裂缝性储层孔隙指数、饱和度及裂缝孔隙度计算研究

裂缝性储层的裂缝孔隙度、饱和度和孔隙指数等参数的计算一直是测井界亟待解决的难题,它直接关系到对裂缝性储层的发育程度、含油气性、储量规模等方面的评价,前人已在这些方面做了大量的研究工作,但仍需进一步提高和深化对裂缝性储层参数计算的认识.基于考虑裂缝倾角和裂缝曲折度问题的Aguilera孔隙指数计算模型,研究了裂缝性储层孔隙指数的变化规律,研究表明裂缝性地层的孔隙指数受裂缝倾角、岩石总孔隙度、裂缝孔隙度和裂缝曲折度影响大.单组系裂缝性储层饱和度的计算采用将复合系统的孔隙指数代入阿尔奇公式的方法来计算,计算结果与目前国内仍广泛使用的基于串、并联关系建立的双重孔隙饱和度模型计算结果存在较大差别.对比分析了利用成像测井和三种基于双侧向资料的裂缝孔隙度计算模型计算的裂缝孔隙度,表明不同裂缝孔隙度模型计算的裂缝孔隙度大小差别较大.基于双侧向的裂缝孔隙度计算模型只适用于特低孔或致密地层,在由非裂缝因素引起的电阻率降低段使用该模型计算裂缝孔隙度时会出现错误,引入校正系数可拓宽模型的使用范围.     

Modeling and interpretation of Q logs in carbonate rock using a double porosity model and well logs

Attenuation data extracted from full waveform sonic logs is sensitive to vuggy and matrix porosities in a carbonate aquifer. This is consistent with the synthetic attenuation (1 / Q) as a function of depth at the borehole-sonic source-peak frequency of 10 kHz. We use velocity and densities versus porosity relationships based on core and well log data to determine the matrix, secondary, and effective bulk moduli. The attenuation model requires the bulk modulus of the primary and secondary porosities. We use a double porosity model that allows us to investigate attenuation at the mesoscopic scale. Thus, the secondary and primary porosities in the aquifer should respond with different changes in fluid pressure. The results show a high permeability region with a Q that varies from 25 to 50 and correlates with the stiffer part of the carbonate formation. This pore structure permits water to flow between the interconnected vugs and the matrix. In this region the double porosity model predicts a decrease in the attenuation at lower frequencies that is associated with fluid flowing from the more compliant high-pressure regions (interconnected vug space) to the relatively stiff, low-pressure regions (matrix). The chalky limestone with a low Q of 17 is formed by a muddy porous matrix with soft pores. This low permeability region correlates with the low matrix bulk modulus. A low Q of 18 characterizes the soft sandy carbonate rock above the vuggy carbonate.This paper demonstrates the use of attenuation logs for discriminating between lithology and provides information on the pore structure when integrated with cores and other well logs. In addition, the paper demonstrates the practical application of a new double porosity model to interpret the attenuation at sonic frequencies by achieving a good match between measured and modeled attenuation.     

地震密度反演及地层孔隙度估计

地层密度直接与孔隙度、孔隙流体类型、饱和度和骨架矿物成分有关.本文通过理论分析和计算,讨论了油气藏储层物性参数变化引起的密度变化及密度变化对地震波速度、阻抗和振幅的影响,提出了基于完全纵波方程的全波形地震密度反演和孔隙度估计方法,克服了常规地震密度反演对地震数据更多处理引起的信号畸变,提高了地震密度反演和地层孔隙度估计的精度.该方法采用波场导数的时间积分和多炮求和,对地震数据中的噪声具有比较强的压制作用.理论模型研究表明该方法是可行的.通过对我国西部某气田实际数据处理、分析和反演,获得了地层密度和孔隙度,结果与测井基本吻合,证明了预测结果的准确性和方法的有效性,从而为后续的有效储层预测和储量计算提供了可靠的数据.     

