SAnD Research

Mass transport deposits (MTDs) are important stratigraphic elements in deepwater deposits of several basins in the world (e.g. the Gulf of Mexico (GOM), West Africa, Australia). MTDs have been documented as both seal and reservoir, migration pathways, dangerous drilling hazards and their role in seafloor destruction and as tsunami triggering mechanisms remains poorly understood. At present the role of MTDs as effective petroleum seals is difficult to predict a priori because of their facies complexity. During mass-movements, clay and silt particles are exposed to significant mechanical shear deformation, thus it is expected that the structure and fabric of the sediments will be altered, and ultimately the fundamental petrophysical properties will respond to these changes. However, previous studies have shown that the deformation styles vary spatially within the main domains of a MTD (i.e. headwall, translational, and toe) as well as in scale (micro- and mesoscale deformation). Different styles of deformation (e.g. brittle vs. plastic deformation) have implications for the final seal capacity of a deposit. The main goal of this project is to study the impact of gravity-induced deformation on the facies within a MTD and how the facies variations impact the seal integrity of the deposits. We are investigating the systematic spatial variation of the deposits within a well-exposed MTD in the Taranaki basin, New Zealand that was deposited in basin-floor settings during the Upper Miocene. These outcrops have been described as good analogs to deepwater deposits in the GOM. We are also studying the microstructures and microfabrics from samples collected from this MTD by employing high-resolution techniques such as field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and near-infrared (NIR) spectroscopy to characterize the impact of gravity-induced deformation on the microscopic framework of the MTD outcrop. The findings from this research will help in our understanding of the impact of gravity-induced movements on the final deposits as well as spatial multi-scale variations of strain within a MTD and its impact on the petrophysical properties such as porosity and permeability. This will ultimately help in seal-assessment projects (e.g. oil exploration, CO2 sequestration projects, etc.) and better understand the interaction between fluids and MTDs in the subsurface.

Submarine topography has a fundamental control on the movement of sediment gravity flows as well as the distribution, morphology, and internal heterogeneity of resultant overlying, healing-phase, deep-water reservoirs. Some of the most complex deep-water topography is generated through both destructive and constructive mass transport processes. A series of numerical models using Sedflux software have been constructed over high resolution mass transport complex (MTCs) top surfaces mapped from 3D seismic data in offshore Morocco and offshore eastern Trinidad. Morocco MTDs are characterized by large, extant rafted blocks and a flow perpendicular fabric. Trinidad’s margin is characterized by muddier, plastic flow MTDs, and isolated extrusive diapiric buttresses. In addition, Morocco’s margin is a dry, northern latitude margin that lacks major river inputs, while Trinidad’s margin has equatorial, wet climate that is fed by the Orinoco River and delta. These models quantitatively delineate the interaction of gravity flows on the tops of two very different topographies and provide insights into healing-phase reservoir distribution and stratigraphic trap development. Slope roughness, curvature, and surface shapes are measured and quantified relative to input points to define depositional surface character. A variety of sediment gravity flow types have been input and the resultant interval assessed for healing phase top fill thickness and distribution relative to key topography parameters. Mathematical relationships are to be analyzed and compared with seismic data interpretation of healing-phase interval character, toward an improved model of gravity sedimentation and topography interactions.

Figure above shows a series of 2D profiles extracted from a muddy mass failure off the dry coast of Morocco, showing a highly parallel fabric with abundant perpendicular oriented extant rafts. The science of classifying and analyzing “submarine healing phase topography” must preface modeling of post-emplacement flows.

Mass-transport deposits (MTDs) have been documented by previous studies to act in petroleum systems as source rock, reservoir, migration-path, and seal. However the situations under which MTDs exhibit these behaviors are difficult to predict, in part due to the high lateral and vertical heterogeneity exhibited by these enigmatic deposits. To successfully explore in active deforming deepwater fold and thrust belts (DWFTB), one must understanding both pressure and distribution of reservoir sands, as well as the nature, distribution and sealing capacity of MTDs.

