过零点个数地震属性理论诠释及应用

在地震解释与储层预测中,地震属性扮演着重要角色.在砂砾岩储层研究过程中,常规属性效果并不理想,无法满足实际应用的需要.而过零点个数,虽是一种不被人经常使用的地震属性,但我们发现在砂砾岩体油藏预测中应用效果良好.为此,研究过零点个数地震属性的定义与计算方法,讨论子波主频、砂岩厚度、泥岩夹层和地层韵律性等与它的关系,通过模型测试与实际资料应用对其做较全面的诠释.研究表明:(1)对于单一界面地震记录,过零点个数不随子波主频和波长的变化而变化;(2)砂岩厚度与过零点个数呈正相关,厚砂岩的过零点个数要比薄砂岩大;(3)砂体间存在的泥岩夹层,厚度变化对过零点个数影响较小,但它会影响波组的形态;(4)不规则沉积与均匀沉积相比,过零点个数属性值要大,因此,此属性比较适合多期次发育的砂砾岩体或其他薄互层结构的储层预测.总的来说,过零点个数地震属性能够有效地识别砂砾岩体发育区,可为此类储层预测提供了一种新的优势属性.     

Integrating seismic attributes in the accurate modeling of geological structures and determining the storage of the gas reservoir in Gorgan Plain (North of Iran)

Three dimensional seismic operation of Gorgan Plain was studied around a well, which is situated in North of Iran following the hitting of a thin overpressure gas layer (thickness of 9.6 m), with the purpose of the accurate modeling of geological structures and determining the approximate gas storages. The geological structures of the reservoir were modeled using the seismic attributes (coherence, instantaneous amplitude and spectral decomposition (FFT)). The obtained results clearly demonstrated the shape and volume of the existing structural traps in the studied area. In order to estimate the thickness of gas layer in the 3D seismic volume and determining the gas storage, the thickness changes based on the seismic amplitudes were used because its thickness was less than the critical resolution thickness for this layer. However, due to its low thickness, the lack of indicator peak in seismic sections and strong faults of area, it was difficult to pursue this layer in the seismic volume and map its exact amplitude. Considering this issue, a new method with integrating of seismic attributes was recommended. First, the instantaneous amplitude attribute of the thin reservoir layer reflector in computed synthetic seismogram were fabricated and then the frequency regarding the highest amount (dominant frequency) was chosen by Fourier Transform. Finally, spectral decomposition (FFT) with the resulting frequency was gained over the cross-section of the layer's instantaneous amplitude attribute in the 3D seismic volume choosing a proper time window. In such a situation, an increase of its thickness was seen as its amplitude increase and the minimum gas storage of this reservoir was calculated using the area of the restricted part of high thickness (over 9.6 m).     

基于匹配追踪的瞬时能量异常属性在Albertine地堑油气预测中的应用

东非裂谷Albertine地堑是当今世界油气勘探的热点地区之一,具有埋藏浅、演化快、地层新的地质特点。作为主力含油气层段的新生代地层中疏松砂岩异常发育,物性参数差异较大,受控于孔隙度以及孔隙流体的综合影响,含油气储层的地震响应无明显规律,油气预测难度较大。基于能量吸收分析思想的指导,在利用匹配追踪时频分解方法有效提高时频分辨率的前提下,进一步提出瞬时能量异常属性的计算方法。以Albertine地堑的W油田为例,针对含油气储层表现的低频能量增加、高频能量衰减的异常特征,借助瞬时能量异常属性实现了油气预测,预测结果获得了钻井的验证。      

