The full waveform inversion (FWI) utilizes full wavefield data to invert subsurface parameters and is considered one of the most promising data-driven tools for obtaining high precision velocity models. However, the successful application of FWI in geophysical exploration remains limited, primarily due to the cycle-skipping issue caused by the absence of low-frequency data, which is one of the main reasons for FWI failures. Incorporating prior regularization constraints FWI can effectively compensate for the lacking low-frequency components and constrain the iterative updates of FWI toward the desired direction, offering a natural advantage in addressing this challenge. However, the weights of the prior information terms are still determined empirically, which introduces significant subjectivity and randomness to the inversion results. To solve this issue, we propose an adaptive method to determine the weight factor based on posterior probability distribution within the Bayesian theoretical framework. This factor adaptively adjusts during each iteration to balance the contributions of the data error term and the prior information term in FWI, which can effectively mitigate the cycle-skipping problem and alleviating the nonlinearity of the inversion process. Numerical examples from the Overthrust model and the Marmousi model show that our method not only enhance the accuracy of FWI, but also demonstrate strong noise resistance.

Abstract The Ordovician carbonate reservoirs in the northern Tarim Basin lie at great depths (>8000 m). During long distance seismic wave propagation, high-frequency components are severely attenuated, resulting in low dominant frequency, a narrow frequency band, and insufficient resolution in the original seismic data. This makes it difficult to meet the requirements for detailed characterization of ultra-deep carbonate reservoirs. To address this problem, this paper focuses on broadband spectral enhancement (BSE), a frequency-boosting technique, and its application to seismic data from the northern Tarim Basin. The technique effectively broadens the seismic frequency band by applying different gains to each frequency band. Through parameter scanning and optimization, it is possible to determine the optimal processing parameters, low-cut (LC), high-cut (HC), low-pass (LP), and high-pass (HP) frequencies, for each seismic block. Application results in the Shunbei area, northern Tarim Basin, show that the BSE technique expands the effective frequency band of seismic data from 15 Hz to over 24 Hz, significantly improving the vertical resolution of deep seismic data while maintaining a good signal-to-noise ratio and relative amplitude relationships. The processed data exhibit enhanced continuity of coherent events, clearer imaging of deep large faults and interlayer fractures, greatly improved separation of bead-like reflections, and a significantly enhanced capability for identifying fracture-cavity bodies. The correlation coefficient between synthetic records and processed well traces has increased, and the well-seismic match has improved, providing a solid data foundation for subsequent structural interpretation and detailed reservoir prediction.

The ultra-deep,strike-slip fault-controlled condensate gas reservoirs in the Shunbei area of the Tarim Basin exhibit extremely strong heterogeneity,posing significant challenges to both the characterization precision for fractured-vuggy reservoirs and the advancement of exploration technologies.In this study,we investigate the characteristics of such reservoirs in the No.4 strike-slip fault zone in the Shunbei area.The reservoir geological models are constructed for segments with pull-apart,compressive,translational,and oblique weak compression properties in the fault zone.Moreover,key exploration techniques are developed,focusing on three-dimensional quantitative characterization of fault-controlled fractured-vuggy reservoirs,along with optimal landing zone selection and trajectory design for high-yield wells.The results indicate that the ultra-deep,strike-slip fault-controlled reservoirs exhibit grid-like structures,corresponding to an integrated reservoir model with multiple grid-like structures.These reservoirs exhibit high hydrocarbon enrichment and production due to multiple factors:supply from the Cambrian source rocks,hydrocarbon transport along fault slopes,hydrocarbon enrichment governed by fault-controlled grid-like structures,multi-stage hydrocarbon charging,and dynamic hydrocarbon accumulation.The mechanisms underlying the differential hydrocarbon enrichment of the condensate gas reservoirs include early-stage oil charging,multi-episodic differential gas charging during the late stage,and weak secondary modifications.Two key exploration technologies are developed,that is,a three-dimensional quantitative characterization technology for fault-controlled fractured-vuggy reservoirs,which is centered on compressed sensing-based frequency expansion,phase-controlled wave impedance inversion,and three-dimensional analysis,and a spatial positioning technology for landing target zones based on three parameters:source rock-connecting major fault planes,strong beadlike wave troughs,and stress field direction.These technologies provide technical support for the landing zone selection and trajectory design of high-yield wells.The theoretical achievements and technology application in this study have enabled maximum productivity with a minimum number of wells in the No.4 fault zone within the Shunbei area,providing a typical case for the exploration and exploitation of ultra-deep carbonate condensate gas reservoirs.

