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塔河油田碳酸盐岩小尺度缝洞体的刻画是实现该区缝洞储层高效精细开发的迫切需求,由于精细刻画难度大,前期预测精度难以达到生产的要求,为此,本文以桑塔木地区为研究区开展了基于叠前分频偏移成像方法的缝洞体精细描述方法研究.首先,结合实际钻井和地震资料,构建了不同尺度缝洞体模型并开展正演模拟分析,论证了地震主频对分辨率的影响;其次,通过CMP道集分频方式对该区地震资料进行叠前分频处理,并研究不同频带下缝洞体的内部结构,利用不同频带信息进行缝洞体精细刻画;最后,利用实际钻井资料,开展实钻井与缝洞体吻合情况的分析,验证模型预测结果的可靠性.本文研究表明,地震资料分频结果与正演模拟结论一致,中高频带可以有效提高小尺度缝洞体成像精度,叠前分频成像技术显著提高了小尺度缝洞储层的预测精度. 相似文献
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《地球物理学进展》2015,(1)
鄂尔多斯盆地SG气田是我国典型的低孔,低渗,致密砂岩气藏的代表.该区地震勘探开发面临着两大难题:一是含气砂岩和围岩的声波阻抗存在较大范围叠置,利用声波阻抗预测储层存在明显的多解性;二是SG气田局部地区气、水关系复杂,地质上不存在统一的气、水层分界面,产水井严重影响产能建设,流体类型的识别是面临的又一难题.为了降低声波阻抗预测砂岩储层的多解性,提高有效储层预测精度,定量识别储层中流体的类型,本文提出了叠前地震弹性参数交会定量解释技术,从横波测井资料不同岩性、流体的岩石物理参数分析入手,优选了能够区分岩性和流体的最佳敏感弹性参数,制作了敏感弹性参数交会模板,通过地震叠前反演获得反映储层物性和含气性的地震弹性参数体,最后进行地震弹性参数交会定量解释预测有效储层和识别流体.勘探实例证实了该技术方法在SG地区对有效储层的预测是有效的,能够为井位优选提供可信的依据.地震弹性参数交会技术将纵向分辨率较高的测井岩石物理分析和横向分辨率较高的地震叠前反演结合在一起,使用了多个弹性参数交会,减少了以往单一弹性参数预测储层的多解性,最终获得比较可靠、更量化的反映储层物性和含气性的地震弹性参数交会体,为有效储层预测和流体识别探索出了新的途径,这一技术的应用和推广可以降低地震解释的风险,提高储层预测精度. 相似文献
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TH5区地质构造复杂,储层变化幅度大并且砂泥岩纵波阻抗叠置严重,常规地震属性与叠后阻抗预测在该区均没有取得良好的效果.在此背景下,本文分析了叠前纵横波同时反演的可行性,并介绍了该技术的研究思路.然后,通过交会图、剖面图、镂空图、平面图等多种手段对TH5区叠前同时反演结果进行了分析,同时类比已钻产油井的属性特征提出了建议井位.研究表明,通过叠前同时反演得到的纵、横波阻抗以及纵横波速度比等属性能有效地预测储层,为储层评价和井位建议提供可靠依据,应用效果良好. 相似文献
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《地球物理学进展》2017,(6)
为了确定碳酸盐岩地区目标井钻头前方缝洞体的空间位置,提出一种基于零井源距VSP资料的井地联合溶洞定位方法,提高缝洞型碳酸盐岩储层直接钻遇率.该方法主要利用钻井过程中获得的准确VSP速度修正地震三维速度场,对井区一定范围内的地震三维资料进行重新叠前深度偏移处理.通过零井源距VSP资料标定老三维地震资料(原定井位的三维地震)和新处理的三维地震资料,对比解释新、老三维地震资料,确定溶洞的空间位置变化.实时提供钻井靶心坐标,提高中靶精度.目前该方法已经在塔里木盆地塔北碳酸盐岩地区得到验证,并在塔中碳酸盐岩地区成功应用4口井,4口井在钻井期间均发生不同程度的放空和漏失,取得了较好的应用效果.该方法的成功应用为提高缝洞型碳酸盐岩储层直接钻遇率提供了一条新思路. 相似文献
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《地球物理学进展》2015,(5)
南海L盆地深水区,不仅有新近系生物礁发育的良好环境,更有生物礁油气藏形成的优越条件,是未来深水区勘探的重要领域.在生物礁储层评价、油气预测研究中,由于研究对象多为孔缝洞发育的细微储层结构,常规地震勘探多基于理想均匀介质或层状介质来研究储层结构,这显然容易忽略实际生物礁储层的局部非均质性对地震波响应特征和传播规律影响.本文以L盆地生物礁为例,在层序地层划分及沉积相分析双重约束下利用相对阻抗反演技术有效建立了生物礁储层框架模型,采用孔洞随机介质模拟技术对储层内部孔洞裂缝进行精细雕刻,建立能精细描述生物礁储层内强非均质性及孔缝洞物性特征的随机介质模型.最后通过正演模拟,定量地分析了盆地内生物礁储层的物性特征,从而进一步明确了盆地内寻找优质储层的方向,为勘探目标的寻找与优选提供科学的理论指导. 相似文献
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中深层天然气藏地震预测技术研究 总被引：1，自引：0，他引：1
济阳坳陷天然气资源丰富,已在多个层系发现了不同类型的中深层天然气藏,由于气藏地质条件、地震反射复杂,针对不同的气藏需采用不同的地震预测技术。本文在中深层天然气藏地质特点分析的基础上进行了岩石物理、地震反演、地震属性等预测技术研究,结果表明：中层气藏储层物性较好,储层与围岩的岩石物理参数差异明显,应用亮点、AVO、叠前弹性阻抗反演技术可较好地识别预测三角洲砂岩气藏;针对深层低孔低渗砂岩气藏,地震属性及多属性反演是有效的储层预测技术,并预测了孤北地区二叠系有利储集相带分布,结合构造分析,指出了孤北地区深层气勘探方向。 相似文献
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The scattering of elastic energy by random clusters of fractures and/or cavities in a massive rock is studied. The interpretation of the scattered seismic response reveals crucial information about the clusters of inhomogeneities (fractures/cavities), which may correspond to reservoirs. The study is based on a new two‐dimensional numerical‐modelling method that relaxes the constraints on the location and orientation of the inhomogeneities, accounts for inhomogeneities that have almost no volume but a finite surface area (fractures) and improves the accuracy of the calculation when the size of the inhomogeneities is comparable to the mesh size. It is shown that the nature of the seismic response of zones of diffuse fracturing and/or cavities is associated with the non‐uniformity of micro‐inhomogeneities in such zones; accumulations of these micro‐inhomogeneities are known as clusters. The relationship between the non‐uniformity of micro‐inhomogeneities and the strength of the seismic response has been established and measured. Considerable differences in the structure of the