This study aims to analyze several ancient MTDs utilizing 3D seismic, well log analysis and biostratigraphic data to establish recognition criteria of sealing and non-sealing MTD types in the DWFTB offshore Malaysia. 700km2 of high resolution 3D seismic data were used for detailed geomorphological mapping of Middle Miocene-to-recent age, “attached” and “detached” MTDs” found in the deepwater fold and thrust belts of offshore Malaysia. The thick and spatially extensive chaotic seismic reflection packages, interpreted as “attached MTDs” are observed in the pre-kinematic sequence of the fold and thrust belt while the relatively smaller-scale, thinner chaotic seismic reflections of “detached MTDs” are developed in the syn-kinematic sequence. These MTDs all have erosive bases and internal thrusts, but two new exploration wells, which penetrated both the main body and the distal regions of the “attached MTD” provide additional detailed data. Data through these attached MTDs show a proximal main body that is mud-rich, mounded in shape, contains rafted blocks, has muds that show elevated densities compared to surrounding background muds and well bore images show disorganized azimuth/dips. Distal parts of this deposit show unexpected thick sandstones near the base of the MTD with well bore images showing concordant azimuth/dips. Biostratigraphic data in these deposits show an abundance of outer neritic fauna supporting the interpretation that these deposits are derived from near shelf sediment sources.

MTDs were hoped to provide the main seals for hydrocarbons trapped in steep-walled anticlinal traps. However, well data reveal a more complex system involving below-MTD overpressured shales, and several fault conduits through these units. Seal failure was assessed as the main cause of well failure. Pressure profiles of the exploration well drilled in flank of the hanging-wall anticline prospect shows that reservoir pressures exceed the below-MTD shale pressures. As reservoirs climb toward the anticlinal crest it is believed that reservoir pressures exceeded the fracture gradient of these shales hydrocarbons escaped through either vertical fractures or intersecting faults.

Much focus has been put on sand distributions in channel and lobe complexes, but in high net-to-gross (HNG) systems it is the clays that most significantly impact flow behavior. Clay minerals characteristically have small, plate shaped grain sizes, large surface area and high cation-exchange capacity. Spatially and temporally variable clay nature and distribution in deepwater settings can have a dramatic impact on both reservoir quality, seal quality and even the propensity for slopes to fail. Likewise, clay types show different behaviors under deposition and burial conditions. However, little work has been done on predicting the types of clay and their distribution in various deepwater facies associations.

The aim of this study is to (1) identify the types, textures, fabric and spatial distribution of clay minerals within submarine channel and lobe complexes of HNG systems; and (2) test a new approach in clay identification that may be beneficial to industry. To approach these goals have done field analysis and sample collection in the well documented, deepwater outcrops of the onshore Taranaki Basin of New Zealand.

The Mount Messenger Formation in the Taranaki Basin, New Zealand serves as a well-exposed and previously studied analog to HNG fan systems (N1 of Green Canyon, Ram/Powell field, ‘Einstein’ turbidite leveed channel Viosca Knoll/DeSoto areas) in the Gulf of Mexico basin (Browne and Slatt, 1997). Data on clay mineralogy were collected and analyzed from 98 points on site on outcrops along the Taranaki Coast using near-infrared spectrometry (NIRS). Data were binned into upper slope channels, levees, lobes and mass transport deposit facies associations. NIRS is a physical, non-destructive, rapid analysis method that uses reflectance signals produced by vibrations in bonds between carbon, nitrogen, hydrogen, oxygen, phosphate and sulfur atoms. In addition to NIRS data, 18 hand samples were also collected to cross-check spectrometer results via thin section, XRD and SEM analysis. Preliminary results (shown below) are still being analyzed. Additional work will be done on analysis of channel, lobe and MTD elements in a suite of core collected through the deepwater Wilcox Formation (Eocene), Gulf of Mexico Basin.

Submarine canyons occur on every modern margin throughout the world’s oceans, however, the Berbice mega-canyon in the ancient Cretaceous age margin of Guyana may be the largest canyon to have evolved in earth’s Mesozoic to modern history. Recent giant hydrocarbon discoveries in Exxon Mobil’s Liza-1 well north and distal to the Berbice Canyon prove the value of these systems as bypass regions for deepwater fan development. However the complexity of the topography within these canyons may still yield hydrocarbons trapped in stratigraphic updip locations. The aggradational nature of fill within this “canyon” leads us to label it a valley rather than a canyon.

