Characterization of reservoir properties and pore structure based on micro-resistivity imaging logging: Porosity spectrum, permeability spectrum, and equivalent capillary pressure curve

According to the capillary theory,an equivalent capillary model of micro-resistivity imaging logging was built.On this basis,the theoretical models of porosity spectrum(Ф_(i)),permeability spectrum(K_(i))and equivalent capillary pressure curve(pe)were established to reflect the reservoir heterogeneity.To promote the application of the theoretical models,the Archie's equation was introduced to establish a general model for quantitatively characterizing bi,K,and pei.Compared with the existing models,it is shown that:(1)the existing porosity spectrum model is the same as the general equation of gi;(2)the Ki model can display the permeability spectrum as compared with Purcell's permeability model;(3)the per model is constructed on a theoretical basis and avoids the limitations of existing models that are built only based on the component of porosity spectrum,as compared with the empirical model of capillary pressure curve.The application in the Permian Maokou Formation of Well TsX in the Central Sichuan paleo-uplift shows that the Ф_(i),K_(i),and p_(ci) models can be effectively applied to the identification of reservoir types,calculation of reservoir properties and pore structure parameters,and evaluation of reservoir heterogeneity.

Anisotropic dynamic permeability model for porous media

Based on the tortuous capillary network model,the relationship between anisotropic permeability and rock normal strain,namely the anisotropic dynamic permeability model(ADPM),was derived and established.The model was verified using pore-scale flow simulation.The uniaxial strain process was calculated and the main factors affecting permeability changes in different directions in the deformation process were analyzed.In the process of uniaxial strain during the exploitation of layered oil and gas reservoirs,the effect of effective surface porosity on the permeability in all directions is consistent.With the decrease of effective surface porosity,the sensitivity of permeability to strain increases.The sensitivity of the permeability perpendicular to the direction of compression to the strain decreases with the increase of the tortuosity,while the sensitivity of the permeability in the direction of compression to the strain increases with the increase of the tortuosity.For layered reservoirs with the same initial tortuosity in all directions,the tortuosity plays a decisive role in the relative relationship between the variations of permeability in all directions during pressure drop.When the tortuosity is less than 1.6,the decrease rate of horizontal permeability is higher than that of vertical permeability,while the opposite is true when the tortuosity is greater than 1.6.This phenomenon cannot be represented by traditional dynamic permeability model.After the verification by experimental data of pore-scale simulation,the new model has high fitting accuracy and can effectively characterize the effects of deformation in different directions on the permeability in all directions.

Impact of capillary pressure on permeability impairment during CO2 injection into deep saline aquifers

During CO2 injection in deep saline aquifers, salt precipitation happens around the injection well because of capillary driven back flow, inducing permeability impairment. The permeability impairment affects CO2 injectivity and migration. Different values of three characteristic parameters for capillary pressure function (air entry pressure, empirical parameter m and liquid residual saturation) as well as input absolute value of maximum capillary are chosen in numerical simulation to figure out their effects on salt precipitation. Verma & Pruess model is then used for quantifying permeability impairment. Results show that permeability decreases with higher air entry pressure, larger liquid residual saturation, and especially smaller value of empirical parameter m. To enhance CO2 injectivity and avoid blocking of CO2 migration, a homogenous formation with large pore size should be chosen before CO2 injection into deep saline aquifer.

