鄂尔多斯盆地致密油藏注CO2吞吐微观剩余油分布特征  

Microscopic remained oil distribution characteristics of CO2 huff and puff in the tight oil reservoir in Ordos Basin

作　　者：邓宝康 李军建 高银山 王新星 郭愿刚 DENG Baokang;LI Junjian;GAO Yinshan;WANG Xinxing;GUO Yuangang(Sichuan OGT Technology Development of Oilfield Co Ltd,Chengdu 610041,China;No.5 Oil Production Plant,PetroChina Changqing Oilfield Company,Xi’an 710020,China)

机构地区：[1]四川奥吉特油田科技开发有限公司,四川成都610041 [2]中国石油长庆油田分公司第五采油厂,陕西西安710020

出　　处：《大庆石油地质与开发》2020年第6期119-125,共7页Petroleum Geology & Oilfield Development in Daqing

基　　金：国家自然科学基金项目“变形介质复杂储层应力敏感性的岩石流变学机理及动态模型”(51104119)。

摘　　要：注CO2吞吐是提高致密油藏原油采收率的重要技术,研究吞吐过程中剩余油分布特征是提高CO2吞吐效果的关键。基于核磁共振T2谱测试原理,以鄂尔多斯盆地姬塬油田长7储层为研究对象,分别开展了不同注气压力下CO2吞吐岩心驱替实验,研究了注气压力、吞吐次数和闷井时间对不同直径孔隙中剩余油分布的影响。结果表明:随着注气压力的升高,驱油方式发生变化,原油最终采收率不断增大,所需吞吐次数不断减少,平均采油速度不断提高;当注气压力大于最小混相压力(MMP)时,CO2能够进入微细孔隙,甚至抽提出死孔隙中的原油,降低最小孔隙动用下限;当注气压力保持恒定时,增加吞吐次数无法降低微细、小孔隙中剩余油饱和度,但却能够有效降低中等、大孔隙内的剩余油饱和度;当注气压力大于最小抽提压力(MEP)时,增加闷井时间不但能够提高中等、大孔隙中原油采收率,还能降低最小孔隙动用下限;中等孔隙和大孔隙内的剩余油仍然是CO2吞吐挖潜的主要方向。研究成果为姬塬油田长7段储层的注气开发提供了方法和依据。CO2 huff and puff is the important technology to enhance the oil recovery in tight oil reservoirs,and the study on the distribution characteristics of the remained oil during the huff and puff is the key to improve the effects of CO2 huff and puff. Based on the principle of the nuclear magnetic resonance(NMR) T2 spectrum test, taking Reservoir Chang-7 in Jiyuan Oilfield of Ordos Basin as the study object, the core displacing experiments of CO2 huff and puff at different injection pressures were carried out to study the effects of the injection pressure, huff and puff times and soaking time on the remained oil distribution of different-diameter pores. The results show that with the increase of the injection pressure, the mode of the oil displacement changes as well, the ultimate oil recovery increases gradually, the needed times of the huff and puff decreased continuously, and the average oil recovery rate increases;when the injection pressure is higher than MMP, CO2 can enter the micro-pores, and even extract the crude oil from the dead pores, the lower limit of the minimal pore development can be reduced;while the injection pressure is constant, the increase of the huff and puff times cannot reduce the remained oil saturation in the micro and small pores, but can effectively reduce the oil saturation in the medium and large pores;when the injection pressure is larger than the minimal extraction pressure(MEP), the increase of the soaking time can not only improve the oil recovery in the medium and large pores, but also reduce the lower limit of the minimal pore development;the remained oil in the medium and large pores is still the main potential-tapping direction by CO2 huff and puff. The research results have provided the method and evidence for the gas injection for Reservoir Chang-7 in Jiyuan Oilfield.

关 键 词：CO2吞吐 剩余油分布 鄂尔多斯盆地 核磁共振 注气吞吐 孔隙直径 闷井时间 

分 类 号：TE357.45[石油与天然气工程—油气田开发工程]