Miller Field Research Articles

Pore network analysis of Brae Formation sandstone, North Sea

In this work, we apply digital rock physics (DRP) to characterize the pore networks of the Brae Formation sandstones from two different wells in the Miller field area (North Sea, UK). Using X-ray micro-CT scans, we calculate the porosity and permeability and generate pore network models to assess pore shape characteristics. The porous samples are marked by macroporosities ranging from 4.9% to 15.2% with the effective porosities varying from 0 to 14.8%. The samples also contained some microporosity hosted in secondary and accessory mineral phases, varying between 2.6% and 10.7%. Pore network model results for total porosity indicate that the samples have median pore and throat radii ranging from 5.5 μm to 16.8 μm and 6.4 μm–12.9 μm, respectively. The throat length of all samples has a median value ranging between 36.3 μm and 82.4 μm. The ratio between effective porosity and total porosity (φ*) varies with total porosity (φ) following the exponential relation φ*=0.98−e−(φ−0.032)/0.028. Pore network connectivity is established at a porosity of 3% and full communication is achieved at porosities exceeding 10%. Permeability was found to vary with total porosity with an exponent of 3.67. Based on these observations and the results from our models, the connectivity of the pore network has important implications for predicting reservoir performance during large scale subsurface projects such as hydrocarbon production and CO2 storage.

Streamline Simulation of Barium Sulfate Precipitation Occurring Within the Reservoir Coupled With Analyses of Observed Produced-Water-Chemistry Data To Aid Scale Management

SummaryIn waterflooded reservoirs under active scale management, produced-water samples are routinely collected and analyzed, yielding information on the evolving variations in chemical composition. These produced-water chemical-composition data contain clues as to the fluid/fluid and fluid/rock interactions occurring in the subsurface, and are used to inform scale-management programs designed to minimize damage and enable improved recovery.In this interdisciplinary paper, the analyses of produced-water compositional data from the Miller Field are presented to investigate possible geochemical reactions taking place within the reservoir. The 1D and 2D theoretical model has been developed to test the modeling of barium sulfate precipitation implemented in the streamline simulator FrontSim. A completely 3D streamline simulation study for the Miller Field is presented to evaluate brine flow and mixing processes occurring in the reservoir by use of an available history-matched streamline reservoir-simulation model integrated with produced-water chemical data. Conservative natural tracers were added to the modeled injection water (IW), and then the displacement of IW and the behaviors of the produced water in two given production wells were studied further. In addition, the connectivity between producers and injectors was investigated on the basis of the comparison of production behavior calculated by the reservoir model with produced-water chemical data. Finally, a simplified model of barite-scale precipitation was included in the streamline simulation, and the calculation results with and without considering barite precipitation were compared with the observed produced-water chemical data. The streamline simulation model assumes scale deposition is possible everywhere in the formation, whereas, in reality, the near-production-well zones were generally protected by squeezed scale inhibitor, and, thus, the discrepancies between modeled and observed barium concentrations at these two given wells diagnose the effectiveness of the chemical treatments to prevent scale formation.

Changes in plant abundance on a coastal beach following two major storm surges1

Abstract Coastal beaches often harbor a relatively small number of specialized herbaceous species that are locally abundant, providing stabilization of sediments regularly subjected to wind and sand movement. However, rare storm events can cause water surges that completely wash over the beach and cause a major disturbance to the plant community. This study examines frequencies and densities of key herbaceous species on Miller Field Beach, Staten Island, New York, before and after major storm surges caused by Hurricane Irene (August 2011) and Superstorm Sandy (October 2012). Changes in vegetation were documented by surveys of the same 45–75-m section of beach, using quadrats (33 cm diameter) placed at 3-m intervals along transects, in mid-September of 2007, 2009, 2011 (2 wk after Irene), 2012 (1 mo before Sandy), and 2013. Native annual species, including Cenchrus tribuloides L. (dune sandbur), Heterotheca subaxillaris (Lam.) Britton & Rusby (camphorweed), and Triplasis purpurea (Walter) Chapm. (purple sa...