地震属性技术在四维地震监测中的应用

四维地震(4D seimic)主要是指利用重复三维地震测量资料进行油藏动态监测。在油田开发过程中,由于储层特性变化所引起的地震振幅异常、频率变化以及反射同相轴下拖现象等均可作为注蒸汽波及范围四维地震监测的良好识别标志。由于叠后地震资料中常常存在动校正速度不准、动校正拉伸畸变、剩余静校正误差、以及CDP道集中各道波形的差异性等多方面的问题,这会对叠后地震资料所反映出的四维地震异常特性产生影响,造成解释结果的差异性和不确定性。为此,本文尝试开展叠前地震属性反演研究,利用瞬时频率、瞬时频率梯度、能量衰减85%时的频率、最大振幅频率、最大振幅、总能量等多种衰减属性的叠前剖面及其差值剖面来定性解释四维地震实验区的注入蒸汽在剖面上的反映。     

复数子波匹配追踪算法识别薄层砂体

针对东营凹陷滩坝砂岩薄砂体的预测识别问题,研究了复小波匹配追踪方法.从地震信号morlet小波分解及重构分析入手,讨论了重构地震信号时关于频率、振幅、相位及时移参数的选取方法及其具体的选取变量.并就关键的振幅参数,研究了改善的计算方法.常规的匹配追踪算法扫描地震信号的所有时间点和频率.在本文中,为了改善时频分辨率,采用局部扫描主频和子波的时间延迟.在具体实现过程中,采用计算地震信号的平均瞬时频率和地震信号的瞬时包络处的时间,做为采样频率和时间采样点,得到与地震信号最佳相关的子波.对研究的方法从理论模型和实际资料进行了论证分析,证明理论上正确合理,实际应用效果显著.     

地震相控混沌反演在岩性油气藏储层预测中的应用——以RY坳陷M井区为例

RY坳陷M井区位于浅水三角洲前缘斜坡带,多发育水下分流河道沉积,砂岩储层厚度薄、横向变化快,且同一时期的砂体在平面上表现为多套油水系统,容易形成岩性油气藏,利用常规手段进行储层预测的难度较大。本文通过引入地震相控制,利用纵向及横向上的构造起伏、岩性变化、沉积环境变迁等先验信息降低了反演的多解性;同时将混沌理论与反演算法结合,根据反演迭代的实时状态自适应地修改正则化算子,调节反演稳定性和分辨率达到最佳平衡,既避免了混沌现象的出现,又最大限度地揭示薄层信息。M井区的实际应用显示,相控混沌反演可以突出地震波形的细节变化,准确刻画储层尖灭和分叉点位置,达到精准预测岩性油气藏的目的,对后续岩性油气藏的勘探开发具有较大指导意义。      

地震属性优化及其在储层预测中的应用

利用地震资料属性信息预测油气储层已越来越受到石油地球物理工作者的广泛重视。但如何优化地震属性,从而更加精确地预测薄砂岩储层特征,提高其描述精度,更是地质及地球物理勘探家们始终不懈的追求。本文在借鉴主成分分析思想的基础上,提出一种新的地震属性优化方法-约束主成分分析。经理论模型的计算及油田区的实际应用表明:该方法不仅能提高储层预测的精度,而且具有更好的适用性。     

秦皇岛32-6油田明化镇组河流相储层地球物理参数影响因素研究

秦皇岛32-6油田明化镇组储层为河流相沉积,单砂体规模小,砂体间接触关系复杂,受到地震分辨率限制,对叠置砂体储层地震响应规律认识不明确,导致基于地震信息的储层砂体解释错误.通过数值正演模拟,可以正确认识砂体储层的地震响应规律,提高砂体储层预测的准确率.所以,在进行地震响应正演模拟前,非常有必要对该区储层地球物理参数影响因素展开研究,通过分析研究区14口测井资料,建立了岩石物理参数(孔隙度、泥质含量、合流体性)与地球物理参数(速度、密度、波阻抗等)之间的相关关系,分析了不同沉积微相对地球物理参数的控制作用,并给出了相应的数学表达式,为正确认识河流相储层砂体地震响应规律奠定了准确的地球物理参数基础.     

