Research on Multi-Wave Pore Pressure Prediction Method Based on Three Field Velocity Fusion

The optimization of velocity field is the core issue in reservoir seismic pressure prediction. For a long time, the seismic processing velocity analysis method has been used in the establishment of pressure prediction velocity field, which has a long research period and low resolution and restricts the accuracy of seismic pressure prediction;This paper proposed for the first time the use of machine learning algorithms, based on the feasibility analysis of wellbore logging pressure prediction, to integrate the CVI velocity inversion field, velocity sensitive post stack attribute field, and AVO P-wave and S-wave velocity reflectivity to obtain high-precision seismic P and S wave velocities. On this basis, high-resolution formation pore pressure and other parameters prediction based on multi waves is carried out. The pressure prediction accuracy is improved by more than 50% compared to the P-wave resolution of pore pressure prediction using only root mean square velocity. Practice has proven that the research method has certain reference significance for reservoir pore pressure prediction.

Multi-wave amplitude-preserved AVO modeling considering wave propagation effects

Traditional AVO forward modeling only considers the impact of reflection coefficients at the interface on seismic wave field amplitude and ignores various propagation effects. Introducing wave propagation effects including geometric spreading, transmission loss, attenuation into seismic wave propagation, multi-wave amplitude-preserved AVO forward modeling for horizontally layered media based on ray theory is proposed in this paper. We derived the multi-wave geometric spreading correction formulas for horizontally layered media in order to describe the geometric spreading effect of multi-wave propagation. Introducing the complex traveltime directly, we built the relationship between complex traveltime and quality factor without the help of complex velocity to describe the attenuation of viscoelastic media. Multi-wave transmission coefficients, obtained by solving the Zoeppritz equations directly, is used to describe the transmission loss. Numerical results show that the effects of geometric spreading, attenuation, and transmission loss on multi-wave amplitude varies with offset and multi-wave amplitude-preserved AVO forward modeling should consider the reconstructive effect of wave propagation on reflection amplitude.

Monitoring the change in horizontal stress with multi-wave time-lapse seismic response based on nonlinear elasticity theory

Monitoring the change in horizontal stress from the geophysical data is a tough challenge, and it has a crucial impact on broad practical scenarios which involve reservoir exploration and development, carbon dioxide (CO_(2)) injection and storage, shallow surface prospecting and deep-earth structure description. The change in in-situ stress induced by hydrocarbon production and localized tectonic movements causes the changes in rock mechanic properties (e.g. wave velocities, density and anisotropy) and further causes the changes in seismic amplitudes, phases and travel times. In this study, the nonlinear elasticity theory that regards the rock skeleton (solid phase) and pore fluid as an effective whole is used to characterize the effect of horizontal principal stress on rock overall elastic properties and the stress-dependent anisotropy parameters are therefore formulated. Then the approximate P-wave, SV-wave and SH-wave angle-dependent reflection coefficient equations for the horizontal-stress-induced anisotropic media are proposed. It is shown that, on the different reflectors, the stress-induced relative changes in reflectivities (i.e., relative difference) of elastic parameters (i.e., P- and S-wave velocities and density) are much less than the changes in contrasts of anisotropy parameters. Therefore, the effects of stress change on the reflectivities of three elastic parameters are reasonably neglected to further propose an AVO inversion approach incorporating P-, SH- and SV-wave information to estimate the change in horizontal principal stress from the corresponding time-lapse seismic data. Compared with the existing methods, our method eliminates the need for man-made rock-physical or fitting parameters, providing more stable predictive power. 1D test illustrates that the estimated result from time-lapse P-wave reflection data shows the most reasonable agreement with the real model, while the estimated result from SH-wave reflection data shows the largest bias. 2D test illustrates the feasibility of the proposed inversion method for estimating the change in horizontal stress from P-wave time-lapse seismic data.

储层特征约束频散AVO流体检测方法及应用

以AVO方法为根本的流体识别技术,是通过求解Zoeppritz方程获得储层流体响应特征,从而实现地下储层中油气水等流体的识别技术;但直接求解Zoeppritz方程难度极大,所以学者们提出了不同形式的AVO近似方程,这些近似方程均是通过对地下地层进行一系列假设后推演而来,与Zoeppritz方程精确解存在误差,影响储层流体检测的效果和精度。基于储层特征约束的AVO反演方法,先将反射系数用一个线性通用公式来表示,再通过使用蒙特卡罗随机模拟方法构建能够反映储层信息的基函数,从而完成AVO方程的优化。将储层先验信息作为约束条件,使得该方法对储层流体的研究具有针对性,同时又保障反演流体属性的精度。将高精度时频分析与储层特征约束AVO反演方法相结合,实现了与频率相关的频散AVO反演,经应用证实该方法可进一步提高储层含流体性质检测的精度。

