The processing, production, and transport of heavy crude oils are big challenges for the petroleum industry. Central to this challenge is the fluid viscosity: the key variable responsible for the oil fluidity throughout the entire production process. From the reservoir to delivery conditions, oils undergo large variations in temperature and pressure, which may cause important phase behavior and physicochemical changes, directly affecting the fluid’s thermophysical properties. In the case of heavy oils, such a broad change of conditions categorically results in several orders of magnitude viscosity span, including the possible Newtonian to non-Newtonian rheological behavior transitions. It is, therefore, of primary importance that heavy oils be rheologically well-characterized to ensure their production process is successful and viable. The viscosities of heavy and extra-heavy crude oils in extreme conditions (high pressure, high to low temperature, high to low shear rate) are, however, difficult for most service laboratories to fully measure directly. Several lapses may occur when measuring the full range of required conditions using traditional rheometers; for example, for such viscous fluids, the development of laminar-flow structural anomalies (eddies) and magnetic decoupling in the high-pressure cell are common practical problems. In an attempt to pragmatically address these problems, in this work, a methodology that may allow for the rheological characterization of heavy and extra-heavy oils within the full field operational range, but based on limited laboratory measurements, is proposed. The proposed approach does not follow from a simple extrapolation but is rather derived from the concept of control-variable shifting. For achieving this, the superposition principle is applied to shear-temperature and shear-pressure reliable measurements to construct master curves to rheologically characterize the fluid within conditions that may be too severe for direct laboratory measurements. This methodology has been successfully applied to a database of 20 Mexican fluids, going from extra-heavy to light fluids. The rheologies of the samples were originally studied using three different types of equipment: (1) a strain-controlled rheometer (for the measurement of the fluid rheology at ambient pressure and different temperatures), (2) a sliding piston viscometer for high-pressure and low-shear-rate viscosity measurements, and (3) a hybrid rheometer coupled with a pressure cell for the estimation of the fluids rheological behavior under pressure and high shear rate. The rheological behavior of crude oils could then be obtained at conditions as severe as the equipment allowed (up to 1000 bar and, in some cases, shear rate up to 1000 s^–1). The master curves allowed, however, to extend the rheological characterization of the fluids within conditions that were beyond the laboratory capabilities.

中文翻译：

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重质和超重质原油在高压下的流变行为

重质原油的加工，生产和运输对石油工业是巨大的挑战。挑战这一挑战的核心是流体粘度：在整个生产过程中负责机油流动性的关键变量。从储层到输送条件，油的温度和压力会发生很大变化，这可能会导致重要的相行为和理化变化，直接影响流体的热物理性质。在重油的情况下，这样广泛的条件变化会导致粘度跨度达到几个数量级，包括可能的牛顿流变行为向非牛顿流变行为转变。因此，最重要的是流变特性要好，以确保重油的生产过程是成功和可行的。但是，对于大多数服务实验室而言，在极端条件（高压，高温至低温，高剪切率至低剪切率）下，重质和超重原油的粘度很难直接进行全面测量。使用传统流变仪测量所需条件的整个范围时，可能会发生几次失误。例如，对于这种粘性流体，高压电池中层流结构异常（涡流）的发展和磁解耦是常见的实际问题。为了尝试务实地解决这些问题，在这项工作中，提出了一种方法，该方法可以允许在全田操作范围内，但基于有限的实验室测量值，对重油和超重油进行流变学表征。所提出的方法不是从简单的推断中得出的，而是从控制变量移位的概念中得出的。为此，将叠加原理应用于可靠的剪切温度和剪切压力测量，以构建主曲线，以在对于直接实验室测量可能过于苛刻的条件下，对流体进行流变学表征。该方法已成功应用于从重油到轻油的20种墨西哥油液的数据库。最初使用三种不同类型的设备研究了样品的流变性能：（1）应变控制的流变仪（用于在环境压力和不同温度下测量流体流变学），（2）高压的滑动活塞粘度计和低剪切速率粘度测量，（3）混合流变仪与压力传感器相结合，用于估算在压力和高剪切速率下的流体流变行为。然后可以在设备允许的最高条件下（高达1000 bar，在某些情况下，剪切速率高达1000 s）获得原油的流变行为。^–1）。但是，主曲线允许在超出实验室能力的条件下扩展流体的流变特性。