Ultra-deep carbonate reservoirs are developed in the Shunbei area and are highly heterogeneous,forming a"grid-like"reservoir combination in which tight bedrock and reservoirs are staggered.Existing information indicates that the internal reservoir structure of this type of combination is complex.Not only are the individual reservoirs smaller in size,but the intervals between reservoirs are also smaller.Although the amplitude attribute of seismic data can indicate the location of the area where the reservoir is combined,due to the resolution of the seismic data,it is difficult to effectively characterize the internal structure of the reservoir based on seismic data and traditional seismic attribute analysis.The difficulty impacts the accuracy of reservoir prediction as well as drilling track design.This paper uses the W transform to carry out high-resolution time-frequency analysis and expand the one-dimensional time-domain seismic traces into the two-dimensional time-frequency domain.The peak energy of the time-frequency spectrum estimated with the W transform is consistent with the peak frequency of seismic traces.And the spectrums are symmetrically distributed to seismic peak frequency,with higher resolution at frequencies deviated from the peak frequency,form a spindle-like shape.What is more,the resolution at peak frequency is consistent with that of seismic trace.Therefore,we use rich,high-resolution seismic time-frequency spectral information to more accurately identify and characterize the ultra-deep"grid-like"reservoir combination in the Shunbei area.

The selection of imaging conditions is one of the most critical factors determining the quality of reverse time migration (RTM) images. Among the widely used imaging conditions, the cross-correlation imaging condition (CCIC) consistently delivers high-resolution images. However, it is accompanied by substantial calculational costs and I/O tasks, particularly in 3D scenarios. In contrast, the excitation amplitude imaging condition (EAIC) offers advantages in computational efficiency, low storage requirements, and high precision. Nevertheless, it suffers from image distortion when dealing with multi-path propagation or strong reflection interfaces. The local Nyquist cross-correlation imaging condition (LNCIC) effectively combines the advantages of the two aforementioned imaging conditions. It uses the local wavefield near the time corresponding to the maximum amplitude at each grid point for imaging, and introduces the Nyquist sampling theorem to establish the search time step. This approach offers the benefit of high imaging quality while maintaining low storage cost. In this paper, we adopt an adaptive finite difference operator to solve the eikonal equation and calculate the accurate first-arrival traveltimes, thereby modify LNCIC and further enhancing the imaging accuracy. The effectiveness of the proposed method is demonstrated through numerical examples, including the Marmousi model, noise-resistance tests, and field data applications.

Accurately predicting the external morphology and internal structure of fractured-vuggy reservoirs is of significant importance for the exploration and development of carbonate oil and gas reservoirs. Conventional seismic prediction methods suffer from serious non-uniqueness and low efficiency, while recent advances in deep learning exhibit strong feature learning capabilities and high generalization. Therefore, this paper proposes an intelligent prediction technique for fault-controlled fracture-vuggy reservoirs based on deep learning methods. The approach involves constructing 3D seismic geological models that conform to the geological characteristics of the study area, simulating seismic wavefield propagation, and combining the interpretation results of fractured-vuggy reservoirs. Training sample datasets are separately established for strike-slip faults, karst caves, and fault-controlled fractured-vuggy reservoir outlines, which are then input into the U-Net model in batches for training. This leads to the creation of a deep learning network model for fault-controlled fractured-vuggy reservoirs. The trained network model is applied to the intelligent identification of fault, karst cave, and fault-controlled fracture-vuggy reservoir outlines using actual seismic data from the Shunbei area. A comparison with traditional methods is conducted, and the experimental results demonstrate that the proposed deep learning approach shows excellent performance in the identification and prediction of fault-controlled fractured-vuggy reservoirs.