Determination of porosity and saturation using seismic waveform inversion

Characterization of a reservoir model requires determination of its petrophysical parameters, such as porosity and saturation. We propose a new method to determine these parameters directly from seismic data. The method consists of the computation and inversion of seismic waveforms. A high frequency method is presented to model wave propagation through an attenuative and dispersive poroelastic medium. The high frequency approximation makes it possible to efficiently compute sensitivity functions. This enables the inversion of seismic waveforms for porosity and saturation. The waveform inversion algorithm is applied to two laboratory crosswell datasets of a water saturated sand. The starting models were obtained using travel time tomography. The first dataset is inverted for porosity. The misfit reduction for this dataset is approximately 50%. The second dataset was obtained after injection of a nonaqueous-phase liquid (NAPL), possibly with some air, which made the medium more heterogeneous. This dataset was inverted for NAPL and air saturation using the porosity model obtained from the first inversion. The misfit reduction of the second experiment was 70%. Regions of high NAPL and high air saturation were found at the same location. These areas correlate well with the position of one of the injection points as well as regions of higher NAPL concentrations found after excavation of the sand. It is therefore possible to directly invert waveforms for pore fluid saturation by taking into account the attenuation and dispersion caused by the poroelasticity.     

煤岩变形破坏电磁辐射记忆效应的力电耦合规律

理论分析了煤岩变形破坏过程中电磁辐射脉冲数与损伤之间的关系,探讨了煤岩变形破坏电磁辐射产生机制及电磁辐射记忆效应的力电耦合规律,建立了等围压三轴应力状态下含瓦斯煤岩变形破坏电磁辐射记忆效应的力电耦合模型,实验测定并分析了单轴压缩状况下含瓦斯煤岩变形破坏电磁辐射记忆效应的力电耦合规律.结果表明,含瓦斯煤岩变形破坏电磁辐射记忆效应力电耦合模型很好地反映了煤岩变形破坏电磁辐射记忆效应特征规律和微观损伤机理.     

Heterogeneous stretching, simple shear and basin development

The models of basin development which involve either homogeneous stretching of the whole lithosphere or displacement on a lithospheric-scale shear zone, are but two end members of a range of possible extensional models. The homogeneous extension model thins the lower lithosphere beneath the thinned upper crust and superimposes a thermal subsidence basin on the earlier fault bounded basin. The shear zone model offsets the zone of lower lithospheric stretching and thermal subsidence. It is more likely that the zones of upper and lower lithospheric stretching will be heterogeneous and patchy, but will often overlap in plan view. This will produce localised uplift and subsequent thermal subsidence within the faulted basin and may explain many of the anomalies between the various stretching estimates made using different structural, stratigraphic and geophysical techniques. The model which combines heterogeneous lithospheric stretching and associated simple shear may explain: (1) variations in dip of the major detachment zones in the large basins, (2) variations in types of strain on or beneath the detachment zones, (3) regional uplift of part of a basin, to erode the earlier fault blocks, and (4) the development of volcanism in basins with only low values of upper crustal extension. The zone of stretched lower crust and lithospheric mantle may lie beneath the centre of the zone of upper crustal stretching, or to one side. It may be linked to the upper crustal zone by faults which dip consistently in one direction, or by extensional systems which change their dominant dip direction with depth, pulling out the mid-crust as one or more wedges. Possible examples are discussed from the Basin and Range province and northwest European continental shelf.     

受载煤体变形破裂微波辐射前兆规律的实验研究

对煤体在单轴压缩条件下的微波辐射效应和规律进行了实验研究.实验结果表明,受载煤体具有微波辐射效应,在煤体的变形破裂过程中伴随有6.6 GHz微波辐射信号产生,其前兆规律具有3种类型.基于电介质物理学对实验现象进行了解释.在单轴压缩实验中,煤体的亮温最大变化值为1.9~2.7 K,这表明煤体的微波辐射特性明显优于红外辐射特性.运用微波遥感基本原理的理论知识,分析了受载煤体变形破裂过程中微波辐射特性的影响因素.利用受载煤体变形破坏过程中的微波辐射前兆特性预报煤岩动力灾害具有广泛的应用前景.     

Modeling doline populations with logistic growth functions

Initiation and evolution of a large karst depression population consisting of parent and daughter dolines were spatially and temporally modeled using logistic growth functions. Logistic growth models are well suited for analyzing doline population initiation and evolution because they reflect the density‐dependent growth mechanisms present in the evolution of karst depressions. Seven assumptions based upon previous studies were refined into mathematical statements and tested using more than 2000 dolines from a subpopulation of both parent and daughter karst depressions on the Western Highland Rim and Pennyroyal Plain of Tennessee and Kentucky. Logistic growth models quantify the initiation and evolution of doline populations and interface well with recent models describing the evolution of three‐dimensional conduit systems. Logistic growth models should apply to modeling other doline populations in karst terranes with hydraulically efficient, three‐dimensional conduit systems. Copyright © 2006 John Wiley & Sons, Ltd.     