Improving reservoir thickness prediction using seismic attributes and attributes fusion

Usage of any single attribute would introduce unacceptable uncertainty due to limited reservoir thickness and distribution, and strong lateral variations in lithological traps. In this paper, a wide range of prestack and post-stack seismic attributes is utilized to identify a range of properties of turbidity channel sandstone reservoir in Block L118 of J Oilfield, China. In order to better characterize the turbidity channel and lower the uncertainty, we applied multi-attribute fusion to weight a variety of seismic attributes in terms of their relevance to the identification of turbidity channel reservoir. Turbidity channel boundary is clearly present in the new attribute and the reservoir thickness prediction is improved. Additionally, fluid potential of reservoir was predicted using this fused attribute with a high value anomaly indicating high fluid potential. The multi-attribute fusion is a valid approach for the fine prediction of lithologic reservoirs, reducing the risks typically associated with exploration.     

基于频率域峰值属性的河道砂体定量预测及应用(英文)

河道砂体是陆相含油气盆地最重要的储集类型之一,其边界识别和厚度定量预测是储层预测的热点难题。本文在总结现有方法技术的基础上,提出一种利用频率域峰值属性进行河道砂体边界识别和厚度定量预测的新方法。对典型河道薄砂体地震反射进行了正演模拟,构造了一种新的地震属性——峰值频率-振幅比,研究表明:峰值频率属性对地层厚度变化敏感,振幅属性对地层岩性变化敏感,两者比值突出河道砂体的边界,同时,借助峰值频率与薄层厚度间存在的定量关系进行薄砂体厚度计算。实际数据应用表明,地震峰值频率属性可以较好的刻画河道的平面展布特征;峰值频率-振幅比属性可以提高对河道砂体边界的识别能力;利用频率域地震属性进行砂体边界识别及厚度定量预测是可行的。     

物探方法在临清坳陷某区块山西组沉积相分析中的应用

临清坳陷某区块缺少岩心、薄片、录井及常规测井资料。为了研究其目的层山西组沉积相对储层的控制作用,指导非常规天然气的高效开发。通过利用较少的录井岩性统计资料,结合地震物探方法,分析地震剖面特征、优选地震均方根振幅及相对波阻抗属性,确定该区目的层沉积相。通过上述地震属性研究的物探方法,确定山西组储层为河控浅水三角洲相和碳酸盐台地相,主要发育分流河道、分流间湾及局限台地沉积微相。其中三角洲相是主要的沉积相类型,分流河道是有效储层发育的主要微相类型。      

Integrated application of 3D seismic and microseismic data in the development of tight gas reservoirs

The development of unconventional resources, such as shale gas and tight sand gas, requires the integration of multi-disciplinary knowledge to resolve many engineering problems in order to achieve economic production levels. The reservoir heterogeneity revealed by different data sets, such as 3D seismic and microseismic data, can more fully reflect the reservoir properties and is helpful to optimize the drilling and completion programs. First, we predict the local stress direction and open or close status of the natural fractures in tight sand reservoirs based on seismic curvature, an attribute that reveals reservoir heterogeneity and geomechanical properties. Meanwhile, the reservoir fracture network is predicted using an ant-tracking cube and the potential fracture barriers which can affect hydraulic fracture propagation are predicted by integrating the seismic curvature attribute and ant-tracking cube. Second, we use this information, derived from 3D seismic data, to assist in designing the fracture program and adjusting stimulation parameters. Finally, we interpret the reason why sand plugs will occur during the stimulation process by the integration of 3D seismic interpretation and microseismic imaging results, which further explain the hydraulic fracture propagation controlling factors and open or closed state of natural fractures in tight sand reservoirs.     

