R. S. Haszeldine
University of Edinburgh
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Featured researches published by R. S. Haszeldine.
Clay Minerals | 2000
Calum I. Macaulay; Anthony E. Fallick; R. S. Haszeldine; Colin M. Graham
Abstract The stable isotopic compositions of diagenetic minerals can provide valuable constraints on the sources, precipitation temperatures and relative timing of cements in reservoir rocks. This type of information is essential when trying to understand and predict the distribution of cements in the subsurface, and their impact on reservoir quality. Conventional isotope methods contribute to answers to many diagenetic problems, but where core or time are scarce, or where good mineral separation is unobtainable, laser-based stable isotope methods offer several advantages. These include the ability to analyse carbonates, sulphides and anhydrite in situ with 50-100 m resolution, simple and clear sample and analysis viewing optics, savings on sample preparation time and greatly reduced sample size requirements. Diagenetic silicates such as quartz and clay cements cannot be analysed in situ by laser but, where in situ analysis of quartz δ18O is demanded, ion microprobe analysis can provide very high resolution (20-30 μm) capability with a precision of ±1‰.
Clays and Clay Minerals | 1993
Anthony E. Fallick; Calum I. Macaulay; R. S. Haszeldine
AbstractAuthigenic kaolinite and illite are important diagenetic minerals in the Magnus Sandstone, a giant oil reservoir in the northern North Sea. These clay minerals, separated from three wells, show considerable ranges in their oxygen isotopic composition (δ8OSMOW = +9 to + 16%) and hydrogen isotopic composition (δDSMOW = - 55 to - 105%). The variations in δ18O and δD are positively linearly correlated with a high degree of statistical significance for both kaolinite and illite:
AAPG Bulletin | 1997
M W Wilkinson; David Darby; R. S. Haszeldine; Gary Couples
Clay Minerals | 2000
Ame Marchand; R. S. Haszeldine; Calum I. Macaulay; Rudy Swennen; Anthony E. Fallick
\begin{array}{c}{\rm{Kaolinite}}:\;\;{\rm{n}}=12;\;\;\;{\rm{\delta}D}=6.1\;\;{\rm{{\delta}}^{18}}{\rm{O}}-169;\;\;\;{\rm{r}}=0.66(>95\%)\\ {\rm{Illite}}:\;\;\;\;\;{\rm{n}}=11;\;\;\;\;\;\;{\rm{\delta}D}=5.9\;\;\;{\rm{{\delta}}^{18}}{\rm{O}}-159;\;\;\;{\rm{r}}=0.78(>99\%).\end{array}
Petroleum Geoscience | 1997
D. Darby; Mark Wilkinson; Anthony E. Fallick; R. S. Haszeldine
Clay Minerals | 2000
Calum I. Macaulay; Anthony E. Fallick; R. S. Haszeldine; G. McAulay
Kaolinite:n=12;δD=6.1δ18O−169;r=0.66(>95%)Illite:n=11;δD=5.9δ18O−159;r=0.78(>99%). Formation of the clays in a pore fluid of uniform isotopic composition over a range of temperatures appears unlikely. It is suggested that the observed relationships between clay mineral δ18O and δD are perhaps best explained by a model of precipitation at more or less constant temperature from pore fluids which varied isotopically across the oilfield. The isotopic composition of the formation waters would then lie along the line: δDw = 6.2 δl8Ow - 50. This is most plausibly interpreted as a mixing line with suggested minimal endmembers at (δ18O, δD) values of (+4, -24) and (-4, -76). The first of these represents reasonable isotopic values for Magnus Sandstone formation waters. Although δ18O of the second is compatible with an evolved Cretaceous meteoric water, its δD value is difficult to understand in the context of the model.