Prediction of effective porosity from seismic attributes using locally linear model tree algorithm

In this study, a locally linear model tree algorithm was used to optimize a neuro‐fuzzy model for prediction of effective porosity from seismic attributes in one of Iranian oil fields located southwest of Iran. Valid identification of effective porosity distribution in fractured carbonate reservoirs is extremely essential for reservoir characterization. These high‐accuracy predictions facilitate efficient exploration and management of oil and gas resources. The multi‐attribute stepwise linear regression method was used to select five out of 26 seismic attributes one by one. These attributes introduced into the neuro‐fuzzy model to predict effective porosity. The neuro‐fuzzy model with seven locally linear models resulted in the lowest validation error. Moreover, a blind test was carried out at the location of two wells that were used neither in training nor validation. The results obtained from the validation and blind test of the model confirmed the ability of the proposed algorithm in predicting the effective porosity. In the end, the performance of this neuro‐fuzzy model was compared with two regular neural networks of a multi‐layer perceptron and a radial basis function, and the results show that a locally linear neuro‐fuzzy model trained by a locally linear model tree algorithm resulted in more accurate porosity prediction than standard neural networks, particularly in the case where irregularities increase in the data set. The production data have been also used to verify the reliability of the porosity model. The porosity sections through the two wells demonstrate that the porosity model conforms to the production rate of wells. Comparison of the locally linear neuro‐fuzzy model performance on different wells indicates that there is a distinct discrepancy in the performance of this model compared with the other techniques. This discrepancy in the performance is a function of the correlation between the model inputs and output. In the case where the strength of the relationship between seismic attributes and effective porosity decreases, the neuro‐fuzzy model results in more accurate prediction than regular neural networks, whereas the neuro‐fuzzy model has a close performance to neural networks if there is a strong relationship between seismic attributes and effective porosity. The effective porosity map, presented as the output of the method, shows a high‐porosity area in the centre of zone 2 of the Ilam reservoir. Furthermore, there is an extensive high‐porosity area in zone 4 of Sarvak that extends from the centre to the east of the reservoir.     

用地震资料估算珊溪水库岩层孔隙度和饱和度

本文首先从室内岩石力学实验数据出发,利用Biot-Gassmann方程和Pride模型建立的岩石骨架与岩石基质体积模量函数关系式求出珊溪水库区岩石基质模量和固结系数,然后分别利用联合地震波走时方程组和多台和达曲线求得P波速度和波速比,最后以流纹斑岩为例,计算了岩石饱和度、孔隙度,并分析了地震中造成的饱和度和孔隙度的变化。结果表明:(1)地震过程中岩石饱和度均大于99%,且大多为100%,即地震中岩石处于水饱和或接近水饱和状态,波速和波速比的变化主要由岩石孔隙度的变化引起。(2)珊溪水库震中区流纹斑岩孔隙度的上限值为6.6%~15.5%,下限值为3.6%~4.2%。下限值与地震前由实验室测得的孔隙度相近。如果实验室测得的流纹斑岩孔隙度是其初始值,则地震中岩石孔隙度增大了3.2%~12.09%。(3)2008年1月地震以后震中区岩石孔隙度逐渐闭合,直到2014年8月孔隙度开始迅速增大,9月15日起原震区再次发生一组新的地震活动,震群活动前岩石出现了扩容现象。     

On using simple time-of-travel capture zone delineation methods

As part of its Wellhead Protection Program, the U.S. EPA mandates the delineation of "time-of-travel capture zones" as the basis for the definition of wellhead protection zones surrounding drinking water production wells. Depending on circumstances the capture zones may be determined using methods that range from simply drawing a circle around the well to sophisticated ground water flow and transport modeling. The simpler methods are attractive when faced with the delineation of hundreds or thousands of capture zones for small public drinking water supply wells. On the other hand, a circular capture zone may not be adequate in the presence of an ambient ground water flow regime. A dimensionless time-of-travel parameter T is used to determine when calculated fixed-radius capture zones can be used for drinking water production wells. The parameter incorporates aquifer properties, the magnitude of the ambient ground water flow field, and the travel time criterion for the time-of-travel capture zone. In the absence of interfering flow features, three different simple capture zones can be used depending on the value of T . A modified calculated fixed-radius capture zone proves protective when T < 0.1, while a more elongated capture zone must be used when T > 1. For values of T between 0.1 and 1, a circular capture zone can be used that is eccentric with respect to the well. Finally, calculating T allows for a quick assessment of the validity of circular capture zones without redoing the delineation with a computer model.     

