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基于分形理论的非常规油气渗流规律研究
Alternative TitleResearch on transport behavior of unconventional natural gas and oil based on fractal theory
李曹雄
Thesis Advisor林缅
2019-05-28
Degree Grantor中国科学院大学
Place of Conferral北京
Subtype博士
Degree Discipline工程力学
Keyword混合分形 非常规油气 页岩 致密砂岩 渗透率
Abstract

非常规储层具有非均质性强、渗透率超低,且油气运移规律复杂的特性,与常规储层有很大不同。探寻非常规储层中影响油气运移的关键因素,准确高效地评价渗流趋势,是国内外学者和工程师们的关注焦点。本文以分形理论为基础,以页岩和致密砂岩为对象,构建了单相流体和两相流体在页岩和致密砂岩中的渗流模型,为研究非常规储层的油气渗流规律提供了新方法。

页岩渗流空间尺度跨度大,包括纳米级的有机孔、微米级的无机孔以及百微米级的微裂缝。如何综合不同尺度的各类孔隙信息,将微观孔隙和宏观渗流特性结合起来,准确地表征页岩的渗流规律是重要的科学问题,也是工程上非常关心的问题。本文抓住各渗流空间的自相似性特征,引入了混合分形理论来表征跨尺度渗流空间,大大简化了页岩孔隙空间表征难度。进一步与孔隙连通概率法结合,成功构建了新型跨尺度页岩渗透率快速评估方法。

致密砂岩孔隙结构复杂,孔隙壁面性质变化大,不同矿物的壁面润湿性和粗糙度不同。两相流体在致密砂岩中的流动过程受多重应力的综合作用,运移过程非常复杂。由于基质储层过于致密,其两相渗流规律和主控因素目前很难通过室内实验获取。利用使用混合分形的方法,将矿物润湿性信息和粗糙度信息赋予分形的三维孔隙空间,并将相界面受到的壁面摩阻、浮力、毛管力、排驱力综合到导通概率上,通过扩展的孔隙连通概率法,建立了基于分形理论的油水两相渗流模型。并依靠模型揭示了影响致密油运移的主控因素。

利用混合分形理论,建立的页岩渗透率快速评估方法,涵盖了多种微纳米尺度信息,具有严格的理论基础,能够更加快速准确的描述页岩的多尺度流动规律;建立的致密砂岩油水两相微观渗流评价方法,有效地将微观参数与宏观渗流规律结合起来。本文提出的基于分形理论的非常规储层油气渗流模型和分析方法计算速度快,评价效率高,为工程应用提供一种新的方法。

Other Abstract

Unconventional reservoir has relatively strong heterogeneity and low permeability, with complicated permeable characteristic, which is different with normal reservoir. It is one of the primarily concerns of engineers to investigate the key factors influencing oil and gas transport behavior in unconventional formation, and to evaluate permeable behavior reliably and efficiently. In this work, we introduced fractal theory into the flowing behavior investigation within shale and tight sandstone, to build percolation model for both single phase (shale) and multiphase (oil-water displacement within tight sandstone), which provided a new way to research flow behavior within unconventional reservoir.

Shale possess a complicated flowing space, including nanopores in organic bulk, micropores in matrix and macro slits. It is a key problem to rebuilt different kinds of multi-scale pores and slits efficiently to evaluate permeability precisely. In this work, by using self-similar behavior of each component, we introduced fractal theory to rebuild the pore space. The fractal parameters are gained by intermingled fractal method. And finally derived the novel cross-scale permeability evaluation method by combining the pore connective probability theory and 3D intermingled fractal method.

The tight sandstone also possesses a relatively complicated pore structure. The wettability and roughness of pore walls are different within different mineral pores. Also, oil-water displacement process behavior within tight sandstone is complicated and it is not easy to observe by laboratory experiment. In this work, we used intermingled fractal method to combine random fractal pores in matrix and mineral characteristics like wettability and roughness of pore walls. In intermingled fractal method, we derived a parameter, connecting possibility, to express complicated influencing factors on meniscus, like flow resistant on pore wall, buoyancy of oil, capillary force and driving forces. By using the extended pore connective probability method, we finally calculated multi-phase flowing displacement model, which is useful to describe multi-phase flowing behavior of tight sandstone.

Generally, in this work, we utilized fractal theory to build a permeability evaluation method for shale, which covered information from different kinds of pores. The method is convincible and helpful to evaluate permeability of shale reliably and efficiently. Also, we provided a method to calculate relative permeability for tight sandstone. This method combines microscopic structure and macroscopic flowing behavior, and is helpful to extend the limitations of laboratory tests. The intermingled fractal methods provided in this work is efficient and reliable to evaluable flowing behavior of oil and gas in unconventional reservoir.

Language中文
Document Type学位论文
Identifierhttp://dspace.imech.ac.cn/handle/311007/79226
Collection流固耦合系统力学重点实验室
Recommended Citation
GB/T 7714
李曹雄. 基于分形理论的非常规油气渗流规律研究[D]. 北京. 中国科学院大学,2019.
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