Effect of H_(2)S content on relative permeability and capillary pressure characteristics of acid gas/brine/rock systems:A review

Geological storage of acid gas has been identified as a promising approach to reduce atmospheric carbon dioxide(CO_(2)),hydrogen sulfide(H_(2)S)and alleviate public concern resulting from the sour gas production.A good understanding of the relative permeability and capillary pressure characteristics is crucial to predict the process of acid gas injection and migration.The prediction of injection and redistribution of acid gas is important to determine storage capacity,formation pressure,plume extent,shape,and leakage potential.Herein,the existing experimental data and theoretical models were reviewed to gain a better understanding of the issue how the H_(2)S content affects gas density,gas viscosity,interfacial tension,wettability,relative permeability and capillary pressure characteristics of acid gas/brine/rock systems.The densities and viscosities of the acid gas with different H_(2)S mole fractions are both temperature-and pressure-dependent,which vary among the gas,liquid and supercritical phases.Water/acid gas interfacial tension decreases strongly with increasing H_(2)S content.For mica and clean quartz,water contact angle increases with increasing H_(2)S mole fraction.In particular,wettability reversal of mica to a H_(2)S-wet behavior occurs in the presence of dense H_(2)S.The capillary pressure increases with decreasing contact angle.At a given saturation,the relative permeability of a fluid is higher when the fluid is nonwetting.The capillary pressure decreases with decreasing interfacial tension at a given saturation.However,the existing datasets do not show a consistent link between capillary number and relative permeability.The capillary pressure decreases with increasing H_(2)S mole fraction.However,there is no consensus on the effect of the H_(2)S content on the relative permeability curves.This may be due to the limited availability of the relative permeability and capillary pressure data for acid gas/brine/rock systems;thus,more experimental measurements are required.

Calculation Method of Power Law Fluid Equivalent Permeability Considering Capillary Shape

While studying the flow of oil and gas in the reservoir, it is not realistic that capillary with circular section is only used to express the pores. It is more representative to simulate porous media pore with kinds of capillary with triangle or rectangle section etc. In the condition of the same diameter, when polymer for oil displacement flows in the porous medium, there only exists shear flow which can be expressed with power law model. Based on fluid flow-pressure drop equation in single capillary, this paper gives a calculation method of equivalent permeability of power law fluid of single capillary and capillary bundles with different sections.

Using Capillary Pressure Derived Parameters for Improving Permeability Prediction

This paper presents the construction and verification of a new better semi-analytical, statistically derived universal model than that modified from Huet and Blasingame equation for estimating absolute permeability from mercury injection capillary pressure data. The foundation of my new model is the petrophysical relation between absolute permeability and capillary-pressure/wetting phase saturation properties. I also incorporate characteristics of capillary pressure behavior using the classic Brooks-Corey power-law model. The final form of my new proposed model allowed us to predict absolute permeability as a function of effective porosity, irreducible wetting phase saturation, displacement or threshold pressure corresponding pore throat radius, and basic pore size characteristics. I built my model using 189 sets of mercury—injection (Hg-air) capillary pressure data and measured permeability-including core samples from several reservoirs both carbonate and sandstone lithologies. I identified this correlation by quantifying its accuracy and precision based on regression analysis. I compared permeability estimates obtained from Huet and Blasingame mercury-injection capillary-pressure-based model and my new universal predicted permeability model to a set of laboratory measured permeability of my studied core sample and previously published data results respectively, where I quantified the method’s accuracy and precision based on error analysis. The measured permeability samples range is from 0.003 mD to 5341 mD. I review current employed models that are classified as belonging to Poiseuille model.

Effects of Curing Methods on the Permeability and Mechanism of Cover Concrete

Curing methods are one of the most important factors in determining the quality and compactness of cover concrete.The effect of curing methods on the water absorption and sorptivity coefficient of cover concrete with the substitution ratio of fly ash(FA)and ground granulated blast slag(GGBS)for cement between 30 wt%and 40 wt%was studied by capillary water absorption test.The vacuum saturation test and mercury intrusion test were employed to characterize these differences in the pore structure of cover concrete under different curing methods.With further analysis of the compactness of microstructure by SEM,the mechanism of the impact of curing methods on the permeability of cover concrete was revealed.The results obtained indicate that the effect of curing methods on the water absorption,sorptivity coefficient and porosity of cover concrete shows the trend of natural curing>cover curing>water curing>standard curing.It is also shown that reasonable curing is advantageous to reduce the porosity and permeability of cover concrete.In natural curing conditions,the appearance of porosity increasing and pore structure coarsening is more critical for covering concrete with mineral admixtures than for pure cement concrete.Therefore,the permeability of cover concrete with mineral admixtures is more sensitive to the early-age curing methods.