致密砂岩AVO属性的贝叶斯岩相划分方法——以川中地区侏罗系沙溪庙组沙一段为例

地震勘探中“高速或低速致密砂岩储层”地震响应复杂、非均质性强、反演中的低频模型难以建立。在基于Bayesian分类的AVO(BF-AVO)截距、梯度属性及孔隙度等指标约束下,对川中地区侏罗系沙溪庙组致密砂岩的岩相进行了划分。研究结果表明:(1)AVO分析是以弹性波理论为基础,根据其振幅随偏移距的变化规律来反映地下岩性及其孔隙流体的性质,在应用过程中,根据不同岩性和流体的相关参数组合进行AVO正演,获得已知岩性和流体性质的AVO特征,与实际地震记录进行对比,建立岩性和油气识别的地震响应模型。(2)利用模型和实际数据建立的孔隙度与截距、梯度属性的交会分析,厘清三者的内在联系,确定岩相划分标准,并拟合出不同岩相的概率密度函数,划分出不同孔隙度区间的岩相,从而实现孔隙度的半定量预测。(3)川中侏罗系沙溪庙组沙一段致密砂岩的岩相预测过程中,基于Bayesian分类,以概率分布预测的岩相与实钻结果吻合度高,达93.75%,验证了该方法的可行性和有效性。

Evaluation of Hydrocarbon Potential Using AVO Analysis in the FORMAT Field, Niger Delta Basin, Nigeria

The study involved the evaluation of the hydrocarbon potential of FORMAT Field, coastal swamp depobelt Niger delta, Nigeria to obtain a more efficient reservoir characterization and fluid properties identification. Despite advances in seismic data interpretation using traditional 3D seismic data interpretation, obtaining adequate reservoir characteristics at the finest level had proved very challenging with often disappointing results. A method that integrates the amplitude variation with offfset (AVO) analysis is hereby proposed to better illuminate the reservoir. The Hampson Russell 10.3 was used to integrate and study the available seismic and well data. The reservoir of interest was delineated using the available suite of petrophysical data. This was marked by low gamma ray, high resistivity, and low acoustic impedance between a true subsea vertical depth (TVDss) range of 10,350 - 10,450 ft. The AVO fluid substitution yielded a decrease in the density values of pure gas (2.3 - 1.6 g/cc), pure oil (2.3 - 1.8 g/cc) while the Poisson pure brine increased (2.3 to 2.8 g/cc). Result from FORMAT 26 plots yielded a negative intercept and negative gradient at the top and a positive intercept and positive gradient at the Base which conforms to Class III AVO anomaly. FORMAT 30 plots yielded a negative intercept and positive gradient at the top and a positive intercept and negative gradient at the Base which conforms to class IV AVO anomaly. AVO attribute volume slices decreased in the Poisson ratio (0.96 to - 1.0) indicating that the reservoir contains hydrocarbon. The s-wave reflectivity and the product of the intercept and gradient further clarified that there was a Class 3 gas sand in the reservoir and the possibility of a Class 4 gas sand anomaly in that same reservoir.

Multi-wave forward modeling of a reservoir and AVO analysis

In the process of accurate interpretation of multi-wave seismic data,we wanted to solve the problem of multi-wave information recognition.Based on techniques of elastic wave forwarding,targeting the geological model of a reservoir of an oil field exploration area,we used a high-order staggered-grid difference technology to simulate many shots of seismic records of nonzero offset shots,implemented multi-wave seismic data processing to acquire the CMP of P waves and converted waves,NMO traces of CCP pre stacks,including AVA information and superposition profiles.Based on the AVA calculation of the model,the layer parameters of the model and the forwarding wave field relations of the P-S wave,we also compared and studied the correspondence between P waves and converted waves.The results of our analysis show that the results from simulation and from the AVO analysis are consistent.Significant wave field differences between P waves and converted waves in the same reservoir were found,which are helpful in recognizing and interpreting the multi-wave information in this area.We made use of the multi-wave data to provide the important guidelines for reservoir prediction.

