酸压裂缝中酸液微观流动数值模拟及分析  

Numerical Simulation and Analysis of Micro Flow of Acids in Fractures Generated in Acid Fracturing

作　　者：刘享 伊向艺[1,2] 吴元琴 李沁[1] LIU Xiang;Yi Xiangyi;WU Yuanqin;LI Qin(College of Energy Resources, Chengdu University of Technology, Chengdu, Sichuan 610059;State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu, Sichuan 610059)

机构地区：[1]成都理工大学能源学院,成都610059 [2]油气藏地质及开发工程国家重点实验室,成都610059

出　　处：《钻井液与完井液》2017年第4期106-111,共6页Drilling Fluid & Completion Fluid

基　　金：国家自然科学基金青年基金"碳酸盐岩储层酸岩反应表面形态与演化"(51504200)

摘　　要：酸压是储层增产的重要措施,搞清楚酸液在裂缝中的流动规律对酸压改造具有重要意义。前人的研究主要是通过物理实验来研究酸压裂缝中的酸液流动,所采用的裂缝模型与实际的裂缝有较大差别,很少考虑到裂缝的粗糙度对酸液流动的影响。因此,利用数值模拟方法,借助于fluent软件模拟了裂缝中酸液的流动,分析了裂缝壁面粗糙度对酸液流动的影响。实验结果表明:单相流和两相流在水平中轴线上流速曲线都呈现"厂"字形,在垂直中轴线上流速曲线呈现"几"字形,在单相流中,波峰处流速明显大于其他部位的流速,中轴线上的流速反而较小,相反在两相流中,中轴线上的流速是最大的;随着粗糙度的增加,酸液的驱替长度增加;在同一粗糙度下驱替长度与黏度比M并不成线性关系,当M等于6时,4种粗糙度下的酸液驱替长度都达到最小,当M小于6时,驱替长度随黏度比增加而减小,M大于6时,驱替长度又随黏度比的增加而增加,其中粗糙度λ=0.1、0.2、0.3时,在8<M<11之间黏度比对酸液的驱替长度影响相对较小。酸液驱替长度的增加可以增加酸蚀作用距离,形成酸蚀沟槽,从而增加裂缝的导流能力,达到酸压改造目的,在考虑到施工和成本的条件下,应该使前置液和酸液的黏度避开下降段和平台段的黏度值。Acid fracturing is an important stimulation measure used in enhancing oil recovery.The understanding of flow of acids in fractures generated in reservoir fracturing is of great importance.Physical experiments have been conducted previously in the study of acid flow in fractures,and the fracture model used in the experiments are quite different than the actual fractures generated in acid fracturing,the effects of the roughness of the surfaces of fractures on acid flow are seldom considered.This paper introduces the use of a software Fluent to numerically simulate acid flow in fractures,and analyzes the effects of the roughness of the surfaces of fractures on acid flow.Experimental results showed that the flow rate curves of both single-phase flow and two-phase flow along the horizontal central axis demonstrated a shape of“厂”,while along the vertical central axis,the curve showed a shape of“几”.In single-phase flow,flow rates around wave crest were much greater than the flow rates in other area,and the flow rate along the central axes were low.On the other hand,in two-phase flow,highest flow rates were found along central axes.With an increase in roughness of the surfaces of fractures,the length of flow of acid is extended.At the same roughness,the flow length of acid and acid viscosity are not in linear relationship.When M=6,the flow lengths of acid in fractures with4different surface roughness all are the shortest.When M<6,the flow lengths decrease with increase in viscosity ratio.When M>6,the flow lengths increase with increase in viscosity ratio.A plateau appears with M between8and11,meaning that the effects of viscosity ratio on acid flow length are becoming weak.Increase in acid flow length increases the length of acid erosion,forms more cannelures,thereby enhancing the flow conductivity of fractures and fulfilling the purpose of acid fracturing.Taking into account operation cost,in selecting prepad fluid and acid,viscosities corresponding to the values around the descending section and the plateau

关 键 词：酸液流动 fluent模拟 VOF模型 粗糙度 黏度比 

分 类 号：TE357.12[石油与天然气工程—油气田开发工程]