Publications
54 results found
Aliyu MM, Murphy W, Lawrence JA, et al., 2018, Impact of tectonic faults on the morphology and mechanical properties of grey flints, Pages: 515-520
Grey flints of different morphologies (tabular and nodular) located proximally and distally to large tectonic faults were investigated. Different positions to tectonic faults were considered to examine the influence of geological structures on mechanical properties of flints. Different morphologies were considered to investigate the variation in mechanical properties of flints with morphology. Uniaxial compressive strength, point load strength, tensile strength, density and deformability of grey flints were tested. The results show grey flints are stronger, denser and more rigid than similar flints from zones of tectonic disturbance and faulting, but do not show any trend between flint morphology and mechanical properties. Understanding field variables such as the influence of proximity to tectonic faults and the variation in mechanical properties of flint may provide important input for the successful design of engineering projects and the behaviour of chalk oil reserviours.
Hadlow NW, Lawrence JA, Mortimore RN, 2018, Evaluation and prediction of anticipated depths of weathering (engineering rockhead) as a function of geomorphology in areas of chalk outcrop in southern England and northern France, Pages: 711-720
Conceptual models of weathering in areas of chalk outcrop in southern England indicate that the depth of weathering and engineering rockhead are variable with respect to geomorphology. This variation is typically demonstrated by the transition from interfluve to valley with the depth of weathering changing as result of elevation and aspect. Valley axes are shown to have the deepest weathering, inter-fluves the shallowest and valley slopes a transitional depth with slope gradients on north-west facing slopes generally greater than southeast facing slopes. The main processes considered to have formed the weathering profiles in the Chalk of southern England are periglacial processes associated with seasonal freeze-thaw and mass movement in the last ice-age. In this study, analysis of historical site investigation data, including geophysical surveys, has allowed these conceptual models to be reviewed. This analysis has suggested that two physical transitions occur within the near-surface chalk rock mass that relate to geomorphology. The first, and deepest, transition is considered to represent an opening of discontinuities in the rock mass as a consequence of relaxation in the near surface due to unloading. The second transition is considered to represent an increase in discontinuity frequency in the rock mass due to formation of new discontinuities which progressively intensifies towards the surface. The base of the second transition is generally considered to be engineering rockhead for most engineering situations. Using the data reviewed, a model was developed to estimate the approximate position of these transitions based on relative ground surface elevation within a geomorphological domain. This model may be used to estimate the depth of engineering rockhead based on topographical data, such as a digital terrain model (DTM), in the absence of site investigation data for a site. This has applications for preliminary design where piled foundations or shallow tunnelli
Hussein D, Collier R, Lawrence JA, et al., 2017, Stratigraphic correlation and paleoenvironmental analysis of the hydrocarbon-bearing Early Miocene Euphrates and Jeribe formations in the Zagros folded-thrust belt, Arabian Journal of Geosciences, Vol: 10, ISSN: 1866-7538
The Lower Miocene Euphrates and Jeribe formations are considered as the main targets of the Tertiary petroleum system in the western part of the Zagros Basin. The formations consist of carbonates with some evaporate intercalations of the Dhiban Formation. This study utilized data from a field investigation including newly described outcrop sections and newly discovered productive oil fields within the Kirkuk embayment zone of the Zagros fold and thrust belt such as Sarqala and Kurdamir wells. This work is the first to show a stratigraphic correlation and paleoenvironmental interpretation by investigating both well data and new outcrop data. Three depositional environments were identified, (1) an inner and outer ramp belts environment, (2) shoal environment, and (3) restricted lagoon environment. Within these 3 environments, 12 microfacies were identified, based on the distribution of fauna mainly benthonic foraminifera, rock textures, and sedimentary structures. The inferred shallow water depths and variable salinities in both the Euphrates Formation and Jeribe Formation carbonates are consistent with deposition on the inner ramp (restricted lagoon and shoal) environments. Those found in the Euphrates Formation constrained the depositional environment to the restricted lagoon and shoal environment, while the microfacies in the Jeribe Formation provided evidence for an inner ramp and middle to outer ramp belt environments. This study represents the first detailed research that focuses on the stratigraphic correlation and changes in carbonate facies with the main aim to provide a wider understanding of stratigraphy of these carbonate reservoirs throughout the northern part of Iraq.