seismic response of zones of diffuse fracturing and diffuse cavities have been identified. Converted PS‐waves dominate in the scattered wavefield associated with fractures. This is explained, as the modelling results show, by a greater transparency of fluid‐filled fractures, which reduces the reflected energy of compressional waves. The wavefield associated with cavities is characterized by the predominance (in terms of strength) of compressional PP‐waves. The strength of converted PS‐waves in the scattered wavefields for both media is approximately the same. On the whole, according to the results of the modelling, the energy of the scattered response of fractured reservoirs is considerably less (about two times) than that of cavernous reservoirs. 相似文献
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Fluid identification in fractured reservoirs is a challenging issue and has drawn increasing attentions. As aligned fractures in subsurface formations can induce anisotropy, we must choose parameters independent with azimuths to characterize fractures and fluid effects such as anisotropy parameters for fractured reservoirs. Anisotropy is often frequency dependent due to wave-induced fluid flow between pores and fractures. This property is conducive for identifying fluid type using azimuthal seismic data in fractured reservoirs. Through the numerical simulation based on Chapman model, we choose the P-wave anisotropy parameter dispersion gradient (PADG) as the new fluid factor. PADG is dependent both on average fracture radius and fluid type but independent on azimuths. When the aligned fractures in the reservoir are meter-scaled, gas-bearing layer could be accurately identified using PADG attribute. The reflection coefficient formula for horizontal transverse isotropy media by Rüger is reformulated and simplified according to frequency and the target function for inverting PADG based on frequency-dependent amplitude versus azimuth is derived. A spectral decomposition method combining Orthogonal Matching Pursuit and Wigner–Ville distribution is used to prepare the frequency-division data. Through application to synthetic data and real seismic data, the results suggest that the method is useful for gas identification in reservoirs with meter-scaled fractures using high-qualified seismic data. 相似文献
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相对于常规砂岩,致密砂岩在岩石物理性质、力学性质等方面具有明显差异,并呈现出很强的非均质性.岩石物理模型能将储层参数与地震特性信息联系起来,因此可以作为致密砂岩储层参数与地震特性信息转换的桥梁.常规的岩石物理模型通常只考虑单一因素(例如非均匀性,单一孔隙,单一尺度等),建立的岩石物理模板并不适用于致密砂岩.本文针对高饱和气、微裂隙发育、非均质性强的致密砂岩储层,利用Voigt-Reuss-Hill模型计算混合矿物的弹性模量,采用微分等效介质(DEM)模型描述含裂隙、孔隙岩石的骨架弹性模量,基于Biot-Rayleigh波动方程构建了岩石物理弹性模板,给出了致密砂岩储层弹性参数与物性的关系.基于测井数据和实验数据对岩石物理弹性模板进行校正,并将校正后的岩石物理弹性模板结合叠前地震资料应用于川西地区储层孔隙度与裂隙含量预测.结果显示,反演裂隙含量、孔隙度与储层试气报告、测井孔隙度基本吻合,表明该模板能够较合理地应用于致密砂岩储层孔隙度及裂隙含量解释中. 相似文献
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Boris Gurevich 《Geophysical Prospecting》2015,63(1):141-150
Naturally fractured reservoirs are becoming increasingly important for oil and gas exploration in many areas of the world. Because fractures may control the permeability of a reservoir, it is important to be able to find and characterize fractured zones. In fractured reservoirs, the wave‐induced fluid flow between pores and fractures can cause significant dispersion and attenuation of seismic waves. For waves propagating normal to the fractures, this effect has been quantified in earlier studies. Here we extend normal incidence results to oblique incidence using known expressions for the stiffness tensors in the low‐ and high‐frequency limits. This allows us to quantify frequency‐dependent