A new mathematical model of asymmetric hydraulic fracture growth

Hydraulic fractures generated by fluid injection in rock formations are often mapped by seismic monitoring. In many cases, the microseismicity is asymmetric relative to the injection well, which has been interpreted by stress gradient along the direction of the hydraulic fracture. We present a mathematical model of asymmetric hydrofracture growth based on relations between the solid‐phase stress and the fracture hydraulics. For single fracture and single injection point, the model has three parameters, hydraulic conductivities of the fracture wings, and normalised stress gradient and predicts the positions of the fracture tips as functions of time. The model is applied to a set of microseismic event locations that occurred during and after an injection process. Two different methods are suggested that make it possible to delineate the fracture tips from the set of microseismic events. This makes it possible to determine the model parameters and to check the agreement between the model prediction and the measured data. The comparison of the measured and modelled growth of fracture wings supports both the assumption of the non‐zero stress gradient and the existence of the post‐injection unilateral growth.     

基于小波变换图像分割技术的电成像测井资料裂缝、孔洞面孔率提取方法

对于裂缝、溶蚀孔洞发育的碳酸盐岩缝洞储层,如何从测井资料中提取裂缝、溶蚀孔洞信息是评价储层有效性的关键问题.为了从电成像测井静态图像上准确地分割出清晰的裂缝、溶蚀孔洞子图像进而提取其参数信息,本文提出了一种基于小波变换模极大值图像分割技术的电成像测井资料缝洞面孔率提取方法.以钮扣电极电导率曲线为对象,先消除井壁凹凸不平导致的地层背景噪声的影响,利用小波变换模极大值图像分割方法得到包含裂缝和溶蚀孔洞目标的子图像,根据子图像提取裂缝-孔洞总面孔率、裂缝面孔率、孔洞面孔率等信息.本文利用塔里木盆地奥陶系碳酸盐岩地层的电成像测井数据提取了缝洞面孔率参数,还利用同井岩心CT扫描图像计算的平均缝洞面孔率、双侧向电阻率、常规测井资料三孔隙度模型计算的相对连通缝洞孔隙度进行了对比,并进行了试油验证.对比表明,电成像测井裂缝-孔洞总面孔率、裂缝面孔率、孔洞面孔率与岩心CT扫描图像平均缝洞面孔率、双侧向电阻率、相对连通缝洞孔隙度、试油结果均有较好的一致性.这一方面验证了采用本文方法提取的裂缝-孔洞总面孔率、裂缝面孔率、孔洞面孔率的合理性,另一方面表明所提取参数可用于指示缝洞型碳酸盐岩储层的渗透性和有效性.

     

应用三分量地震数据反演煤系地层孔隙含水量

地层孔隙水含量的计算主要受地层孔隙度与孔隙含水饱和度的影响.通过实验室煤层及其顶底板岩芯物理测试与孔隙度测量,可以获得煤系地层岩芯的孔隙度与岩芯纵、横波速度的经验公式;结合三分量地震勘探获得的纵波与横波速度,能够计算出煤系地层的孔隙度;含水饱和度的计算通过实验室岩电参数测试和阿尔奇公式可以计算得到.结合淮南某矿区三维三分量地震勘探和地球物理测井及岩样的岩电试验,实现了三维空间煤系地层孔隙含水体积百分比的精确计算.该预测方法与传统的、钻孔控制的地下水评价方法相比可以提供相对精细的、三维空间的、定量化的煤系地层孔隙相对含水量,对煤炭与煤层气资源开采中所涉及的地下水分布规律预测有一定的参考意义.     