多属性融合技术在苏14井区的应用

In this study area the geological conditions are complicated and the effective sandstone is very heterogeneous. The sandstones are thin and lateral and vertical variations are large. We introduce multi-attribute fusion technology based on pre-stack seismic data, pre-stack P- and S-wave inversion results, and post-stack attributes. This method not only can keep the fluid information contained in pre-stack seismic data but also make use of the high SNR characteristics of post-stack data. First, we use a one-step recursive method to get the optimal attribute combination from a number of attributes. Second, we use a probabilistic neural network method to train the nonlinear relationship between log curves and seismic attributes and then use the trained samples to find the natural gamma ray distribution in the Su-14 well block and improve the resolution of seismic data. Finally, we predict the effective reservoir distribution in the Su-14 well block.     

Experimental study on frequency-dependent elastic properties of weakly consolidated marine sandstone: effects of partial saturation

Investigating seismic dispersion and attenuation characteristics of loosely compacted marine sandstone is essential in reconciling different geophysical measurements (surface seismic, well logging and ultrasonic) for better characterization of a shallow marine sandstone reservoir. We have experimented with a typical high-porosity and high-permeability sandstone sample, extracted from the Paleogene marine depositional setting in the Gulf of Mexico, at the low-frequency band (2–500 Hz) as well as ultrasonic point (10⁶ Hz), to investigate the effects of varying saturation levels on a rock's elasticity. The results suggest that the Young's modulus of the measured sample with adsorbed moisture at laboratory conditions (room temperature, 60%–90% humidity) exhibits dispersive behaviours. The extensional attenuation can be as high as 0.038, and the peak frequency occurs around 60 Hz. The extensional attenuation due to moisture adsorption can be dramatically mitigated with the increase of confining pressure. For partial saturation status, extensional attenuation increases as increasing water saturation by 79% with respect to the measured frequencies. Additionally, the results show that extensional attenuation at the fully water-saturated situation is even smaller than that at adsorbed moisture conditions. The Gassmann–Wood model can overall capture the P-wave velocity-saturation trend of measured data at seismic frequencies, demonstrating that the partially saturated unconsolidated sandstone at the measured seismic frequency range is prone to be in the relaxed status. Nevertheless, the ultrasonic velocities are significantly higher than the Gassmann–Wood predictions, suggesting that the rocks are in the unrelaxed status at the ultrasonic frequency range. The poroelastic modelling results based on the patchy saturation model also indicate that the characteristic frequency of the partially saturated sample is likely beyond the measured seismic frequency range.     

A procedure to reduce side lobes of reflection wavelets: A contribution to low frequency information

Side lobes of the wavelets arise from the lack of low frequency content in a reflection wavelet. They tend to increase the time span of an individual reflection event and interfere with the other primary reflections or side lobes. Furthermore, their trace-by-trace consistency may produce pseudo-reflections and may cause misinterpretations of the side lobes as weak reflections.A procedure in order to improve the low frequency content of the seismic traces by suppressing the side lobe amplitudes based on the complex trace envelope is proposed. Using the average energies of the seismic trace and its envelope, the polarity table of the trace is obtained and used to correct the phase of the envelope. The resultant trace is termed “side lobe reduced (SLR) trace”. The method can be applied to the stack or migrated seismic data by a trace-by-trace basis. The only required parameter of the method is the moving average operator length which is used to calculate average energies of the input traces. In general, shorter operator lengths yield better results when the dominant frequency of the input increases.Results from synthetics and real seismic data sets show that the procedure improves the low frequency components of the input trace and side lobes in the output SLR trace are significantly suppressed. The method may be considered as a seismic amplitude attribute, which aids the interpreter to obtain the true seismic signature of the geological formations by removing the side lobes of the wavelet and restoring the low frequency components if the lower frequencies of deeper reflections are of primary concern.     

