Wide/narrow azimuth acquisition footprints and their effects on seismic imaging

Acquisition footprint is a new concept to describe the seismic noise in three-dimensional seismic exploration and it is closely related to geometry and observation shuttering. At present, the study on acquisition footprints has become a hot spot. In partnership with the Dagang Oilfield, we used the channel sand body seismic physical model to study the characteristics of wide/narrow azimuth acquisition footprints and analyzed and compared the two types of footprints and their effects on target imaging. In addition, the footprints caused by data processing of the normal moveout offset （NMO） stretching aberration were discussed. These footprints are located only in the shallow or middle layer in the time slice, and possibly affect the imaging of shallow target layers, and have no influence on deep target imaging. Seismic physical modeling has its advantages in the study of acquisition footprints.

Detection performance and inversion processing of logging-while-drilling extra-deep azimuthal resistivity measurements

We present systematic investigations on the physics,detection performance and inversion of logging-while-drilling extradeep azimuthal resistivity measurements(EDARM).First,the definitions of EDRAM measurements are discussed,followed by the derivation of the attenuation and phase-shift geometrical factors to illustrate the relative contributions of formation units to the observed signals.Then,a new definition of detection depth,which considers the uncertainty of inversion results caused by the data noise,is proposed to quantify the detection capability of ED ARM.Finally,the B ayesian theory associated with Markov chain Monte Carlo sampling is introduced for fast processing of EDARM data.Numerical results show that ED ARM is capable of detecting the azimuth and distance of remote bed boundaries,and the detection capability increases with increasing spacing and resistivity contrast.The EDARM tool can accommodate a large range of formation resistivity and is able to provide the resistivity anisotropy at arbitrary relative dipping angles.In addition,multiple bed boundaries and reservoir images near the borehole are readily obtained by using the Bayesian inversion.

New slant range model and azimuth perturbation resampling based high-squint maneuvering platform SAR imaging

Strong spatial variance of the imaging parameters and serious geometric distortion of the image are induced by the acceleration and vertical velocity in a high-squint synthetic aperture radar(SAR)mounted on maneuvering platforms.In this paper,a frequency-domain imaging algorithm is proposed based on a novel slant range model and azimuth perturbation resampling.First,a novel slant range model is presented for mitigating the geometric distortion according to the equal squint angle curve on the ground surface.Second,the correction of azimuth-dependent range cell migration(RCM)is achieved by introducing a high-order time-domain perturbation function.Third,an azimuth perturbation resampling method is proposed for azimuth compression.The azimuth resampling and the time-domain perturbation are used for correcting first-order and high-order azimuthal spatial-variant components,respectively.Experimental results illustrate that the proposed algorithm can improve the focusing quality and the geometric distortion correction accuracy of the imaging scene effectively.

Modeling and inversions of acoustic reflection logging imaging using the combined monopole–dipole measurement mode

In this paper, we theoretically and numerically study a combined monopole–dipole measurement mode to show its capability to overcome the issues encountered in conventional single-well imaging, i.e., the low signal-to-noise ratio of the reflections and azimuth ambiguity. First, the azimuth ambiguity, which exists extensively in conventional single-well imaging, is solved with an improved imaging procedure using combined monopole–dipole logging data in addition to conventional logging data. Furthermore, we demonstrate that the direct waves propagating along the boreholes with strong energy, can be effectively eliminated with the proposed combined monopole–dipole measurement mode. The reflections are therefore predominant in the combined monopole–dipole data even before the signals are filtered; thus, the reflections' arrival times in each receiver are identified, which may help minimize the difficulties in filtering conventional logging data. The optimized processing flow of the combined measurement mode logging image is given in this paper. The proposed combined monopole–dipole measurement mode may improve the accuracy of single-well imaging.

Azimuth space-variant properties of BiSAR with nonequal velocities

Bistatic SAR possesses characteristic of the azimuth space-variant when the velocities of transmitter and receiver are not equal. The geometric model of BiSAR with the parallel trajectories and the nonequal platform velocities is presented. Analyzing the motion relationship of transmitter and receiver, the formula of azimuth spacevariant is derived in time domain. Via Taylor polynomial expansions, the azimuth space-variant is factorized by four terms： zero-order, first-order, second-order, and third-order term. And, their impacts on impulse response are illuminated. Some characteristics about azimuth space-variant of airborne BiSAR case are exhibited by simulation experiments, and these simulated results are coincident with the formulae of azimuth space-variant.

