A novel experimental approach for studying spontaneous imbibition processes with alkaline solutions

Spontaneous imbibition processes can play an important role in oil production. It can be enhanced or influenced by wettability changes generated by properly designed chemicals or by the natural surfactants resulting from reactive crude oils in the presence of alkaline solutions. The reaction of basic salts with some components of oil can, indeed, lead to the formation of natural soaps that reduces the interfacial tension between oil and brine. The latter scenario is studied herein on samples and oil from the St Ulrich oil field in the Vienna basin. To that end, spontaneous imbibition experiments were performed with two brines differing by the absence or presence of alkali. We first present a general novel technique to monitor saturation changes on small rock samples for the purpose of assessing the efficiency of a given recovery process. Samples of only 15 mm in diameter and 20 mm in length and set at irreducible saturation were fully immersed in the solution of interest, and the evolution of the samples’ saturation with time was monitored thanks to a dedicated NMR technique involving the quantification of the sole oil phase present within the sample. A fully-3D imbibition configuration was adopted, involving counter-current flows through all faces of the sample. The experimental method is fast for two reasons: (i) the kinetics of capillary imbibition process is proportional to the square of sample size, i.e. very rapid if accurate measurements can be acquired on tiny samples, (ii) the present 3D situation also involves faster kinetics than the 1D configuration often used. The NMR technique was crucial to achieve such conditions that cannot be satisfied with conventional volumetric methods. The kinetics of oil desaturation during spontaneous imbibition is interpreted with the help of an analytical 3D diffusion model. For the alkaline solution, the diffusion coefficient is reduced by a factor of only two compared to the non-alkaline brine, although the interfacial tension between the oil and the imbibing solution is reduced by a factor of 10. Hence, a wettability change to a more water wet state has to be assumed when the alkaline solution replaces the non-alkaline solution in the imbibition process. However, no significant impact on the final saturation was observed

ATES Contribution to the Housing Energy Balance: a Simple Assessment Methodology

The reduction of Green-House Gas Emissions (GHGE) goes through a sum of solutions that need to be tuned to the local context in terms of energy needs and resources, and also to the demand and offer variations with time. The housing heat consumption is particularly concerned as it is seasonal and rarely in phase with the deliverability of alternative or renewable energy sources. This paper studies heat storage in saline untapped aquifers as a solution to overcome the time lag between production and consumption. This process applies to heat networks that supply dense housing complexes. Firstly, a methodology is described to size an Aquifer Thermal Energy Storage (ATES) project as a function of the heat production and consumption characteristics on the one hand, and of the recovery factor of the stored heat on the other hand. The major role played by this recovery factor leads to a review of thermal losses of various origins and to a sensitivity study of influent reservoir parameters such as the aquifer thickness, productivity and heterogeneity, for the purpose of aquifer selection and storage project management

Low salinity effects on oil recovery performance: underlying physical mechanisms and practical assessment

This paper is a tentative synthesis of the main knowledge and experience gained from recent studies and application of Low Salinity Water Injection (LSWI) in carbonate and clayey silico-clastic rocks. A physical model based on ionic force is presented to explain the so-called Dual Layer Expansion (DLE) mechanism often invoked to account for the Low Salinity Effects (LSE) on rock wettability and oil recovery. The role played by the Multi Ion Exchange (MIE) mechanism is clarified, at least for clayey rocks. Eventually, the proposed physical analysis shows the complementary roles that injected brine concentration and composition can play on waterflood recovery efficiency depending on the Crude Oil Brine Rock (COBR) system under consideration. To account for the diversity of COBR systems, a straightforward modelling methodology is then proposed to simulate laboratory LSWI tests on a case-by-case basis and infer the actual evolution of residual oil saturation with brine concentration and/or composition. The simulation involves a wettability driver that may be either the global salinity or the square root of ionic force. The analysis of published results actually shows that the latter predicts low salinity effects on residual oil saturation better than the former. Hopefully, this paper contributes to the understanding of the DLE and MIE mechanisms induced by a smart water injection and provides a simple and robust methodology to simulate the reference coreflood experiments that remain necessary to assess and optimize LSWI

Integrated Reservoir Management: a Powerful Method to Add Value to Companies' Assets. a Modern View of the Eor Techniques

Integrated reservoir management is an attractive process to add value to the oil companies' assets. Indeed, increasing the reserves of their reservoirs already in production through an improved development strategy constitutes for the oil companies a real opportunity and an economic alternative to costly and risky exploration surveys. Integrated reservoir management is basically a way of combining complementary approaches and techniques such as reservoir characterization, use of complex well architecture, special core analysis design of recovery processes, reservoir monitoring and reservoir simulation, and creating a positive synergy between them. Thanks to the advances that have been observed in the domain of the computer science, reservoir management means also real time management. Thus, the large amount of data acquired can be while producing a reservoir used to develop the knowledge of the reservoir, update the reservoir model, reduce the underlying uncertainties, design the most suitable production architecture, ensure the productivity and the injectivity of the wells, target bypassed zones, select the most appropriate recovery process, and hence, increase the overall recovery. Most of the ingredients of such a strategy are already available. What still needs to be developed is a productive way of linking those ingredients together to build an integrated system. Such a system, when made available will constitute a major toolkit in the toolbox of the production engineers. In this paper, we review and illustrate the different ingredients that have to be included in such an integrated system

