Abstract A large-scale sand injection complex, the Hamsun prospect, was the specific target of exploration well 24/9-7, drilled in 2004 offshore Norway. The well and subsequent sidetracks proved, as predicted, the presence of high-reservoir-quality sand injection facies. An oil column in excess of 100 m (330 ft) was demonstrated with a small associated gas cap. To our knowledge, this is the first deliberate exploration well to successfully target an injection complex.

Abstract Alba is a heavy oil (19 –20° API) field discovered in 1984 and brought on production in 1994. The oil is reservoired within middle Eocene turbiditic sands deposited within hemipelagic background argillaceous sediments. Alba sands have been subjected to postdepositional remobilization and sand injection on a field- wide scale. Sand geometries are highly complex. Prediction of sand-shale lithology from the Alba field four-component Ocean Bottom Cable seismic data set is refined through detailed horizontal and vertical well-seismic integration. Reservoir sands are subdivided into remobilized or injected and depositional facies in all wells by recognition in cores and/or logging-while-drilling response and by elastic impedance seismic character. An abundance of multiple horizontal well sidetrack data (commonly in the same vertical plane) in the Alba field allows the construction of facies cross sections against a seismic impedance data backdrop with some confidence. A new, threedimensional (3-D) geomodeling software is used that can directly include these facies cross sections as constraints on geomodeling, in addition to conventional well and seismic data constraints. This allows a degree of geological interpretation to be imposed and supported with outcrop analogs within the uncertainties of the available data. Numerous equiprobable 3-D cellular geomodel possibilities are created that differentiate remobilized or injected reservoir facies from depositional reservoir facies. The impacts of facies variability on production profiles are tested in a streamline reservoir simulator at the geological model scale.

Abstract The Yellow Bank creek complex (YBCC) is a large, upper Miocene injectite complex, one of numerous injectites northwest of Santa Cruz, California. The feeder for these injectites is the Santa Margarita Sandstone, a shelfal sandstone unit that is also the reservoir rock in several exhumed oil fields. The impermeable cap rock for these oil fields, the Santa Cruz Mudstone, was breached by sand injectites, some of which reached the sea floor. Located near the edge of one of these oil fields, the YBCC is a dike-sill complex that shows evidence for multiple phases of injection by fluidized sand that was initially gas or water saturated and later possibly oil bearing. Vertical injection of a large sand dike along a fracture was followed by lateral injection of a sill from the dike along bedding planes in the Santa Cruz Mudstone. Flow differentiation during injection of fluidized sand into the sill formed centimeter-scale layering in its lower part. Subsequent emplacement of oil into this sand may have occurred by injection and by seepage that displaced pore water, producing sand masses that became preferentially cemented by dolomite. Some evidence suggests that the injection and cementation occurred at relatively shallow burial depths beneath the sea floor, with the injection resulting from a combination of possible seismic shaking and migration of overpressured fluids from more deeply buried parts of the Santa Margarita Sandstone. A pervasive lamination marked by limonite staining developed following uplift and subaerial exposure of the complex, possibly in a groundwater environment.

Abstract The occurrence of sand injectites is well documented in many hydrocarbon-bearing, deep-water clastic reservoirs. In some fields, injectite sand bodies, and depositional sand bodies that have been modified by liquefaction and fluidization, hold major reserves. These fields were not drilled as sand injectite prospects, but the significance of the injectites became apparent during field appraisal and/or development. However, the first exploration well that deliberately targeted a sand injectite was drilled as recently as 2004 ( Rawlinson et al., 2005 ). Thus, sand injectites (intrusive traps sensu Hurst et al., 2005) constitute a virtually unexplored trapping style. We believe that many sand injectites are routinely overlooked and/or misinterpreted in subsurface studies. Further, if identified, their significance is frequently underestimated and, except where we know their significance, are not incorporated into static or dynamic models of reservoir performance. We provide illustrations of some of the most spectacular known outcrops of sand injectites, which may be analogs for subsurface reservoir and intrareservoir-scale occurrences.

Abstract Sand injectites are described as an increasingly common occurrence in hydrocarbon reservoirs, in particular in deep-water clastic systems, where they are known to influence reserves distribution and recovery. Seismically detectable injected sand bodies constitute targets for exploration and development wells, and subseismic sand bodies provide excellent intrareservoir flow units that create fieldwide vertical communication through depositionally extensive, low-permeability units. Because sand injectites form permeable conduits in otherwise low-permeability units, they facilitate the expulsion of basinal fluids; hence, they act both as a seal risk as well as mitigating timing and rate of hydrocarbon migration. Injected sand bodies form intrusive traps, which are distinct from structural or stratigraphic traps. Reservoir quality is typically excellent, with a high level of connectivity between sand bodies of all sizes. In a production context, sand injections enhance sweep efficiency but may cause more rapid-than-expected water breakthrough if wells are placed too near injectite complexes. Despite experience from the North Sea, recognition of sand injectites and their significance in hydrocarbon basins globally are at an early stage.