Rashid F, Glover PWJ, Lorinczi P, et al., 2017, Microstructural controls on reservoir quality in tight oil carbonate reservoir rocks, Journal of Petroleum Science and Engineering, Vol: 156, Pages: 814-826, ISSN: 0920-4105
In carbonate reservoir rocks the complex interaction between the petrophysical properties corresponds to the various depositional microstructures which are modified by various diagenetic process es that ultimately define the reservoir quality, and pose challenges to the prediction of permeability. The permeability heterogeneity in the carbonate oil reservoirs of northern Iraq varies widely and is thought to be controlled by a number of different factors. In this work, controls of matrix permeability for the Cretaceous Kometan formation selected from five oil fields in Kirkuk embayment zone have been investigated. Helium porosity, helium pulse decay permeability, brine permeability, Nuclear Magnetic Resonance (NMR), Mercury Injection Capillary pressure (MICP), Scanning Electronic Microscopy (SEM), X-Ray diffraction (XRD), and photomicrography of thin section have been used to investigate the effect of microstructure on the variation of permeability in the Kometan Formation. The formation has porosities and permeabilities which range from 0.5 ± 0.5% to 29 ± 0.5% and from 0.65 ± 0.08 μD to 700 ± 0.08 μD respectively. Three types of pore systems have been investigated using pore type, pore size and pore-throat size as characterizing parameters. We have recognized three microstructural types: (i) matrix composed of nano-intercrystalline pores (pore diameter d p smaller than 1 μm and a nanoporous pore-throat size), (ii) matrix composed of micro-intercrystalline pores (1 < d p < 10 μm with a corresponding micron-scale pore-throat distribution), and (iii) meso-intragranular and moldic pores (d p > 10 μm) also with microporous pore-throat radii. The nano-intercrystalline pore system is common across northern Iraq and represents the effective pore system type in the reservoirs of the Kirkuk embayment zone. For these tight carbonate reservoirs, the mineralogy, especially of quartz and clay minerals (illite and smectite
Aliyu MM, Murphy W, Lawrence JA, et al., 2017, Engineering geological characterization of flints, Quarterly Journal of Engineering Geology and Hydrogeology, Vol: 50, Pages: 133-147, ISSN: 1470-9236
The petrographic and mechanical properties of flints from the Burnham (North Landing, Yorkshire, UK), Seaford (East Sussex, UK, and Dieppe, France), and Lewes Nodular (Mesnil-Val, France) Chalk formations have been investigated. Microtexture and mineral composition of flints are studied to understand how the geological and petrophysical properties of the flint affect drilling responses to the rock and investigate any spatial variation. The flints are categorized based on physical observation into white crust and light brownish grey, dark brownish grey and grey flints. Scanning electron microscopy shows textural variation in the classes. The white crust, light brownish grey, brownish grey and grey flints from the Burnham Chalk Formation from North Landing contain more calcite and have coarser, more poorly cemented silica spherules in comparison with similar classes of flint from the Seaford and Lewes Chalk formations from the Anglo-Paris Basin. In these latter flints, the structure is dominated by massive quartz cement with trace calcite independent of location. Strength tests show that the grey flints from North Landing are weaker than equivalents from the Anglo-Paris Basin. It is suggested that variation in engineering properties between grey and the dark brownish grey flints is caused by mineral composition, microtexture, structure and the local or site geology of flint materials.
Stavrou A, Murphy W, Lawrence JA, 2015, Evaluating the influence of block size in cable bolt performance, Future Developments of Rock Mechanics. EUROCK2015 & 64th Geomechanics Colloquium, Publisher: Austrian Society for Geomechanics, Pages: 859-864
Aliyu MM, Murphy W, Collier R, et al., 2015, Classification of flints for drill wear potential, Future Developments of Rock Mechanics. EUROCK2015 & 64th Geomechanics Colloquium, Publisher: Austrian Society for Geomechanics, Pages: 309-314
The assessment of abrasiveness and hardness of rocks have been extensively coveredby previous researchers, with little attention to flints, which were only described as highly abrasive.However, analysis of flints has shown that abrasivity of flints varies. These parameters areimportant inputs for the prediction of drill bit wear rate and design of various parts ofdrilling/tunneling/mining equipment. In this paper, a classification of flints (sampled from theEnglish, French and Danish Chalk) which correlates with the abrasivity and hardness of flints isproposed. The results showed lighter/grey flints (with more calcite) have lower potential to causedrill bit wear as indicated by hardness and geotechnical wear indices than dark flints. This tends tosuggest that even small variations in the carbonate content results in significant variation inabrasivity and that colour can be used as an indication of the potential of flints to cause tool wear.
