Effect of Gels on Geological Heterogeneity of Porous Media: An MRI and X-Ray Computer-Aided Tomography Study - DELFGEL (DAR.5756)

Project nummer: dar5756

Omschrijving van het onderzoek

Project Summary
Hydrocarbons (oil and gas) exploration and production combined with a rational carbon dioxide handling remains crucial for the sustained development of our society. However, oil and gas recovery suffers from extremely high water production. Typically 75% of the production of oil companies is water,
representing several millions of barrels of water. High water production leads to a drastic deterioration of the economics of oil and gas production. Moreover, it poses serious threat to the environment due to the need to the
dispose of such huge amounts of wastewater. Water production during oil and
gas recovery can be considerably reduced by using chemicals that form gels after being injected in the near well region of the reservoir. This technology is known as water shutoff. For decades, water shutoff applications as well
as related research and development focused on hydrophilic gels
which are formed by cross-linking water soluble polymers such as neutral or hydrolysed polyacrylamides. Often the crosslinker used was a metal ion. This technology usually requires oil zones to be mechanically isolated to
to prevent them from getting clogged when the gel is formed. However, the
selective mechanical isolation of oil layers is not possible in many wells. In previous project we have proposed a chemical that is soluble in oil
without any reaction but forms a strong "rubbery" gel when it comes in contact with water. This chemical is deemed capable of helping reduce water production without harming oil production in conditions where the mechanical isolation of oil layers is not possible.

Proposed Research
Oil and gas can occur at very large depths (3000-5000 m) in complex geological formations among which sandstone is the most important reservoir rock type. The inter-granular pore space found in sandstones varies strongly with the grain size and sorting and the amount of compaction. Intercalation of sandstone with different properties leads to lamination and layering, two of the most important types of heterogeneities found in reservoir rocks. The heterogeneity features a strong influence on fluid distribution and ease of fluid flow through natural rocks. in order to ensure that oil flows more easily than water through heterogeneous porous systems, we need to modify the rock properties. To do this in a controlled manner using the oil soluble chemical mentioned in the previous paragraph we
need to understand better the physicochernical phenomena and geological aspects involved when the gel is formed inside porous media. The purpose of this project is to investigate the modification of the subsurface properties including single and multiphase flow behaviour induced by the formation of the gel, considering two observation scales, i.e. the micro-scale (I to 100 micro-metres) and the macro- scale (1 to 10 centimetres).

Micro-scale studies: Gel formation involves the transfer of the base chemical from the oleic phase to the water phase followed by gelation. The purpose of the micro-scale studies is to obtain insight on this diffusion-gelation phenomenon using a detailed physicochernical and mathematical analysis.

Particular attention will be paid to the dependence of the kinetic parameters (diffusion and gelation kinetic coefficients, etc.) on the controlling parameters (gel concentration in the water phase, temperature, pH, salinity, etc.). The experiments will be conducted using Magnetic Resonance Imaging (MRI). To carry out these studies we shall co”perate with and benefit from experience at the Departement of Physics of the Eindhoven University of Technology. This group has extensively studied non-linear diffusion using NMR imaging. The mechanical properties of the gels will be studied using theometry. The outcome of these studies will be a robust model and a detailed NMR-imaging study of diffusion-gelation phenomenon. This will serve as input to the macroscopic studies.

Macro-scale studies: The available description of difftision-gelation phenomenon in porous media under either static or dynamic conditions is conjectural at best. The macro-scale studies are aimed at providing a better description of the modification of geological features using physicochemical phenomena during diffusion-gelation. To this end we shall use core flow experiments combined with real time in-situ imaging of the flow through the rock using X-ray computer-aided tomography. By supplementing conventional core flow experiments with this non-intrusive and high spatial resolution
technique, we plan to probe directly the geological heterogeneities of the porous materials ranging from I to 10 cm, as well as their modification by the formation of the gel. We plan to use different sandstone samples, representative of actual reservoir rocks.

A complete laboratory characterization of the mineralogical, textural, and structural properties of these rocks will be carried out. To reflect the modification of the pore structure by the gel and its effect on single-phase and multiphase flow properties we will develop a phenomenological model based on statistical network concepts. The two major outcomes of this study will be a comprehensive description of the diffusiongelation effect on real porous media and of the modification of geological heterogeneities by the gel. The latter will include a phenomenological model for the modification of two-phase flow properties by a gel.

Utilization of the Results
The main users of the knowledge generated in this multidisciplinary project are oil and service companies mostly through their technology development groups.
A timely transfer of the results to the field operators will be ensured by the synergistic co-operation of researchers and practitioners. To promote this co-operation we have set-up a users committee composed mainly of oil and service companies. The use of gels as versatile blocking agents of flow through porous media will cover other applications in earth sciences and engineering as well. Indeed, gel barriers are suitable to contain subsoil and ground water contaminants such as non-aqueous phase liquid pollutants and waters that infiltrate natural occurring coal and ore bodies or (radioactive) waste disposal facilities. The knowledge established in this project will help ground water contaminants.

Gebruikers

Er zijn één andere universiteit en vijf bedrijven bij dit project betrokken.

Projectleider

Dr. P.L.J. Zitha

Technische Universiteit Delft
Civiele Techniek en Geowetenschappen
Centrum voor Technische Geowetenschappen

Postbus 5028
2600 GA Delft

Status van het project

Gestart	: 01-01-2003
Einddatum	: 10-04-2007

Trefwoorden

Gesteente, MRI, Mijnbouw, Poreus materiaal, Tomografie, Vloeistof stroming

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