The AVO Effect of Formation Pressure on Time-Lapse Seismic Monitoring in Marine Carbon Dioxide Storage

The phase change of CO_(2) has a significant bearing on the siting, injection, and monitoring of storage. The phase state of CO_(2) is closely related to pressure. In the process of seismic exploration, the information of formation pressure can be response in the seismic data. Therefore, it is possible to monitor the formation pressure using time-lapse seismic method. Apart from formation pressure, the information of porosity and CO_(2) saturation can be reflected in the seismic data. Here, based on the actual situation of the work area, a rockphysical model is proposed to address the feasibility of time-lapse seismic monitoring during CO_(2) storage in the anisotropic formation. The model takes into account the formation pressure, variety minerals composition, fracture, fluid inhomogeneous distribution, and anisotropy caused by horizontal layering of rock layers(or oriented alignment of minerals). From the proposed rockphysical model and the well-logging, cores and geological data at the target layer, the variation of P-wave and S-wave velocity with formation pressure after CO_(2) injection is calculated. And so are the effects of porosity and CO_(2) saturation. Finally, from anisotropic exact reflection coefficient equation, the reflection coefficients under different formation pressures are calculated. It is proved that the reflection coefficient varies with pressure. Compared with CO_(2) saturation, the pressure has a greater effect on the reflection coefficient. Through the convolution model, the seismic record is calculated. The seismic record shows the difference with different formation pressure. At present, in the marine CO_(2) sequestration monitoring domain, there is no study involving the effect of formation pressure changes on seismic records in seafloor anisotropic formation. This study can provide a basis for the inversion of reservoir parameters in anisotropic seafloor CO_(2) reservoirs.

基于AVO技术的岩性含气储层预测

针对AH地区,其白碱滩组地震反馈特性较模糊,预测储层的多解性较强,这使得提升含气储层预测精确性成为此地面对的关键问题。近期获取的钻井资讯和对岩石物理的研析发现,纵向和横向波速的比率对于含气储层的反应更为敏锐,比率越高,储层的发育就越显著。采用AH地区的纵横波速比特性来预测白碱滩组储层的发展状态,预测结果与实地钻井的数据非常一致。研究显示,根据白碱滩组发育与非发育储层所呈现的AVO特性,能有效地辨识AH地区的含气储层。利用白碱滩组地震道集纵横波速比特性预测储层的方式,能很好地解决AH地区含气储层预测的多解性问题,提高岩性储层预测的准确性,对AH地区未来的探索和开发具有指导价值。

基于叠前AVO技术的煤矿瓦斯富集区检测方法研究

煤矿瓦斯富集区在地球物性特征及地震响应上与煤矿瓦斯含量较低区域有显著不同,造成煤矿瓦斯富集区的地震波属性变化异常,通过对异常的检测来划定煤矿瓦斯富集区。煤矿瓦斯富集区地段在地震资料上出现地震波初至时间加长、振幅减弱、频率降低的特征。本文以此理论为基础,利用叠前AVO技术对某矿区瓦斯富集区进行了尝试性检测,与实际抽采资料表明:这种方法检测出的煤矿瓦斯富集区与实际抽采的结果基本吻合。这种方法的应用为后续的煤层气开发奠定了基础。

分频高阶扩展AVO技术在低孔低渗储层中的应用——以准噶尔盆地前哨地区三工河组二段为例

以叠前角道集、测井和试油资料为基础,利用广义S变换时频分析技术确定储层优势频带,在优势频带的约束下,利用高阶Aki-Richards近似方程拟合AVO曲线,求取更准确的截距和梯度;利用扩展弹性阻抗技术的坐标旋转方法,获得流体区分能力最优的AVO属性,结合试油结果进行有利区预测。结果表明:前哨地区三工河组二段储层的优势频段为33~68 Hz,进行AVO分析可以提高有利储层的预测精度。经分频高阶扩展AVO技术处理,有利储层的符合率由69%提高到94%。气层有利区主要集中于QS2—QS4、QS7井区及未钻探的QS1井西区域,其中未钻探面积为6.5 km^(2),是前哨地区天然气增储上产的重点潜力区。该结果为前哨地区天然气勘探部署提供技术支持。

基于改进的介观裂缝岩石物理模型的频散AVO特征分析

地下储层中存在介观尺度的裂缝是导致地震波的速度频散和能量衰减的一个重要原因。从Galvin介观裂缝模型出发,重构其低频极限和高频极限的表达形式,将频散关系施加到裂缝模型上构建依赖频率的裂缝柔度参数,建立了一种改进的介观尺度的裂缝型岩石物理模型。基于该改进模型,利用附加柔度的组合性质,可以容易地构建更复杂的模型并进行依赖频率的地震响应特征分析。在传统的反射系数公式中引入频率参数,分析了具有不同裂缝长度、背景渗透率、流体粘度等频散敏感参数的反射界面上的频散AVO及地震记录响应特征。通过数值模拟得出频散敏感参数主要影响发生频散的频段,即影响岩石的特征频率;当模型的特征频率与地震波频段主频相近时,频散现象最突出,当特征频率大于地震波频段主频一个数量级时,可以忽略频散作用,此时采用传统的Gassmann方程即可较准确地分析地震剖面的特征。基于改进模型得到的认识为地震频散特征的实际应用提供了岩石物理模型的构建方面的指导。

