Guo Qing, Li Ze, Zeng Xuanxiang, Li Dan, An Huiming, Zhao Li, Tao Liang, Li Qiang
BaiLie School of Petroleum Engineering, Lanzhou City University, Lanzhou 730070, China.
Xi'an Key Laboratory of Tight Oil (Shale Oil) Development (Xi'an Shiyou University), Xi'an 710065, China.
ACS Omega. 2024 May 20;9(22):23294-23302. doi: 10.1021/acsomega.3c09728. eCollection 2024 Jun 4.
Reduction of the reservoir permeability during supercritical CO fracturing caused significant reservoir damage, which directly affects the crude oil recovery rate. This investigation explored a novel thickener for supercritical CO fracturing fluid, this CO thickener not only effectively improves the viscosity and rheological properties of CO fracturing fluid but also contributes to reduce reservoir damage and improve permeability. The research results indicated that the synthesized CO thickener (3 wt %) can increase the apparent viscosity of supercritical CO fracturing fluid to 7 mPa·s, and a 9% matrix permeability damage rate and a 0.5 mD permeability decrease value are shown in a 3% CO fracturing fluid. However, 3 wt % of commercial CO thickener only increases the apparent viscosity of supercritical CO fracturing fluid to 3 mPa·s, while the reservoir damage rate increases to 13%. Two thickeners exhibit completely different damage capabilities to the reservoir, and the synthesized CO thickener shows excellent characteristics of reducing reservoir permeability and is also conducive to protecting shale reservoirs. Furthermore, supercritical CO fracturing fluid containing synthetic thickeners has better temperature and shear resistance compared with commercial thickeners. This may be because the synthesized thickener and the micro grid formed by supercritical CO reduce the adsorption in shale crevices, but a large amount of commercial thickeners can adsorb on the surface of shale.
超临界CO₂压裂过程中储层渗透率的降低造成了显著的储层损害，这直接影响原油采收率。本研究探索了一种用于超临界CO₂压裂液的新型增稠剂，这种CO₂增稠剂不仅能有效提高CO₂压裂液的粘度和流变性能，还有助于减少储层损害并提高渗透率。研究结果表明，合成的CO₂增稠剂（3 wt%）可将超临界CO₂压裂液的表观粘度提高到7 mPa·s，在3%的CO₂压裂液中表现出9%的基质渗透率损害率和0.5 mD的渗透率降低值。然而，3 wt%的市售CO₂增稠剂仅将超临界CO₂压裂液的表观粘度提高到3 mPa·s，而储层损害率则增至13%。两种增稠剂对储层的损害能力完全不同，合成的CO₂增稠剂表现出优异的降低储层渗透率的特性，也有利于保护页岩储层。此外，与市售增稠剂相比，含有合成增稠剂的超临界CO₂压裂液具有更好的耐温性和抗剪切性。这可能是因为合成增稠剂与超临界CO₂形成的微网格减少了在页岩缝隙中的吸附，而大量的市售增稠剂会吸附在页岩表面。