基于毛细管连通率和水力迂曲度的碳酸盐岩渗透率分形模型

碳酸盐岩非匀质性强,孔隙结构呈现出连通率低、迂曲度高的典型特征。而以往的渗透率分形模型假设岩石孔隙由相互不干扰的毛细管束组成,忽略了复杂成岩过程中胶结作用导致的毛细管连通性降低和迂曲度增大的情况,难以准确评估低渗碳酸盐岩的渗透特性。针对渗透率被高估的研究现状,利用满足阿波罗填充的等径颗粒致密堆积分形毛细管束模型,提出了毛细管连通率表征进出口毛细管过流面积损失,并在流体渗透路径几何迂曲度与孔隙度关系的基础上,引入曲折度指数来反映岩石的实际水力迂曲度,最终建立基于连通率、水力迂曲度的碳酸盐岩渗透率分形模型。考虑曲折度指数的水力迂曲度计算值与试验压汞法测定值更为一致;基于毛细管连通率、实际水力迂曲度的碳酸盐岩渗透率分形模型计算结果与细观测定及渗透试验数据吻合较好,表明提出的碳酸盐岩渗透率分形模型能够更好地预测碳酸盐岩真实渗透率。参数敏感性分析发现,孔隙度相同,粒径不同的碳酸盐岩,渗透率均随着孔径增加而增加;同时相同粒径岩石,渗透率随着孔隙度的增大而增大,但由于孔隙面积最小/最大值、孔隙面积分形维数均与孔隙度相关,渗透率与孔隙度的关系不是单纯的线性关系,渗透率随着孔隙度增大的增幅逐渐减小、敏感性逐渐降低。

多孔介质各向异性动态渗透率模型

基于迂曲毛细管网络模型,推导建立了各向异性渗透率与岩石正应变间的关系式,即各向异性动态渗透率模型(ADPM),采用孔隙尺度流动模拟对模型进行了验证,并对单轴应变过程进行了计算,分析了变形过程中影响不同方向渗透率变化的主要因素。研究表明:层状油气藏开采的单轴应变过程中,有效面孔率对各方向的渗透率影响规律一致,随着有效面孔率的减小,渗透率对应变的敏感程度增大;垂直于压缩方向的渗透率对应变的敏感程度随迂曲度的增加而减小,沿压缩方向的渗透率对应变的敏感程度随迂曲度的增加而增大。初始各方向迂曲度相同的层状油气藏,在压力下降的过程中,迂曲度对各方向渗透率变化幅度的相对关系起决定性作用,迂曲度小于1.6时,岩石水平方向渗透率的降幅要高于垂向渗透率,迂曲度大于1.6时则相反,传统动态渗透率模型无法表征这一现象。经孔隙尺度模拟实验数据的验证,新模型拟合精度高,可以有效表征不同方向变形对各方向渗透率的影响。

岩心油水两相渗流启动压力梯度实验研究

低渗储层油水两相渗流时存在启动压力梯度,充分认清水驱油时启动压力梯度的变化和影响因素对油藏水驱开发至关重要。为了搞清油藏储层油水两相渗流启动压力梯度特点及其影响因素,对不同渗透率、不同含水饱和度、不同润湿性岩心水驱油两相渗流的启动压力梯度进行了室内实验测定,根据实验现象和实验结果,分析了产生启动压力的岩心孔隙内部的阻力效应和微观成因。研究结果表明:气体渗透率小于50×10^(-3)μm^(2)的低渗岩心随含水饱和度增加,启动压力梯度增大;气体渗透率大于50×10^(-3)μm^(2)的中高渗岩心启动压力梯度随含水饱和度变化不大,总体呈下降趋势,且数值较小;对于低渗油藏,启动压力梯度随岩心渗透率降低而增大,随岩心润湿指数增加而减小;岩心边界层液体厚度越大,启动压力梯度越大。产生启动压力的附加阻力效应有油滴毛管力产生的摩擦阻力、静润湿滞后导致油珠变形产生的阻力及液阻效应产生的阻力,其大小和岩石孔喉半径、润湿指数、微观孔隙的油水分布状态、边界层厚度及固液界面张力有关。