基于改进Bayes信息量准则的锂电池自适应变阶AVO模型

提出了一种融合Bayes信息量准则和樽海鞘优化算法的自适应变阶(AVO)模型。该模型以端电压误差的Bayes信息量作为一阶和二阶RC模型的变阶依据,利用樽海鞘优化算法(SSA)搜索Bayes信息量序列的全局最优解,实现对模型最优变阶序列的求解;通过开展混合动力脉冲特性(HPPC)实验,选用含遗忘因子递推最小二乘法(FFRLS)获取精确的模型参数,完成AVO模型的电阻及电容参数辨识和精度在线验证。结果表明:所建立的锂电池自适应变阶AVO模型平均误差为0.011 9 V,精度及实用性较高。

分频AVO技术在安岳气田须二段储层含气性分析中的应用

四川盆地安岳气田须二段致密气储量丰富,地质特征相对复杂,常规AVO分析方法预测储层含气性分布的精度较低,需要研究采用更加精细的地震预测方法。基于单井岩石物理和正演模型特征分析,采用基于小波变换下的分频AVO反演,优选出优势频段的AVO属性进行融合构建含气性因子,进而对安岳气田须二段有利含气富集区带进行分布预测。结果表明,须二段气层主要表现为Ⅳ类AVO响应异常。优势频段35~45 Hz的气、水层AVO响应比全频段的AVO响应的差异特征较明显,差异性更大,更易突出含气响应特征;AVO含气性敏感属性为相对横波速度差异、相对泊松比差和流体因子,经融合得到含气指示因子的负异常区域指示含气有利区;井震对比可知优势频段AVO属性的含气性预测效果较好。该方法以期为非常规油气勘探提供技术支撑。

叠前AVO反演技术在塔河油田三种类型油气藏流体识别中的适用性分析

塔河油田奥陶系油气藏储层非均质性极强,烃源岩长期生排烃、多期充注成藏及混合改造,导致油气性质变化大,给流体识别带来巨大挑战。通过模型正演,分析缝洞型储层厚度、孔隙度、含流体性质对AVO特征的影响,明确气藏、轻质油藏、重质油藏三种不同类型油气藏的AVO特征及敏感参数;在此基础上,开展叠前反演,获得地下不同流体纵波阻抗及纵横波速度比特征,然后基于实际测井数据,建立三种不同类型油气藏岩石物理量版,在岩石物理量版指导下,利用双参数进行流体概率分析,获得缝洞储层流体定量识别结果。对塔河A区(气藏)、B区(轻质油藏)和C区(重质油藏),各50 km 2三维地震资料开展基于叠前AVO反演的流体识别应用研究,将识别结果用于盲井检验,气藏识别符合率为80%,轻质油藏符合率为76%,重质油藏符合率为72%。研究结果为塔河碳酸盐岩储层流体识别提供了参考依据。

STABILITY OF STEADY MULTI-WAVE CONFIGURATIONS FOR THE FULL EULER EQUATIONS OF COMPRESSIBLE FLUID FLOW

We are concerned with the stability of steady multi-wave configurations for the full Euler equations of compressible fluid flow. In this paper, we focus on the stability of steady four-wave configurations that are the solutions of the Riemann problem in the flow direction, consisting of two shocks, one vortex sheet, and one entropy wave, which is one of the core multi-wave configurations for the two-dimensional Euler equations. It is proved that such steady four-wave configurations in supersonic flow are stable in structure globally, even under the BV perturbation of the incoming flow in the flow direction. In order to achieve this, we first formulate the problem as the Cauchy problem （initial value problem） in the flow direction, and then develop a modified Glimm difference scheme and identify a Glimm-type functional to obtain the required BV estimates by tracing the interactions not only between the strong shocks and weak waves, but also between the strong vortex sheet/entropy wave and weak waves. The key feature of the Euler equations is that the reflection coefficient is always less than 1, when a weak wave of different family interacts with the strong vortex sheet/entropy wave or the shock wave, which is crucial to guarantee that the Glimm functional is decreasing. Then these estimates are employed to establish the convergence of the approximate solutions to a global entropy solution, close to the background solution of steady four-wave configuration.

