齐宏鹏,梁凤鸣,邓宝康
QI Hongpeng,LIANG Fengming,DENG Baokang

• 1:延长油田股份有限公司吴起采油厂
• 2:延长油田股份有限公司靖边采油厂
• 3:西安石油大学地球科学与工程学院
• 4:西安商鼎能源科技有限公司

摘要(Abstract)：

为提高页岩储层基质渗流能力，改善衰竭采收率低等问题，提出一种液氮压裂辅助气体吞吐提高采收率新方法，利用该方法对液氮压裂后岩心开展注N_2和CO_2循环吞吐实验，研究不同注气介质、注气压力和注气方式对页岩油采收率的影响，并结合核磁共振T_2谱测试，明确液氮压裂辅助气体吞吐后微观孔隙结构的变化特征。结果表明：液氮能够在5 min内将76.2℃的岩石表面温度急剧降至-170℃，瞬间形成约为303 MPa的热应力，挤压岩石诱发裂缝形成；采用液氮压裂后在相同注气压力条件下，CO_2吞吐、N_2吞吐和先N_2后CO_2吞吐3种注气方式下的3轮累计采收率分别为57.34%、27.35%和50.17%，第3种吞吐方式不但能降低CO_2需求量，还能充分发挥2种注气介质的驱油优势；纯CO_2吞吐后的岩心孔隙度由6.74%增大至12.04%，渗透率由0.024×10~(-3)μm~2大幅增加至6.242×10~(-3)μm~2，平均孔径由4.94 nm增至47.79 nm。研究成果为助力页岩油气高效开发提供了新思路和新方法。
In order to improve matrix fluid flow capability of shale reservoir and solve the problem of low depletion recovery, a new method of liquid nitrogen fracturing assisted gas huff-and-puff to enhance oil recovery is proposed. This method is used to carry out N_2 and CO_2 injection cyclic huff-and-puff experiment on the cores after liquid nitrogen fracturing, and to study the influence of different gas injection media, gas injection pressure and gas injection methods on shale oil recovery. NMR T_2 spectrum test is combined to clarify the characteristics of micro-pore structure changes after liquid nitrogen fracturing assisted gas huff-and-puff. The results show that liquid nitrogen can sharply reduce the surface temperature of rock from 76.2 ℃ to-170 ℃ within 5 minutes, instantly forming thermal stress of about 303 MPa, and compressing rock with induced fractures formed. With same gas injection pressure after liquid nitrogen fracturing, cumulative recovery of 3 rounds of 3 injection modes including CO_2 huff-and-puff, N_2 huff-and-puff and N_2 huff-and-puff followed by CO_2 huff-and-puff are 57.34%, 27.35% and 50.17%, respectively. The 3 rd injection mode not only reduces CO_2 demand but also gives full play to displacement advantages of the 2 kinds of gas injection media. Core porosity increases from 6.74% to 12.04%, permeability increases from 0.024×10~(-3) μm~2 to 6.242×10~(-3) μm~2, and average pore size increases from 4.94 nm to 47.79 nm. The research provides new idea and method for efficient development of shale oil and gas.

关键词(KeyWords)： 页岩;液氮;压裂;吞吐;裂缝;孔隙结构
shale;liquid nitrogen;fracturing;production;fractures;pore structure

Abstract:

Keywords:

基金项目(Foundation): 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）;; 国家自然科学基金项目“盐度响应型水包稠油乳状液的构建及其再多孔介质中的运移行为研究”（51804036）

作者(Author): 齐宏鹏,梁凤鸣,邓宝康
QI Hongpeng,LIANG Fengming,DENG Baokang

DOI: 10.19597/J.ISSN.1000-3754.202501033

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