基于数字岩心的低渗储层微观渗流机理研究

发布时间：2018-03-27 23:36

本文选题：低渗储层　切入点：数字岩心　出处：《西南石油大学》2017年硕士论文

【摘要】：低渗致密储层孔喉细小、孔隙空间复杂,尤其针对浅层疏松砂岩储层,在压实成岩过程中由于上覆压力小导致岩石胶结差,很难取得完整岩心,此时进行岩心分析实验耗时长、误差大,而深井、复杂结构井取心困难、费用昂贵,物理实验难于开展。流体在低渗储层中流动时会产生微流动效应,使得以Darcy定律为基础的宏观渗流规律无法适用于低渗储层的勘探开发,因此亟需深入到多孔介质内部从微观尺度上对储层开展研究,如孔隙空间的拓扑结构、孔喉大小对流体渗流的影响,流体在其中的分布规律、流体之间相互作用机理,才可以从根本上达到对油藏微观机理的认知,以此为基础找到更有效的油气开采技术。本文通过对低孔低渗砂岩进行微CT扫描,结合高级可视化软件Avizo和多物理场有限元软件Comsol对岩心灰度图像进行滤波处理、二值化分割和连通性判断,完成了多孔介质孔隙空间的三维微观精细重构和岩心孔隙参数的定量表征。以岩心孔喉结构为研究对象通过孤立孔隙清除和数据体表面平滑对孔隙介质进行网格划分,同时对重构的数据体进行表面简化和修复,减少了数字岩心建模和微观渗流数值模拟所需的时间和计算机存储空间,选取STL文件作为数据交互的接口类型,实现了 Avizo数字岩心可视化和Comsol有限元模拟软件的交互对接。基于岩心的图像预处理和数据对接逐一开展了孔隙微观结构中的渗透率模拟计算、微观层面上的热传导数值模拟等研究,最后着重考察了 Avizo和Comsol对接在微观渗流中的运用和润湿性对储层微观渗流的影响。研究取得的主要成果和认识如下:(1)完善了岩心CT图像处理流程,确立了基于分水岭算法进行低渗储层岩石的二值化分割,基于图像数据距离变换提取连通孔隙的中轴线从而建立岩心的孔隙网络模型,对岩心的孔隙度、孔喉半径体积、孔喉表面积等参数进行了定量表征,达到了对岩心微观拓扑结构的准确描述。(2)基于纳维-斯托克斯方程的多孔介质体积平均方法实现了流体在岩心孔隙空间中的渗流模拟,获取了岩心的绝对渗透率,通过比对岩心分析实验验证了以数字岩心为基础的数值模拟方法具有很好的可靠性。(3)运用基于多尺度均匀化理论的傅里叶定律计算了非接触3D圆柱体、非接触3D球体、粒子接触的3D球体以及双层复合材料等四种模型的热导率,考察了微观尺度下岩石的热传导性质。(4)完成了 Avizo与Comsol的对接,实现了流体在岩心中流动的可视化,计算了绝对渗透率和相对渗透率,着重研究了存在界面层的微观渗流机理。(5)基于孔隙重建方法和CT图像提取的真实三维孔隙网络,假定孔隙网络模型中水驱程度逐渐加深,多孔介质中含水饱和度逐渐增加,接着进行气体驱替,直到含油量达到残余油饱和度,针对老化之后的不同润湿性状态,控制第一次排水之后的渗吸得到水驱后气驱的饱和路径和相应的残余油饱和度三元相图,考察了润湿性对多孔介质三相渗流的影响。
[Abstract]:Low permeability reservoir small pore throat, complicated pore space, especially in shallow unconsolidated sandstone reservoir in the diagenetic compaction process due to overburden pressure to rock cementation difference, it is difficult to obtain a complete core, this core analysis experiment is time-consuming and error, deep, complex structure wells coring problems that is expensive, difficult to carry out physical experiments. Fluid flow in the reservoir in low will produce micro flow effect, the macroscopic seepage law based on Darcy's law is not applicable to the exploration and development of low permeability reservoir, so it is necessary to go deep into the internal porous media to carry out research on the reservoir from the micro scale. The topological structure such as pore space, influence of pore throat size on fluid flow, fluid distribution in the interaction mechanism between the fluid, it can fundamentally achieve the microcosmic mechanism of the reservoir on the basis of cognition, find more Oil and gas exploration technology effectively. Based on the low porosity and low permeability sandstone micro CT scanning, combined with the advanced visualization software Avizo and finite element software Comsol to filter core gray image binarization segmentation and connectivity analysis, quantitative characterization of the pore space of porous media to complete the three-dimensional reconstruction and micro fine the core pore parameters. On the basis of core pore structure as the research object to mesh pore medium through the smooth surface of isolated pore removal and data, the reconstructed data were surface simplification and repair, computer time and storage space required to reduce the numerical modeling of digital core and micro flow, select the STL file as the type of data exchange interface, realizes the interactive docking of Avizo digital core visualization and Comsol finite element simulation software. And based on the core of image pre processing The data carried out one by one docking micro pore structure in the permeability calculation, the micro level study of the heat transfer numerical simulation, finally focuses on the impact of the use of Avizo and Comsol and wettability on the butt in the micro seepage micro seepage of reservoir. The main results are as follows: (1) perfect the core of CT image processing, established based on the watershed algorithm of reservoir rock binarization segmentation of low permeability, pore network model of image data extraction distance transform connected pores axis so as to establish the core based on the rock porosity, pore throat size, pore throat size and other parameters table is characterized quantitatively and reach an accurate description of the topological structure of the micro core. (2) porous medium volume average method, Navier Stokes equations to achieve the fluid in the core pore space in the seepage flow simulation based on The absolute permeability of core, and through the comparison of core analysis experiments verify the numerical simulation based on digital core method has a good reliability. (3) 3D non contact cylinder is calculated by Fourier law based on multi-scale homogenization theory, 3D non contact ball, thermal contact 3D and double sphere particles composite materials in four kinds of models to study the thermal conduction rate, properties of rock micro scale. (4) completed the butt joint of Avizo and Comsol, realize the visualization of fluid flow in rock, absolute permeability and relative permeability calculation, focuses on the microscopic seepage mechanism of interface layer (5) is true. The 3D pore network pore and CT image reconstruction method based on the extraction of water flooding, assuming pore network model deepen gradually, gradually increase the water saturation in porous medium, followed by gas flooding, until The oil content reaches the residual oil saturation. Aiming at the different wettability state after aging, we control the imbibition after the first drainage, get the three phase diagram of the gas flooding saturation path and the corresponding residual oil saturation after water drive, and investigate the influence of wettability on the three-phase seepage in porous media.

【学位授予单位】：西南石油大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE312

【相似文献】