顺北油气田二叠系地层火成岩广泛发育,断控缝洞储集体横向非均质性强因而精确速度建模及目标地质体成像困难.在常规地震数据处理中,传统的OVT分扇区处理技术无法获得地下真实角度信息,不能准确反映引起的速度突变,为进一步提高顺北复杂构造区的宽方位地震成像精度,利用全方位局部角度域偏移成像技术实现了顺北油气田的分方位、分角度的精确成像.利用全方位网格层析速度建模技术分析全方位道集的剩余延迟,建立层析成像矩阵,实现各向异性场的精确速度建模.采用全方位地下局部角度域分解与成像技术,对全方位共倾角道集进行分倾角叠加、散射增强和镜像增强处理,提高深层小尺度地质体的可识别能力;利用倾角道集的特点进行散射成像,获得散射数据体,突出了地下缝洞体的能量;利用不同波场的传播特点进行镜像能量成像,获得信噪比更高、细节更清晰的叠加数据,清晰刻画断裂展布特征,为顺北油气田缝洞储层及小尺度地质体的预测提供了基础数据该项技术.也可为其它地区的缝洞型地质异常体的预测提供技术参考.顺北油气田的应用结果表明,火成岩建模及成像精度明显提升,突出了缝洞储层的串珠反射能量,提高了断裂识别的准确度.相较于常规克希霍夫偏移技术,全方位局部角度域偏移成像技术保留了不同传播方向波场成像值的局部方位信息,能更准确地反映地下成像点地质特征.

超深层碳酸盐岩储层非均质性强,其内部结构受地震资料精度限制,规模储层预测和分布认识存在难度.选取顺北中部北东向断裂体系的顺北4号断裂带为研究对象,开展断裂构造破碎成储物理模拟实验、井震精细标定、模型正演、储集体表征、储集体地质模型研究,提出断裂面附近发育多个由空腔、裂缝带组成的多组缝洞集合体,建立了走滑断裂栅状储集体结构模式,阐明走滑断裂栅状储集体的成因机制与主控因素,构建了断裂带规模储集体"一体多栅"结构模型,形成了断控储集体空间定位与"一井多控、一井一靶、一井多靶"分类井轨迹设计方案.成果应用指导了顺北4号、顺北8号断裂带钻井轨迹设计,实现了断控缝洞型复杂油气藏的"少井高产",新增一个百万吨产能新阵地,对我国其他盆地超深层断控型油气藏的勘探具有一定指导与借鉴意义.

Ordovician fractured carbonates under study are over 7000 m deep in northwest China. Multistage tectonic activities result in numerous fractures along the strike-slip faults, accompanied with karst collapses due to atmospheric freshwater seepage. The resultant cave-fracture system provides numerous channels favorable for the migration and storage of hydrocarbons. Azimuthal anisotropy analyses with wide-azimuth and high-density 3D seismic data facilitate fracture estimation from migrated CRP gathers in this area. Compared with azimuthal velocity variations, azimuthal amplitude variations are quite sensitive to fractures, but suffer many negative factors. Major difficulties with azimuthal amplitudes to map superdeep fractured reservoirs include non-uniform distribution of azimuths and offsets, extremely low S/N ratio (SNR), anisotropic effect of strike-slip faults, and shielding effect of overlying irregular igneous strata. We propose an integrated scheme with azimuthal P-P amplitude/frequency attributes for prestack prediction of fractures based on the migrated CRP gathers. First, we analyze the distribution of azimuths, offsets, and bins to identify appropriate bins with the best range of offsets and the uniform distribution of azimuths. The selected wide-azimuthal CMP gathers are regrouped in terms of five azimuths, followed by azimuthal prestack migration. The resulting subazimuthal CRP gathers are optimized by denoising, flattening by residual static correction, and wavelet shaping to improve both SNR and resolution. We then conduct a local stacking in 100 m x 100 m bin for the best range of offsets from 1000 to 5600 m, followed by matched filtering to remove the footprint effect of overlying igneous strata. Frequency-related amplitude attributes are extracted for sensitive analyses in azimuths by ellipse fitting, yielding several optimal attributes for fracture prediction. We demonstrate that the coupled amplitude and frequency attributes in terms of energy percentages are the best in this area. Case studies show the applicability of the presented scheme for detecting superdeep fracture sets from extremely low SNR seismic data.

