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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.

RationaleThe deep geological repository is considered the international reference for radioactive waste management. All gas exchanges must be understood in the context of the feasibility of such a repository. The technological challenge is to continuously monitor a wide range of gaseous molecules at low concentrations in confined spaces.MethodsA gas monitoring station, composed of two complementary analyzers, was developed: an electron impact quadrupole mass spectrometer (HPR‐20 R&D Hiden Analytical) and an infrared laser spectroscope (Picarro). The spectrometer was calibrated using simple mixtures (i.e., C2H6 in N2) and multiple mixtures (i.e., H2, He, CO2, CH4, and O2 in N2) at different concentrations to correct interferences. A matrix calculation is proposed to calculate the relative concentrations.ResultsThe method developed allows the measurement of gaseous species: light hydrocarbons, noble gases, sulfides, greenhouse gases, oxygen, hydrogen, and nitrogen in the same mixture. For each gas, the SDs and the limits of detection and quantification were calculated. The method was validated by comparing the concentrations of the measured gas species with the reference values of two standard gas cylinders.ConclusionsCalibration of a complex gas mixture remains a challenge because fragmentation of molecules, especially hydrocarbons, reduces the sensitivity of the method. The method developed is suitable for continuous gas monitoring in a confined environment and can be implemented to perform experiments in underground structures: galleries, microtunnels (cells), and boreholes.

Within the framework of radioactive waste management, the evolution of the gaseous composition inside the underground repository structures must be understood. Indeed, chemical and microbial reactions and exchanges occur between the rock, the structures and the air. These processes are studied in the Andra’s Meuse/Haute-Marne Underground Research Laboratory’s (URL). Recently, a gas monitoring station “Flair soil™” has been designed to monitor the gaseous composition inside this URL. This station is composed by two analyzers: a quadrupole mass spectrometer (QMS) which allows to follow the evolution of several gases and an infrared laser spectroscope (Picarro) providing simultaneous measurements of CH4, CO2 and CO. Thus, a multivariate calibration method for the quantitative detection of interfering and non-interfering gases in a nitrogen matrix has been developed for the QMS. The MS was calibrated from pure gases in a nitrogen matrix, with known concentrations and ion currents obtained from the measurement of each species of gas. This method uses matrix calculations to calculate the relative concentrations of an unknown gas mixture from the ion currents measured directly in the MS. The test gases T1 and T2 were used to assess the accuracy of the method. Daily ion currents are corrected from theoretical ion currents obtained from calibration coefficients and test gas concentrations. Some gases are less well quantified due to their low concentration in the test gases and interferences on the measured masses. One of the motivations of this study lay in developing an advanced measurement tool allowing to be low in sensitivity, and thus to improve the detection and quantification of gases at low concentrations. The objective of this paper is to propose an analytical method to measure the gaseous composition with several molecules. This method was able to detect hydrocarbons, noble gases, sulfides, greenhouse gases, oxygen, hydrogen, nitrogen in the same mixture.

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.

Indonesian oil and gas reserves have been depleting since 2000 with no major addition of new oil reserves. Therefore, it is imperative to increase national oil production by optimizing the mature fields through the implementation of successful EOR technology. Out of this approach, a comprehensive study has been carried out on the targeted field by exploring the potential of surfactant-polymer (SP) flooding. This article describes the formulation design, optimization, and lessons learned leading up to a successful and robust chemical EOR formulation designing for a low permeability and high clay (>20% clay) containing Indonesian oil field. The detailed workflow consists of analysis of fluid and rock characterization, tailor-made SP formulation designing, optimization and coreflood validation as presented in previous papers (Bazin, 2010). A series of surfactant formulation were designed and screened synthetically through a validated High Throughput Screening (HTS) methodology using a robotic platform combined with microfluidic tools for ultra-low interfacial tension (IFT), solubility, compatibility with brine and polymer. Rock mineralogy has played an important role due to heterogeneity and very high (>20%) clay content. Surfactants retention through adsorption on reservoir rocks was the main constraint to achieve high performance and economical chemical EOR for the targeted field. Specific strategies by optimizing the surfactant formulation and by injecting adsorption inhibitor thus needed to be deployed to mitigate high surfactant retention. The detailed laboratory screening experiments conclude that the designed robust SP formulation is able to induce ultra-low IFT, excellent solubility and compatibility at the injection water salinity. The dynamic coreflood experiment using reservoir rock shows high incremental oil recovery (>60% ROIP) in short SP slug injection. As expected from the nature of rock, adsorption was the main challenge encountered during the course of this study, which resulted in a very promising oil recovery in economically realistic conditions.