2-D纳米黑卡室内评价及缝洞型碳酸盐岩油藏矿场应用

2-D smart nanocard nanofluid laboratory evaluation and field application in fractured-vuggy carbonate reservoirs

塔河油田是国内一种缝洞型碳酸盐岩油藏,具有巨大的开发潜力和广阔的开发前景。针对塔河缝洞型碳酸盐岩油藏孔、缝、洞介质发育且储层非均质性严重,天然能量底水开发过程中易形成水锥;注水开发过程中,驱替介质易从裂缝窜进并产出,导致井间富集大量剩余油,注水开发效果差的问题;注气过程中,易发生气窜等问题。为了克服以上问题,中国石油大学(北京)自主合成了具有亲水—亲油性的纳米黑卡材料并开展了纳米黑卡调驱潜力室内实验研究。纳米黑卡具有95 nm横向尺寸,0.5~1.5 nm的厚度。借助Turbiscan多重光散射仪筛选出体系最稳定的纳米黑卡浓度为50 mg/L;室内静态实验证明纳米黑卡能够寻找油水界面并形成黑卡吸附层,改变界面性质。再者,当纳米黑卡浓度为50 mg/L时,油水界面张力达到0.6 m N/m,将模拟油乳化成10~50μm的稳定乳状液,也能够将油湿石英片(116°)转变成中性润湿(91.2°)。根据二维可视化微观模型和细管模型证明纳米黑卡具有调驱的作用机理,一维岩心驱替实验表明纳米黑卡流体可使驱油效率增加9.2%。基于室内评价结果,初步在塔河TK779井组开展纳米黑卡调驱先导性矿场试验。在注入4900 m^3纳米黑卡后(纳米黑卡浓度50 mg/L),三口邻井显著受效,注入井组受效井累计增油2233.9 t,平均含水从82%降低至25.7%。纳米黑卡调驱作为一种高效、低廉的调驱技术,有望为缝洞型碳酸盐岩油藏后期开发提供重要的技术支持。

Tahe oilfield, a fractured-vuggy carbonate reservoir in China, has great potential and broad prospects during its oil development stage. The full development of holes, fractures and vugs in fractured-vuggy carbonate reservoirs in the Tahe oilfield results in high heterogeneity. The water cone is easily formed during natural energy bottom water development. The displacement aqueous solution is easily produced along the fractures, causing more remaining oil among wells and a poor result of water flooding. It is easy to form gas channels during gas injection development. To overcome the issues mentioned above, a smart nanocard nanofluid with hydrophilicity-lipophilicity was synthesized independently by China University of Petroleum(Beijing) and then utilized to study the ability of profile control and flooding in the laboratory. Smart nanocard is a kind of nano-flake material with sizes of 95 nm in plane and 0.5~1.5 nm in height. The Turbiscan scatterometer was used to evaluate the stability of the smart nanocard nanofluid. The result demonstrated the system was most stable when the concentration of smart nanocard was 50 mg/L. In addition, laboratory experiment results proved that the smart nanocard could intelligently find the oil-water interface and form smart nanocard adsorption layers to change the interface properties. Moreover, the interfacial tension reached 0.6 m N/m and stable emulsions in size of 10 to 50 μm were also formed between simulated oil and water phases when the concentration of the smart nanocard was 50 mg/L. It is also worth mentioning that an oil-wet quartz sheet(contact angle^116°) was transferred into neutral wet(contact angle ~91°). It was also proved that smart nanocard has a mechanism of profile control and flooding according to the results derived from a 2D visualization model and a thin tube model. Besides, it demonstrated that oil displacement efficiency was increased by 9.2% after smart nanocard flooding in core. Based on the laboratory results, a field test of smart nanocard profile control and flooding technology was initially carried out in the TK779 well groups in Tahe oilfield. Three adjacent wells were significantly affected after 4900 m^3 smart nanocard aqueous solutions were injected(smart nanocard concentration^50 mg/L). The three affected wells increased oil by 2233.9 tons and the average water content decreased from 82% to 25.7%. Smart nanocard intelligent profile control and flooding technology, as an economical and high efficiency enhanced oil recovery technology, is expected to provide important technical support for the development of later stage fractured-vuggy carbonate reservoirs.