Simulation of Naturally Fractured Reservoirs. State of the Art

Use of fractured reservoir simulators can help reservoir engineers in the understanding of the main physical mechanisms and in the choice of the best recovery process and its optimization. Significant progress has been made since the first publications on the dual porosity concept in the sixties. This paper presents the current techniques of modeling used in industrial simulators. Following a description of the recovery processes and of the main physical mechanisms involved, a history of the fractured reservoir simulation is presented. Then the general mathematical formulation of dual porosity simulators is described. The paper ends with a presentation of the numerical simulation of flow in fractures and faults and of well modeling. The matrix-fracture transfer formulations, as well as techniques for uncertainty analysis and geology&flow-constrained history matching, will be addressed in the companion paper, Part 2: Matrix-Fracture Transfers and Typical Features of Numerical Studies

From 3D Seismic to 3D Reservoir Deterministic Model Thanks to Logging Data:the Case Study of a Near Surface Heterogeneous Aquifer

International audienceDifferent surface seismic surveys have been recorded on an experimental hydrogeological site that has been developed for several years near Poitiers (France). The paper shows how 3D seismic imaging can be used to describe the near-surface heterogeneous aquifer. The acquisition spread is designed to perform both 3D refraction and reflection seismic surveying. Refraction survey enables us to obtain a 3D image in depth of a low velocity superficial zone contrasting with the underlying water – bearing carbonates. Refraction survey shows the main orientations (N90 and N50) of fracture corridors. These two directions have been selected as the drilling azimuths of two deviated wells C3 and C4. Reflection survey enables us to generate a 3D seismic pseudo velocity block in depth. The 3D seismic pseudo velocity block shows the large heterogeneity of theaquifer reservoir in the horizontal and vertical planes, and confirms the main structural orientations (N90 and N50) identified by the refraction survey. The low velocity areas correspond to high hydraulic conductivity. In order to quantify the porosity of the different productive layers of the aquifer, the interval seismic velocities have been converted in resistivity. For that purpose, the empirical relationship between seismic velocity and true formation resistivity proposed by Faust (1953) [Geophysics 18, 271-288] has been used. The 3D resistivity block is converted in porosity, by using the Archie law (1942) [Petrol. Technol. 146, 54-62]. The 3D seismic pseudo porosity block allows us to identify three different water productive layers: an upper layer at 35-40 m depth, an intermediate layer at 85-87 m depth and a lower layer at 110-115 m. The intermediate layer is composed of bodies having a porosity larger than 30%. These bodies represent the most karstic part of the reservoir. The very high resolution seismic surveying has led to obtain a 3D porosity seismic block which represents a deterministic high resolution reservoir model. After further calibration, that reservoir model could be used for flow simulation

Modelling of Conductive Faults with a Multiscale Approach

Some of the most productive oil and gas reservoirs are found in formations crossed by multiscale fractures/faults. Among them, conductive faults may closely control reservoir performance. However, their modelling encounters numerical and physical difficulties linked with: - the necessity to keep an explicit representation of faults through small-size gridblocks; - the modelling of multiphase flow exchanges between the fault and the neighbouring medium. In the present work, a physically representative and numerically efficient modelling approach is proposed to incorporate subvertical conductive faults in single- and dual-porosity simulators. To validate our approach and demonstrate its efficiency, simulation results of multiphase displacements in representative field sector models are presented

Flowpath structure in a limestone aquifer: multi-borehole logging investigations at the hydrogeological experimental site of Poitiers

Since 2002, a new hydrogeological experimental site (HES) has been developed in Poitiers, France. The overall research objective related to this site is to improve the understanding of flow and solute transport in carbonate aquifers. The benchmarking of various types of numerical models against the HES field data is one of the main research projects supported by three national scientific programs. Within this framework, the purpose of this report is to synthesize existing knowledge about both aquifer geology and flowpath structure, based on core analysis and well logging. The combined use of core-hole data, borehole logs and outcrop data provide valuable information about lithostratigraphy and fracturing. The comparison of flow-meter data with borehole images indicates that flowpaths in the HES aquifer are strongly constrained within (1) subhorizontal karstic structures and (2) subvertical fractures. The presence of karstic levels appears to be conditioned by the stratigraphy and are unevenly developed in the HES. The vertical interconnectivity between the three karstic levels seems to result from fractures occurrence in this limestone formation. Following the observations, data and interpretations, a conceptual model of the Dogger aquifer is proposed