Brian Willis

Chevron · Earth Science Dept., Clastic R&D Team

Sea‐level fall is commonly inferred to generate a sharp‐based shoreface succession that displays an abrupt vertical transition from heterolithic, lower shoreface to sandy, upper shoreface deposits across a marine erosion surface. Three‐dimensional, process physics based, coupled hydrodynamic‐morphodynamic models are constructed to compare bedding a...

Process-physics-based, coupled hydrodynamic–morphodynamic delta models are constructed to understand preserved facies heterogeneities that can influence subsurface fluid flow. Two deltaic systems are compared that differ only in the presence of waves: one river dominated and the other strongly influenced by longshore currents. To understand an enti...

Reservoir development forecasts depend on accurate descriptions of the spatial distribution of rock properties that impact subsurface fluid-flow pathways and volume connectivity. Reservoir models constructed using geostatistical methods combine analogous facies dimension data with sparse subsurface data to predict spatial variations in rock propert...

Understanding the deposits of different fluvial styles is fundamental to improve the characterization of fluvio-deltaic petroleum reservoirs. Fluvio-deltaic systems host significant hydrocarbon accumulations around the world, including reservoirs of the Mungaroo Formation, North West Shelf, Australia. The Mungaroo Formation is a Triassic-aged, over...

Fluvial channel belt deposits formed by a meandering river are modelled to predict variations in fluid flow patterns through subsurface hydrocarbon reservoirs and aquifers. A series of numerical experiments examine the impact of channel belt connectivity and intra‐channel belt facies patterns on reservoir behaviour during tracer flood displacement....

The geometry of fluvial channel belts and their internal facies are predicted by considering patterns of erosion and deposition during river channel migration and bend cutoff. Along‐belt heterogeneities are defined by the geometry and internal facies of one or more rows of storeys, each divided into five lithic sub‐units that formed adjacent to spe...

With GoogleEarth™ and simular collections of Earth images widely available it is now standard practice to select images of coastal environments based on inferred depositional process as templates for expected subsurface facies patterns (e.g., MPS training images). Although remote imagery can be enlightening: 1) Relationships between environments ob...

Reservoir delineation and characterisation of the shallow marine Triassic Brigadier Formation (Fm.), northwest shelf (NWS), Australia is challenged by the thin-bedded nature of the reservoir. These reservoirs are generally below seismic resolution in stark contrast to the underlying, seismically well-imaged Mungaroo Formation fluvial channel belt r...

Stratigraphic rule-based modeling methods approximate sedimentary dynamics to generate numerical descriptions of reservoir architecture and the spatial distribution of petrophysical properties. A few intuitive rules included in a reservoir model construction workflow are shown to render realistic reservoir heterogeneity, continuity, and spatial org...

Fluvial systems are typically classified based on river channel morphology, with meandering and braided river patterns being the two most common end-member types. Seismic data commonly cannot resolve reservoir depth channels, but rather only image the larger-scale channel belts. Thus it is a challenge to apply modern river channel classifications t...

The Miocene Sihapas Group in the Minas field, Indonesia, is composed of a succession of tens-of-meters-thick, erosionally based, tide-influenced sandstone intervals interbedded with marine shale-dominated intervals. Despite more than 1600 wells drilled into this 12-km-wide by 30-km-long mature super-giant field, complex internal tidal facies archit...

We describe an in situ fossil flora of Late Cretaceous age (∼73 Ma [mega-annum or million years]) from Big Cedar Ridge in central Wyoming, USA, which we sampled using a modified line-intercept method to quantify the relative abundances of 122 taxa at 100 sites across 4 km of exposed sedimentary deposits. We also measured three physical variables at...

http://deepblue.lib.umich.edu/bitstream/2027.42/116378/1/ecm201282123.pdf

The geometry of heterogeneities within fluvial channel-belt deposits is predicted using an existing model of flow and sediment transport in river channel-meander bends. The thickest and coarsest-grained sediment accumulations are deposited near a channel-bend apex, and finer-grained sediments accumulate higher on the downstream end of a channel bar...

Vertical changes in the proportion of fluvial channel to overbank deposits over tens to hundreds of meters and associated spatial changes in fluvial depositional style is widely observed in alluvial successions. In most cases these variations are inferred to reflect accommodation variations within the context of fluvial sequence stratigraphic model...

Few ancient river-channel deposits have been described in enough detail to allow interpretation of channel-bar geometry and migration. Such interpretations require an understanding of the interaction between the style of channel migration, temporal and spatial variation in channel-bar geometry and facies, and outcrop orientation. This interaction i...

This study uses stable isotope variation within individual Mio-Pliocene paleosols to investigate subkilometer-scale phytogeography of late Miocene vegetation change in southeast Asia between ca. 8.1 and 5 Ma, a time interval that coincides with dramatic global vegetation change. We examine trends through time in the distribution of low-latitude gra...