Improved structural interpretation of legacy 3D seismic data from Karee platinum mine (South Africa) through the application of novel seismic attributes

Seismic detection of faults, dykes, potholes and iron-rich ultramafic pegmatitic bodies is of great importance to the platinum mining industry, as these structures affect safety and efficiency. The application of conventional seismic attributes (such as instantaneous amplitude, phase and frequency) in the hard-rock environment is more challenging than in soft-rock settings because the geology is often complex, reflections disrupted and the seismic energy strongly scattered. We have developed new seismic attributes that sharpen seismic reflections, enabling additional structural information to be extracted from hard-rock seismic data. The symmetry attribute is based on the invariance of an object with respect to transformations such as rotation and reflection; it is independent of the trace reflection amplitude, and hence a better indicator of the lateral continuity of thin and weak reflections. The reflection-continuity detector attribute is based on the Hilbert transform; it enhances the visibility of the peaks and troughs of the seismic traces, and hence the continuity of weak reflections. We demonstrate the effectiveness of these new seismic attributes by applying them to a legacy 3D seismic data set from the Bushveld Complex in South Africa. These seismic attributes show good detection of deep-seated thin (∼1.5 m thick) platinum ore bodies and their associated complex geological structures (faults, dykes, potholes and iron-rich ultramafic pegmatites). They provide a fast, cost-effective and efficient interpretation tool that, when coupled with horizon-based seismic attributes, can reveal structures not seen in conventional interpretations.     

Predicting the distribution of thin bed reservoirs by broad frequency band seismic

Recognition of thin interbedded reservoirs in the middle-shallow strata in the Songliao Basin is a great difficulty. In order to resolve this problem, we present a technique for predicting the distribution of thin reservoirs using a broad frequency band and ultra high resolution seismic. Based on forward modeling, we recognized that a thin bed seismic reflection is characterized by changing amplitude with changing frequency （amplitude versus frequency, AVF）. We calculate the thickness of thin reservoirs from their AVF characteristics and predict the distribution of thin bed reservoir using broad frequency band and ultra high resolution seismic. The technique has been applied in the 3D seismic area of Zhaoyuan in the northern part of the Songliao Basin. The seismic resolution is increased by two or three times over that of conventional seismic and many thin reservoirs have been identified. The technique has extensive application to the exploration and development of oil and gas, such as optimizing the location of exploration wells, the design of wells （especially horizontal wells）, choice of production test layers, analyzing reservoir continuity in development wells, and so on.     

井间高分辨率纵横波层析成像研究井间油藏

采用视速度-偏振井间波场分离法分离得到纵波和横波波场,使用跨孔地震走时层析成像级联方法计算井间纵波和横波速度结构以及泊松比空间分布.综合纵横波速度、泊松比和测井参数,分析两井间岩性和储层特性.数值模型试验表明该方法垂直分辨率达到主频波长的1/4,并能准确分辨倾斜断层和垂直断层.处理相同纵波资料结果表明本文方法分辨率远远高于以往的井间走时层析成像方法,比井间声波层析成像分辨率更高.使用该方法处理垦71区井间资料,得到同台同源纵波和横波速度结构和泊松比分布.泊松比的低/高变化与测井参数指示的砂/泥岩层基本吻合.根据泊松比分布,参考岩石地震物理学测试数据,可以区分井间介质中的泥岩层、砂岩层,以及砂岩层中的饱水和饱油区,确定储层的连通性,圈定井间的剩余油藏.     

用宽频带高分辨率地震预测薄层储层分布

针对松辽盆地北部中浅层薄层识别难的问题,我们研究了用宽频带高分辨率地震预测薄层储层分布的方法。通过正演数据分析,发现薄层地震反射具有振幅随频率变化而变化的特征-简称为AVF特征,并提出利用储层反射AVF特征计算薄层储层的厚度,用薄层厚度对应的宽频带高分辨率地震方法预测薄层储层分布。该方法在松辽盆地肇源3D地区的实际应用中,大大提高了地震分辨率,查明了一大批薄层储层。该方法在油气勘探与开发中也有着广泛的应用领域,例如,井位设计,尤其是水平井设计,试油层位选择,开发井油层连通性分析等。