In this review on the exploration and development process of the Shunbei ultra-deep carbonate oil and gas field in the Tarim Basin, the progress of exploration and development technologies during the National 13th Five-Year Plan of China has been summarized systematically, giving important guidance for the exploration and development of ultra-deep marine carbonate reservoirs in China and abroad. Through analyzing the primary geological factors of "hydrocarbon generation-reservoir formation-hydrocarbon accumulation" of ancient and superposed basin comprehensively and dynamically, we point out that because the Lower Cambrian Yuertusi Formation high-quality source rocks have been located in a low-temperature environment for a long time, they were capable of generating hydrocarbon continuously in late stage, providing ideal geological conditions for massive liquid hydrocarbon accumulation in ultra-deep layers. In addition, strike-slip faults developed in tectonically stable areas have strong control on reservoir formation and hydrocarbon accumulation in this region. With these understandings, the exploration focus shifted from the two paleo-uplifts located in the north and the south to the Shuntuoguole lower uplift located in between and achieved major hydrocarbon discoveries. Through continuing improvement of seismic exploration technologies for ultra-deep carbonates in desert, integrated technologies including seismic acquisition in ultra-deep carbonates, seismic imaging of strike-slip faults and the associated cavity-fracture systems, detailed structural interpretation of strike-slip faults, characterization and quantitative description of fault-controlled cavities and fractures, description of fault-controlled traps and target optimization have been established. Geology-engineering integration including well trajectory optimization, high efficiency drilling, completion and reservoir reformation technologies has provided important support for exploration and development of the Shunbei oil and gas field.

Conventional multichannel spectral inversion (SI) methods are usually implemented in a 2-D model, which only considers the lateral continuity inside a section and ignores the continuous features between sections in 3-D space. On the other hand, the principle of odd–even decomposition, which can significantly improve the thin-layer recognition ability, is poorly adapted in multichannel with complex structures. We propose a structural geosteering shear backfill mapping (SBM) method to alleviate these issues. After that, we establish a 3-D bipolar SI objective function based on structural geosteering SBM and solve it with 3-D norm regularization. Examples using synthetic and 3-D field data show that the 3-D bipolar SI based on structural geosteering SBM is highly adaptable to complex structures and can provide a better inversion result than the conventional multichannel sparse spike inversion in terms of guaranteeing strata continuities and retrieving weak reflectivity.

溶洞识别对于缝洞型油气藏的勘探与开发具有重要意义.传统溶洞识别方法多解性强且效率低,因此将具有强特征学习能力、高泛化性的深度学习方法引入溶洞识别中,但溶洞的地震波场响应特征复杂、异常体尺寸较小、训练样本难以获取等导致深度学习在识别溶洞时仍具挑战性.为此,提出一套识别地震数据溶洞的"两步法"深度学习方法:首先通过U-Net模型识别地震剖面上的"串珠状"异常反射;再根据"串珠状"异常识别结果对地震数据进行小范围截取,输入深度残差网络中,实现对实际溶洞轮廓的预测.对于实际溶洞预测训练数据难以获取这一问题,采用波动方程正演模拟的方法制作具有准确标签的溶洞地震数据.实际地震数据的应用表明,该方法对于溶洞识别准确性高,抗噪能力强,可以极大地节约人工解释成本.

塔里木盆地巴麦地区的地震资料受复杂地震地质条件的影响,层间多次波广泛发育,识别和压制难度大,导致奥陶系碳酸盐岩断控缝洞型储层成像不准确,制约了该地区油气勘探部署.通过模型正演及邻区VSP波组特征标定分析,明确了层间多次波产生的必要条件、发育特征及对有效反射信号的影响,并有效识别出二叠系火成岩巴楚组标准灰岩、二叠系不整合面小海子组灰岩等多套产生层间多次波的"源镜"组合,形成了"两步法"层间多次波叠后压制技术:首先利用多次波分布规律,采用匹配追踪法压制层间多次波;然后基于剖面频率特征,利用优势频率信息提取技术,压制高频层间多次波并增强资料信噪比.研究区实际资料处理结果表明,该方法能够有效压制奥陶系内幕层间多次波,提升目的层断控碳酸盐岩缝洞型储层成像质量.