珠江口盆地古近系典型低渗透油藏产能测试分析

珠江口盆地古近系低渗透储层具有孔隙度低、孔隙结构复杂、喉道细小等特点,探井钻杆测试(DST)测试产能低。对比分析模块式地层动态测试器(MDT)取样分析结果及关井压力恢复资料,发现储层在测试前浸泡时间长,产生较为严重的水锁效应。剖析低渗透储层产生水锁效应的机理,推导出泥浆滤液侵入储层深度的公式,结果表明泥浆滤液侵入储层深度与浸泡时间呈正相关关系,针对区域深层低渗透油藏因水锁效应而导致的风险,提出措施建议。

裂缝性油藏渗流特征及注水策略

为提高裂缝性油藏数值模拟精度,提供有效注水策略,以渤海大型裂缝性油藏锦州25-1南潜山油藏为研究对象,采用数字岩心技术,结合多相流模拟,明确半风化壳上段和下段微观孔喉特征及相渗曲线特征,结合数值模拟和矿场实践,开展采油速度化及注水方式优化研究。研究表明:微裂缝发育程度对基质岩块相渗曲线和毛细管力曲线形态具有重要的控制作用;微裂缝越发育的岩心,驱油效率越高,越有利于产生基质渗吸作用;微裂缝长度和裂缝频数满足幂律分布规律,其幂律指数约为1.5;开发初期裂缝系统的产量占主导地位,开发中后期基质系统的产量贡献逐步增加,裂缝系统和基质系统累计产量贡献比约为2∶1;开发初期通过优化采油速度,含水上升阶段采用循环注水的方式,采收率预计提高4.5个百分点。该研究对于裂缝性油藏开发策略及注水方案的制订具有重要指导意义。

赣南野生黄花倒水莲抗炎作用及其作用机制的初步研究

目的 分析赣南野生黄花倒水莲抗炎作用及其作用机制。方法 提取黄花倒水莲总黄酮后取对数生长期的RAW264.7细胞,分为空白对照组(以无血清DMEM孵育)、模型组(加入脂多糖100μg/L孵育24 h)及低、中、高剂量总黄酮组,ELISA方法测定一氧化氮(NO)、肿瘤坏死因子-α(TNF-α)、白介素(IL)-1α、IL-1β、IL-6、IL-10含量,Western blot法检测细胞中诱导型一氧化氮合酶(iNOS)、环氧合酶-2(COX-2)蛋白相对表达。应用对角叉菜胶致大鼠足肿胀模型,分为模型组(灌胃蒸馏水)、阳性对照组(灌胃给予阿司匹林)、低、中、高剂量总黄酮组,各组分别以0.2、2、20μmol/L的黄花倒水莲总黄酮提取物灌胃,连续给药5 d,观察各组大鼠足跖肿胀度及大鼠血清iNOS、COX-2、TNF-α、IL-1β水平。应用冰醋酸致大鼠腹腔毛细血管通透性模型,观察各组大鼠伊文斯蓝含量及毛细血管抑制通透性率。结果 与空白对照组比较,模型组RAW264.7细胞NO、TNF-α、IL-1α、IL-1β、IL-6水平升高,IL-10水平降低(P<0.01);与模型组比较,低剂量总黄酮组、中剂量总黄酮组及高剂量总黄酮组NO、TNF-α、IL-1α、IL-1β、IL-6水平降低,IL-10水平依次升高(P<0.05)。与空白对照组比较,模型组iNOS、COX-2蛋白相对表达量升高(P<0.05);与模型组比较,低剂量总黄酮组、中剂量总黄酮组及高剂量总黄酮组iNOS、COX-2蛋白相对表达量依次降低(P<0.05)。与模型组比较,阳性对照组、中剂量总黄酮组致炎成功后1、3 h及高剂量总黄酮组致炎成功后1、2、3 h的大鼠足跖肿胀度均降低(P<0.05或P<0.01)。与模型组比较,阳性对照组、低剂量总黄酮组、中剂量总黄酮组及高剂量总黄酮组血清iNOS、COX-2、TNF-α、IL-1β水平均依次降低(P<0.01)。与模型组比较,阳性对照组、低剂量总黄酮组、中剂量总黄酮组及高剂量总黄酮组腹膜毛细血管伊文斯蓝含量均降低(P<0.05或P<0.01);阳性对照组、低剂量总黄酮组、中剂量总黄酮组及高剂量总黄酮组腹膜毛细血管抑制率均增加(P<0.05或P<0.01)。结论 赣南野生黄花倒水莲总黄酮可有效发挥抗炎作用,抑制大鼠角叉菜胶所致足趾肿胀程度,降低大鼠腹腔毛细血管通透性,具有良好的市场发展前景和社会效益。