The Agbada Formation in Robertkiri field is a 2.7-km (9000-ft)-thick succession of Miocene shallow-marine and nonmarine deposits formed as the continental margin of the Niger Delta structurally collapsed under accumulating sediments. A high-resolution sequence-stratigraphic framework for these strata was constructed by combining data from 20 well l...

The sequence stratigraphy of fluvial-deltaic strata deposited near the center of the wide, gradually subsiding Sunda Shelf differs from standard highstand examples because low accommodation and low depositional gradients restricted the thickness of fluvial-deltaic sequences and the depth of lowstand fluvial incision. In this setting sea-level fluct...

Quantitative determination of palaeochannel geometry and hydraulics from point bar deposits requires an understanding of the interaction between channel-bend migration, temporal and spatial variation of point bar geometry and facies, and outcrop orientation. This interaction is modelled with the aid of a computer program which predicts three-dimens...

Niger Delta depositional patterns are complicated by structural collapse of prograding deposits into underlying mobile shale. Delta field, along the northwest margin of Niger Delta, is located on the dominantly extensional proximal margin of a major collapse structure. This structure defines a sub-basin ‘‘depobelt’’ within this prograding clastic w...

Some geological events occur infrequently but still have a significant impact upon reservoir characteristics. By their very nature, however, it can be difficult to properly estimate the proportions of uncommon events because they may not appear during limited sampling. For example, even with 40 observations and an event proportion of 0.05, there is...

John B. Anderson and Richard H. Fillon (Eds.), 2004, SEPM, Tulsa, USA, 314 p. (Hardcover, US $135.00 non-members, US $97.00 members, US $68.00 student members) ISBN 1-56576-088-3. Sequence stratigraphy has advanced significantly over the past few decades. It is not that the fundamental concepts have changed— namely that periodic variations in the...

A study of a tide-influenced deltaic sandstone investigated geologic variations that affect hydrocarbon production in analogous reservoirs. The Cretaceous-aged Frewens Allomember was deposited by a delta prograding into a narrow shoreline embayment between an older, wave-dominated delta lobe to the south and a basin-floor ridge created by subtle st...

Large variations in the perfection of order and in substitution of calcium for magnesium occur in sedimentary dolomite, and complicate the trace element and isotopic chemistry of this complex mineral. The stabilization of metastable disordered and/or Ca-rich phases is as important in forming ancient dolomitic rocks as is the stabilization of aragon...

The relatively new method of using wavelets in log analysis is a powerful tool to define multiple superimposed scales of lithic contacts and trends. Wavelet analysis of grain-size variations in a 2.1 km thick section through the fluvial Chinji and Nagri Formations, northern Pakistan, revealed three major wavelengths. These dominate wavelengths are...

Diagenetic cements commonly reduce sandstone porosity and permeability and change patterns of subsurface flow in oil and gas reservoirs and aquifers. Calcite concretions were mapped on an outcrop exposure of a Cretaceous-age tide-influenced deltaic sandstone in Wyoming, USA. A digitized image of this outcrop was analyzed to compute descriptive stat...

The Upper Cretaceous Sego Member of the Mancos Shale in east-central Utah is composed of tidally deposited sandstones interbedded with intervals containing marine shales and thin wave-deposited sandstones. The tidal sandstones have been interpreted to comprise multiple amalgamated estuarine valley fills above a major sequence boundary that is incis...

The Cretaceous Interior Seaway has been at the center of debates about the origin of elongate "shelf? sandstones encased in marine shales. Some of these basin-distal sandstones have been interpreted to be tidally-influenced incised-valley fill deposits. We suggest that many of these deposits are top-eroded lowstand deltas, as indicated by lobate to...

Standard sequence stratigraphic models suggest a single deeply incised lowstand erosion surface (sequence boundary) forms during relative sea level fall associated with sediment bypass to more basin distal locations. This erosion surface is assumed to be continuous; extending laterally across adjacent interfluves and seaward into a ‘‘correlative co...

INTRODUCTION Most shoreline and marine sandstones in the Cretaceous Western Interior Seaway of North America are basinward thinning wedges that coarsen upward from offshore marine shales, to thinly interbedded wave-rippled sandstones and shales, and then to amalgamated beds of hummocky cross-stratified sandstones. These upward-coarsening succession...

Precipitation of extensive calcite cement during burial diagenesis can strongly modify the depositional permeability of a sandstone reservoir and affect fluid flow during production. To predict sub- surface flow through cemented reservoirs, permeability distribu- tions used in fluid-flow models must reflect this diagenetic over- print. Calcite ceme...

Variability in production predictions caused by geologic heterogeneity and uncertainty was examined with a new method. The experimental design maximized the information derived from the flow simulation of various geologic models. Empirical response surface models were fit to simulation results to assess the consequences of varying several geologic...

Deposits of lowstand deltas formed on the floor of the Cretaceous Interior seaway of North America are found in the Cenomanian, lower Belle Fourche Member of the Frontier Formation, central Wyoming. Sandstones located in similar distal basin locations, hundreds of kilometers basinward of highstand shoreline deposits, form important hydrocarbon rese...