anisotropy due to the wave‐induced flow between pores and fractures and gives a simple recipe for computing phase velocities and attenuation factors of quasi‐P and SV waves as functions of frequency and angle. These frequency and angle dependencies are concisely expressed through dimensionless velocity anisotropy and attenuation anisotropy parameters. It is found that, although at low frequencies, the medium is close to elliptical (which is to be expected as a dry medium containing a distribution of penny‐shaped cracks is known to be close to elliptical); at high frequencies, the coupling between P‐wave and SV‐wave results in anisotropy due to the non‐vanishing excess tangential compliance. 相似文献
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R. Agersborg M. Jakobsen B. O. Ruud T. A. Johansen 《Studia Geophysica et Geodaetica》2007,51(1):89-118
An effective medium model for the stress-dependent seismic properties of fractured reservoirs is developed here on the basis
of a combination of a general theory of viscoelastic waves in rock-like composites with recently published formulae for deformation
of communicating and interacting cavities (interconnected pores/cracks and fractures at finite concentration) under drained
loading. The inclusion-based model operates with spheroidal cavities at two different length scales; namely, the microscopic
scale of the pores and (grain-boundary) cracks, and the mesoscopic scale of the fractures (controlling the flow of fluid).
The different cavity types can in principle have any orientation and aspect ratio, but the microscopic pores/cracks and mesoscopic
fractures were here assumed to be randomly and vertically oriented, respectively. By using three different aspect ratios for
the relatively round pores (representing the stiff part of the pore space) and a distribution of aspect ratios for the relatively
flat cracks (representing the compliant part of the pore space), we obtained a good fit between theoretical predictions and
ultrasonic laboratory measurements on an unfractured rock sample under dry conditions. By using a single aspect ratio for
the mesoscopic fractures, we arrived at a higher-order microstructural model of fractured porous media which represents a
generalization of the first-order model developed by Chapman et al. (2002,2003). The effect of cavity size was here modelled
under the assumption that the characteristic time for wave-induced (squirt) flow at the scale of a particular cavity (pore/crack
vs. fracture) is proportional with the relevant scale-size. In the modelling, we investigate the effect of a decreasing pore
pressure with constant confining pressure (fixed depth), and hence, increasing effective pressure. The analysis shows that
the attenuation-peak due to the mesoscopic fractures in the reservoir will move downward in frequency as the effective pressure
increases. In the range of seismic frequencies, our modelling indicates that the P-wave velocities may change by more than
20% perpendicular to the fractures and close to 10% parallel to the fractures. In comparison, the vertical S-wave velocities
change by only about 5% for both polarization directions (perpendicular and parallel to the fractures) when the effective
pressure increases from 0 to 15 MPa. This change is mainly due to the overall change in porosity with pressure. The weak pressure
dependence is a consequence of the fact that the S waves will only sense if the fractures are open or not, and since all the
fractures have the same aspect ratio, they will close at the same effective pressure (which is outside the analysed interval).