Abstract Sand injectites are described in scientific literature as an increasingly common occurrence in hydrocarbon reservoirs, in particular in deep-water clastic systems, where they are known to influence reserves distribution and recovery. Seismically-detectable injected sand bodies constitute targets for exploration and development wells and, subseismic sand bodies provide excellent intra-reservoir flow units that create field-wide vertical communication through depositionally extensive, low-permeability units. As sand injectites form permeable conduits in otherwise low-permeability units they facilitate the expulsion of basinal fluids; hence they act both as a seal risk and mitigate timing and rate of hydrocarbon migration. Injected sand bodies form intrusive traps, which are distinct from structural or stratigraphic traps. Included in this publication are 10 chapters on subsurface examination of sand injectites, 1 chapter on theoretical considerations, and 13 outcrop analogs in reservoirs across the world. Captured in this volume is at least a taste of the global and stratigraphic distribution of sand injectites, and an attempt to introduce readers to sand injectites and their significance in the context of hydrocarbon exploration and production. The book is not intended as a complete review of the field-based literature, but emphasizes high quality case studies from the surface and subsurface. The geographic scope of the book is large, and illustrates the diversity of geological settings in which these fascinating and economically significant features are found.

Abstract Hardly detected with logs and recognized with difficulty on cores, clastic injectites (sills and dikes) can be troublemakers in oil-field development. Moreover, they provide a precious record of early fracturation. To predict their geometry, extension, and relationship to their feeders, field analysis of selected analog outcrops is conducted to propose some simple rules. In southeast France, the Aptian–Albian formation provides exceptional outcrops (Bevons, Rosans, and Nyons) where it is possible to characterize large sets of injectites: dikes and sills are associated in the same metric-to-kilometric network. The injection occurred per ascensum (more frequently) or per descensum, during or after the sand deposition. Specific geometric-based field methods have been developed to analyze the geometry based on the best conditions. A three-dimensional (3-D) model of the Rosans area injectite network has been built through gOcad ™ tool using outcrop analysis and an original, very high-resolution twodimensional seismic acquisition (0.6 km 2 ; 0.23 mi 2 ). This field analysis, the seismic survey, and the 3-D modeling provide some keys to consider possible occurrences of injectites and associated facies related to a turbiditic channel fill. We dedicate this article to the memory of our colleagues and friends G. P. Allen and D. Claude.

Abstract Outcrop accessibility: easy Outcrop Coordinates: 51.5394°S; 72.6291°W Refer to outcrop 9 on location map The injectites at Lago Sofia were first reported by Scott (1966) and Winn and Dott (1979) . The first comprehensive evaluation of the features was done by Schmitt (1991) , with a more recent summary published by Hubbard et al. (2007) , who noted the geometrically analogous nature of the injectites to similar features in the North Sea. The injectites at Lago Sofia are exposed in 3-D, characterized by a near vertical outcrop of channel deposits in the lowest part of the succession. The middle part of the succession where the injectites are most prevalent is exposed on an ancient terrace, allowing for plan-view mapping of the injectite complex. The upper part of the stratigraphic succession is exposed sub-vertically, permitting visualization of the cross-cutting relationships between injectites and host strata ( Fig. 9.1 ). A series of three channel bodies (C1–C3) are laterally offset and progressively younger eastward. Each channel body is associated with injected bodies at its margins. Both margins of C1 experienced sediment remobilization and injection. Channel C2 experienced injection solely on its western margin; the associated injectite, I3, bifurcates and is observed to cross-cut >125 m of overlying stratigraphy. Channel C3 is the smallest, as is its accompanying injectite (I4).

Abstract Although long-recognized features in the geological record, the hydrocarbon reserve potential of sand injectites has only recently become apparent. Advances in the quality and resolution of 3D seismic data allow the definition of a range of trap and reservoir geometries that have, in the past, not been deliberately targeted by exploration wells. Sand injectites form a new trapping style. They are intrusive, occuring as discrete traps and in combination with structural and stratigraphical features. Dykes, sills, emergent sills, scalloped tops and irregular bodies are identified as trapping styles. Reservoir quality is typically homogeneous and good, even when in an overall low net:gross system. The North Sea Palaeogene, in which at least 2.4 × 10 9 BOE reserves are associated with injectite fields, or fields modified by sand injection, is used as an example of sand injectite plays. Statistically, the additional reserve potential for sand injectites in the North Sea Palaeogene is high. Globally, the presence and significance of sand injectites is largely overlooked. As most sand injectite reservoirs of commercial significance develop during early burial and are associated with overpressure, play concepts are developed that combine mechanisms for overpressure development with sedimentology. Recognition of the presence of sand injectites will have a major affect on many deep-water and other plays both in terms of exploration and production.