Rashid F, Glover PWJ, Lorinczi P, et al., 2015, Permeability prediction in tight carbonate rocks using capillary pressure measurements, Marine and Petroleum Geology, Vol: 68, Pages: 536-550, ISSN: 0264-8172
The prediction of permeability in tight carbonate reservoirs presents ever more of a challenge in the hydrocarbon industry today. It is the aim of this paper to ascertain which models have the capacity to predict permeability reliably in tight carbonates, and to develop a new one, if required. This paper presents (i) the results of laboratory Klinkenberg-corrected pulse decay measurements of carbonates with permeabilities in the range 65 nD to 0.7 mD, (ii) use of the data to assess the performance of 16 permeability prediction models, (iii) the development of an improved prediction model for tight carbonate rocks, and (iv) its validation using an independent data set. Initial measurements including porosity, permeability and mercury injection capillary pressure measurements (MICP) were carried out on a suite of samples of Kometan limestone from the Kurdistan region of Iraq. The prediction performance of sixteen different percolation-type and Poiseuille-type permeability prediction models were analysed with the measured data. Analysis of the eight best models is included in this paper and the analysis of the remainder is provided in supplementary material. Some of the models were developed especially for tight gas sands, while many were not. Critically, none were developed for tight gas carbonates. Predictably then, the best prediction was obtained from the generic model and the RGPZ models (R2 = 0.923, 0.920 and 0.915, respectively), with other models performing extremely badly. In an attempt to provide a better model for use with tight carbonates, we have developed a new model based on the RGPZ theoretical model by adding an empirical scaling parameter to account for the relationship between grain size and pore throat size in carbonates. The generic model, the new RGPZ Carbonate model and the two original RGPZ models have been tested against independent data from a suite of 42 samples of tight Solnhofen carbonates. All four models performed very creditably with the
Rashid F, Glover PWJ, Lorinczi P, et al., 2015, Porosity and permeability of tight carbonate reservoir rocks in the north of Iraq, Journal of Petroleum Science and Engineering, Vol: 133, Pages: 147-161, ISSN: 0920-4105
The distribution of reservoir quality in tight carbonates depends primarily upon how diagenetic processes have modified the rock microstructure, leading to significant heterogeneity and anisotropy. The size and connectivity of the pore network may be enhanced by dissolution or reduced by cementation and compaction. In this paper we have examined the factors which affect the distribution of porosity, permeability and reservoir quality in the Turonian-Campanian Kometan Formation, which is a prospective low permeability carbonate reservoir rock in northern Iraq. Our data includes regional stratigraphy, outcrop sections, well logs and core material from 8 wells as well as a large suite of laboratory petrophysical measurements. These data have allowed us to classify the Kometan Formation into three lithological units, two microfacies and three petrofacies. Petrofacies A is characterized by dense and compacted and cemented wackstone/packstone with nanometer size intercrystalline pores and stylolites and presents a poor reservoir quality (porosity range 0.005±0.01 to 0.099±0.01, permeability range 65nD-51μD). Occasional open fractures in Petrofacies A improve reservoir quality resulting in a 2-3 order of magnitude increase in permeability (up to 9.75mD). Petrofacies B is a dissolved wackstone/packstone that contains moldic and vuggy pores (porosity range 0.197±0.01 to 0.293±0.01; permeability range 0.087-4.1mD), with both presenting good reservoir quality, while Petrofacies C is a carbonate mudstone that has undergone dissolution and possibly some dolomitization (porosity range 0.123±0.01 to 0.255±0.01; permeability range 0.065-5mD). All three petrofacies can be distinguished from wireline log data using porosity and NMR measurements. A poroperm plot of all of the data is fitted by a power law of the form k(mD)=aϕ<sup>b</sup> with a=28.044 and b=2.6504 with coefficient of determination, R<sup>2</sup>=0.70