Temporal and spatial development of scale formation: One-dimensional hydrogeochemical transport modeling

Abstract Seawater injection is commonly applied for reservoir pressure maintenance even though it may cause scaling. The admixture of injected seawater to reservoir aquifers triggers a series of complex hydrogeochemical water–rock–gas interactions leading to scale formation within the aquifer and also at the location of the production wells. Basically, the fraction of seawater in the produced water depends on the prevailing hydraulic flow conditions, and determines the type and amount of minerals precipitated or dissolved. To quantify such processes with temporal and spatial resolution, we developed a one-dimensional hydrogeochemical transport model that relies on chemical equilibrium thermodynamics and that additionally considers temporal and spatial aspects in contrast to a batch modeling approach. Our test site is the Miller oilfield, UK North Sea, where hydrogeochemical interactions achieve near-equilibrium conditions within a reaction time span of less than 2 years. Our modeling results for the Miller field test site show a fairly good accordance between (1) the modeled and measured temporal compositional development of produced water as well as between (2) the observed and modeled composition of the scale mineral assemblage formed in the production well. This validates that our one-dimensional hydrogeochemical transport model is capable of reproducing the simultaneously occurring and coupled hydraulic (fluid flow) and hydrogeochemical processes (water–rock–gas interactions). Besides identification and quantitative prediction of mineral dissolution and precipitation, the transport model allows us to determine where such processes occur within the reservoir and/or at the location of the wells. In the Miller field test site, primary calcite and microcrystalline quartz dissolve close to the injection well, which could enhance the secondary porosity locally within the reservoir aquifer. In contrast, massive formation of scale minerals (strontium bearing barite is greatly favored over calcite and microcrystalline quartz) occurs close to or in the production well. Moreover, specific scale minerals (mainly strontium bearing barite in the test site) precipitate along the flow path of formation water–seawater mixtures. Additionally, the modeling results demonstrate that batch modeling and calculation of mineral saturation indices based on one original seawater analysis and one formation water analysis are incapable of predicting which scale minerals actually form.

Hydrogeochemical modelling of fluid–rock interactions triggered by seawater injection into oil reservoirs: Case study Miller field (UK North Sea)

Abstract A hydrogeochemical model is presented and applied to quantitatively elucidate interdependent reactions among minerals and formation water–seawater mixtures at elevated levels of CO 2 partial pressure. These hydrogeochemical reactions (including scale formation) occur within reservoir aquifers and wells and are driven by seawater injection. The model relies on chemical equilibrium thermodynamics and reproduces the compositional development of the produced water (formation water–seawater mixtures) of the Miller field, UK North Sea. This composition of the produced water deviates from its calculated composition, which could result solely from mixing of both the end members (formation water and seawater). This indicates the effect of hydrogeochemical reactions leading to the formation and/or the dissolution of mineral phases. A fairly good match between the modelled and measured chemical composition of produced water indicates that hydrogeochemical interactions achieve near-equilibrium conditions within the residence time of formation water–seawater mixtures at reservoir conditions. Hence the model enables identification of minerals (including scale minerals), to quantitatively reproduce and to predict their dissolution and/or formation. The modelling results indicate that admixing of seawater into formation water triggers the precipitation of Sr–Barite solid solution, CaSO 4 phases and dolomite. In contrast, calcite and microcrystalline quartz are dissolved along the seawater flow path from the injection well towards the production well. Depending on the fraction of seawater admixed, interdependent reactions induce profound modifications to the aquifer mineral phase assemblage. At low levels of seawater admixture, Ba–Sr sulfate solid solution is precipitated and coupled to concurrent dissolution of calcite and microcrystalline quartz. Massive dissolution of calcite and the formation of CaSO 4 phases and dolomite are triggered by intense seawater admixture. Hydrogeochemical modelling to reproduce observed compositional trends, resulting from an increase of the seawater fraction, can help (1) to explain changing production properties and (2) to predict the type and the degree of scaling depending on the content of injected seawater.

Late Holocene slip rate of the San Andreas fault and its accommodation by creep and moderate-magnitude earthquakes at Parkfield, California

