Publications
254 results found
Al-Sharji HH, Grattoni CA, Dawe RA, et al., 2006, Flow of oil and water through elastic polymer gels, OIL & GAS SCIENCE AND TECHNOLOGY-REVUE D IFP ENERGIES NOUVELLES, Vol: 56, Pages: 145-152, ISSN: 1294-4475
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- Citations: 21
Al-Ajmi AM, Zimmerman RW, 2006, A new 3D stability model for the design of non-vertical wellbores
The Mohr-Coulomb failure criterion is known to be too conservative in estimating the critical mud pressure required to maintain wellbore stability, due to ignoring the strengthening effect of the intermediate principal stress. To eliminate this deficiency, we have developed a new analytical model to estimate the mud pressure required to avoid shear failure at the wall of non-vertical boreholes (i.e., the collapse pressure). This has been achieved by using a linear elastic and isotropic constitutive model for the stresses, and the Mogi-Coulomb criterion to predict failure. For comparison, the stability analysis has been also carried out using Mohr-Coulomb, the modified Lade criterion, and the Drucker-Prager criterion. We have found that implementing the Mogi-Coulomb law instead of Mohr-Coulomb does indeed lessen the conservative nature of the wellbore stability analysis. In general, the Mogi-Coulomb criterion gives an estimate of the collapse pressure that is similar to that given by the modified Lade criterion in polyaxial stress states, and similar to Mohr-Coulomb in triaxial stress states. By comparison, the Drucker-Prager criterion always underestimates the required mud weight. The developed 3D stability model has been applied in a field case study. © 2006, ARMA, American Rock Mechanics Association.
Al-Ajmi AM, Zimmerman RW, 2006, Stability analysis of vertical boreholes using the Mogi-Coulomb failure criterion, INT J ROCK MECH MIN, Vol: 43, Pages: 1200-1211, ISSN: 1365-1609
A main aspect of wellbore stability analysis is the selection of an appropriate rock failure criterion. The most commonly used criterion for brittle failure of rocks is the Mohr-Coulomb criterion. This criterion involves only the maximum and minimum principal stresses, a, and sigma(3), and therefore assumes that the intermediate stress 92 has no influence on rock strength. As the Mohr-Coulomb criterion ignores the strengthening effect of the intermediate stress, it is expected to be too conservative in estimating the critical mud weight required to maintain wellbore stability. Recently, Al-Ajmi and Zimmerman [Relationship between the parameters of the Mogi and Coulomb failure criterion. Int J Rock Mech Min Sci 2005;42(3):431-39.] developed the Mogi-Coulomb failure criterion, and showed that it is reasonably accurate in modelling polyaxial failure data from a variety of rocks. We then develop a model for the stability of vertical boreholes, using linear elasticity theory to calculate the stresses, and the fully-polyaxial Mogi-Coulomb criterion to predict failure. Our model leads to easily computed expressions for the critical mud weight required to maintain wellbore stability.
Ekneligoda TC, Zimmerman RW, 2006, Compressibility of two-dimensional pores having <i>n</i>-fold axes of symmetry, PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, Vol: 462, Pages: 1933-1947, ISSN: 1364-5021
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- Citations: 33
Al-Mahrooqi SH, Grattoni CA, Muggeridge AH, et al., 2006, Pore-scale modelling of NMR relaxation for the characterization of wettability, J PETROL SCI ENG, Vol: 1-4, Pages: 172-186
Several research groups are currently investigating the determination of wettability using NMR relaxation times. Although correlations with traditional wettability indices have been presented with some success, further effort is needed to relate the wettability at pore-scale to a core-scale measurement of NMR response. For example, a qualitative method using the arithmetic mean of relaxation times at various saturations has been presented [Guan, H., Brougham, D., Sorbie, K.S., Packer, K.J., 2002. Wettability effects in a sandstone reservoir and outcrop cores from NMR relaxation time distributions. J. Petroleum Sci. and Eng. 34, 35-54] and a wettability index that quantifies the amount of surface area that is wetted either by oil or by water, by using the T2 peak at four different saturations has been proposed [Fleury, M., Deflandre, F., 2003. Quantitative evaluation of porous media wettability using NMR relaxometry. Mag. Reson. Imaging 21, 385-387]. Our group at the Imperial College have previously shown experimentally that the T2 distribution provides valuable information about wettability and overall fluid distribution within the pore-space, which is lost if only a single value from the T-2 distribution is considered [Al-Mahrooqi, S.H., Grattoni, C.A., Moss, A. K., Jing, X.D., 2003. An investigation of the effect of wettability on NMR characteristics of sandstone rock and fluid systems. J. Petroleum Sci. and Eng. 39, 389-398].In this paper we use a simple pore-scale model to understand the effect of wetting and its relationship with NMR relaxation times. The model uses triangular capillary pores with a given pore size distribution. The oil/water distribution within the pores is obtained as a function of capillary pressure and wettability. At a given capillary pressure, the volumes and surface areas of water and oil are calculated for each individual pore. This allows us to calculate the theoretical T-2 distribution for that pore size distribution as a function of