基于正则化约束的方位伽马成像测井分辨率提高方法

随钻方位伽马测井可以用于地层放射性强度分析及地质导向、储层界面识别,但受到统计误差的影响非常大,曲线和成像分辨率不高,特别是在对比度不高的地层中,这种影响更明显。为了提高随钻方位伽马测井的成像分辨率,提出一种基于仪器响应特性对方位伽马数据进行正则化处理的方法,以获得更准确的地层放射性强度。首先根据探测器响应原理,采用数值模拟和实验方法得到方位伽马测井的响应灵敏函数,并验证得到的灵敏因子的准确性。然后,通过构造正则化计算公式、调整计算参数对测量的原始方位伽马数据进行处理。结果表明:经该方法处理后得到方位伽马曲线的聚焦性能、对比度得到提高,避免了过去使用线性求解方法所导致的过拟合问题,且伽马成像分辨率有显著增强,薄层识别能力也得到一定改善。该方法能够提供更加准确和清晰的成像结果,提高仪器的地质导向能力和储层钻遇率。

多子阵SAS方位空变运动补偿子孔径算法

为解决方位空变的侧摆和偏航误差存在情形下合成孔径声纳的快速运动补偿与成像问题,提出一种多子阵合成孔径声纳方位空变运动补偿子孔径算法。首先,建立运动误差存在情形下的双程距离历程模型,并利用泰勒级数展开对双根号形式距离历程进行近似;然后,利用子孔径运动补偿和单基等效处理,将含有方位空变的侧摆和偏航误差的多子阵回波数据转换为理想的单阵回波数据;最后,利用经典的单阵频域逐线成像算法,实现快速运动补偿和高分辨成像。仿真实验与实测数据成像结果均验证了所提算法的有效性。

井中方位纵波远探测: 理论、实验与现场应用

能够测量井外数十米地质构造距离和方位的远探测声波测井正成为一种重要的地球物理应用技术.1:1地层条件下井外含反射界面的远探测测量和分析为此技术提供了物理验证.本文首先利用虚源和柱面波展开理论推导了充液井孔中单极反射纵波方位接收声场的解析形式,通过模拟证明了单井的声波辐射和接收与双井之间的辐射和接收的等效性,在此基础上提出利用两口模型井来实现方位纵波远探测实验,即在测量井中放置多方位反射纵波接收声系,在另一口副井中放置单极子声源向测量井定向辐射纵波以等效来自井外地质体的反射波,依托实验室的模型井群进行井中方位纵波远探测实验研究.实验测量结果表明井中接收反射纵波的幅度和到时对井外反射体(定向辐射波)具有较好的方位灵敏度,可由此来实现井外地质异常体的精准定位.在理论与实验指导下自主设计研制了方位纵波远探测仪器样机并开展了现场井测试成功获得高信噪比的方位反射信号,充分验证了方位纵波远探测技术的准确性和有效性.

基于扫描旋转同步运动的三维成像方法

为满足在役战机隐身性能的快速检测需求,提出了一种基于垂直扫描、方位旋转同步运动的三维成像方法。成像系统主要由射频收发设备、收发天线对、竖直方向导轨、转台和数据处理终端构成。天线发射频率步进信号时,对转台上的被测目标进行水平旋转,同时,收发天线对在垂直方向上扫描被测目标。以点目标组合为例,通过理论分析和仿真计算,确定该成像系统的参数配置,比较不同参数配置下系统的三维成像性能。仿真结果表明:采用垂直扫描、方位旋转同步运动方法能够实现三维成像,该方法与经典圆柱面扫描方法相比,扫描时间可缩短92%,同时保持11 dB峰值旁瓣比率。所提方法具有测试效率高、系统搭建简单、易于调节的特点,为服役阶段的隐身飞机散射源诊断提供了一种有效的测量方法选择。

多子阵合成孔径声呐6阶方位空变运动补偿快速算法

为解决6自由度运动误差存在情形下的多子阵合成孔径声呐快速运动补偿与成像问题,本文提出一种多子阵合成孔径声呐6阶方位空变运动补偿快速算法。在考虑6自由度运动误差随方位时间6阶空变特性的基础上,对双根号形式距离历程进行泰勒级数展开并保留至6阶项,进而推导得到严格解析的点目标响应二维谱,通过对传统四阶模型的距离多普勒算法进行改进,同时实现了6自由度运动误差的快速补偿和图像重建。仿真分析和实测数据成像结果表明了所提算法的有效性和高效率,可为大场景宽测绘带多子阵合成孔径声呐快速运动补偿和高分辨成像提供理论依据。

