In this work, unstable displacements were conducted using special equipment designed to run in-situ CT-scanner experiments. All the displacements were conducted on a homogeneous Bentheimer sandstone plug, of 10 cm in diameter and 40 cm in length. Digitations (or fingering) have been observed under varying conditions of injection flowrate, displaced fluid viscosity, and core wettability. They have been characterized at both the core scale, using the core average oil saturation and the water breakthrough; and at the local scale, using the local saturations and had-hoc image processing analysis. It was found that the effect of the different flowing conditions on the front digitations could not be interpreted independently. The oil recovery at brine breakthrough showed a good correlation with the viscous fingering number for the water-wet case. However, a different scaling was observed for the oil-wet case. The interplay of the different flowing conditions mitigates the possibility of constructing a unique scaling number to account for all experimental condition. The local saturation monitoring has provided a new insight to characterize the finger shapes and analyze the production mechanisms. It allowed to distinguish two independent contributions to early breakthrough: viscous dominated digitations and capillary dominated digitations. A two-phases diagram has been constructed to plot and compare these contributions for all flowing conditions. Their evolutions show the main production mechanisms during the flooding. We observed that the viscous digitations were not causing phase trapping at core scale: the core is completely swept after breakthrough. For the water-wet case, we found that the local oil recovery of swept zone remained constant before and after breakthrough while for the oil-wet case it is improving during all the water flooding process.
To speed up coreflood experiments, we have developed a state of the art experimental setup (CAL-X) designed for high throughput coreflood experimentation. The setup is composed of an X-ray radiography facility, a fully instrumented multi-fluid injection platform and a dedicated X-ray transparent core holder. The equipment was designed to handle small samples of 10 mm in diameter and 20 mm in length, and can be operated at up to 150 bar and 150 °C. The X-ray facility consists of a high power X-ray tube and a high speed-low noise detector allowing real-time radiography acquisition and offering sufficient density resolution to use dopant-free fluids. The injection platform is fully automated and allows the control and monitoring of different parameters (pressure, temperature, flow rate…). 1-D and 2-D saturation profiles are followed in real-time, allowing a precise determination of the recovery curve, reducing thus drastically time-consuming effluent measurements. Using this setup, a typical coreflood experiment can be run in less than a day. To validate the setup we have run a series of experiments on water-wet sandstone samples to determine capillary desaturation curve, steady-state relative permeabilities and recovery factor for a formulation designed for high temperature conditions (110°C). The results show good repeatability as well as good agreement when compared to standard coreflood experiments. In the recovery factor experiment, during surfactant injection, the formation and displacement of an oil bank was observed, yielding a recovery factor of 92% OOIP.
The phenomenology of steady-state two-phase flow in porous media is recorded in SCAL relative permeability diagrams. Conventionally, relative permeabilities are considered to be functions of saturation. Yet, this has been put into challenge by theoretical, numerical and laboratory studies that have revealed a significant dependency on the flow rates. These studies suggest that relative permeability models should include the functional dependence on flow intensities. Just recently a general form of dependence has been inferred based on extensive simulations with the DeProF model for steady-state two-phase flows in pore networks. The simulations revealed a systematic dependence of the relative permeabilities on the local flow rate intensities that can be described analytically by a universal scaling functional form of the actual independent variables of the process, namely, the capillary number, Ca, and the flow rate ratio, r. In this work, we present the preliminary results of a systematic laboratory study using a high throughput core-flood experimentation setup, whereby SCAL measurements have been taken on sandstone core across different flow conditions -spanning 6 orders of magnitude on Ca and r. The scope is to provide a preliminary proof-of-concept, to assess the applicability of the model and validate its specificity. The proposed scaling opens new possibilities in improving SCAL protocols and other important applications, e.g. field scale simulators.
Designing robust EOR surfactant formulations implies performing a number of experiments related to the impact of variable parameters such as injection brine composition and reservoir temperature from near wellbore to in-depth zones. Performance evaluation assays are commonly employed in parametric studies, ahead of the time-consuming coreflood tests. Phase diagram in tubes and spinning drop tests are commonly used, but they do not easily allow deriving representative values of the o/w IFT and can lead to contradictory outcomes. In this work, we addressed the crucial question of the methods implemented to estimate the IFT in bulk tests and we investigated a model case where the robustness of a surfactant formulation was assessed versus temperature. In the first part, we compared, at optimal salinity, the IFT as classically evaluated by the Huh relationship in tubes to the IFT as determined in a spinning drop tensiometer between, respectively, the microemulsion and the water and oil phases in equilibrated and non-equilibrated situations. In the second part, we evaluated the robustness of a surfactant formulation in terms of IFT versus temperature variation by phase diagrams and spinning drop methods and performed simplified oil recovery coreflood tests, using the CAL-X high throughput device. Results showed that IFT discrepancies up to one order of magnitude exist between the Huh estimation and the spinning drop results as well as between the different strategies for determining the spinning drop IFT. Such discrepancies can be interpreted from a scientific point of view, but they highlight the need to discriminate between the IFT determination methods in view of representativeness regarding the actual oil recovery mechanisms in the reservoir. The tests campaign for the temperature robustness, performed in the 40-90°C temperature range, showed, again, discrepancies between the two bulk methods. Namely, Winsor III situation was observed from 60°C to 90°C in the phase diagrams with an optimum at 70°C whereas ultra-low IFT was observed only at 60°C in the spinning drop tests. The coreflood tests revealed that very good oil recoveries were achieved from 40°C to 90°C, with evidence of formation of oil banks leading to final oil saturation as low as 5% only from 60°C to 90°C. These outcomes suggest that, for cases where the various phases are clearly distinguishable in tubes, phase diagrams should be selected as preferred bulk assays. However, these tests provide only coarse estimates of the IFT, which makes performance prediction based on capillary desaturation curves challenging. For this reason, high throughput coreflood tests could also be included in surfactant formulation design workflows to better forecast for the formulation performances.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.