CAJ | 학술논문

酸压改造后的酸蚀裂缝是储层流体的主要流动通道，研究流体在酸蚀裂缝中的流动规律是十分必要的。本文介绍了目前裂隙流动研究中的4种常用控制方程及各自的适用条件，确定了Navier-Stokes方程为酸蚀裂缝流场数值模拟的控制方程。为了分析酸蚀裂缝流场分布规律以及非达西效应对裂缝导流能力的影响，利用逆向工程技术对两种不同刻蚀形态的酸蚀岩样壁面进行了实体重构，并采用有限元数值模拟方法进行了不同流量下的酸蚀裂缝流动试验。结果表明：酸刻蚀形态和裂缝接触关系对流场分布的影响较大。隙宽分布平滑的均匀刻蚀裂缝，其流态稳定、曲折度低，但由于裂缝开度较窄且比表面较高，边界层效应明显，流体流动时产生的黏滞阻力较高；沟槽裂缝曲面粗糙，隙宽分布复杂，流体流动时流态不稳定，曲折度高，在高流量下会产生明显的涡流流动，增大惯性阻力。裂缝通道存在缩颈现象会引起流体绕流和多次加减速，产生额外的压力损耗。随着模拟流量的增大，压降与流量会逐渐偏离线性关系而呈现出非达西流动现象。酸蚀裂缝壁面越粗糙，产生非达西效应时的临界流量和临界雷诺数就越小，在相同流量下非达西效应就越强烈，导流能力下降速率更快。
산압개조후적산식렬봉시저층류체적주요류동통도，연구류체재산식렬봉중적류동규률시십분필요적。본문개소료목전렬극류동연구중적4충상용공제방정급각자적괄용조건，학정료Navier-Stokes방정위산식렬봉류장수치모의적공제방정。위료분석산식렬봉류장분포규률이급비체서효응대렬봉도류능력적영향，이용역향공정기술대량충불동각식형태적산식암양벽면진행료실체중구，병채용유한원수치모의방법진행료불동류량하적산식렬봉류동시험。결과표명：산각식형태화렬봉접촉관계대류장분포적영향교대。극관분포평활적균균각식렬봉，기류태은정、곡절도저，단유우렬봉개도교착차비표면교고，변계층효응명현，류체류동시산생적점체조력교고；구조렬봉곡면조조，극관분포복잡，류체류동시류태불은정，곡절도고，재고류량하회산생명현적와류류동，증대관성조력。렬봉통도존재축경현상회인기류체요류화다차가감속，산생액외적압력손모。수착모의류량적증대，압강여류량회축점편리선성관계이정현출비체서류동현상。산식렬봉벽면월조조，산생비체서효응시적림계류량화림계뢰낙수취월소，재상동류량하비체서효응취월강렬，도류능력하강속솔경쾌。
Acid etched fracture caused by acid fracturing is the main flow channel for fluid, thus, it is necessary to study the flowing rules of fluid in acid etched fracture. Four governing equations commonly used in fracture flow research and their applied conditions are introduced, among which Navier-Stokes equation is chosen as the governing equation for numerical simulation on acid etched fracture. In order to analyze the behavior of fluid flow through acid etched fractures and high-speed non-Darcy effect on fracture conductivity capacity, two kinds of fractures with different acid etching morphologies are reconstructed to solid models by using reverse engineering techniques, and flow experiments are carried out under different flow rates by using finite element numerical simulation. It indicates that, the acidized surface morphology and contact area of acid etched fracture have a great impact on the flow field distribution. The uniform etching fracture with smooth aperture distribution leads to stable flow pattern and low tortuosity, however, with the presence of obvious boundary layer effect caused by narrow fracture width and wide surface area, high viscous resistance will be generated while flowing. The channeling fracture with rough surface and complex aperture distribution results in unstable flow pattern and high tortuosity, and there is an obvious vortex under high flow rate, hence, increasing the inertial resistance loss. The necking phenomenon in contact area leads to circumfluence, and multiple acceleration-decelerations cause additional pressure loss. Meanwhile, with the increase in simulating flow rate, pressure drop and flow rate will gradually deviate from the linear relationship and present the non-Darcy flow phenomenon. The rougher the fracture surface is, the smaller the critical flow and critical Reynolds number are, the stronger the non-Darcy effect of fluid is under the same flow rate, the faster the conductivity capacity decreases.