基于储层物性参数的毛管压力曲线和孔喉分布表征

为了开展毛管压力曲线和储层孔喉分布表征研究,通过对渤海油田压汞实验资料进行分析,对已有毛管压力曲线进行线性插值、分段拟合及多元回归方法建立了预测模型,并对模型的合理性进行了验证。结果表明,储层孔隙度和渗透率与毛管压力和孔喉分布具有较强的相关性;对汞饱和度为5%~90%的毛管压力曲线进行拟合,显示进汞饱和度为10%时拟合相关性最好,拟合精度随着进汞饱和度的增大而逐渐降低,表明进汞饱和度较大时对应的细小孔喉与孔隙度和渗透率的相关性减弱,不是影响的主控因素;对模型合理性进行检验,最大进汞饱和度拟合平均误差为5.1%,样本毛管压力曲线的主要部分及孔喉分布预测值与实验值较为吻合。建立的预测模型能够较准确地表征区域内储层毛管压力曲线和孔喉分布,研究结果具有统计学意义,可为储层研究提供技术支持。

多孔吸液芯均热板的现状研究

随着时代的进步,技术的不断革新,电子产品为了满足人们的需求在不断变小变薄,但功耗却在不断变大,更小的散热面积以及更大的功耗使得芯片热通量和工作温度的控制问题十分严峻,而一旦热流无法及时排出,会导致产品性能表现变差甚至烧坏。均热板具有优异的导热性能,较大传热面积、较好的均温性能和高可靠性等优点,是解决电子设备散热问题的首要途径。基于此,对均热板传热原理进行概述,重点综述国内外以多孔材料为吸液芯的均热板结构设计研究现状,包括气液通道排布结构和工质选择等,介绍目前多孔材料吸液芯的部分研究方法和方向,并分析了目前研究成果,最后对均热板未来的研究趋势和发展前景进行了科学的展望。

Does computed tomography permeability predict hemorrhagic transformation after ischemic stroke?

