三次采油与提高原油采收率(3/4): 三大采油机制与旋转滴界面张力测量

第三部分：三大采油机制与旋转滴界面张力测量

Part 3: Three EOR Families and Spinning Drop IFT Measurement

经历了“石油峰值”理论带来的行业焦虑与水驱失效的物理困境，石油工业转向了新的技术路线。本部分将详细探讨克服上述挑战的解决方案与策略，全面解析三次采油技术的分类与深层机理。更为关键的是，我们将说明一项核心技术前提：测定超低界面张力是如何依赖于旋转滴界面张力仪（Spinning Drop Tensiometer，如CNGTX等）及其独特测量方法的。这一仪器的应用，是连接微观化学合成与宏观油田增产的关键环节。

Having worked through the industry anxiety brought by the "Peak Oil" theory and the physical dilemmas of waterflooding failure, the petroleum industry turned to a new technical route. This section will detail the solutions and strategies to overcome the aforementioned challenges, comprehensively analyzing the classifications and deep mechanisms of Tertiary Oil Recovery technologies. More crucially, we will set out a core technical prerequisite: how the determination of ultra-low interfacial tension depends on the Spinning Drop Tensiometer (such as CNGTX, etc.) and its unique measurement method. The application of this instrument is the link connecting microscopic chemical synthesis with macroscopic oilfield production enhancement.

为了开采二次采油后依然滞留在岩石网络中的“剩余油”，石油工程师们引入了更为前沿的物理化学手段，这便是三次采油（Tertiary Oil Recovery），业内统称为提高采收率（EOR）技术。此时，开采的驱动逻辑发生了根本性的转变：从利用压力梯度的宏观“推”或“挤”，转变为通过注入特殊流体，改变原油、水和岩石界面的热力学状态，把岩石孔隙里的油“洗”出来。根据注入介质和机理的不同，三次采油主要分为化学驱、气驱和热力采油三大阵营。

To extract the "remaining oil" still stranded in the rock network after secondary recovery, petroleum engineers introduced more cutting-edge physicochemical methods, which is Tertiary Oil Recovery, collectively referred to in the industry as Enhanced Oil Recovery (EOR) technologies. At this point, the driving logic of extraction underwent a fundamental shift: from utilizing macroscopic "pushing" or "squeezing" via pressure gradients, to injecting special fluids to alter the thermodynamic state of the crude oil, water, and rock interfaces, essentially "washing" the oil out of the rock pores. Based on the different injected media and mechanisms, Tertiary Oil Recovery is primarily divided into three major camps: Chemical Flooding, Gas Flooding, and Thermal Recovery.

气驱（Gas Flooding） 侧重于相态和体积的改变。通过向油藏注入二氧化碳（CO2）、天然气或氮气，在特定的地层压力和温度下，注入气体能与原油达到混相（Miscible）状态。当达到混相时，气液两相之间的物理界面完全消失，界面张力降为零，理论洗油效率可达 100%。特别是CO2驱，它不仅能显著降低原油黏度、使油体积膨胀，还为碳捕集与封存（CCUS）提供了适宜的地下场所。热力采油（Thermal Recovery） 则主要针对黏度极高的稠油。通过蒸汽吞吐、蒸汽驱或SAGD（蒸汽辅助重力泄油）技术，向地下注入高温热能。根据热力学原理，温度的升高会导致重质原油分子间的内摩擦力急剧下降，黏度呈指数级降低，从而使原本接近沥青状态的稠油恢复流动性。

Gas Flooding focuses on changes in phase state and volume. By injecting carbon dioxide (CO2), natural gas, or nitrogen into the reservoir, under specific formation pressures and temperatures, the injected gas can reach a Miscible state with the crude oil. When miscibility is achieved, the physical interface between the gas and liquid phases completely disappears, the interfacial tension drops to zero, and the theoretical oil-washing efficiency can reach 100%. CO2 flooding, in particular, not only significantly reduces crude oil viscosity and expands oil volume but also provides a suitable underground location for Carbon Capture, Utilization, and Storage (CCUS). Thermal Recovery is primarily aimed at heavy oil with extremely high viscosity. Through Steam Soaking, Steam Flooding, or SAGD (Steam Assisted Gravity Drainage) technologies, high-temperature thermal energy is injected underground. According to thermodynamic principles, an increase in temperature causes the internal friction between heavy crude oil molecules to drop sharply, decreasing viscosity exponentially, thereby restoring mobility to heavy oil that was previously close to asphalt in consistency.