多方位角融合SAR图像中“扇形”旁瓣分析

随着相控阵天线电子扫描能力的提升,多方位角观测成为星载合成孔径雷达(Synthetic Aperture Radar,SAR)发展方向之一,从多维度提高目标信息解译能力。然而,在公开的多方位角融合SAR图像中存在较强的二维“扇形”旁瓣现象,且二维分布特点不同,容易造成目标误判。因此本文针对此旁瓣方向和多方位角观测目标分辨率开展研究。首先,概述了多方位角观测模式和特性,提出了基于CUDA并行加速的快速后向投影(Back Projection,BP)算法,高效率生成多方位角序贯SAR图像,避免耗时的图像配准和几何校正;其次,基于多方位角观测中斜距平面和地距平面的几何投影关系,重点分析了地距平面目标方位向、距离向分辨率和旁瓣方向,揭示了融合SAR图像中“扇形”旁瓣的形成机理,并解释了二维旁瓣特性不同的原因,基于此可反演获取该SAR图像时卫星和观测场景之间的几何关系,以及融合SAR图像数;最后,通过点目标和扩展目标仿真开展实验,结果表明方位斜视观测中,地距平面方位向、距离向分辨率理论分析精度优于0.02 m,旁瓣方向理论分析精度优于1o,验证了所提分析方法的正确性。

随钻方位成像测井数据压缩与还原方法

在地质导向施工中,随钻数据实时上传是保障导向精准的关键。目前受限于MWD传输速度,随钻成像测井数据难以实时传输到地面,影响导向过程中地层特征的实时获取,制约导向实施效果。对此,提出了一种随钻成像测井数据高效压缩与还原方法,利用随钻方位成像在层界面位置成等值线特征,建立等高线方程;采用函数映射关系代替图像数据,通过传输函数关系所对应的图像映射关系参数大大降低数据量,再通过反函数解压,获取高质量成像图像,减轻泥浆脉冲数据传输带宽限制的压力。该技术试验结果表明,对井下随钻方位伽马测量数据压缩率达92.9%,大大减少了地质导向时井底数据实时上传量,实现了随钻成像数据的实时上传,可为岩性、层界面等地层关键信息实时解释提供数据支撑,助力精准地质导向。

海上双方位地震资料OVT域联合成像技术在断层阴影区的应用

断控油藏是勘探开发的重要目标之一,断层导致的地震阴影区普遍存在构造成像畸变,常规海上窄方位三维地震数据难以满足该背景下构造研究需要。针对南海典型断控构造油藏不同年份拖缆采集的双方位地震资料,通过速度调查分析了不同方位三维地震资料的差异。对于叠前一致性以及五维规则化处理后的融合道集数据,采用双方位OVT(Offset Vector Tile)域断控约束网格层析速度建模以及TTI(Tilted Transversely Isotropic)介质深度偏移,获得了高精度各向异性速度模型。实际地震资料处理结果表明,双方位融合的深度域数据品质得到明显改善,断面成像精度高,断层阴影区地震反射能量聚焦、同相轴连续,构造畸变基本消除,深度误差大幅降低,为构造研究以及油田高效开发提供了可靠依据,同时也为该地区同类型断控油藏的勘探提供了新思路。

结合伽马成像技术的三维地质建模在页岩油地质导向中的应用

长庆油田鄂尔多斯盆地陇东地区长7页岩油属于重力流沉积,横向上岩性变化快,非均质性强,砂体分布不稳定,纵向上隔夹层发育,小层间物性、含油性等差异大,地质条件相对复杂,在地质导向方面带来了很大的困难。为了准确识别储层甜点,提高储层钻遇率,提出充分利用钻井、测井和地震数据,开展构造建模、属性建模和随钻近钻头方位伽马成像技术,形成了三维地质建模与近钻头方位伽马成像技术相结合的地质导向技术。现场应用实践表明,该技术在长庆油田页岩油水平井地质导向中有着重要的指导意义,其中的研究思路可为其他非常规油气藏提供借鉴。