This study will examine the nature of the canyon morphology, fill phases and fill architecture within the Berbice Valley using ~5000 sq km of excellent 3D seismic time and depth data, as well as several wells drilled closely adjacent to or within the valley fill. The Berbice valley is compared to a compilation of modern canyons/valleys on both active and passive margins (Harris and Whiteway, 2011) and contrasted with other known ancient canyons documented in the rock record through outcrop or seismic studies. In addition, this study intends to document the temporal and spatial relationship between the Berbice and possible continental or submarine structural influences on the formation of such a large geomorphic feature.

The Berbice Valley is documented by previous workers as ranging in width from 25 to 100 km. It is actually composed of five phases of incisions, some as deep as 1250 meters making it an extremely large, multi-phase valley by world standards. The Berbice would be considered a shelf incised canyon (in the nomenclature of Harris and Whiteway, 2011). The canyon evolved in the late Cretaceous along a margin which was separating from the Equatorial Guinea region of the South African margin in response to the opening of the northern South Atlantic ocean. Large, high volume sediment supplies were shed from the continents at this time and it is likely that hyperpycnal and high fluvial output flows contributed to the magnitude of incision in the Berbice Canyon. The fill appears to be composed of more than one period of reincision and filing and we intend to investigate the variability in these fill using seismic geomorphologic techniques and ground truthed with well data from the Horseshoe 1, and other wells.

The Tocito Sandstone (TS) has been long proven to be a highly prolific reservoir system in the largest domestic onshore conventional gas basin in the U.S., the San Juan Basin (SJB). Similar shelf sand types associated with the pre-Tocito Gallup Sands and the more transgressive post-Tocito El Vado Sandstones have proven equally productive in recent wells resulting in a mini-boom of sorts in the SJB. Studies of the nature of all these shelf sand systems from outcrop, core, logs and seismic reveal thick (1-2 m) cycles of heterolithic wave-rippled, moderately to intensely bioturbated marine sands stacked in 8-12 m thick shelf sequences that are spatially extensive throughout the eastern as well as western SJB. Tocito sands in the western SJB outcrop are much more proximal in nature with tidal channel and bar facies associations predominate. Tocito intervals in the southeastern SJB outcrop show at least six sanding and thickening upward cycles composed of thinly-laminated, wave-rippled sands (Facies 3) interbedded with marine shales (Facies 1) progressing upward to moderately bioturbated, sand-rich parasequences (Facies 4). Shelf parasequences compensationally stack in near paleo-shoreline regions around Cabazon Peak northward to subsurface localities at least 140 km north of the paleoshoreline. Near-shore cycles near Cabazon Peak transition just 8 kilometers northward to contain extensive mega-hummocks (Facies 2). Analysis of hummocks in the Tocito sands suggest mega-swell waves up to 9 m high may have impacted the paleo-shelf distributing sands widely across the region, and possibly contributed to the submarine erosion of up to 60 meters of material from the paleo-shelf. This regional study of SJB shelf reservoir sands is the first to quantify the regional nature of sand distribution, link super-greenhouse processes to potential shelfal submarine erosion and redistribution of sediments, and to examine prograding versus transgressive shelf reservoir systems.

Figure above, showing meters thick cycles of cm to sub-cm, wavy-laminated, rippled fine to very fine sands showing internal migrating ripples and drapes of mud over ripple surfaces. Rare, thin swaley to hummocky-like beds do occur and appear to represent very small-scale process events. Only a traces of bioturbation can be found. This is a typical low net:gross sand reservoir in the San Juan Basin subsurfaces.

