应用模糊综合评判方法识别水驱优势渗流通道井和层

在油田注水开发过程中,由于储层平面非均质性、流体非均质性及开发条件的影响,在平面上会出现注入水突进的情况.注水井中的注入水向不同方向驱油,推进往往是不均匀的,一般总有一个方向突进最快,且经过长期水洗之后,这个方向有可能发展成大孔道,形成水驱优势渗流通道.建立应用模糊综合评判方法识别水驱优势渗流通道井和层的数学模型,应用水驱优势渗流通道分析判定软件,对河南双河油田ⅦⅣ油组主力油层(Ⅷ1、Ⅳ1、4、5)274口井进行了实例计算,识别出水驱优势渗流通道油水井共97口,其中水井43口,油井54口,识别出14个水驱优势渗流层位.通过油藏工程和数值模拟方法进行了验证,表明运用综合评判方法识别水驱优势渗流通道井和层是一种客观有效的方法,评价方法计算方便,易于操作和推广.     

A Critical Review of the Role of Thin Liquid Films for Modified Salinity Brine Recovery Processes

Low salinity water injection (LSWI) is the process of injecting modified salinity brine with controlled ionic composition to achieve increased oil recovery compared to conventional waterflooding. This paper reviews the most recent advances in proposed low salinity mechanisms, but specifically emphasizes the role of thin liquid films in crude oil/brine/rock systems. Importantly, thin water films on rock surfaces affect hydraulic resistance of pore channels as well as phase-trapping mechanisms. As films become thicker, they provide greater lubrication of oil droplets and hence, flow resistance decreases. Consequently, films dictate oil and water distribution in porous media and determine the wettability of crude oil/brine/rock systems under static and dynamic conditions. The stability of the thin water films depends on the interactions between the oil/brine and the calcite/brine interfaces through van der Waals, electrostatic, and structural forces.     

Well Test Solutions for Vertically Fractured Injection Wells

The transient behavior of a vertically fractured pressure response due to the presence of an infinite-conductivity vertical fracture is determined by solving the diffusivity equation in elliptical coordinates. The solution is then extended to a composite elliptical system to provide for the different fluid banks present during water injection. The validity of the analytical solutions presented is demonstrated by comparing limiting forms with those available elsewhere in the literature. Computational issues which became evident during the verification stage of our work are also discussed. The solutions have been developed in the Laplace domain to facilitate the addition of fissures and variable rate production (i.e. wellbore storage).A pressure transient test for tracking the advancement of a water front during the early stages of waterflooding is described. We utilize the composite elliptical model developed herein to provide for two distinct regions in which the flow behavior resulting from an induced fracture is elliptical rather than radial. A relationship between the increasing elliptical distance to the waterfront and the resulting change in the apparent (total) skin factor is obtained. Through the analysis of successive falloff tests, this relationship may be used to monitor the advancement of the front provided the cumulative volume of injected water is known. The fluid saturations and the mobilities of the swept and unswept regions are assumed unknown and are obtained from the test analysis.Finally, we present methods for computing the Mathieu functions necessary in solving the diffusivity equation in elliptical coordinates. Mathieu functions are utilized in many applications involving elliptical geometry and we feel the efficient evaluation of these functions is an important contribution of this work.     

Dynamics of the Water–Oil Front for Two-Phase, Immiscible Flow in Heterogeneous Porous Media. 1 – Stratified Media

We study the evolution of the water–oil front for two-phase, immiscible flow in heterogeneous porous media. Our analysis takes into account the viscous coupling between the pressure field and the saturation map. Although most of previously published stochastic homogenization approaches for upscaling two-phase flow in heterogeneous porous media neglect this viscous coupling, we show that it plays a crucial role on the dynamics of the front. In particular, when the mobility ratio is favorable, the viscous coupling induces a transverse flux that stabilizes the water–oil front, which follows a stationary behavior, at least in a statistical sense. Calculations are based on a double perturbation expansion of equations at first order: the local velocity fluctuation is defined as the sum of a viscous term related to perturbations of the saturation map, on one hand, plus the perturbation induced by the heterogeneity of the permeability field with a base-state saturation map, on the other hand. In this first paper, we focus on flows in stratified reservoirs, with stratification parallel to the mean flow. Our results allow to predict the evolution of large Fourier mode of the front, and the emergence of a stationary front, for favorable mobility ratios. Numerical experiments confirm our predictions. Our approach is applied to downscaling. Extension of our theory to isotropic media is presented in the companion paper.