏,无统一油水界面,油层呈薄层状分散分布,对比性和连续性均较差,优质储层多为高频三级层序旋回中上部的高生长率滩体及不整合面附近的岩溶储层。③采用基于层位-测井约束的初始模型的地震波阻抗储层反演技术预测碳酸盐岩薄储层,可更清晰地呈现KT-Ⅰ和KT-Ⅱ油层组储层的纵、横向展布特征。研究区有利储层主要发育在KT-Ⅱ油层组顶部的G1和G4小层。

钙质砂岩强轴影响下的深水扇储层预测技术

珠江口盆地白云深水区构造珠江组储层为陆坡重力流水道—朵叶复合体沉积,油气勘探潜力巨大,储层分布和圈闭条件是该构造研究需要解决的主要问题。由于研究区珠江组L砂岩上方普遍发育钙质砂岩,砂岩顶界面对应的地震波谷具有连续强反射的特点,致使深水扇储层预测及岩性圈闭落实难度大。针对上述问题,从地震正演出发综合分析了珠江组储层地震响应特征,证实了波谷连续反射是受到钙质砂岩的影响,下波峰反射是储层的真实反映。钙质砂岩的存在改变了含气砂岩AVO曲线的变化规律,并因此降低了纵、横波速度比(VP/VS)的岩性识别能力。基于叠前反演得到的纵波阻抗IP和VP/VS构建了一种新的岩性指示因子,实现了对珠江组深水扇砂体的精确识别,为岩性圈闭评价奠定了基础。实际应用表明,所提方法能够有效提高研究区岩性识别能力和岩性边界刻画效果,预测结果与钻井数据吻合,为研究区下一步探井部署提供了可靠依据。

丽水凹陷基岩岩性分布预测——以丽水A洼为例

东海陆架盆地丽水凹陷基岩潜山十分发育,钻井已证实其含油气性,勘探潜力巨大。综合现有基岩岩芯、铸体薄片、测井、测年、三维地震资料,在构建基岩岩相-地震相模板及岩石物理分析的基础上,对丽水凹陷基岩岩性开展定性和半定量预测,进而预测岩性平面分布特征。丽水凹陷基岩主要由片麻岩、花岗片麻岩、花岗岩组成,片麻岩为古元古界变质岩陆核,花岗岩来自中生代岩浆,沿深大断裂上涌侵入。地震剖面上片麻岩表现为中−高频,中−强振幅,同相轴连续性、成层性好;花岗岩表现为中−低频,弱−中振幅,呈杂乱反射;花岗片麻岩地震相介于前二者之间。岩石物理分析结果显示,密度参数对岩性区分效果最好,叠前密度反演能较好地半定量预测基岩分布特征。研究表明,丽水A洼主体基岩纵向呈片麻岩上覆花岗岩的二元结构特征;平面上不同构造单元的基岩顶面岩性各异,凸起区花岗岩剥蚀程度高,基岩为片麻岩或花岗片麻岩,洼槽区缺乏深大断裂,为原始区域片麻岩基底,其他区域为花岗岩。

陆丰南珠江组下段#2370层岩性圈闭识别方法

目前,砂岩储层尖灭的判别方法主要是通过针对地震振幅变化和地震属性进行分析,而针对高速灰岩屏蔽影响下砂岩储层尖灭的判别方法研究较少。受灰岩高速、高密度影响,灰岩之下的薄砂岩与围岩的弱反射特征往往被淹没,常规识别方法难以有效判断砂岩的尖灭线形态,影响岩性圈闭的落实。通过三维地震资料分析,提出了一种针对该地区编号为#2370层砂岩尖灭线的地质地球物理综合判别方法,即以统计地震反射特征为主线,以正演模拟为验证,以地震属性和反演为辅助,以地质模式类比为依托,综合刻画砂岩尖灭线。研究结果表明,通过该方法所刻画的砂岩尖灭线与实钻结果基本吻合。同时,结合砂岩尖灭线和局部构造背景,初步落实了该地区南部的#2370层岩性圈闭分布。该方法对灰岩广泛发育地区高速灰岩下岩性圈闭的落实具有重要借鉴意义。