Clay Minerals | 2000
R. N. T. Stewart; R. S. Haszeldine; Anthony E. Fallick; Mark Wilkinson; Calum I. Macaulay
The overpressure history of a sandstone can be estimated using a numerical model if the burial curve and geological setting are known. From the resulting effective stress, the maximum potential porosity (MPP) can be calculated. The MPP is the maximum porosity the rock could theoretically hold open at the modeled burial depth and pore pressure. Measured rock porosities should be at or below the MPP. We have determined the MPP history for the Fulmar Formation sandstones (Upper Jurassic) of the Central Graben, North Sea, and have compared the predictions to measured core data. We conclude that for the majority of the Fulmar Formation sandstones, the porosity evolution is a simple pattern of reduction during burial caused by compaction and cementation. However, in wells sited close to regional overpressure leak-off points, the porosity has been significantly increased from an end-of-Oligocene low (mean 21%) to the present-day values (mean 31%). This porosity increase occurred by feldspar dissolution, with the reaction products being removed from the sandstones. Secondary porosity generation and the export of solute occurred while the sandstone was highly overpressured, although still part of an open hydrogeological system. The generation of porosity within deeply buried sandstones is of commercial importance and potentially can be predicted.
Clay Minerals | 2000
Mark Wilkinson; R. S. Haszeldine; Anthony E. Fallick; M. Osborne
Abstract In the Miller Field, diagenetic quartz abundance, isotopic compositions and salinities of quartz-cementing fluids display a distinct pattern which is related to the structural depth of the reservoir sandstones. Quartz cement volumes increase from the crest of the field (average 6.0±1.5%) towards the flanks of the field (average 13.2±2.1%) and directly reduce reservoir porosity. By integrating petrographic observations with results of fluid inclusion measurements and O isotope analyses of diagenetic quartz, the pattern of quartz cementation is seen to be related to the reservoir filling history. Oil filled the crest of the reservoir first and prevented extensive quartz cementation. At greater depth in the reservoir oil zone, quartz overgrowths continued to precipitate until inhibited by the developing oil column. Oxygen isotope compositions of diagenetic quartz imply that quartz cement continued to precipitate in the water zone of the reservoir up to the present day.
Geological Society, London, Petroleum Geology Conference series | 1999
R. S. Haszeldine; Mark Wilkinson; D. Darby; Calum I. Macaulay; Gary Douglas Couples; Anthony E. Fallick; C. G. Fleming; R. N. T. Stewart; G. McAulay
K-Ar age dates of authigenic illite from sandstones in the UK south Central Graben have a bimodal distribution. In contrast to established hypotheses of thermal triggers, this illite growth is explained by changes in hydrogeological history. Fluid motion during burial can hence be dated. Illite growth at 84-58 Ma on the graben margins was coincident with rapid subsidence of the Graben axis and consequent expulsion of pore fluids onto the margins. This event pre-dated both overpressure, and the secondary migration and accumulation of hydrocarbon in the region. Illite growth was probably caused by increased solute transport rates during pore fluid motion. Illite growth on an axial high (33-30 Ma) occurred during overpressured conditions. This was triggered either by: (1) downward fluid migration as a consequence of overpressure release. These fluids carried carboxylic acids or hydrocarbons from the highly overpressured Kimmeridge Clay Formation into the less pressured Fulmar Sandstone Formation; or (2) a decrease in water-rock ratios as fluid flow declined within the sandstones, as a consequence of overpressure build-up. Published experiments show that illite growth is favoured by low water-rock ratios.
AAPG Bulletin | 1992
Calum I. Macaulay; R. S. Haszeldine; Anthony E. Fallick
Abstract Carbonate cements in Tertiary reservoir sandstones from the northern North Sea have distinctive carbon isotopic compositions (δ13C). Oil migration up faults from deeper structures and biodegradation of oil pools are factors of particular importance in influencing the δ13C of carbonate cements in these sandstones. As a result, δ13C can be used as an exploration guide to locating the positions of vertical leakoff points from the Jurassic source rocks. The histogram distribution of δ13C in these carbonate cements is trimodal, with peaks at around -26, -3 and +12‰ (ranges -22 to -30, +2 to -10 and +8 to +18‰, respectively). Bacterial processes played major roles in determining this distribution, with oxidative biodegradation of oil resulting in carbonate cements with very negative compositions and bacterial fermentation resulting in the positive δ13C cements. δ13C distribution patterns may be used to differentiate Tertiary reservoir sandstones from Jurassic in the northern North Sea, and these regional carbonate cement δ13C datasets allow geologically useful inferences to be drawn from δ13C data from new sample locations.