The Sensitive Properties of Hydrate Reservoirs Based on Seismic Stereoscopic Detection Technology

Higher-precision determinations of hydrate reservoirs, hydrate saturation levels and storage estimations are important for guaranteeing the ability to continuously research, develop and utilize natural gas hydrate resources in China. With seismic stereoscopic detection technology, which fully combines the advantages of different seismic detection models, hydrate formation layers can be observed with multiangle, wide-azimuth, wide-band data with a high precision. This technique provides more reliable data for analyzing the distribution characteristics of gas hydrate reservoirs, establishing velocity models, and studying the hydrate-sensitive properties of petrophysical parameters;these data are of great significance for the exploration and development of natural gas hydrate resources. Based on a velocity model obtained from the analysis of horizontal streamer velocity data in the hydrate-bearing area of the Shenhu Sea, this paper uses three VCs(longitudinal spacing of 25 m) and four OBSs(transverse spacing of 200 m) to jointly detect seismic datasets consisting of wave points based on an inversion of traveltime imaging sections. Accordingly, by comparing the differences between the seismic phases in the original data and the forward-modeled seismic phases, multiangle coverage constraint corrections are applied to the initial velocity model, and the initial model is further optimized, thereby improving the imaging quality of the streamer data. Petrophysical elastic parameters are the physical parameters that are most directly and closely related to rock formations and reservoir physical properties. Based on the optimized velocity model, the rock elastic hydrate-sensitive parameters of the hydrate reservoirs in the study area are inverted, and the sensitivities of the petrophysical parameters to natural gas hydrates are investigated. According to an analysis of the inversion results obtained from these sensitive parameters, λρ, Vp and λμ are simultaneously controlled by the bulk modulus and shear modulus, while Vs and μρ are controlled only by the shear modulus, and the latter two parameters are less sensitive to hydrate-bearing layers. The bulk modulus is speculated to be more sensitive than the shear modulus to hydrates. In other words, estimating the specific gravity of the shear modulus among the combined parameters can affect the results from the combined elastic parameters regarding hydrate reservoirs.     

Thermo‐hydro‐mechanical modeling with Langmuir's adsorption isotherm of the CO2 injection in coal

In this paper, we used a theoretical model for the variation of Eulerian porosity, which takes into account the adsorption process known to be the main mechanism of production or sequestration of gas in many reservoir of coal. This process is classically modeled using Langmuir's isotherm. After implementation in Code_Aster, a fully coupled thermo‐hydro‐mechanical analysis code for structures calculations, we used numerical simulations to investigate the influence of coal's hydro‐mechanical properties (Biot's coefficient, bulk modulus), Langmuir's adsorption parameters, and the initial liquid pressure in rock mass during CO₂ injection in coal. These simulations showed that the increase in the values of Langmuir's parameters and Biot's coefficient promotes a reduction in porosity because of the adsorption process when the gas pressure increases. Low values of bulk modulus increase the positive effect (i.e., increase) of hydro‐mechanical coupling on the porosity evolution. The presence of high initial liquid pressure in the rock mass prevents the progression of injected gas pressure when CO₂ dissolution in water is taken into account. Copyright © 2014 John Wiley & Sons, Ltd.     

苏5区块东部地区高精度气水识别技术

针对苏里格气田的储层非均质性强且气水关系复杂等难点,提出一套适用于苏里格气田苏5区块的高精度气水识别技术,该技术遵循“先找砂体、再找储层、后气水识别”的思路,基于三维地震资料叠前时间偏移处理数据体,综合运用高精度叠后GR随机反演方法、基于等效弹性模量反演的横波速度估算方法、扩展的弹性阻抗反演方法、组合流体因子构建方法等,有效地凸显了气层、气水层与干层或微气层之间的差异。通过对研究区盒8段的37口实钻井的过井剖面特征进行统计分析,获得了气层、气水层与干层或微气层的判别准则,与实钻井的符合率达到83%,可以有效地用于研究区的气水识别,具有重要的理论和实际应用推广价值。     

裂缝体的弹性模量和裂缝密度

当岩石中含有裂缝时,岩石的弹性模量(主要指体模量、剪切模量、泊松比以及地震波的速度)会发生变化,而且这种弹性模量的变化又随裂缝中是否含有流体而不同。如果我们用地震的方法探测出地下目的层弹性模量的变化情况,无疑对我们了解目的层的裂缝发育情况将会有很大的帮助。在以往的研究中,人们常常把裂缝的产状定义成垂直裂缝和水平裂缝来研究。但是,实际中存在的裂缝多表现为几种体系的裂缝分布。本文在假设裂缝是随机分布的情况下,研究了含流体裂缝体和不含流体裂缝体的弹性模量与裂缝密度的关系。     