东海古近系致密碎屑岩“甜点”地震预测方法及应用

东海Q构造古近系低孔低渗储层普遍发育,砂泥岩阻抗叠置严重,整体非均质性变化剧烈。落实致密碎屑岩“甜点”分布范围是当前该区勘探开发一体化研究亟需解决的关键问题。为此,在地震岩性学研究的基础上,提出了一种基于叠前敏感属性反演的地震“甜点”预测技术。采用振幅随偏移距变化(AVO)截距和梯度合成的扩展弹性阻抗(EEI35°)属性开展地震岩相预测。利用高孔砂岩储层的低密度特征解决地震物相预测的问题,并结合地震岩石物理定性和定量判析技术,优选复合属性进行地震流相识别。最终在层递式相控思想指导下,实现相对高孔高气饱优质储层的准确预测。实例应用表明:本方法能够有效刻画研究区致密碎屑岩“甜点”展布规律,为后续目标搜索和井位优化提供重要参考,具有较高的可靠性和推广应用价值。

乌石凹陷流一段岩性圈闭形成机制及精细刻画

钻井揭示流一段砂体单层普遍较薄,而乌石凹陷地震资料频率偏低,利用沉积模式指导流一段岩性体揭示,利用地球物理技术精细刻画流一段砂体,从而达到落实岩性边界,描述岩性圈闭的目的。小波分频技术能在保幅的基础上大大提高地震分辨率,有色反演则能精细地刻画无井区、少井区的岩性边界。通过以上技术手段,精细描述了乌石凹陷流一段三期砂体的横向展布范围,新落实多个岩性圈闭,推动乌石岩性油气藏勘探,引领乌石凹陷领域勘探突破方向。

弹性阻抗在岩性与流体预测中的潜力分析

给出了弹性阻抗的概念,并根据弹性阻抗与波阻抗定义的相似性,提出了利用叠后测井约束反演方法实现弹性阻抗反演的思想。利用Gassmann方程对渤海湾地区上第三系储层进行了流体替代模拟,得出横波速度随水饱和度变化很小,纵波速度和密度随水饱和度变化较大,对流体变化较敏感的结论。用不同饱和度的纵、横波速度和密度参数,利用波动方程正演模拟得到叠前合成道集,并提取角道集剖面,然后反演得到弹性阻抗剖面。反演结果表明,利用叠后测井约束反演方法实现弹性阻抗反演是有效和可靠的。对弹性阻抗和波阻抗与水饱和度的关系进行了对比分析,结果表明,弹性阻抗可以更好地反映流体饱和度的变化,在岩性和流体的识别和预测中具有很大的潜力。对鄂尔多斯苏里格气田的实际资料进行了处理,发现入射角为16°时弹性阻抗与自然伽马有很好的相似性,因此利用16°入射角对应的弹性阻抗可以识别有效储层。此外,通过井点弹性阻抗与自然伽马的对比分析,可以确定区分有效储层的门槛值,如苏里格地区有效储层的弹性阻抗门槛值为2900。

井震联合地质建模技术在扶杨油层油藏描述中的应用

GTZ区块扶杨油层为网状河化的三角洲平原亚相沉积,储层砂体薄、相变快、规律性差,具低孔、低渗特点;砂岩的测井响应表现为高电阻率值与低自然伽马值,砂岩总体上为高速砂岩。由于上述地质、地球物理特征,进行精确油藏描述难度很大。本文通过井震联合地质建模技术,以地质资料和地震解释层位数据为基础建立了构造模型,采用相控技术和截断高斯及协序贯高斯模拟方法,得到了三维储层岩性和物性模型、油藏模型。对扶杨油层3个砂层组和7个小层的单砂体进行了厚度和含油性预测,预测结果与后验井验证结果符合率达到80%以上,油藏类型既有砂体上倾尖灭形成的岩性油藏,也有断层遮挡形成的构造—岩性油藏。

利用岩性解释方法圈定岩浆岩侵入煤层范围

岩性地震反演技术是根据钻孔测井数据纵向分辨率很高的有利条件,对井旁地震资料进行约束;并在此基础上对孔间地震资料进行反演,推断煤系地层岩性在平面上的变化情况.谱分解技术是利用薄层调谐体离散频率特性,通过分析复杂岩层内陷频谱变化和局部相位的不稳定性,识别薄地层横向分布特征.本文根据崔庄煤矿三采区的地震资料,综合利用地震反演技术和谱分解技术等岩性解释方法圈定岩浆岩侵入煤层的范围.