复杂山地深度域地震成像处理方法--以龙门山山前带海棠铺复杂构造区为例

山前带复杂构造区蕴藏了丰富的油气资源。地震资料信噪比低和速度建模困难是目前山前带地震数据精确成像面临的主要问题。以龙门山山前带海棠铺地区地震数据为例,开展了叠前深度域地震成像处理方法攻关研究,重点在叠前噪声压制和叠前深度偏移速度建模等两方面开展了研究,具体如下。①加强低频弱信号保护,采用二次信噪分离技术,对噪声记录中有效信号进行二次信噪分离,最大限度保护低频弱信号不受损伤。②优化叠前深度偏移速度建模流程:首先优化传统深度域速度场更新输入道集与偏移输入道集共用一个道集的方式,对驱动速度场更新的输入道集进行五维数据规则化处理以提高其信噪比;然后以地质导向为基础,精细刻画强反射速度缺失界面,联合层析反演并融合深度域近地表速度模型,建立具有地质模型约束的深度域速度场;得到了精确的速度模型后,再修改偏移成像输入道集及偏移方法,将五维数据规则化前的地震道集作为输入道集,将全方位角度域叠前深度偏移作为最终偏移成像方法。将该方法应用于川西北海棠铺地区的地震数据处理,结果表明所提方法大幅提高了研究区的地震成像精度,最终得到的叠前深度偏移成像结果信噪比高,偏移归位合理,为进一步推动该区的深入勘探开发,提供了可供借鉴的深度域地震成像处理经验。

非平衡状态下合成孔径雷达图像几何畸变仿真

合成孔径雷达成像过程中,受地形高低起伏影响,图像上几何信息会发生畸变,严重影响图像的清晰度。为此,提出非平衡状态下合成孔径雷达图像几何畸变校正方法。使用非下采样Shearlet变换、硬阈值算法去除几何畸变图像内噪声,利用模糊对比度、隶属度函数增强畸变图像的层次感,通过矩技术算法得出目标对象方位角,结合牛顿迭代、间接定位算法获得目标对象在畸变图像中坐标,根据距离-多普勒频率模型、插值方法对图像重新采样,通过遍历DEM完成畸变图像校正。实验结果表明,所提方法畸变校正效果好,且校正80个图像用时低于1.5s。

库车坳陷阿瓦特地区高精度地震成像技术及应用

阿瓦特区块位于塔里木盆地库车坳陷克拉苏冲断带西段,地表高程变化大、起伏剧烈,地下构造极其复杂。受地表及地下地质条件的影响,地震资料叠前深度偏移处理准确成像困难。笔者针对该区特殊的地质特征,通过近真地表叠前深度偏移技术、高精度浅表层速度建模技术、特殊岩性体速度精细刻画技术、多方位网格层析成像技术等系列高精度地震成像技术的应用,大幅度提升了该区地震资料的叠前深度偏移成像品质,为后续地质解释及油气勘探开发奠定了坚实的数据基础。

方位伽马成像技术在长庆油田陇东页岩油地质导向中的应用

随着长庆油田水平井数量大幅增多,提高储层钻遇率变得尤为重要,常规随钻地质导向系统测量参数单一且盲区长、地层响应滞后,因此,需要搞清井眼轨迹与地层的相对位置关系并及时探测地层边界、调整轨迹。通过了解近钻头方位伽马成像系统的工作原理、仪器性能、测量参数和技术优势,应用近钻头方位伽马成像技术快速识别岩性变化、判断井眼轨迹与地层的切割关系、识别砂泥岩薄互层、计算地层倾角,在随钻地质导向过程中为轨迹调整提供依据,做到早发现、早调整,追踪目的层,减少浪费井段,有效提高储层钻遇率。现场应用表明,华XX井应用近钻头随钻方位伽马成像测井技术后,储层遇率高达96.6%,应用效果较好,为近钻头方位伽马成像仪器在长庆油田推广应用提供可靠的技术支撑。

A seismic modeling analysis of wide and narrow 3D observation systems for channel sand bodies

The effect of the wide and narrow azimuth 3D observation systems on seismic imaging precision is becoming a hot area for studies of high precision 3D seismic acquisition methods in recent years. In this paper we utilize 3D physical seismic modeling experiments. A 3D channel sand body physical seismic model is constructed and two acquisition systems are designed with wide azimuth （16 lines） and narrow azimuth （8 lines） to model 3D seismic data acquisition and processing seismic work flows. From analysis of migrated time slice data with high quality and small size, we conclude that when the overlying layers are smooth and lateral velocities have little change, both wide and narrow azimuth observation systems in 3D acquisition can be used for obtaining high precision imaging and equivalent resolution of the channel sand body.