Discrimination of pore fluid and lithology of a well in X Field,Niger Delta,Nigeria

Quantitative rock physics analyses were used to determine the lithology and pore fluid of a reservoir in the Niger Delta. Inaccurate prediction of lithology and pore fluid results in the inaccurate determination of other petrophysical properties and parameters such as porosity, permeability, and net pay. This research is to predict lithology and pore fluid using rock physics analysis. However, reservoir zones were also predicted. Density, compressional wave velocity, and shear wave velocity logs were used as input to calculate elastic parameters such as velocity ratio, Poisson’s ratio, and bulk modulus. The calculated velocity ratio log was used to differentiate between sand and shale. Poisson’s ratio and velocity ratio using Goodway interpretation template were carried out and used to delineate pore fluid content, gas sand, oil sand, and sandstone formation from crossplot analysis.     

Assessment of Reservoir Rock Properties from Rock Physics Modeling and Petrophysical Analysis of Borehole Logging Data to Lessen Uncertainty in Formation Characterization in Ratana Gas Field,Northern Potwar,Pakistan

Petrophysical evaluation and rock physics analysis are the important tools to relate the reservoir properties like porosity, permeability, pore fluids with seismic parameters. Nevertheless, the uncertainties always exist in the quantification of elastic and seismic parameters estimated through wireline logs and rock physics analysis. A workflow based on statistical relationships of rock physics and logs derived elastic and seismic parameters with porosity and the percentage error exist between them is given. The statistical linear regressions are developed for early Eocene Chorgali Formation between various petrophysically factors determined from borehole logging of well Ratana–03 drilled in tectonically disturbed zone and the seismic and elastic parameters estimated through rock physics modeling. The rock physics constraints such as seismic velocities, effective density and elastic moduli calculated from Gassmann fluid substation analysis are in harmony and close agreement to those estimated from borehole logs. The percentage errors between well logs and rock physics computed saturated bulk modulus (K _sat ), effective density (ρ _eff ), compressional and shear wave velocities (V _P and _V S) are 1.31%, 4.23 %, 5.25% and 4.01% respectively. The permeability of reservoir intervals show fairly strong linear relationship with the porosity, indicating that the reservoir interval of the Chorgali Formation is permeable and porous thus having large potential of hydrocarbon accumulation and production.     

弹性模量、波速与应力的关系及其应用

为充分了解不同尺度地质系统的岩石动力学特征,更好利用不同规模勘探资料有效解释地质系统的特征,在岩石物理实验对岩石弹性模量、波速与应力的关系进行研究总结的基础上,探讨野外实际地震勘探中地震波速与地应力的关系。研究表明,岩石、岩体或地质系统是多相(固液气)、多种矿物、各种构造的综合体,不论尺度如何均可以用多重介质孔隙裂隙地质模型描述,而波速是一定尺度不均匀地质体的等效波速,在一定地质条件下,各种尺度介质波速、岩石弹性模量与有效应力存在依存关系。坚硬的岩石通常很脆,如果岩石处于很大的应力之下,应力的释放将在岩石中产生微裂隙,微裂隙会降低地震速度。只要把岩石恢复到原来的应力状态就可能消除所引发的微裂隙。在岩体未达到破坏时,应力越大,波速愈高。压力释放引发的微裂隙有助于现场确定最大/最小水平应力方向,波速的椭圆长轴即为主应力方向。而上覆地层压力不变(或变化很小),净储层压力的影响正好与储层压力对地震特性的影响相反。随着净储层压力的增加,所有岩石的地震特性都增高。这种增高的量级取决于若干其它的因素(孔隙形状、孔隙度、孔隙流体、岩性等等)。不论野外地震勘探还是实验研究,地震波速与地应力的一致性为地质系统的正反演解释提供了宏观控制依据:通过测量弄清     