AIM: To use perfusion-derived permeability-surface area product maps to predict hemorrhagic transformation following thrombolytic treatment for acute ischemic stroke.METHODS: We retrospectively analyzed our prospectively kept acute stroke database over five consecutive months for patients with symptoms of acute ischemic stroke(AIS) who had computed tomography(CT) perfusion(CTP) done at arrival. Patients included in the analyses also had to have a follow-up CT. The permeability-surface area product maps(PS) was calculated for the side of the ischemia and/or infarction and for the contralateral unaffected side at the same level. The cerebral blood flow map was used to delineate the ischemic territory. Next, a region of interest was drawn at the centre of this territory on the PS parametric map. Finally, a mirror region of interest was created on the contralateral side at the same level. The relative permeability-surface area product maps(r PS) provided an internal control and was calculated as the ratio of the PS on the side of the AIS to the PS on the contralateral side. A student t-test was performed after log conversion of r PS between patients with and without hemorrhagic transformation. Log conversion was used to convert the data into normal distribution to use t-test. For the group of patients who experienced intracranial bleed, a student t-test was performed between those with only petechial hemorrhage and those with more severe parenchymal hematoma with subarachnoid haemorrhage.RESULTS: Of 84 patients with AIS and CTP at admission, only 42 patients had a follow-up CT. The r PSderived using the normal side as the internal control was significantly higher(P = 0.003) for the 15 cases of hemorrhagic transformation(1.71 + 1.64) compared to 27 cases that did not have any(1.07 + 1.30). Patients with values above the overall mean r PS of 1.3 had an increased likelihood of subsequent hemorrhagic transformation. The sensitivity of using this score to predict hemorrhagic transformation was 71.4, the specificity was 78.6, with a positive predictive value of 62.5 and negative predictive value of 84.6. The accuracy was 76.2. The odds ratio of an event occurring with such an r PS was 9.2. Of the 15 cases of hemorrhagic transformation, there was no difference(P = 0.35) in the r PS between the eight cases of petechial and the seven cases of more severe hemorrhagic events.CONCLUSION: Pretreatment PS can predict the occurrence of hemorrhagic transformation on follow-up of AIS patients with relatively high sensitivity, specificity, positive and negative predictive value.

Effect of absorption boundary layer on nonlinear flow in low permeability porous media

Taking low permeability cores of Daqing oilfield for example,the flow characteristics at low velocity were studied with the self-designed micro-flux measuring instrument.Considering the throat distribution and capillary model,the thickness of fluid boundary layer under different pressure gradients was calculated,and the mechanism and influencing factors of nonlinear percolation were discussed.The results show that the percolation curve of ultra-low rocks is nonlinear,and apparent permeability is not a constant which increases with pressure gradient.The absorption boundary layer decreases with the increase of pressure gradient,and changes significantly especially in low pressure gradient,which is the essence of nonlinear percolation.The absorption boundary layer is also found to be impacted by the surface property of rocks.

Differential Capillary Effect Model of Fabric and Its Application

The concept of the differential capillary effect was presented by foreign scholars several years ago, and the principle was used to design sportswear fabrics with good wet permeability and good drying functions for famous sports teams. Because the differential capillary effect model was not established in theory,it was impossible to fulfill the best functions. In this paper, by setting up the differential capillary effect of fabric, the factors to influence wet permeability and drying functions of the model is discussed in theory, and the means to optimize the design of the fabric is presented and proven practically by the experiment. The optimum fabric with good permeability and good drying functions can be designed using the model at last.

Capillary Micro-flow Through a Fiber Bundle(Part 2)

A numerical model was proposed to simulate the capillary micro-flow through a fiber bundle. The capillary pressure was predicted by the Young-Laplace equation and the corresponding optimal values of permeability were found by a trial-and-error method. The empirical Kozeny constants which are dependent on fiber volume fraction were recormnended for the prediction of permeability.

Analysis of the Microstructure and Permeability of the Laminates with Different Fiber Volume Fraction

Microstructures of laminates produced by epoxy/carbon fibers with different fiber volume fraction were studied by analyzing the composite cross-sections.The main result of the compaction of reinforcement is the flatting of bundle shape,the reducing of gap and the embedment of bundles among each layer.The void content outside the bundle decreased sharply during the compaction until it is less than that inside the bundle when the fiber volume fraction is over 60%.The resin flow velocity in the fiber tow is 102-104 times greater than the flow velocity out the fiber tow no matter the capillary pressure is taken into account or not.