然而，在应用最为广泛的化学驱（Chemical Flooding） 领域，核心机制是通过改变微观界面的自由能来实现的。化学驱包括聚合物驱、表面活性剂驱和碱驱。聚合物的作用是大幅增加注入水的黏度，改善流度比以抑制水窜。而表面活性剂（类似高效洗洁精）和碱的作用则直接针对界面：它们通过吸附在油水界面上，旨在将界面张力从常规的几十 mN/m 降低到 10⁻³ 甚至 10⁻⁴ mN/m 的超低水平。尤其是三元复合驱（ASP），碱与原油中的石油酸发生皂化反应生成原位表面活性剂，再配合外加的表面活性剂和聚合物，产生明显的协同效应，能够高效剥离吸附在岩石上的残余油膜。

However, in the most widely applied field of Chemical Flooding, the core mechanism is achieved by altering the free energy of microscopic interfaces. Chemical flooding includes polymer flooding, surfactant flooding, and alkali flooding. The role of polymers is to significantly increase the viscosity of injected water, improving the mobility ratio to suppress water channeling. Meanwhile, the role of surfactants (similar to highly efficient dish soap) and alkalis acts directly on the interface: by adsorbing at the oil-water interface, they aim to reduce the Interfacial Tension from conventional tens of mN/m to an ultra-low level of 10⁻³ or even 10⁻⁴ mN/m. Especially in Alkali-Surfactant-Polymer (ASP) composite flooding, the alkali undergoes a saponification reaction with petroleum acids in the crude oil to generate in-situ surfactants, which, combined with added surfactants and polymers, produce a clear synergistic effect capable of efficiently stripping residual oil films adsorbed on rocks.

为了研发出能够达到这一苛刻标准的高效药剂配方，科研人员必须精确测量油水之间的张力。这是整个化学驱技术的前提条件：如果无法测量，就无法优化配方。传统的表面张力测量方法（如Wilhelmy吊片法、DuNouy白金环法或常规悬滴法）在面对低于 10⁻² mN/m 的张力时会完全失效，因为在极低张力下，重力会使液滴变形破裂，无法形成稳定的界面供仪器分析。因此，在石油化学和胶体物理学领域，测量超低界面张力只能依赖旋转滴界面张力仪（Spinning Drop Tensiometer，如北京盛维基业科技有限公司研发的 CNGTX 等型号）及其独有的测量方法。

To develop highly efficient chemical formulations capable of meeting this stringent standard, researchers must precisely measure the tension between oil and water. This is the precondition for the entire chemical flooding technology: if it cannot be measured, the formulation cannot be optimized. Traditional surface tension measurement methods (such as the Wilhelmy plate method, DuNouy ring method, or conventional pendant drop method) completely fail when facing tensions below 10⁻² mN/m, because at extremely low tensions, gravity deforms and breaks up the droplet, so no stable interface can form for instrument analysis. Therefore, in the fields of petroleum chemistry and colloidal physics, measuring ultra-low Interfacial Tension relies on the Spinning Drop Tensiometer (such as the CNGTX model developed by Beijing Shengwei Technology Co., Ltd.) and its unique measuring method.

下表展示了不同测量方法在界面张力测试中的能力对比：

The following table displays a comparison of the capabilities of different measurement methods in interfacial tension testing:

测量方法	适用张力范围 (mN/m)	核心物理原理	在超低张力下的表现
白金环/吊片法	> 1.0	机械拉脱力平衡	完全失效，无法成型
悬滴法	> 10⁻²	重力与界面张力平衡	误差显著增大，液滴易脱落
旋转滴法（CNGTX等）	10⁻²—10⁻⁶	离心力场与界面张力平衡	目前唯一有效的方法，精度高