Research Article| March 01, 2011 Late Holocene slip rate of the San Andreas fault and its accommodation by creep and moderate-magnitude earthquakes at Parkfield, California Nathan A. Toké; Nathan A. Toké 1School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, USA Search for other works by this author on: GSW Google Scholar J Ramón Arrowsmith; J Ramón Arrowsmith 1School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, USA Search for other works by this author on: GSW Google Scholar Michael J. Rymer; Michael J. Rymer 2U.S. Geological Survey, 345 Middlefield Road, MS 977, Menlo Park, California 94025-3591, USA Search for other works by this author on: GSW Google Scholar Angela Landgraf; Angela Landgraf 3Institut für Erd- und Umweltwissenschaften, Universität Potsdam, 14476 Potsdam, Germany Search for other works by this author on: GSW Google Scholar David E. Haddad; David E. Haddad 1School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, USA Search for other works by this author on: GSW Google Scholar Melanie Busch; Melanie Busch 1School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, USA Search for other works by this author on: GSW Google Scholar Joshua Coyan; Joshua Coyan 1School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, USA Search for other works by this author on: GSW Google Scholar Alexander Hannah Alexander Hannah 4Department of Geological Sciences, California State University Northridge, Northridge, California 91330, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Nathan A. Toké 1School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, USA J Ramón Arrowsmith 1School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, USA Michael J. Rymer 2U.S. Geological Survey, 345 Middlefield Road, MS 977, Menlo Park, California 94025-3591, USA Angela Landgraf 3Institut für Erd- und Umweltwissenschaften, Universität Potsdam, 14476 Potsdam, Germany David E. Haddad 1School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, USA Melanie Busch 1School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, USA Joshua Coyan 1School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, USA Alexander Hannah 4Department of Geological Sciences, California State University Northridge, Northridge, California 91330, USA Publisher: Geological Society of America Received: 19 Jun 2010 Revision Received: 05 Oct 2010 Accepted: 08 Oct 2010 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2011 Geological Society of America Geology (2011) 39 (3): 243–246. https://doi.org/10.1130/G31498.1 Article history Received: 19 Jun 2010 Revision Received: 05 Oct 2010 Accepted: 08 Oct 2010 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Nathan A. Toké, J Ramón Arrowsmith, Michael J. Rymer, Angela Landgraf, David E. Haddad, Melanie Busch, Joshua Coyan, Alexander Hannah; Late Holocene slip rate of the San Andreas fault and its accommodation by creep and moderate-magnitude earthquakes at Parkfield, California. Geology 2011;; 39 (3): 243–246. doi: https://doi.org/10.1130/G31498.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Investigation of a right-laterally offset channel at the Miller's Field paleoseismic site yields a late Holocene slip rate of 26.2 +6.4/−4.3 mm/yr (1σ) for the main trace of the San Andreas fault at Parkfield, California. This is the first well-documented geologic slip rate between the Carrizo and creeping sections of the San Andreas fault. This rate is lower than Holocene measurements along the Carrizo Plain and rates implied by far-field geodetic measurements (∼35 mm/yr). However, the rate is consistent with historical slip rates, measured to the northwest, along the creeping section of the San Andreas fault (<30 mm/yr). The paleoseismic exposures at the Miller's Field site reveal a pervasive fabric of clay shear bands, oriented clockwise oblique to the San Andreas fault strike and extending into the uppermost stratigraphy. This fabric is consistent with dextral aseismic creep and observations of surface slip from the 28 September 2004 M6 Parkfield earthquake. Together, this slip rate and deformation fabric suggest that the historically observed San Andreas fault slip behavior along the Parkfield section has persisted for at least a millennium, and that significant slip is accommodated by structures in a zone beyond the main San Andreas fault trace. 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Carbonate cements in Miller field of the UK North Sea: a natural analog for mineral trapping in CO2 geological storage

Miller field of the North Sea has had high concentrations of natural CO2 for ~70 Ma. It is an ideal analog for the long-term fate of CO2 during engineered storage, particularly for formation of carbonate minerals that permanently lock up CO2 in solid form. The Brae Formation reservoir sandstone contains an unusually high quantity of calcite concretions; however, C and O stable isotopic signatures suggest that these are not related to the present-day CO2 charge. Margins of the concretions are corroded, probably because of reduced pH due to CO2 influx. Dispersed calcite cements are also present, some of which postdate the CO2 charge and, therefore, are the products of mineral trapping. It is calculated that only a minority of the reservoired CO2 in Miller (6–24%) has been sequestrated in carbonates, even after 70 Ma of CO2 emplacement. Most of the CO2 accumulation is dissolved in pore fluids. Therefore, in a reservoir similar to the Brae Formation, engineered CO2 storage must rely on physical retention mechanisms because mineral trapping is both incomplete and slow.

