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1.
The presence of impermeable horizontal barriers (such as shales) in a reservoir is known to have a significant effect on its
vertical permeability. Since calculation of an effective vertical permeability of such a reservoir is important, approximation
of the distribution of vertical permeability may also be useful for analysis of the two-phase vertical flow of buoyant fluid,
such as may occur in the subsurface injection of carbon dioxide into saline formations. In this situation, the maximum likely
vertical permeability of a reservoir with impermeable barriers, which could be estimated from the probability distribution
of the vertical permeability, is a more useful metric than an overall effective value for the vertical permeability due to
its presumed relationship to breakthrough time. In this article, we derive expressions for the mean and variance of the vertical
permeability of both two and three-dimensional reservoirs using the statistical streamline method of Begg and King (Paper
No. 13529, 1985), and calculate the probability distribution of the vertical permeability of a reservoir with impermeable
barriers. In addition, we also provide a simple statistical analysis of the presence of high vertical permeability regions
in the reservoir, which may be of importance in coarse-scale simulations of vertical migration. 相似文献
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Using an asymptotic methodology we formulate a fast, accurate algorithm for the inversion of multi-phase flow data. The approach is appropriate for many common reservoir production strategies such as CO2 and water flooding. The technique compares well to a purely numerical method with a significant reduction in computation time. In an application to fractional flow data from the North Robertson field in West Texas, 100,000 permeability and porosity parameters are determined on a workstation. Generally, higher permeability, approaching 1milli-Darcy, is found in the eastern portion of the reservoir. The permeability estimates agree with type curve analysis for material and volumetric balances and a previous numerical pilot-point inversion. 相似文献
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The ability to calculate an effective permeability of a heterogeneous reservoir based on knowledge of its small-scale permeability
is fundamental to practical numerical reservoir characterization. One elegant technique that forms the basis of this process
is renormalization (King, P.R.: Transport Porous Med. 4, 37–58 (1989)). In two dimensions, renormalization can be implemented using a simple analytical formula. In three dimensions,
however, no such analytical result exists, and renormalization must be performed using a numerical implementation. In this
article, we present a simple analytical approximation to the method of renormalization in three dimensions. A detailed comparison
with numerical results demonstrates its accuracy and highlights the significant reduction in computational cost achieved. 相似文献
6.
深海天然气水合物降压开采过程中,沉积物的压缩会改变储层的物理力学特性,进而对天然气的开采效果产生显著影响.为揭示沉积物压缩效应下井周围储层物理力学特性演化规律,本文建立了考虑沉积物压缩效应的理论模型,通过COMSOL模拟研究了不同初始固有渗透率、初始水合物饱和度和井底压力条件下的降压开采中生产井周围储层的物理力学特性演化规律以及开采效果.结果表明:受沉积物压缩的影响,水合物分解区的渗透率随着与井筒距离的增加先增加后减少;产气与产水速率由零立即上升至峰值,然后迅速下降,并且考虑沉积物压缩时的产气与产水速率比不考虑时低;在水合物完全分解区,渗透率的大小与有效应力成负相关关系,未分解区渗透率的大小与水合物饱和度成负相关关系;井底压力越小,有效应力越大,生产井周围储层的渗透率下降越明显;初始水合物饱和度对产气与产水的影响存在拐点,饱和度拐点位于0.25与0.35之间,高水合物饱和度并不代表储层开采效果好,产气速率的高低还与储层的渗透率有关,高水合物饱和度储层的渗透率较低,产气速率较低;储层初始固有渗透率较高时显著促进了开采效果,但储层变形量较大增加了储层的不稳定性. 相似文献
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In carbonate reservoirs, acid is injected into the formation under breakdown pressure to react with the rock to remove the contaminations caused by drilling and production, which is called carbonate acidizing in reservoir development. In carbonate acidizing, acid flows selectively through large pores to create wormholes. Wormhole propagation under experimental condition has been studied by many experts. In this paper, a model which couples a two-scale continuum model simulating wormholing in the invaded zone and a reservoir flow model for the compressed zone was used to study the wormhole propagation behavior under reservoir condition. In this model, the porosity values which are uniformly distributed used in former literature follow the normal law. Based on the model, we first compared the results of the two porosity generation methods, and then studied the wormhole propagation behavior under reservoir condition, and finally simulated a two-layer formation to study the effects of distance and permeability ratio between the two layers. The results show that the normally distributed porosities simulate wormholing better. The effect of compressed zone on wormhole propagation increases with the decrease of compressibility factor and wormhole has a maximal value in length. The effect of distance between the two layers on wormhole lengths and acid distributions can be divided into three zones based on the wormhole length in the lower layer. A critical value of permeability ratio between the two layers exists, below and above which the wormhole length in the low permeability layer decreases sharply and almost keeps constant, respectively. 相似文献
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在无源汇条件下,根据流过某一个横截面的流体流量等于流过这一横截面内所有精细网格的流体流量之和这一特点提出了粗化网格等效渗透率的计算方法。在粗化区内,利用直接解法求解二维渗流方程,再用这些解合成粗化网格的三维合成解,并由合成解计算粗化网格的等效渗透率。根据精度的要求采用了不均匀网格粗化,在流体流速大的区域采用精细网格。利用所得等效渗透率计算了粗化网格的某三维非均匀不稳定渗流场的压降解,结果表明三维非均匀不稳定渗流方程的二维不均匀粗化解非常逼近采用精细网格的解,但计算的速度比采用精细网格提高了80倍。 相似文献
9.
Fractures and faults are common features of many well-known reservoirs. They create traps, serve as conduits to oil and gas migration, and can behave as barriers or baffles to fluid flow. Naturally fractured reservoirs consist of fractures in igneous, metamorphic, sedimentary rocks (matrix), and formations. In most sedimentary formations both fractures and matrix contribute to flow and storage, but in igneous and metamorphic rocks only fractures contribute to flow and storage, and the matrix has almost zero permeability and porosity. In this study, we present a mesh-free semianalytical solution for pressure transient behavior in a 2D infinite reservoir containing a network of discrete and/or connected finite- and infinite-conductivity fractures. The proposed solution methodology is based on an analytical-element method and thus can be easily extended to incorporate other reservoir features such as sealing or leaky faults, domains with altered petrophysical properties (for example, fluid permeability or reservoir porosity), and complicated reservoir boundaries. It is shown that the pressure behavior of discretely fractured reservoirs is considerably different from the well-known Warren and Root dual-porosity reservoir model behavior. The pressure behavior of discretely fractured reservoirs shows many different flow regimes depending on fracture distribution, its intensity and conductivity. In some cases, they also exhibit a dual-porosity reservoir model behavior. 相似文献
10.
The Kakkonda geothermal reservoir, Japan, is a typical high-temperature liquid-dominated geothermal reservoir, except for its distinctive two-layered temperature structure. It has a shallow permeable reservoir of 230–260°, and a deep less permeable reservoir of 350–360°. Geology and hydrology indicate that the shallow reservoir is one to two orders of magnitude more permeable than the deep reservoir, but that the two reservoirs communicate. It has been widely assumed in engineering and scientific circles that the connection between the two reservoirs is a zero or low permeability barrier to fluid flow. We show that this hypothesis is untenable, based on both physical evidence and numerical simulation. We numerically model the evolution of the geothermal system as it heats after emplacement of an intrusion. The two-layered temperature structure is found to be a consequence of the permeability difference, i.e. the two-layered permeability structure. 相似文献