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The Evolutionary Characteristics of Reservoir Microstructure under Long-Term Waterflooding Development and Its Fractal Description
Geofluids ( IF 1.7 ) Pub Date : 2021-06-09 , DOI: 10.1155/2021/5557125
Fengjiao Wang 1, 2 , Xu Wang 1 , Yikun Liu 1 , Qingjun Deng 3 , Jianjun Xu 4 , Yong Zhang 5 , Huaiyuan Li 6
Affiliation  

Generally, long-term waterflooding development often leads to the change of reservoir pore and clay mineral composition, which results in the change of permeability and wettability. In order to explore the relationship between core micropore structure and water cut, based on physical simulation experiments and fractal theory, we proposed a fractal evolutionary model to describe the evolution characteristics of microstructure of long-term water driving reservoirs. In this paper, core pore structure by SEM was first conducted to analyze the change of core pore structure before and after waterflooding under the conditions of magnification of 200 times, 800 times, and 2000 times, respectively. Then, conventional and constant rate mercury injection tests were combined to perform the comparative analysis of core structural parameters before and after waterflooding. Finally, a micropore-throat structure evolution model of core was established. Research shows that the connectivity of larger pores becomes better after long-term water driving, the degree of heterogeneity weakens, and the micro heterogeneity of small pores becomes stronger and stronger. The throat characteristics change in a complex manner, the radius tends to increase, and the sorting becomes better, while the connectivity of small throat changes complex. In general, the heterogeneity of throat increases with the time of water injection in reservoirs with low porosity and permeability. On the basis of fractal theory and variation characteristics of rock pore structure in water driving reservoirs, we have established a micropore-throat structure evolution model of core pore-throat characteristics. This fractal evolution model quantitatively characterized the complexity and evolution law of pore structure and clarified the relationship between fractal dimension of core pore structure and water cut under different stages of water driving.

中文翻译:

长期注水开发储层微观结构演化特征及其分形描述

一般来说,长期注水开发往往会导致储层孔隙和粘土矿物组成发生变化,从而导致渗透率和润湿性发生变化。为探究岩心微孔结构与含水率的关系,基于物理模拟实验和分形理论,提出了描述长期水驱油藏微观结构演化特征的分形演化模型。本文首先通过扫描电镜对岩心孔隙结构进行分析,分别在放大倍数为200倍、800倍和2000倍的条件下,分析了注水前后岩心孔隙结构的变化。然后,结合常规和恒速压汞试验,对注水前后岩心结构参数进行对比分析。最后,建立了岩心微孔喉结构演化模型。研究表明,长期水驱后,大孔隙的连通性变好,非均质性程度减弱,小孔隙的微观非均质性越来越强。喉道特征变化复杂,半径趋于增大,分选性变好,而小喉道的连通性变化复杂。一般而言,低孔渗储层中,喉道非均质性随着注水时间的延长而增大。以水驱油藏岩石孔隙结构的分形理论和变化特征为基础,建立了岩心孔喉特征的微孔喉结构演化模型。该分形演化模型定量表征了孔隙结构的复杂性和演化规律,阐明了不同水驱阶段下核心孔隙结构分形维数与含水率的关系。
更新日期:2021-06-09
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