Numerical modeling of two-phase binary fluid mixing using mixed finite elements

Diffusion coefficients of dense gases in liquids can be measured by considering two-phase binary nonequilibrium fluid mixing in a closed cell with a fixed volume. This process is based on convection and diffusion in each phase. Numerical simulation of the mixing often requires accurate algorithms. In this paper, we design two efficient numerical methods for simulating the mixing of two-phase binary fluids in one-dimensional, highly permeable media. Mathematical model for isothermal compositional two-phase flow in porous media is established based on Darcy’s law, material balance, local thermodynamic equilibrium for the phases, and diffusion across the phases. The time-lag and operator-splitting techniques are used to decompose each convection–diffusion equation into two steps: diffusion step and convection step. The Mixed finite element (MFE) method is used for diffusion equation because it can achieve a high-order and stable approximation of both the scalar variable and the diffusive fluxes across grid–cell interfaces. We employ the characteristic finite element method with moving mesh to track the liquid–gas interface. Based on the above schemes, we propose two methods: single-domain and two-domain methods. The main difference between two methods is that the two-domain method utilizes the assumption of sharp interface between two fluid phases, while the single-domain method allows fractional saturation level. Two-domain method treats the gas domain and the liquid domain separately. Because liquid–gas interface moves with time, the two-domain method needs work with a moving mesh. On the other hand, the single-domain method allows the use of a fixed mesh. We derive the formulas to compute the diffusive flux for MFE in both methods. The single-domain method is extended to multiple dimensions. Numerical results indicate that both methods can accurately describe the evolution of the pressure and liquid level.     

碳酸盐岩油气储层高精度成像方法研究

碳酸盐岩油气储层在世界油气储层中占据着重要的地位,其油气总量约占全球油气总量的70%,具有埋藏深、构造复杂、非均质性强等特点。如何获得碳酸盐岩油气储层在地下的准确位置及构造特征,是油气勘探急需解决的难题。叠前逆时偏移成像技术采用精确的地震波动理论,能够对任意复杂构造进行高精度成像。本文针对碳酸盐岩油气储层成像难的问题,研究各向异性叠前逆时偏移成像技术,并将其应用于碳酸盐岩油气储层勘探中。通过采用精确的频散关系,推导各向异性纯qP波方程,利用高精度有限差分进行纯qP波模拟,通过叠前逆时偏移方法对纯qP波进行叠前深度偏移成像。基于典型的碳酸盐岩油气储层实际地质条件,建立逼近真实地质情况的碳酸盐岩地球物理模型,对上述模型进行偏移成像试验,结果表明各向异性逆时偏移成像技术是一种有效的碳酸盐岩油气储层勘探方法。最后将该方法应用于典型碳酸盐岩靶区的实际地震资料,并获得了精确的成像结果,进一步验证了各向异性逆时偏移成像技术在碳酸盐岩油气储层勘探中的重要作用。     

各向异性煤层裂隙流体因子及地震波速度响应

煤层中瓦斯和水的赋存及运移与裂隙的密度、走向、填充物类型等因素密切相关,为了预防和控制矿井突水、瓦斯突出等灾害性事故,进行煤层裂隙的识别和预测研究,对煤矿开采的安全性评价有重要指示作用。基于裂隙等效模型理论,将Schoenberg线性滑动模型与煤层干裂隙（气充填）和饱水裂隙相结合,分析煤层缝隙中流体因子随不同充填物与裂隙弱度参数（裂隙密度、纵横比、体积模量、剪切模量、拉梅系数）的变化特征,并通过对含垂向裂隙的煤储层进行地震波各向异性速度的响应计算。从HTI型煤层理论模型的正演模拟结果可知,模型中裂隙流体因子与裂隙密度和几何形态呈正相关函数关系,而与充填流体体积模量呈负相关。HTI型煤层P波群、相速度对裂隙中的气、水都比较灵敏,SV波群、相速度对干裂隙（气充填）不敏感,SV波群速度对裂隙中的水很灵敏。通过HTI型煤层裂隙流体因子与各向异性速度等参数的响应分析实现煤层裂隙流体预测的可行性,为分析裂隙型煤层地震波传播特征打下基础,为煤层裂隙流体预测提供理论支持。      

Study of intergranular films and interstitial phases in geomaterials using high temperature centrifuge and ultrasonic method at high pressure

Water fluids in the Earth's crust may initiate a number of mineral reactions resulting in different microstructure changes, which may appear in the form of intergranular melt films and interstitial phases. Therefore, they have an essential influence on elastic wave velocities of rocks (for example, sandstone, amphibolite, basalt). The aim of the experiment was to determine the conditions of the silicate liquid and others interstitial phases distribution in the rock intergranular space.The results obtained using the ultrasonic method at temperature up to 950 °C and under fluid pressure of 300 MPa revealed that the formation of intergranular melt films and interstitial phases network depend on chemical composition of fluids. The experiments with use of a high-temperature centrifuge at temperature 1400 °C showed that the amount of melt films, higher than 6 %, is sufficient to form a system of interconnected intergranular channels. These studies can be contributed to the petrophysical and geochemical interpretation of geophysical measurements.     