An architectural analysis documents variations in bedding geometry and rock properties within a tide-influenced deltaic sandstone exposed in the Cretaceous Frontier Formation of central Wyoming, USA, Digital maps of bedding, lithofacies, and diagenetic cements, as well as vertical logs of grain size, lithofacies, and permeability, describe rock pro...

Dimensions of shales and other geologic bodies that affect fluid flow through reservoirs and aquifers are often estimated from analogous deposits exposed in outcrops. Shale lengths observed in outcrops are biased because the finite length of outcrops truncates longer shales and long shales tend to be overrepresented in the sample. Shale length dist...

Petrographic study of the Frewens sandstone, Upper Cretaceous Frontier Formation, documents reservoir-scale diagenetic heterogeneity. Iron-bearing calcite cement occurs as large concretions that generally follow bedding and are most common near the top of the sandstone. Median thickness of the concretions is 0.6 m, length 4.5 m, and width 5.7 m; me...

This paper was prepared for presentation at the 1999 SPE Reservoir Simulation Symposium held in Houston, Texas, 14-17 February 1999.

Quantification of permeability structure in outcrop reser- voir analogs documents the distribution of flow units and barriers im- portant for reservoir management and simulation. Differences in buri- al history and diagenesis of the outcrop analog and the subsurface reservoir must be quantified, however, before outcrop permeability data can be used...

A cross section through a compound valley fill sandstone in the Lower Cretaceous Fall River Formation is exposed in Red Canyon, on the southwest flank of the Black Hills in South Dakota. A mapping of changes in stratal architecture, facies, and permeability along this cross section records rock heterogeneities that can influence subsurface fluid fl...

A cross section through a compound valley fill sandstone in the Lower Cretaceous Fall River Formation is exposed in Red Canyon, on the south-west flank of the Black Hills in South Dakota. A mapping of changes in stratal architecture, facies, and permeability along this cross section records rock heterogeneities that can influence subsurface fluid f...

Quantification of permeability structure in outcrop reservoir analogs documents the distribution of flow units and barriers important for reservoir management and simulation. However, differences in burial history and diagenesis of the outcrop analog and the subsurface reservoir must be quantified before outcrop permeability data can be used to mod...

Overbank deposits of the fluvial Chinji Formation (Siwalik Group) can be divided into sequences 1-20 m thick defined by the alternation of stratified sediments and paleosols. Infilling of floodplain topography may reflect a continuous process, whereby local areas were always being filled somewhere on the floodplain by sediments from minor tributary...

The 3 km thick Miocene Siwalik Group (Himalayan foredeep in northern Pakistan) and the 2 km thick Paleogene Fort Union/Willwood formations (Bighorn Basin in Wyoming) both preserve long records of fluvial deposition adjacent to rising mountain belts. Depositional environments and associated habitats change across large basins along with changing phy...

Comparative study of fossil-bearing fluvi' deposits in the Eocene Willwood Formation of northern Wyoming and the Miocene Chinji Formation of northern Pakistan indicate how tectonic and climatic processes operating at different scales controlled physical and chemical features of floodplain environments and affected preservation of the paleontologica...

Because of the worldwide importance of resources in fluvial-deltaic reservoirs, a consortium of companies is funding research at The University of Texas aimed at reservoir characterization of fluvial-deltaic depositional systems. The goals of this industrial associates program are to develop an understanding of sandstone architecture and permeabili...

The spatial organization of environments in the shore zone of the Middle Devonian Catskill clastic wedge in New York State suggests a wave- and tide-influenced deltaic shoreline. Asymmetrical regressive-transgressive sequences that range from tens of meters to >100 m thick can be correlated over many kilometers with fully marine and fluvial deposit...

Sedimentological variations through a kilometer-thick coarsening-upward succession in the Miocene Himalayan foredeep basin (fluvial Chinji and Nagri Formations of the Siwalik Group) are documented in the Chinji Village area on the Potwar Plateau of northern Pakistan. From the Chinji Formation upwards into the Nagri Formation: (1) the proportion of...

The Miocene Chinji and Nagri Formations (Siwalik Group) of northern Pakistan record ancient fluvial environments in the Himalayan foredeep basin. Excellent exposures on the Potwar Plateau (Chinji Village area) allowed detailed documentation of the geometry and stacking of sediment bodies that comprise these strata, and of variation of large-scale b...

The Siwalik fluvial deposits of Pakistan are characterized by varying proportions of red to brown silts, fine sands, and minor clays representing overbank deposition. In the Chinji Formation (~15–10.5 Ma), floodplain facies consist of overlapping packages of: 1) well-bedded siltstones and occasional sheet sands or small channel sands, 2) an overlyi...

The 3-km thick Neogene Siwalik Group (Himalayan foredeep in northern Pakistan) and the 2-km thick Paleogene Fort Union/Willwood Formations (Bighorn Basin, Wyoming) both preserve long records of fluvial deposition adjacent to rising mountain belts. Depositional environments and associated habitats change with spatially varying physiography and depos...