The abundance and size of annual herbs in a coastal beach community is related to their distance from seaside goldenrod (Solidago sempervirens)1

The plant community of a coastal beach typically shows great spatial heterogeneity in distribution and abundance. Solidago sempervirens (seaside goldenrod) is a large perennial that can potentially impact the many smaller annual plants, both native and exotic, that comprise the primary vegetation in the pioneer zone. The primary question addressed was: do plants of two native and two alien annuals nearer to S. sempervirens show a detectable reduction in density and size compared to those further away? Populations of Triplasis purpurea and Cenchrus tribuloides (native grasses), and Digitaria sanguinalis and Mollugo verticillata (ruderals), were surveyed in quadrats at distances of 20–200 cm from S. sempervirens individuals at Miller Field Beach, Staten Island, NY. Densities of both native grasses and D. sanguinalis, but not M. verticillata, showed significant reductions closest to S. sempervirens. Size of C. tribuloides was significantly reduced close to S. sempervirens. Intraspecific density had an effect on T. purpurea size, but not proximity to S. sempervirens. Because the opportunistic weeds were not greatly affected by S. sempervirens, it is suggested that the effect of seaside goldenrod on this beach community, whatever the mechanism, is primarily manifested by a reduction in the density of the native species T. purpurea and C. tribuloides. Seaside goldenrod joins American beachgrass (Ammophila breviligulata) as another perennial apparently structuring annual coastal plant communities.

Innovative, Integrated, and Cost-Effective Chemical Management on the Miller Platform

Summary The BP-operated Miller Field poses a unique chemical challenge as it has, arguably, the harshest oilfield scaling regime in the North Sea, if not the world. Some 3 million litres of chemical are consumed each year and the management, supply, use, and performance of every aliquot of chemical is imperative to see Miller through to its planned cessation of production. The Miller Field is a mature North Sea asset and produces a potential of 80,000 BWPD with its 16,000 BOPD. The unique challenge posed by Miller is that the produced water contains very high concentrations of scale-forming components combined with a very high corrosivity potential. Chemicals are routinely deployed to control scale, corrosion, emulsions, foam, biological fouling, and hydrates. Two major step changes have occurred in the past 12 months that have delivered significant improvement to chemical management processes. The first step is the use of a novel, best-in-class, scale-inhibitor chemistry. Two years were spent in an industrywide search as well as developing and extensively testing the chemical in the laboratory. The new chemical is now deployed on more than 75% of the Miller wells. The longevity of scale-prevention treatments has been doubled on some wells when compared to the incumbent products. The second step change was the application of innovative relative permeability modifier chemistries that not only increase oil production but actually shut off water production. Cross-linked polymer gels are pumped down wells and inflate in the presence of water, effectively blocking the flow path, but deflate in the presence of oil, allowing flow. By implementing these changes, significant steps have been taken toward ensuring that continuation of production to the proposed cessation of production remains a viable proposition.

Rapid fluid-rock interaction in oilfield reservoirs

We report here on production data from a North Sea oilfield that demonstrates that significant mineral-fluid interactions took place in the reservoir on a time scale of months. A time series of produced water compositions from the BP-operated Miller Field, in the UK sector of the North Sea, was generated over a period of more than 7 yr when seawater was being injected for secondary recovery and pressure maintenance. Deviation of the produced water chemistry from linear mixing of seawater and formation water indicates that mineral-water interactions took place in the reservoir. Of particular significance is the evidence for rapid reaction of injected water with silicates. The safety case for CO 2 storage in such reservoirs is greatly facilitated if it can be shown to react with the host pore waters and rocks on a human time scale, and the results of this study indicate that this is indeed the case.

Deep Downhole Chemical Injection on BP-Operated Miller: Experience and Learning

Summary The BP-operated Miller field poses a unique chemical challenge because it has arguably the harshest oilfield scaling regime in the North Sea, if not the world. An average of three to four squeeze treatments per week are performed across the online wells, creating tremendous operational, chemical, and logistical challenges. This produces the ideal environment in which to evaluate new technologies and engineering solutions in an attempt to increase the wells’ overall efficiency. Deep downhole chemical injection (DDHCI) was installed on Well A26/08 and brought on line in July 2003. The Miller DDHCI is unique to the industry because it allows the injection of a scale inhibitor at the perforations by means of a tail pipe, essentially protecting the whole of the tubing from scale deposition. This approach has the potential to reduce the need for additional scale control through squeeze treatments. Much emphasis has been placed on the efficiency of scale protection that DDHCI offers. A year of flowing the well under the protection of the continuous-injection chemical has yielded much information about the nature of the chemical delivery and inhibitor efficiency. Much also has been learned about the pumping hardware required to ensure continued performance. Further information has been provided by two intensive sampling exercises that have allowed independent analysis of the squeeze chemicals and the injected chemical. This paper details the design criteria of the DDHCI completion as well as the philosophy of installing such a device. It then gives details on the management strategy of using DDHCI in a proactive manner to maximize the time between squeeze treatments.

