低渗透裂缝性油藏 CO₂驱两级封窜驱油效果研究

Effect of Two-stage Sealing Gas Channeling and Flooding in Low Permeability Fracture Reservoirs during CO₂ flooding

王维波 余华贵 杨 红 黄春霞 王 伟 陈龙龙

WANG Weibo YU Huagui YANG Hong HUANG Chunxia WANG Wei CHEN Longlong

为了解决低渗透裂缝性油藏实施 CO2驱油过程中发生的气体窜逸问题， 提出了在用改性淀粉凝胶体系调堵裂缝的基础上继续用乙二胺封堵高渗通道的 “改性淀粉凝胶+乙二胺” 两级封窜驱油技术， 即选择改性淀粉凝胶体系（4%改性淀粉+4%丙烯酰胺+0.05%交联剂 N，N-亚甲基双丙烯酰胺+0.18%成胶控制剂叔丁基邻苯二酚）和乙二胺分别作为裂缝、 基质中高渗通道的封堵剂。分别考察了改性淀粉凝胶体系对岩心裂缝、 乙二胺对基质中高渗通道的封堵、 驱油效果， 研究了 “改性淀粉凝胶+乙二胺” 两级封窜驱油作用。结果表明， 45℃下， 单独使用改性淀粉凝胶可对渗透率 0.65×10-3 μm2岩心的填砂裂缝进行有效封堵， 封堵后 CO2气驱时岩心进出口压差基本恒定， 凝胶具有良好的封堵强度， 气体流速降低 81%， 采出程度提高 25%； 单独使用加入乙醇保护段塞的乙二胺体系可对渗透率 1.37×10-3μm2的岩心的相对高渗带形成封堵， 气体流速降低 85%， 采出程度提高 5.3%， 但是不加乙醇保护段塞的乙二胺很难注入低渗岩心； 渗透率 4.5×10-3μm2填砂裂缝岩心在用改性淀粉凝胶体系封堵裂缝的基础上继续用乙二胺封堵高渗通道， 注入压力分别高达 3.5 MPa和 5.6 MPa， 注入改性淀粉凝胶后再注入乙二胺后岩心采出程度分别提高 29.2%和 23.3%， 两级封窜驱油效果明显。图3表 2参 18

In order to solve the problem that CO2 flooding in low permeability fractured reservoir is prone to gas channeling， two-stage Sealing Gas Channeling and Flooding technique，sealing the fracture with the modified starch gel and followed by plugging the high permeability channels with the ethylenediamine，was put forward. the modified starch gel（4% modified starch+4% acrylamide+0.05% crosslinking agent N，N-methylene bis acrylamide +0.18% gelling control agent 4-tert-butylcatechol）and ethylenediamine was chosen as plugging agent of fracture and high permeability channels in matrix，respectively，the sealing and displacement effects of the modified starch gel system on core cracks and ethylenediamine on high permeability channels in matrix was investigated，respectively，and two-stage sealing and displacement experiment of“modified starch gel + ethylenediamine”was also conducted. The results showed that，at 45℃，the sand-filling cracks of the core with the permeability of 0.65×10-3μm2 could be sealed effectively only by using the modified starch gel. The pressure difference of the core after plugged was substantially constant when CO2 flooding，the gas flow rate was reduced by 81% and the recovery rate was increased by 25%，which indicated that the modified starch gel had a good plugging strength. The core with relative high permeability of 1.37 × 10-3μm2 could be plugged effectively only by using ethylenediamine with ethanol protection slug，the gas flow rate was reduced by 85% and the recovery rate was enhanced by 5.3% . However，it was difficult to inject ethylenediamine into the low permeability core without ethanol protection slug. The core of the permeability of 4.5×10-3 μm2 with sand-filling cracks was sealed with the modified starch gel and then plugged by ethylenediamine，the injection pressure reached 3.5 MPa and 5.6 MPa，respectively，and the enhanced oil recovery was 29.2% and 23.3%，respectively，the effect of the two-stage sealing and displacement was obvious.

10.19346./j.cnki.1000-4092.2017.01.015