Hudson JA, Zimmerman RW, 2006, Peer review policy for the IJRMMS, International Journal of Rock Mechanics and Mining Sciences, Vol: 43, ISSN: 1365-1609
Zimmerman R, Gurevich M, Mosyak A, et al., 2006, Heat transfer to air-water annular flow in a horizontal pipe, INTERNATIONAL JOURNAL OF MULTIPHASE FLOW, Vol: 32, Pages: 1-19, ISSN: 0301-9322
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- Citations: 18
A Al-Ajmi, R W Zimmerman, 2006, Stability analysis of deviated boreholes using the Mogi-Coulomb failure criterion, with applications to some oil and gas reservoirs (SPE 104035), 2006 SPE Asia-Pacific Drilling Technical Conference, Publisher: Society of Petroleum Engineers
Tavassol Z, Zimmerman RW, Blunt MJ, 2005, Analytic analysis for oil recovery during counter-current imbibition in strongly water-wet systems, Upscaling Multiphase Flow in Porous Media: From Pore to Core and Beyond, Pages: 173-189, ISBN: 9781402035135
We study counter-current imbibition, where a strongly wetting phase (water) displaces non-wetting phase spontaneously under the influence of capillary forces such that the non-wetting phase moves in the opposite direction to the water. We use an approximate analytical approach to derive an expression for saturation profile when the viscosity of the non-wetting phase is non-negligible. This makes the approach applicable to water flooding in hydrocarbon reservoirs, or the displacement of non-aqueous phase liquid (NAPL) by water. We find the recovery of non-wetting phase as a function of time for one-dimensional flow. We compare our predictions with experimental results in the literature. Our formulation reproduces experimental data accurately and is superior to previously proposed empirical models. © 2005 Springer.
Tavassoli Z, Zimmerman RW, Blunt MJ, 2005, Analysis of counter-current imbibition with gravity in weakly water-wet systems, JOURNAL OF PETROLEUM SCIENCE AND ENGINEERING, Vol: 48, Pages: 94-104, ISSN: 0920-4105
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- Citations: 57
Al-Ajmi AM, Zimmerman RW, 2005, Relation between the Mogi and the Coulomb failure criteria, INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES, Vol: 42, Pages: 431-439, ISSN: 1365-1609
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- Citations: 352
Makurat A, Zimmerman RW, 2005, Special issue: Rock physics and geomechanics - Preface, INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES, Vol: 42, Pages: 871-872, ISSN: 1365-1609
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- Citations: 1
Lutz MP, Zimmerman RW, 2005, Effect of an inhomogeneous interphase zone on the bulk modulus and conductivity of a particulate composite, INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES, Vol: 42, Pages: 429-437, ISSN: 0020-7683
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- Citations: 82
Tavassoli Z, Zimmerman RW, Blunt MJ, 2005, Analytic analysis for oil recovery during counter-current imbibition in strongly water-wet systems, TRANSPORT IN POROUS MEDIA, Vol: 58, Pages: 173-189, ISSN: 0169-3913
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- Citations: 73
J J de la Porte, C A Kossack, R W Zimmerman, 2005, The effect of fracture relative permeabilities and capillary pressures on the numerical simulation of naturally fractured reservoirs (SPE 95241), Dallas, 2005 SPE Annual Technical Conference and Exhibition, Publisher: Society of Petroleum Engineers
Al-Yaarubi AH, Pain CC, Grattoni CA, et al., 2005, Navier-Stokes simulations of fluid flow through a rock fracture, Dynamics of Fluids and Transport in Fractured Rocks, Editors: Faybishenko, Witherspoon, Gale, Washington, DC, Publisher: American Geophysical Union, Pages: 55-64, ISBN: 9780875904276
Ai-Yaarubi AH, Pain CC, Grattoni CA, et al., 2005, Navier-Stokes simulations of fluid flow through a rock fracture, 2nd International Symposium on Dynamics of Fluids in Fractured Rock, Publisher: AMER GEOPHYSICAL UNION, Pages: 55-64, ISSN: 0065-8448
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- Citations: 22
Grattoni CA, Luckham PF, Jing XD, et al., 2004, Polymers as relative permeability modifiers: adsorption and the dynamic formation of thick polyacrylamide layers, JOURNAL OF PETROLEUM SCIENCE AND ENGINEERING, Vol: 45, Pages: 233-245, ISSN: 0920-4105
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- Citations: 53
Al-Wardy W, Zimmerman RW, 2004, Effective stress law for the permeability of clay-rich sandstones, JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, Vol: 109, ISSN: 2169-9313
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- Citations: 87
Zimmerman RW, Al-Yaarubi A, Pain CC, et al., 2004, Nonlinear regimes of fluid flow in rock fractures, INT J ROCK MECH MIN SCI, Vol: 41, Pages: 384-384
Zimmerman RW, Al-Yaarubi A, Pain CC, et al., 2004, Non-linear regimes of fluid flow in rock fractures, Regional ISRM Sinorock 2004 Symposium, Publisher: PERGAMON-ELSEVIER SCIENCE LTD, Pages: 384-384, ISSN: 1365-1609
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- Citations: 368
Zimmerman R, 2004, Deep impressions, Natural History, Vol: 113, Pages: 57-61, ISSN: 0028-0712
The Earth's core may never be sampled directly, but its effects make themselves felt every day.