The phenomenon of S-wave splitting indicates the development of fractures in the shallow crust. Therefore, methods based on S-wave splitting have been established to predict the development of one set of parallel fractures. However, for rocks containing two nonorthogonal sets of vertical fractures, the mechanism of S-wave splitting is more complex, and the available methods cannot be applied. To resolve this inadequacy, we have developed a two-way rotation method to separate split S-waves with the aim of restoring the split S-wave polarizations and predicting the fracture azimuths. First, we calculate the stiffness matrix of fractured media based on the linear slip theory and derive the phase velocities and polarizations of split S-waves induced by fractures using the Christoffel equation. Second, we clarify the S-wave splitting mechanism in this media by using velocity analysis and deconstruct the S-wave polarizations on the horizontal components. Third, we deduce a two-way rotation matrix obtained by the S-wave splitting modes to separate the split S-waves. To solve for the angle parameters related to the fracture azimuths in the two-way rotation matrix, we superpose the subspace polarizations in two dimensions to determine the polarization azimuths of the split S-waves. Numerical model tests demonstrate that our method is stable under noisy conditions. Finally, we apply our method to real near offset and walkaround vertical seismic profiling data, and the predicted fracture results are verified by imaging logs and prior knowledge.

地震数据采集得到的地震波是由反射波、规则干扰和噪声叠合而成的复合波,数据处理将淹没在干扰和噪声之中的反射波提取出来,再经过频率补偿使反射波高频成分的微弱振幅得以提升,从而得到主频高、频带宽的高分辨率数据.记录下来的反射波频率的高低,不能用"60 dB高频死亡线"来衡量,用原始数据滤波扫描也得不到反射波频率的正确范围,而用采集+处理综合动态范围和地层吸收衰减模型可对反射波频率范围作出较客观的估计.对处理后的数据进行滤波扫描,才能得到正确的反射波频率范围.塔里木盆地沙漠区2 ms采样间隔的常规处理数据高通滤波扫描结果表明,反射波频率可高达尼奎斯特频率(约240 Hz),证明井中激发、地面接收采集到的数据已记录了这样的反射波高频成分.特征子波反褶积处理的实例证明了这样的微弱振幅高频成分是展宽高频段的有用信号.然而1 ms采样间隔的高精度数据经叠前时间偏移处理,其反射波高频仅达到120 Hz,甚至更低至60 Hz.之所以如此,是叠前时间偏移前的滤波和频率衰减所致,这种做法变相地将1 ms采样的高精度数据当作4 ms甚至8 ms采样间隔数据使用.此外,抽稀时间和空间采样间隔的算法和处理措施会使反射波高频成分成倍降低.

塔里木盆地顺北地区发育一系列中小尺度的板内走滑断裂,断裂带油气富集,但断裂空间结构、断裂演化及其对断控缝洞型储层的控制机理尚不明确.以富含油气的顺北1号断裂与顺北5号断裂为研究对象,对走滑断裂垂向构造样式、平面分段样式、空间结构开展系统研究,并结合生产动态资料深入探讨了走滑断裂构造变形对油气富集的控制作用.基于重要构造变革期及岩性特征将顺北地区古生界地层划分为6个构造层,提出走滑断裂在不同构造层具有"分层变形、分段演化"的构造变形特征.顺北1号断裂垂向构造序列相对简单,深层线性走滑断裂平面分段数少,断裂纵向空间结构组合较简单;顺北5号断裂垂向构造序列复杂,发育一套膏盐岩滑脱构造."分层变形、分段演化"的构造变形导致断层空间结构复杂,同时走滑断裂在不同构造层中的构造样式对断控缝洞型油气藏成藏要素具有重要控制作用.走滑断裂在平面分段、纵向构造、活动强度和空间结构等方面的差异是导致顺北1号断裂和顺北5号断裂油气差异富集的根本原因.