涟源凹陷流体包裹体特征与天然气成藏

涟源凹陷属于典型的改造型盆地,是湘中坳陷最有利的含油气凹陷之一。应用流体包裹体分析技术,并结合盆地构造演化和圈闭发育史、烃源岩主要生、排烃史,对改造型盆地涟源凹陷主要目的层石炭系储层中流体包裹体特征及气藏形成时间和期次进行了分析。结果表明,研究区存在两种类型流体包裹体,第一类为单一液相或气/液比小于15%的气液两相盐水包裹体,第二类为气液两相含烃盐水包裹体,单一液相包裹体大小一般3~4μm,其它包裹体大小一般1~7μm;流体包裹体特征反映出该区气藏成藏期有两期,即第一期天然气注入时温度120.8~126.2℃,对应成藏时间为早三叠世,第二期天然气注入时温度154.4~169.7℃,对应成藏时间为晚三叠世,其中主要成藏期为晚三叠世。     

地震储层预测技术在塔里木盆地雅克拉地区的应用

塔里木盆地雅克拉地区油气资源丰富,但成藏规律不明显,针对该区侏罗系砂岩储层的展布及物性开展地震综合预测研究。通过叠后纯波地震资料,开展拟声波反演、频谱成像技术刻画砂砾岩体的纵横向分布。在此基础上开展叠前弹性波阻抗反演,包括目标储层段的纵横波阻抗,拉梅系数等分布特征及高频吸收衰减流体检测技术,分析不同岩性、物性、含油气性的地震响应特征。综合地震储层预测技术,研究侏罗系下统砂砾岩体有效储层的分布,寻找油气勘探有利靶区。     

川中安岳构造寒武系龙王庙组油气成藏史

本文从岩芯和薄片观察入手,利用阴极发光分析、流体包裹体分析、激光拉曼分析、充填物的稳定同位素分析、磷灰石裂变径迹年代学分析等技术手段,确定了龙王庙组储层的胶结充填序列、油气成藏历史。龙王庙组储层中可以识别出7个期次的胶结充填序列:海底环境纤维状白云石胶结→浅埋藏环境粒状白云石胶结→表生成岩环境渗流粉砂白云石充填→再次浅埋藏-中埋藏环境白云石充填→深埋藏环境白云石充填→深埋藏环境方解石充填→抬升埋藏环境石英充填,通过所识别出的胶结充填物的流体包裹体特征以及和沥青之间的关系,认为龙王庙组存在至少5期油气成藏。第Ⅳ期白云石-第Ⅶ期石英中捕获的流体包裹体的相态也从液烃包裹体→气液两相烃类包裹体→气相烃类包裹体演化,反映了龙王庙组经历了古油藏形成、古油藏破坏、再次形成古油藏、油裂解为天然气、古气藏形成和喜马拉雅期构造隆升期气藏调整定型的过程;磷灰石裂变径迹分析表明,安岳构造喜马拉雅期的隆升幅度约1865~2030m,为龙王庙组气藏的调整和定型期,这一成藏事件被晚期充填的第Ⅶ期石英所记录。龙王庙组储层中第Ⅳ期白云石充填物的87Sr/86Sr、δ13C、δ18O同位素比值反映了该期白云石与围岩基质的重溶沉淀有关,且是在相对温度较高的埋藏条件下沉淀的。晚期孔洞缝中充填石英的87Sr/86Sr、δ30Si、δ18O同位素表明其主要源于含硅质的成岩流体,与深部幔源热液流体活动无关,龙王庙组油气成藏过程中未见外来破坏性流体的参与。     

Influence of crack density on geomechanical behavior of granular composites with porous grains and fluid‐saturated pores

The analysis of geomechanical behavior for granular systems including fluid‐filled pores depends strongly on the crack density present within the system being studied. Effective overall bulk and shear moduli are both significantly influenced by these crack system parameters. Present effort concentrates on the geomechanical analyses needed to treat anisotropic (specifically orthotropic) poroelastic grains jumbled together to form an overall isotropic polycrystalline poroelastic material. As predicted, poroelastic effects induced by fluids in the cracks are observed to be significant for the effective bulk modulus, but simple pore fluids do not affect the magnitude of effective overall shear modulus. These results are also shown to depend in a quantitatively predictable way on crack density values. Copyright © 2014 John Wiley & Sons, Ltd.     