Lawrence JA, Mortimore RN, 2015, Reply to comment on: Lawrence, JA, Mortimore, RN, Stone, KJ, and Busby, JP, 2013. Sea saltwater weakening of chalk and the impact on cliff instability. Geomorphology 191, 14-22, GEOMORPHOLOGY, Vol: 231, Pages: 393-394, ISSN: 0169-555X
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- Citations: 1
Ahmad F, Murphy W, Lawrence JA, et al., 2015, Strength Mobilisation of Rock Masses in Relation to Deep Seated Landslide, Geophysical Research Abstracts 17, EGU2015, 8151
Lawrence JA, Mortimore RN, Stone KJ, et al., 2013, Sea saltwater weakening of chalk and the impact on cliff instability, GEOMORPHOLOGY, Vol: 191, Pages: 14-22, ISSN: 0169-555X
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- Citations: 15
Castedo R, Murphy W, Lawrence J, et al., 2012, A new process-response coastal recession model of soft rock cliffs, GEOMORPHOLOGY, Vol: 177, Pages: 128-143, ISSN: 0169-555X
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- Citations: 50
Lawrence JA, 2011, Soil and Rock Description in Engineering Practice, D. Norbury: Book review, International Journal of Rock Mechanics & Mining Sciences, Pages: 1381-1381
Stavrou A, Lawrence JA, Mortimore RN, et al., 2011, A geotechnical and GIS based method for evaluating risk exposition along coastal cliff environments: a case study of the chalk cliffs of southern England, NATURAL HAZARDS AND EARTH SYSTEM SCIENCES, Vol: 11, Pages: 2997-3011, ISSN: 1561-8633
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- Citations: 15
Quinn JD, Rosser NJ, Murphy W, et al., 2010, Identifying the behavioural characteristics of clay cliffs using intensive monitoring and geotechnical numerical modelling, GEOMORPHOLOGY, Vol: 120, Pages: 107-122, ISSN: 0169-555X
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- Citations: 44
Lawrence JA, 2010, Informing chalk cliff recession management decisions, Civil Engineering Year Book 2010, Pages: 17-18
Senfaute G, Duperret A, Lawrence JA, 2009, Micro-seismic precursory cracks prior to rock-fall on coastal chalk cliffs: a case study at Mesnil-Val, Normandie, NW France, NATURAL HAZARDS AND EARTH SYSTEM SCIENCES, Vol: 9, Pages: 1625-1641, ISSN: 1561-8633
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- Citations: 86
Quinn JD, Murphy W, West LJ, et al., 2008, The use of terrestrial laser scanning, differential GPS surveying and panoramic photography to characterise the landslides and recession of the Holderness Coast, Yorkshire, England, Geo Edmonton 2008. 61st Canadian Geotechnical Conference and 9th Joint CSG/IAH-CNC Groundwater Conference, Publisher: Canadian Geotechnical Society, International Association of Hydrogeologists-CNC, Geotechnical Society of Edmonton, Pages: 411-418
Lawrence JA, Mortimore RN, Eade M, et al., 2007, Developing a strategy for coastal cliff monitoring and management, International Conference on Landslides and Climate Change, Publisher: TAYLOR & FRANCIS LTD, Pages: 81-+
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- Citations: 2
Busby JP, Senfaute G, Gourry JC, et al., 2004, Developing tools for the prediction of catastrophic coastal cliff collapse, In: Proceedings of the 7th International Symposium – Delivering Sustainable Coasts: Connecting Science and Policy, Pages: 596-601
Mortimore RN, Lawrence J, Pope D, et al., 2004, Coastal cliff geohazards in weak rock: the UK Chalk cliffs of Sussex, International Conference on Coastal Rock Slope Instability - Geohazard and Risk Analysis, Publisher: GEOLOGICAL SOC PUBLISHING HOUSE, Pages: 3-31, ISSN: 0267-9914
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- Citations: 48
Mortimore RN, Stone KJ, Lawrence J, et al., 2004, Chalk physical properties and cliff instability, International Conference on Coastal Rock Slope Instability - Geohazard and Risk Analysis, Publisher: GEOLOGICAL SOC PUBLISHING HOUSE, Pages: 75-88, ISSN: 0267-9914
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- Citations: 36
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