The effect of hydrocarbons on quartz cementation: diagenesis in the Upper Jurassic sandstones of the Miller Field, North Sea, revisited

Variable quartz cementation and porosity distribution in the Upper Jurassic Brae Formation deep-water sandstone reservoir of the Miller Field (UK, North Sea) is mainly controlled by the amount of coatings on the quartz grains. Oil was possibly present in the pore space for the last 40 Ma, but had no significant effect on preserving porosity in the oil leg relative to the water leg. Samples with anomalously high porosities, which commonly occur in the shallowest sandstone intervals, are microquartz coated, and it is a misinterpretation to explain these high porosities as due to hydrocarbons inhibiting quartz cementation. Porosity preservation due to microquartz coating is quite common in Upper Jurassic sandstones in the North Sea. Kinetic modelling of quartz cementation with the Exemplar program correctly predicts observed quartz cement volumes in the Brae Formation outside the microquartz-coated zones, when high quality petrographic data, including abundance of clay coatings, are provided as input. Significant overprediction of quartz cement volumes occurs only for samples where scanning electron microscope analysis shows microquartz coatings to be present. Failure to recognize grain coating as one of the major parameters controlling quartz cementation may lead to incorrect geological models of reservoir quality and selection of inappropriate exploration or production strategies.

Chapter VIII: THE COSMOPOLITAN PERIOD: SINCE 1898

C<scp>hapter</scp> VIII: THE COSMOPOLITAN PERIOD: SINCE 1898

Fractionation of benzocarbazoles between source rocks and petroleums

The concentrations of the [a] and [c] isomers of benzocarbazoles in a number of crude oils and source rock bitumens were obtained by “in house methods” and from reported published data. The changes in benzocarbazole concentrations and the benzocarbazole [a]/([a]+[c]) ratio relating to source maturity, facies and migration are described. With increasing source maturity in North Sea oils and source rocks, up to 0.85% vitrinite reflectance equivalent, benzocarbazole concentrations increase due to generation followed by a decrease above 0.85% vitrinite reflectance equivalent due to expulsion/dilution by newly generated hydrocarbons. Comparison of benzocarbazole concentrations between reservoired petroleum and related source petroleum revealed a concentration bias in favour of source petroleum where concentrations of benzocarbazoles reached up to 10 times that found in equivalent reservoired petroleum. The differences in benzocarbazole concentrations between related oils and source rocks indicate that the major fractionation is introduced during primary migration and expulsion, because when secondary migration is limited, as in the Miller field, we see extensive benzocarbazole fractionation between reservoired petroleum and associated source petroleum. The relationships between source rock TOC content and petroleum benzocarbazole concentrations and [a]/([a]+[c]) ratios indicate that source organic matter exerts a strong influence on benzocarbazole distributions. The introduction of a reservoir source fractionation parameter (RSFP), defined as the ratio between the concentrations of benzo[a]-+benzo[c]carbazole in reservoired petroleum versus the concentration of benzo[a]-+benzo[c]carbazole in source petroleum, enables description of the relationship between reservoired petroleum and source petroleum from different petroleum systems. Petroleum deriving from clastic source rocks demonstrated high levels of benzocarbazole fractionation between reservoired petroleum and source petroleum during primary and secondary migration compared to petroleum deriving from carbonate systems. The RSFP parameter may also be used to examine fractionation effects during migration between different compound types. The more polar benzocarbazoles are fractionated more strongly than dibenzothiophene and phenanthrene between reservoired petroleum and source petroleum. Whereas sometimes source maturity signals do dominate the benzocarbazole signals in migrated oils, in other circumstances, often associated with clastic source rocks, no clear maturity signal is transferred to migrated oils.

