Sand injectites: an emerging global play in deep-water clastic environments

Abstract

Although long-recognized featuresinthe geologicalrecord, the hydrocarbon reservepotentialofsand injectiteshasonly recently becomeapparent. Advancesinthe quality andresolution of3Dseismic dataallow the definition ofarange oftrapandreservoirgeometriest hathave, int he past,not beendeliberately targeted by exploration wells. Sandinjectitesform anewtrappingstyle.Theyareintrusive, occuringasdiscretetraps andin combination withstructuralandstratigraphicalfeatures. Dykes,sills,emergent sills,scalloped tops andirregular bodiesareidentified astrappingstyles. Reservoirquality istypically homogeneous andgood, evenwheninan overall low net:gross system. The NorthSea Palaeogene, inwhich atleast 2.4 £ 10 9 BOE reservesareassociated withi njectitefi elds,or fieldsm odified bys andi njection,i su sed asanexampleofsandi njectiteplays. Statistically,the additionalreservepotentialfor sandinjectitesinthe NorthSea Palaeogeneishigh.Globally,the presence andsignificance ofsandinjectitesislargely overlooked.Asmost sandinjectitereservoirs ofcommercial significance develop duringearly burialandareassociated withoverpressure, playconcepts aredeveloped that combinemechanisms for overpressured evelopment withsedimentology. Recognition ofthe presence ofsand injectitesw ill haveamajor affecto nm any deep-waterandotherp lays bothi nt erms ofe xploration and production.

Long term geological record of a global deep subsurface microbial habitat in sand injection complexes

“…Where they are well-studied, there is also evidence for multiple episodes of injection within the history of a single region2. The scale of the phenomenon is so great that injected sands are now targets for the drilling and extraction of huge oil reserves67. The largest injection structures appear in seismic profiles, and in the North Sea may contain millions of barrels of oil in a single structure1 and billions of barrels in total26.…”

Borehole evidence for wing-like clastic intrusion complexes on the western Norwegian margin

“…3). Based on this observation, sandstone X, and the overlying sandstones Y and Z, can therefore be interpreted either as sills, which were intruded in the subsurface (see Parize & Friès 2003), or as sheet-like sandbodies, which were extruded onto the palaeo-seabed (compare 'emerging sills' of Hurst et al 2005). In the absence of core data, distinguishing between these two models is problematic, although the thickness of sandstone X (15 m) suggests that an intrusive origin for the sandbody may be more plausible (see discussion by Hurst et al 2006).…”

Tertiary deep-marine reservoirs of the North Sea region: an introduction

“…Merganser: Charles & Ryzhikov 2015;Jones et al 2015); large-scale sand injection complexes (cf. Dixon et al 1995;Hurst et al 2005;Schwab et al 2014); isolated channel-form sandstones encased in shale (e.g. Alba: Moore 2014); large-scale compactional relief of the entire basin-floor fan (e.g.…”

“…The subsequent modification by post-depositional remobilization and injection can generate entirely new reservoir architectures that present a challenge to predict, model and develop (Hurst et al 2005). Sand injection has been a locally important process in the North Sea region, impacting hydrocarbon accumulations in a variety of ways.…”