Approximate reflection coefficients were computed for a model consisting of the fractured reservoir embedded as a layer in
an isotropic shale and analysed with respect to variations in Amplitude Versus Offset and aZimuth (AVOZ) properties at seismic
frequencies for increasing effective pressure. For the P-P reflections at the top of the reservoir, it is found that there
is a significant dependence on effective pressure, but that the variations with azimuth and offset are small. The lack of
azimuthal dependence may be explained from the approximate reflection coefficient formula as a result of cancellation of terms
related to the S-wave velocity and the Thomson’s anisotropy parameter δ. For the P-S reflection, the azimuthal dependence
is larger, but the pressure dependence is weaker (due to a single aspect ratio for the fractures).
Finally, using the effective stiffness tensor for the fractured reservoir model with a visco-elastic finite-difference code,
synthetic seismograms and hodograms were computed. From the seismograms, attenuation changes in the P wave reflected at the
bottom of the reservoir can be observed as the effective pressure increases. S waves are not much affected by the fractures
with respect to attenuation, but azimuthal dependence is stronger than for P waves, and S-wave splitting in the bottom reservoir
P-S reflection is clearly seen both in the seismograms and hodograms. From the hodograms, some variation in the P-S reflection
with effective pressure can also be observed. 相似文献
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本文针对油气藏储层预测中的不连续及非均质地质信息识别问题,研究基于地震成像数据的稀疏反演方法.由于该类地质体的地震响应特征为弱信号,因此利用平面波破坏滤波器由地震成像数据中去除强反射同相轴.在此基础上,对剩余的地震数据进行非线性加强滤波,并构建L1稀疏反演模型.为有效求解L1模型,采用非光滑泛函L1范数逼近和拟牛顿求解算法.该方法考虑稀疏先验信息,能够提高反演结果信噪比.缝洞模型测试验证该方法在检测断点、微断裂、散射点等小尺度地质体上的有效性,塔北缝洞型碳酸盐岩储层预测的应用效果进一步证实该方法的实用性. 相似文献
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Frequency-dependent amplitude variation with offset offers an effective method for hydrocarbon detections and analysis of fluid flow during production of oil and natural gas within a fractured reservoir. An appropriate representation for the frequency dependency of seismic amplitude variation with offset signatures should incorporate influences of dispersive and attenuating properties of a reservoir and the layered structure for either isotropic or anisotropic dispersion analysis. In this study, we use an equivalent medium permeated with aligned fractures that simulates frequency-dependent anisotropy, which is sensitive to the filled fluid of fractures. The model, where pores and fractures are filled with two different fluids, considers velocity dispersion and attenuation due to mesoscopic wave-induced fluid flow. We have introduced an improved scheme seamlessly linking rock physics modelling and calculations for frequency-dependent reflection coefficients based on the propagator matrix technique. The modelling scheme is performed in the frequency-slowness domain and can properly incorporate effects of both bedded structure of the reservoir and velocity dispersion quantified with frequency-dependent stiffness. Therefore, for a dispersive and attenuated layered model, seismic signatures represent a combined contribution of impedance contrast, layer thickness, anisotropic dispersion of the fractured media and tuning and interference of thin layers, which has been avoided by current conventional methods. Frequency-dependent amplitude variation with offset responses was studied via considering the influences of fracture fills, layer thicknesses and fracture weaknesses for three classes amplitude variation with offset reservoirs. Modelling results show the applicability of the introduced procedure for interpretations of frequency-dependent seismic anomalies associated with both layered structure and velocity dispersion of an equivalent anisotropic medium. The implications indicate that anisotropic velocity dispersion should be incorporated accurately to obtain enhanced amplitude variation with offset interpretations. The presented frequency-dependent amplitude variation with offset modelling procedure offers a useful tool for fracture fluid detections in an anisotropic dispersive reservoir with layered structures. 相似文献
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复杂孔隙储层往往同时发育孔缝洞等多种孔隙类型,这种孔隙结构的复杂性使得岩石的速度与孔隙度之间的相关性很差.经典的二维岩石物理模版只研究弹性参数与孔隙度和饱和度之间的定量关系,而不考虑孔隙结构的影响,用这样的模版来预测复杂孔隙储层的物性参数时带来很大偏差.本文首先证明多重孔隙岩石的干骨架弹性参数可以用一个等效孔隙纵横比的单重孔隙岩石物理模型来模拟;进而基于等效介质岩石物理理论和Gassmann方程,建立一个全新的三维岩石物理模版,用它来建立复杂孔隙岩石的弹性性质与孔隙扁度及孔隙度和饱和度之间的定量关系;在此基础上,预测复杂储层的孔隙扁度、孔隙度以及孔隙中所包含的流体饱和度.实际测井和地震反演数据试验表明,三维岩石物理模版可有效提高复杂孔隙储层参数的预测精度. 相似文献