Relative Permeability Measurements for Post-Waterflood Depressurization of the Miller Field, North Sea

Summary This paper describes a determination of critical gas saturations and relative permeabilities relevant to the depressurization of the Miller field. A series of reservoir-condition coreflood experiments and associated numerical simulations is described. Three experiments were conducted with aged Miller core and fluids at 120°C. Each was comprised of a waterflood at about 414 barg, followed by depressurization at different rates. The laboratory data included extensive three-phase in-situ saturation measurements that were used to derive gas relative permeabilities through the simulations. The rate-dependent critical gas saturations varied between 0.06 and 0.21, and gas relative permeabilities of the order of 0.0001 were deduced. These laboratory results are consistent with published data and suggest that conventional Corey-type gas relative permeabilities are an order of magnitude too large and do not represent the depressurization process.

Quartz cementation inhibited by crestal oil charge: Miller deep water sandstone, UK North Sea

AbstractIn 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.

Capturing reservoir heterogeneity in a sand-rich submarine fan, Miller Field

Miller production began its decline phase in July 1997. To investigate the challenges of the decline period and the options for extending field life a detailed reservoir heterogeneity model was set up based on analysis of 26 wells, of which 19 were cored. The Miller fan is a high net: gross sandy submarine fan system in which lobe abandonment facies and numerous thin shales form the important heterogeneities. Each reservoir zone was described in terms of eight depositional elements and fourteen lithotypes. These descriptions were incorporated into the model at a resolution which ensured capture of the most significant heterogeneities. A stochastic generator was used to build a detailed static description of the permeability of the reservoir. The important heterogeneities were captured in a cell size of 60 m × 60 m × c. 0.02 m. Volumetric rock properties such as zone isochore, net: gross and porosity were mapped using conventional methods. The static description was up-scaled into an area of local grid refinement of the Eclipse reservoir simulator with 33 dynamic subzones at a cell size of 100 m × 100 m × c. 2.5 m. The detailed reservoir model matched well and field performance in the decline period more closely than the previous deterministic model. Stochastic realizations of the model enabled a better estimate of uncertainty to be demonstrated. The success of the process indicated that greater benefit would be obtained by its extension over a larger area of the field.

Permeability heterogeneity within massive Jurassic submarine fan sandstones from the Miller Field, northern North Sea, UK

Abstract Analysis of high density (5 cm sample spacing) probe permeameter data has been used to evaluate some of the basic controls on permeability heterogeneity in the Miller Field. Probe permeameter data generally show good correspondence with conventional core-plug permeability data gathered at 25 cm spacings, but record a higher frequency of permeability variation than can be resolved using conventional sampling strategies. Comparison of probe permeameter data gathered from four lithofacies recognizable in core has allowed assessment of their reservoir quality and quantification of their internal permeability heterogeneity. Geostatistical analysis of the permeability data using semivariograms suggests permeability correlation structures and periodicities are related to the frequency of sedimentary phenomena visible within core. In particular, a relationship exists between permeability correlation structure and average bedform or fining upward unit thickness, i.e. the vertical scale at which individual lithofacies packages are stacked. Geostatistical analysis of high sample-density probe permeameter data demonstrates the usefulness of permeability data gathered at more than the conventional 25 cm spacings used for core plugs. High density probe permeameter data can yield important measures of the representative geological ‘structures’ which could form the basis of geologically realistic two-phase flow upscaling.

UKCS Miller Field Reservoir Quality Prediction: Back to Basics?: ABSTRACT

UKCS Miller Field Reservoir Quality Prediction: Back to Basics?: ABSTRACT

Miller Field: reservoir stratigraphy and its impact on development

The Miller Field lies in UKCS Blocks 16/7b and 16/8b adjacent to the South Brae Field, and its reservoir is a high net-to-gross system of fine- to medium-grained turbiditic sandstones, interbedded with thin mudstones, which was deposited as part of an extensive submarine fan complex of Late Jurassic age, along the margin of the South Viking Graben. Recent studies of sequence stratigraphy in the area have contributed to a better understanding of the elements of the submarine fans, and, coupled with detailed biostratigraphy, have enabled the reservoir units to be correlated across the field with a fair degree of confidence. Pressure data have been incorporated into these studies. While detailed geophysical interpretation continues, a geological reservoir description has been used to map rock properties and reservoir connectivity across the field, and to indicate areas of greatest uncertainty. These uncertainties will be reduced as further data become available during production.