A simple method for calculating growth rates of petroleum hydrocarbon plumes

Consumption of aquifer Fe(III) during biodegradation of ground water contaminants may result in expansion of a contaminant plume, changing the outlook for monitored natural attenuation. Data from two research sites contaminated with petroleum hydrocarbons show that toluene and xylenes degrade under methanogenic conditions, but the benzene and ethylbenzene plumes grow as aquifer Fe(III) supplies are depleted. By considering a one-dimensional reaction front in a constant unidirectional flow field, it is possible to derive a simple expression for the growth rate of a benzene plume. The method balances the mass flux of benzene with the Fe(III) content of the aquifer, assuming that the biodegradation reaction is instantaneous. The resulting expression shows that the benzene front migration is retarded relative to the ground water velocity by a factor that depends on the concentrations of hydrocarbon and bioavailable Fe(III). The method provides good agreement with benzene plumes at a crude oil study site in Minnesota and a gasoline site in South Carolina. Compared to the South Carolina site, the Minnesota site has 25% higher benzene flux but eight times the Fe(III), leading to about one-sixth the expansion rate. Although it was developed for benzene, toluene, ethylbenzene, and xylenes, the growth-rate estimation method may have applications to contaminant plumes from other persistent contaminant sources.     

Initial growth of phytoplankton in turbid estuaries: A simple model

An idealised model is presented and analysed to gain more fundamental understanding about the dynamics of phytoplankton blooms in well-mixed, suspended sediment dominated estuaries. The model describes the behaviour of subtidal currents, suspended sediments, nutrients and phytoplankton in a channel geometry. The initial growth of phytoplankton and its spatial distribution is calculated by solving an eigenvalue problem. The growth rates depend on the position in the estuary due to along-estuary variations in nutrient concentration and suspended sediment concentration. The model yields an insight into how the onset of blooms in the model depends on physical and biological processes (turbulent mixing, fresh water discharge, light attenuation, imposed nutrient concentrations at the river and sea side). In particular, the model demonstrates that the joint action of spatial variations in turbidity and in nutrients causes the maximum phytoplankton concentrations to occur seaward of the estuarine turbidity maximum.     

Modeling of wind gap formation and development of sedimentary basins during fold growth: application to the Zagros Fold Belt,Iran

Mountain building and landscape evolution are controlled by interactions between river dynamics and tectonic forces. Such interactions have been extensively studied, however a quantitative evaluation of tectonic/geomorphic feedbacks, which is imperative for understanding sediments routing within orogens and fold‐and‐thrust belts, remains to be undertaken. Here, we employ numerical simulations to assess the conditions of uplift and river incision necessary to deflect an antecedent drainage network during the growth of one, or several, folds. We propose that a partitioning of the river network into internal (endorheic) and longitudinal drainage arises as a result of lithological differences within the deforming crustal sedimentary cover. Using examples from the Zagros Fold Belt (ZFB), we show that drainage patterns can be linked to the non‐dimensional incision ratio R between successive lithological layers, corresponding to the ratio between their relative erodibilities or incision coefficients. Transverse drainage networks develop for uplift rates smaller than 0.8 mm yr^?1 and low incision ratios (?10 < R < 10). Intermediate drainage networks are obtained for uplift rates up to 2 mm yr^?1 and large incision ratios (R > 20). Parallel drainage networks and the formation of sedimentary basins occur for large values of incision ratio (R > 20) and uplift rates between 1 and 2 mm yr^?1. These results have implications for predicting the distribution of sediment depocenters in fold‐and‐thrust belts, which can be of direct economic interest for hydrocarbon exploration. They also put better constraints on the fluvial and geomorphic responses to fold growth induced by crustal‐scale tectonics. Copyright © 2016 John Wiley & Sons, Ltd.     

Eutrophication risk assessment in coastal embayments using simple statistical models

A statistical methodology is proposed for assessing the risk of eutrophication in marine coastal embayments. The procedure followed was the development of regression models relating the levels of chlorophyll a (Chl) with the concentration of the limiting nutrient--usually nitrogen--and the renewal rate of the systems. The method was applied in the Gulf of Gera, Island of Lesvos, Aegean Sea and a surrogate for renewal rate was created using the Canberra metric as a measure of the resemblance between the Gulf and the oligotrophic waters of the open sea in terms of their physical, chemical and biological properties. The Chl-total dissolved nitrogen-renewal rate regression model was the most significant, accounting for 60% of the variation observed in Chl. Predicted distributions of Chl for various combinations of the independent variables, based on Bayesian analysis of the models, enabled comparison of the outcomes of specific scenarios of interest as well as further analysis of the system dynamics. The present statistical approach can be used as a methodological tool for testing the resilience of coastal ecosystems under alternative managerial schemes and levels of exogenous nutrient loading.     

简易远震警报器的制作与使用

本文介绍了一款位移触发远震警报器的制作方法与使用情况,由此提高了速报地震的报警率,有效减少了台站在地震速报中的晚报、漏报现象。