Deltaic deposits produce billions of barrels of hydrocarbon worldwide. However, complexities and variations in deltaic geobody geometry, sediment volume, and internal architecture often result in a large amount of unproduced resource. This study focused on creating a detailed 3D reservoir model of one such deltaic system, the Pennsylvanian Atoka Formation, aided by beautiful quarry exposures. The target quarry, the Webco Quarry (WQ) located in White County, Arkansas, encompasses an area of approximately 140,000 m2, with walls ranging from 25 to 45 meters high. These sediments were deposited as a series of Pennsylvanian-age deltas fed from the ancestral Appalachian Mountains, prograding westward and southward into the older Ouachita trough. The elongate nature of the trough and long distance of sediment transport resulted in this siliciclastic deltaic systems being influenced by marine processes, which included both tides and waves. To model these reservoirs, measured sections are collected and details are placed within a hierarchal framework of surfaces interpreted from Gigapan and LiDAR imagery of the quarry walls. Facies differentiation is based upon grain size, bed thickness, composition, texture, sedimentary structures, and fossil content of the rocks. Facies are predominantly fine- to medium-grained sandstones, with some intervals containing lithic clasts, granules, and pebbles. Sedimentary structures include planar laminations, ripples, and cross stratification. Some portions are fossiliferous with bioclasts and trace fossils. Shales vary in thickness and continuity, but can be placed in a hierarchy within the model. Shale lengths, thicknesses, and frequencies are collected to calculate vertical and horizontal permeability ratios for populating grids between the walls. Data has been integrated in Petrel, employing user-created training images and multiple-point geostatistical simulation. The model illustrates fluid flow connectivity of this compositional and geometrically complex reservoir, and details the importance of shale continuity and distribution in baffling and blocking flows.

Facies associations of the transgressive Tidal Influenced Reservoirs (TIR) of the Atoka. These FA for the basis of the future Petrel MPS model.

Leiaka Welcome, 2nd Year PhD

Worldwide rift basins account for up to 30% of the world’s giant hydrocarbon fields (Mann et al., 2001). Rifts are typically restricted terrestrial (lacustrine, alluvial or eolian) basins, bounded by normal faults with subsidence and rapid lateral and vertical facies changes, and can loosely be identified as either modern or ancient. Modern day, active rifts can been located in sub-salt rift strata along Atlantic continental margins, East Africa, North Sea, South East Asia and China respectively. Rifts characteristically display complex histories due to their tectonic settings. Consequently, there are several major challenges in rift basins, understanding location, quality, and extent of quality reservoirs and how fluids will flow through these fills. This research plans to improve understanding of the sedimentology and stratigraphic architecture of rifts to aid in the exploration and production of hydrocarbon, mineral and water resources.

Although rifts having been extensively studied in academia and industry, many questions remain about their origin, evolution; fill architecture and fluid migration histories. It is the intent of this research to use the arid, continental Rio Grande Rift (RGR) as a laboratory for study of these characteristics to de-risk exploration for and development of worldwide hydrocarbon, water and mineral resources. In addition, a true understanding of the sedimentary fill architecture of the RGR has significant regional implications for resource development in southern Colorado, New Mexico and parts of west Texas. Several aspects of sedimentary fill within the RGR will be the focus of this study.

Important questions to be asked and answered include:

• What is the stratigraphic and sedimentologic framework of the RGR basin fill? How does the fill architecture of these arid, continental rift systems differ from those linked directly to marine systems?
• How much sediment is contributed to the RGR through local versus far (greater than 100 miles) sources? How much sediment is contributed from axial versus transverse feeder systems? What is the relationship between channel architecture and drainage size? Can we use the size and nature of the channel systems to discriminate the linkages between different rift sub-basins?
• Is sediment sequestered in these basins or passed through to marine systems? Is sediment preferentially stored in certain parts of these rift systems? Did the RGR influence the pass through of Cenozoic sediments to the Gulf of Mexico or has storage continued throughout the history of the basins?

Image to the left showing the extent of the northern region of the Rio Grande Rift System.

Research of the RGR will be conducted using conventional well logs and extensive databases of water wells, as well as exposures of Tertiary outcrops throughout the rift system. Initial insights may expand the data collection to include geophysical based data acquisition. Newly acquired geologic and geophysical data will be integrated with that of previous workers.