The formation of clear taenite in ordinary chondrites

The metallic phases in six bronzite and six hypersthene chondrites were studied metallographically and by electron microprobe. All of the chondrites studied contain zoned taenite. In bronzite chondrites, only about 5 per cent of the zoned taenite abuts on kamacite (the rest being apparently isolated from it) whereas in hypersthene chondrites an average of over 20 per cent abuts on kamacite. The compositions of the centers of zoned taenite can be used to obtain cooling rates by Wood's method. Including Wood's results, 14 out of 18 ordinary chondrites have cooling rates between 1 and 10°C/m.y.     

HPHT reservoir evolution: a case study from Jade and Judy fields, Central Graben, UK North Sea

3D basin modelling of a study area in Quadrant 30, UK North Sea was performed in order to elucidate the burial, thermal, pressure and hydrocarbon generation, migration and accumulation history in the Jurassic and Triassic high pressure–high temperature sequences. Calibration data, including reservoir temperatures, pressures, petroleum compositional data, vitrinite reflectance profiles and published fluid inclusion data were used to constrain model predictions. The comparison of different pressure generating processes indicated that only when gas generation is taken into account as a pressure generating mechanism, both the predicted present day as well as palaeo-pressure evolution matches the available calibration data. Compositional modelling of hydrocarbon generation, migration and accumulation also reproduced present and palaeo bulk fluid properties such as the reservoir fluid gas to oil ratios. The reconstruction of the filling histories of both reservoirs indicates that both were first charged around 100 Ma ago and contained initially a two-phase system in which gas dominated volumetrically. Upon burial reservoir fluid composition evolved to higher GORs and became undersaturated as a function of increasing pore pressure up to the present day situation. Our results indicate that gas compositions must be taken into account when calculating the volumetric effect of gas generation on overpressure.     

含油水各向异性孔隙介质中地震波传播方程

油气勘探的重点是寻找油气储层的分布 ,而地下油气的存在必然对地震记录产生影响。传统的地震波理论是建立在纯弹性固体基础之上 ,没有考虑固体中所含的流体 ,因此 ,它难以研究含油水岩石的物理性质 ,如岩石的渗透率和孔隙度、油水粘度。从固、液介质系统能量和本构方程出发 ,推导出固体、油相和水相的动力学方程 ,进而建立起含油水两相流体各向异性孔隙介质的地震波传播方程。该方程包括有岩石和油水的物理参数 ,更适合于油田的勘探和开发。     

A two‐invariant pseudoelastic model for reservoir compaction

Predicting the deformations of deep reservoirs due to fluid withdrawal/injection is a challenging task that could have important environmental, social, and economical impacts. Finite element models, if endowed with an appropriate constitutive law, represent a useful tool for computing the displacements, the deformations, and the stress distributions in reservoir applications. Several studies show that hypoelastic laws, based on a stress‐dependent vertical compressibility, are able to provide accurate results, confirmed by in situ and satellite measurements. On the other hand, such laws present some weaknesses related to the numerical implementation, in particular due to the nonsymmetry of the tangent operator. This paper presents a new constitutive model based on 2 invariants (the mean normal and deviatoric stresses), characterized by a variable pressure‐dependent bulk modulus K. This constitutive law allows for overcoming most shortcomings of the hypoelastic law, although preserving the same accuracy, reliability, and ease of use and calibration. This paper presents a procedure to identify the parameters of the new model, starting from the typically available data on the vertical compressibility. Numerical results show a good agreement between the 2 laws, suggesting the proposed approach as a valid alternative in reservoir applications.     

S-变换时频技术在碳酸盐岩孔洞储层预测中的应用

将高时频分辨率的S-变换应用于碳酸盐岩孔洞储层的地震反射波分析,得到与每一个频率对应的振幅,通过分析与某几个单频率对应的振幅的横向变化特征,可以确定充填流体或气体的孔洞储层引起的地震反射波振幅和频率的变化异常.用上述方法对新疆某工区的碳酸盐岩孔洞储层进行了预测,其预测结果与钻井结果一致.