CNGTX 等旋转滴界面张力仪的测量方法，是以离心力场取代重力场的流体力学与光学方案。它的核心部件是一根水平放置的石英玻璃毛细管。在标准操作程序中，首先将密度较大的连续相（如含有表面活性剂的地层水溶液）充满这根毛细管，然后通过微量注射器将一滴密度较小的原油注入到液相中心。随后，仪器启动高速无刷直流电机，带动毛细管以较高转速（通常在 5000 至 15000 RPM 之间）绕其水平轴旋转。在这一人工离心力场中，重力的影响被大幅削弱。较重的水相被压向管壁，而较轻的油滴则被向心挤压，沿着旋转轴心被拉长，呈现出规则的圆柱形或雪茄形。

The measurement method of Spinning Drop Tensiometers such as the CNGTX replaces the gravitational field with a centrifugal one, combining fluid mechanics and optics. Its core component is a horizontally placed quartz glass capillary. In standard operating procedures, this capillary is first filled with a denser continuous phase (such as a formation water solution containing surfactants), and then a drop of less dense crude oil is injected into the center of the liquid phase using a microsyringe. Subsequently, the instrument starts a high-speed brushless DC motor, driving the capillary to rotate around its horizontal axis at high speeds (typically between 5000 and 15000 RPM). In this artificial centrifugal force field, the influence of gravity is largely suppressed. The heavier aqueous phase is pressed against the tube wall, while the lighter oil drop is squeezed centripetally, elongating along the axis of rotation to assume a regular cylindrical or cigar-like shape.

此时，油滴的形状由两种力共同决定：离心力使其沿轴向拉长以增加界面面积，而界面张力则试图使其收缩以维持最小比表面积。当系统达到陀螺静力学平衡（Gyrostatic Equilibrium）时，流体力学中的 Vonnegut 方程或更为精确的 Young-Laplace 算法便发挥作用。界面张力的大小可以通过油滴的赤道直径（或曲率）、两相液体的密度差以及旋转角频率的平方计算得出。为了捕捉这微米级的变化，CNGTX 仪器配备了高分辨率摄像头（如 WVGA）、频闪 LED 光源以及具有高达 18 倍放大倍率的光学变焦镜头。结合内置的气热温控系统（Gas-thermal temperature control mode），它可模拟地下油藏 100°C 以上的高温环境。通过软件的自动边缘识别和长时间连续监测，科研人员能够准确获取体系达到平衡后的超低张力数据，精度可达 10⁻⁶ mN/m。

At this point, the shape of the oil drop is set by the balance of two forces: the centrifugal force elongates it along the axis, increasing the interfacial area, while the Interfacial Tension attempts to shrink it to maintain the minimum specific surface area. When the system reaches Gyrostatic Equilibrium, the Vonnegut equation in fluid mechanics or the more precise Young-Laplace algorithm comes into play. The magnitude of the interfacial tension can be calculated from the equatorial diameter (or curvature) of the oil drop, the density difference between the two liquid phases, and the square of the rotational angular frequency. To capture these micrometer-level changes, the CNGTX instrument is equipped with a high-resolution camera (such as WVGA), strobe LED light sources, and an optical zoom lens with up to 18x magnification. Combined with a built-in Gas-thermal temperature control mode, it can simulate the high-temperature conditions of underground oil reservoirs above 100°C. Through automatic edge recognition software and continuous long-term monitoring, researchers can accurately obtain the ultra-low tension data after the system reaches equilibrium, with precision reaching 10⁻⁶ mN/m.

下期预告：正是有了诸如 CNGTX旋转滴界面张力仪 这类精密仪器提供的定量手段，油田化学家们才得以在分子层面上验证和改进各类复杂的表面活性剂配方，从而使注入水具备剥离顽固油膜的能力。那么，这些在实验室中验证的高效配方，在真实油藏中表现如何？在最后一部分，我们将把视角转向油田现场，看看三次采油技术是如何在实际应用中兑现承诺，并重塑行业未来的。

Next: It is precisely with precision instruments like the CNGTXSpinning Drop Tensiometer providing this quantitative capability that oilfield chemists are able to verify and improve various complex surfactant formulations at the molecular level, thereby giving injected water the ability to wash away stubborn oil films. So, how do these formulations, verified in the laboratory, perform in real reservoirs? In the final part, we will turn to field operations to see how tertiary oil recovery technologies fulfill their promises in practical applications and reshape the future of the industry.