The changes throughout the Lower, Middle and Upper Atoka indicate an evolutionary response to tectonic compression and subsidence, increasing confinement, localized accommodation, variations in basin geometry, natural maturing of the feeder systems during the progression of the transition from Ouachita Trough to Arkoma Basin. Comparative studies of the Atoka and the Jackfork in the same basin have important implications of deciphering deepwater successions of early foreland basin deposits. Such transitions are common throughout basin evolution records worldwide and the Atoka lends an opportunity for improved understanding of source-to-sink system response to such changes.

The methodology in this study involves examining the lithologic facies, stratigraphic architectures, trace fossils, petrography and paleocurrent in both outcrop and subsurface, and analyzing the spatial and stratigraphical difference across the study area to find the impact of the feeder systems, then compare the Atoka system (emerging active margin setting) with the Jackfork (passive margin setting).

Several important questions being addressed in this study include:

• What is the difference between the deep-water fan systems in passive / extensional margin settings versus those in active / compressional margin settings?
• How do the deep-water fan systems differ stratigraphically with different feeder systems updip: deltaic versus shoreface?
• How do those differences affect the reservoir quality, continuity and distribution of the deep-water systems?

Current observations show Atoka consists of sediments from deep to shallow water origins and recorded the transition from a rifted continental margin to a rapidly subsiding foreland basin. This study focuses on the lithofacies, stratigraphic architecture, paleocurrent, and ichnofacies early foreland basin based on 23 outcrops in western Arkansas.

The Atoka is informally divided into Lower, Middle, and Upper intervals in lithologic and chronostratigraphic sense. The Lower Atoka is a fine-grained, sand-rich deepwater complex. Both axial fan and transverse fan systems are predominantly fine-grained turbidite sandstones and mudstones. The main architectural elements are lobes, inter-lobes, MTD for the axial fan, and channels, levees and overbank for transverse fan. Net to gross is high for individual fan, but decreases westward. Paleocurrent shows overall E-W for axial fan, N-S for transverse fan. Trace fossils are identical of Nereites ichnofacies. The Middle and Upper Atoka are mud-rich shelf, deltaic and shallow marine deposits. They are predominantly fine- to medium-grained sandstones sandwiched in thick ripple- or planar-laminated mudstones, with some carbonaceous and fossiliferous horizons. The main architectural elements include sandstone and mudstone sheets, channels, bars. Combined influences of wave, tide, and traction currents are common. Paleocurrent shows bidirectionally N-S or E-W. Trace fossils are very abundant, mostly identical of Cruziana and Zoophycos ichnofacies.

Ancient and modern rift basins can be found on every continent of the world and account for 31% of giant fields discovered (Mann et al., 2003) with over 620,000 (MMBOE) of estimated recoverable hydrocarbons worldwide. New rift plays are just being discovered as we explore beneath salt deposits and penetrate deeper continental margin strata. The biggest challenge in these basins is understanding reservoir location, quality, and extent. Axial- and marginal-sourced rivers provide very different sediments to the system and have significant geomorphologic differences. The architecture of rift systems varies dramatically from those located within continental versus coastal/marine environments (Gawthorpe and Leeder, 2000). A three phase study of rift drainages was undertaken to document these differences and quantify the various morphologies of drainage that characterize rifts. A literature and imagery review of ancient and modern rift drainage systems was undertaken with the focus on ancient systems being issues and challenges to producing discovered, developed, and undeveloped hydrocarbon in rift system reservoirs. In the second phase of this work, a study of the morphology of a modern rift setting in East Africa using ArcGIS and satellite imagery allowed mapping and quantification of rift drainage morphologic characteristics, such as: drainage architecture, rift size, channel size and flow characteristics and the overall drainage nature versus catchment area. Phase 3 of this study focuses on applying the criteria and knowledge built in Phases 1 and 2 to improve prediction of drainage nature and subsequent reservoir distribution and development in a high resolution 3D seismic survey in the Dampier Sub-basin off the NW coast of Australia. Quantitative seismic geomorphological techniques have been employed to assess the morphology, flow character and drainage size of this paleo-rift system toward a better understanding of reservoir distribution and risk.

Figures showing a NW to SE seismic section extracted from the g9pan1e survey in the Dampier Sub-basin. Image on the right is a horizon slice 29 ms above the J40 surface showing deltaic forms cored by channel systems.