塔里木盆地超深层钻井塔深1井揭示在埋深8 408 m条件下依然具有优质白云岩储层,但储集空间的成因机制存在较大争议.在详细的岩心描述、显微岩石学观察与孔洞胶结物充填序列分析基础上,对阴极发光分析后的加厚薄片,通过原位微区取样方法分别获取基质、早期白云石胶结物和晚期白云石胶结物样品并进行碳氧同位素分析.早期白云石胶结物与白云岩基质具有相对一致的碳氧同位素分布特征,而晚期白云石胶结物δ13C值和δ18O值偏负.胶结物充填序列与碳氧同位素分析结果表明,不同类型白云石是多阶段白云石化作用的产物,即孔洞在白云石化作用发生的时候已经形成并随着埋深增加不断消亡.中寒武统阿瓦塔格组深灰色孔洞型白云岩储集空间的形成可能与准同生期近地表成岩事件有关.

近年来,塔里木盆地碳酸盐岩领域取得了丰富的油气成果,尤其是盆地北部深层奥陶系岩溶缝洞型油藏资源量巨大,为准确认识、评价、管理该类型油藏,应用物探手段对储层的精细刻画以及准确合理的对产量、储量的量化描述十分重要。前期对于岩溶缝洞性油藏的量化描述,大多基于二维（平面）范畴,本文讲述的描述方法重点基于高精度采集三维地震资料、实钻井资料及生产动态数据,动静结合,利用属性表征地震相、相控反演确定储层、孔隙度关系式建立地质—地震桥梁,最终以三维空间雕刻的三维范畴来描述和量化地质体。此方法能够有效刻画及求取岩溶缝洞型储层中洞、孔、缝三类储空间的几何形态和有效体积数值,达到该类储层的准确定量化描述。目前,此技术应用于塔里木盆地深层碳酸盐岩缝洞型储层量化描述标准的建立及储量计算方案的编制效果较好,有望实现碳酸盐岩溶缝洞型储层量化描述技术的进步。

塔河油田奥陶系碳酸盐岩缝洞型油藏的储层非均质性强,油水分布状况复杂.弄清其在区域尺度上(10 km× 10 km)的宏观油水分布规律,对于缝洞型油藏开发过程中的控水稳油意义重大.本文以塔河油田十区西为研究区,在全方位高精度三维地震数据处理、解释和反演的基础上,对岩溶古构造和开发过程中的油水动态进行综合分析,探讨研究区碳酸盐岩缝洞型油藏的油水宏观平面分布格局的控制因素.结果 表明:研究区在加里东中期第Ⅰ幕岩溶发生期形成了相对均匀的古岩溶含水层,在海西早期油气充注进古岩溶含水介质以后,海西晚期发生的深部热液活动对缝洞体进行了封闭定容,造成缝洞分隔,并且奠定了目前油水在平面上的宏观分布格局.

首先简单回顾了地震各向异性理论与多分量地震勘探技术的国内外发展现状,然后针对石油工业领域需求,重点讨论了裂缝各向异性等效介质理论应用存在的问题.对于页岩、煤层等强各向异性介质,需要突破Thomsen理论的弱各向异性假设;对于多组多尺度裂缝型储层,需要从单斜介质模型的角度进一步丰富、发展现有的等效介质理论;而对于中国广泛分布的陆相薄互层储层,宽方位P波各向异性分析与S波分裂分析需要在正交各向异性介质的框架下重新认识波场特征,并厘定各向异性异常的影响因素.同时分析了多分量地震数据处理、解释分析中存在的不足,主要问题在于油气勘探开发的高精度要求与多分量地震数据处理技术不够完善所产生的不匹配.最后,提出了一些值得攻关研究的方向,重点在于现有的多分量地震数据处理需要进一步发展保矢量和动力学特征的方法技术,包括多分量的高维插值波场重建技术、宽方位OVT叠加技术、深海OBS/OBN稀疏采样成像技术以及大起伏海底条件下的PS波深度域偏移成像技术等.