摘要
为深入探究裂缝性致密油藏CO_(2)吞吐过程中基质-裂缝间流体渗流机理,采用自主设计的高压无磁岩心夹持器开展脉冲式注CO_(2)吞吐岩心实验。基于核磁共振T 2谱测试原理,对CO_(2)吞吐过程中的岩心进行在线扫描,研究CO_(2)吞吐过程中基质内孔隙中原油的微观动用特征和基质-裂缝间流体的渗流特征。结果表明:CO_(2)进入裂缝后,沿着裂缝驱替原油,而基质中原油无法动用。闷井初期,基质大孔隙(20.5 ms<T 2≤716.0 ms)中饱和CO_(2)后的原油在膨胀作用下进入裂缝;闷井后期,CO_(2)抽提引起的原油浓度差异扩散和不同孔径孔隙毛管力逐渐成为主导动力,延长闷井时间能够有效提高基质中原油动用程度。原油采收率主要贡献来源于大孔隙,而小孔隙的动用程度较差,随着脉冲注气周期的增加,周期基质采出程度不断降低;矿场实施过程中应减少CO_(2)的吞吐周期,延长闷井时间,并将衰竭压力下限设定在饱和压力附近,以提高CO_(2)吞吐过程的总采收率。研究成果为裂缝性致密油藏提高采收率提供了参考和借鉴。
In order to further explore the seepage mechanism of fluid between matrix and fracture in CO_(2)huff-puff process in fractured tight reservoirs,a self-designed high-pressure non-magnetic core holder was used to perform pulsed CO_(2)huff-puff core experiment.Based on the principle of nuclear magnetic resonance T 2 spectrum testing,the core was scanned online in the process of CO_(2)huff and puff to study the micro production characteristics of crude oil in the pores of matrix and the seepage characteristics of fluid between matrix and fracture during CO_(2)huff and puff.he results of the study show that after CO_(2)entered the fracture,the crude oil was displaced along the fracture,but the crude oil in the matrix could not be produced.At the early stage of well shut-in,the crude oil saturated with CO_(2)in the matrix macropores(20.5 ms<T 2≤716.0 ms)entered the fractures under the action of expansion.At the later stage of the shut-in,the differential diffusion of crude oil concentration caused by CO_(2)extraction and the capillary force of pores in different sizes gradually became the the dominant force,and prolongation of shut-in time could effectively increase the production degree of crude oil in the matrix.The recovery efficiency of crude oil was main contributed by the large pores,while the production degree of small pores was poor.With the increase in the pulsed gas injection cycle,the cyclic matrix recovery percent was continuously reduced.The CO_(2)huff-puff cycle should be reduced and the shut-in time should be prolonged during the implementation at the mine.In addition,the lower limit of depletion pressure should be set close tot he saturation pressure to improve the overall recovery efficiency during huff and puff.The study results provide reference and basis for enhancing the recovery efficiency of fractured tight oil reservoirs.
作者
巩联浩
刘继梓
武兴
卜广平
黄凡
杨龙
Gong Lianhao;Liu Jizi;Wu Xing;Bu Guangping;Huang Fan;Yang Long(PetroChina Changqing Oilfield Company,Yulin,Shaanxi 718606,China)
出处
《特种油气藏》
CAS
CSCD
北大核心
2021年第1期118-124,共7页
Special Oil & Gas Reservoirs
基金
国家科技重大专项“鄂尔多斯盆地大型低渗透岩性地层油气藏开发示范工程”(2016ZX05050)。
关键词
致密油藏
核磁共振
CO_(2)吞吐
基质―裂缝
微观孔隙
渗流特征
tight oil reservoir
nuclear magnetic resonance
CO_(2)huff-puff
matrix-fracture
micro-pore
seepage characteristics
作者简介
巩联浩(1982-),男,高级工程师,2006年毕业于西安石油大学资源勘查专业,现主要从事石油开发地质、油藏工程研究与管理工作。
