Transient measurement and modeling of integrated capillary viscometer for live oils at high temperatures with volumetric constraints

Abstract

The viscosity of oils at reservoir conditions whether under natural depletion conditions or under induced conditions (i.e. EOR/IOR) is one of the key parameters for the dynamics of flow in porous media, and it has direct impact on the economically recoverable volumes as well as transportation problems where the fluids can get exposed to potentially wide range of temperatures. It becomes even more essential measurement for thermal based EOR techniques including high temperature steam injection or in-situ upgrading techniques due to strong (exponential) dependency of viscosity to temperature. Unfortunately, viscosity measurements for such applications suffer with the two key challenges. First, most commercial and research labs could measure viscosities up to 200 °C (while the application considered may induce temperatures as high as 300 °C beyond which most naturally occurring hydrocarbons starts decomposing). And second, these measurements are based on steady-state conditions, requiring significant volumes of oil samples. However, the available volume of oil samples for such applications may be very small for various reasons, including emulsions leading to very low useful volumes, cost of sampling, or inheritance of candidate samples from other laboratory processes, such as but not limited to core-flooding or reactive transport experiments.Therefore, in this work, we present a novel but simple technique to overcome these challenges by using simple capillary device that could be integrated to any system that requires charging and/or charging the candidate fluids such as PVT-cells, pressurized vessels that could be operated up to 300 °C or higher. Such integration utilizes the charging of fluids to the cell for viscosity measurements, leading to the following advantages:(i) it requires no additional volume of oil for viscosity measurements, and also saves the operational time and cost(ii) it could produce viscosity data at higher temperatures that are desired for in-situ upgrading or thermal EOR, even small amounts of particulates evolve in the bulk phase(iii) it ensures that the viscosity and PVT measurements are performed on the same sample eliminating the potential sample to sample variations.(iv) the proposed approach along with the developed methodology paves the way for a the implementation of unsteady in-line measurement of viscosities for pressurized systems. This includes not only lab processes, but also the downhole sampling where the method could be implemented in sampling devices.The technique proposed here is based on transient measurements and modeling of capillary viscometer, where pressure at the end points and flow rate through the capillary tube may vary with time (which is the most realistic conditions for variable back pressure systems or systems with frictional pistons). In addition to the experimental process, necessary mathematical model and interpretative analysis tools to quality check, assessment of the experimental data (and the establishment of the range of validity and limitations) are derived from first principals (bottom-up approach) using Navier-Stokes equations.