Zimmerman R, Main I, 2004, Chapter 7 Hydromechanical Behavior of Fractured Rocks, Vol: 89, Pages: 363-421, ISSN: 0074-6142
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- Citations: 77
Zimmerman RW, Al-Yaarubi A, Pain CC, et al., 2004, Non-linear regimes of fluid flow in rock fractures, International Journal of Rock Mechanics and Mining Sciences, Vol: 41, Pages: 163-169, ISSN: 1365-1609
We have conducted high-resolution Navier-Stokes simulations and laboratory measurements of fluid flow in a natural sandstone fracture. First, epoxy casts were made of the two opposing fracture surfaces. The surface profiles of the two surfaces were then measured at a vertical resolution of ±2 μm, every 20 μm in the x and y-directions, over 2 cm × 2 cm regions of the fracture. These data were then used to create a finite-element mesh for the fracture void space, and the Navier-Stokes equations were solved within this domain. Flow experiments were also conducted within the same fracture casts, over a range of flowrates. The simulations confirm the existence of a weak inertia regime for Reynolds numbers in the range of 1-10, in which the non-Darcy pressure drop varies with the cube of the flowrate. Although of theoretical interest, this effect is, however, probably too small to be of engineering interest. At Reynolds numbers above about 20, both the simulations and experiments exhibit a Forchheimer-type regime, in which the non-Darcy pressure drop is quadratic in the flowrate. © 2004 Elsevier Ltd.
Lock PA, Jing X, Zimmerman RW, 2004, Comparison of methods for upscaling permeability from the pore scale to the core scale, Journal of Hydraulic Research, Vol: 42, Pages: 3-8, ISSN: 0022-1686
Several methods are compared for estimating the core-scale permeability of a rock whose pore space is idealized as consisting of a cubic network of pore tubes having a distribution of pore-scale hydraulic conductances. The conductance distribution of the pores is estimated from image analysis of scanning electron micrographs of rock sections. An explicit solution of the network equations is used as a benchmark to establish the "exact" macroscopic permeability. The other three upscaling methods used are Kirkpatrick's isotropic effective medium approximation, Bernasconi's anisotropic effective medium approximation, and the generalized perturbation ansatz (GPA) proposed by Gelhar and Axness. The analysis is carried out on a suite of petroleum reservoir sandstones from the North Sea, with measured core-scale permeabilities ranging from 20 to 500 mD. The log-variances of the pore-scale hydraulic conductance distribution were in the range of 2-3. The predictions of both the Kirkpatrick equation and the GPA are in each case within 10% of those computed by explicit network calculation, and all permeability predictions are generally within a factor of two of the core-scale values measured in the laboratory. © 2004 International Association of Hydraulic Engineering and Research.
Al-Mahrooqi SH, Grattoni CA, Muggeridge AH, et al., 2004, Pore-scale modelling of NMR relaxation for the characterization of wettability, 8th international symposium on reservoir wettability, Houston, Texas
Al-Mahrooqi SH, Grattoni CA, Muggeridge AH, et al., 2004, Pore-scale modelling of NMR relaxation for the characterization of wettability, 8th international symposium on reservoir wettability, Houston, Texas
Lock PA, Jing XD, Zimmerman RW, 2004, Comparison of methods for upscaling permeability from the pore scale to the core scale, International Groundwater Symposium, Publisher: TAYLOR & FRANCIS LTD, Pages: 3-8, ISSN: 0022-1686
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- Citations: 16
Zimmerman RW, Main IG, 2004, Hydromechanical behaviour of fractured rocks, Mechanics of Fluid-Saturated Rocks, Editors: Guéguen, Boutéca, London and San Diego, Publisher: Academic Press, Pages: 363-421, ISBN: 9780123053558
W Al-Wardy, R W Zimmerman, 2004, Skempton coefficient of clean and clay-rich sandstones, 17th Eng. Mech. Conf. Amer. Soc. Civil Engineers
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