Reservoir prediction using multi-wave seismic attributes

The main problems in seismic attribute technology are the redundancy of data and the uncertainty of attributes, and these problems become much more serious in multi-wave seismic exploration. Data redundancy will increase the burden on interpreters, occupy large computer memory, take much more computing time, conceal the effective information, and especially cause the ＂curse of dimension＂. Uncertainty of attributes will reduce the accuracy of rebuilding the relationship between attributes and geological significance. In order to solve these problems, we study methods of principal component analysis （PCA）, independent component analysis （ICA） for attribute optimization and support vector machine （SVM） for reservoir prediction. We propose a flow chart of multi-wave seismic attribute process and further apply it to multi-wave seismic reservoir prediction. The processing results of real seismic data demonstrate that reservoir prediction based on combination of PP- and PS-wave attributes, compared with that based on traditional PP-wave attributes, can improve the prediction accuracy.

煤弹性参数的影响因素分析及其AVO响应特征

研究煤弹性参数的影响因素可以揭示煤层AVO响应的物理含义,有利于指导复杂地质条件下的煤层气勘探。以沁水盆地寺河矿区3号煤层的60块煤样为研究对象,根据煤的工业成分分析、矿物成分分析和地层条件下测试结果,基于BET多层吸附理论(The Brunauer-Emmett-Teller theory)和自洽模型构建不同流体饱和的煤层气储层岩石物理模型。主要考虑3种流体饱和情况:1种为完全水饱和,另外2种为不同的含水、吸附气和游离气的多相混合流体。在此基础上,分析煤基质组成、孔隙率和流体饱和情况对煤的弹性参数的综合影响,进一步开展含煤地层在不同孔隙率、不同流体饱和情况下的地震AVO响应特征分析。结果表明:研究区内,煤的孔隙率是引起煤纵横波速度、多相流体饱和煤体积模量变化的主要影响因素,且孔隙率增大引起多相流体饱和煤体积模量的变化较明显;相比于孔隙率,不同煤基质组成对完全水饱和煤体积模量、密度的影响更为显著;不同流体饱和情况引起的煤弹性参数变化相较于孔隙率、煤基质组成小。分析含煤地层的AVO响应特征可以发现,孔隙率与AVO属性呈一定线性关系,含水饱和度与AVO属性呈一定非线性关系;与其他AVO属性相比,横波阻抗属性在不同孔隙率、不同流体饱和情况下的地震AVO响应最为显著。

AVO梯度谱蓝化在中深层薄砂岩刻画中的应用

传统谱蓝化主要用于叠后地震拓频处理,适用于测井波阻抗能较好辨别砂、泥岩的浅层,对于中深层阻抗混叠区局限性较大。AVO梯度反映相对反射系数随炮检距的变化,与泊松比变化率呈现正相关,而泊松比能较好辨别中深层砂、泥岩。本文首先通过岩性组合、物性及流体等参数变化,正演论证了AVO梯度在中深层辨识砂岩顶界面的可靠性与稳定性;进一步地,针对中深层薄砂岩刻画精度低问题,提出一种基于AVO梯度信息的谱蓝化地震拓频技术,通过对AVO梯度谱蓝化拓频,提高薄储层刻画精度。模型试算及实际应用表明:基于AVO梯度的谱蓝化可以直接运用AVO梯度辨识储层界面信息,简化基于CRP道集或角度部分叠加的多参数岩性预测方法;同时,该方法较好解决了XH凹陷深埋地层薄砂岩刻画难题,对中深层地震高分辨率处理有一定借鉴意义。

An ultrasonic multi-wave focusing and imaging method for linear phased arrays

To overcome the inherent limits of traditional single wave imaging for nondestructive testing,the multi-wave focusing and imaging method is thoroughly studied.This method makes the compressional waves and shear waves focused in both emission and reception processes,which strengthens the focusing energy and improves the signal-to-noise ratio of received signals.A numerical model is developed to study the characteristics of a multi-wave focusing field.It is shown that the element width approaching 0.8 wavelengths of shear waves can keep a balance between the radiation energy of two waves,which can achieve a desirable multi-wave focusing performance.And an experiment using different imaging methods for a linear phased array is performed.It can be concluded that due to the combination of the propagation and reflection characteristics of two waves,the multi-wave focusing and imaging method can significantly improve the imaging distinguishability of defects and expand the available sweeping range to a sector of-650 to 65°.