Base of Salt Structure and Stratigraphy—Data and Models from Pompano Field, VK 989/990, Gulf of Mexico

Harrison, Holly; Kuhmichel, Lew; Heppard, Phil; Milkov, Alexei V.; Turner, Joshua C.; Greeley, Dave

doi:10.5724/gcs.04.24.0243

Cited by 10 publications

(15 citation statements)

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“…There is a discrete surface of advance at the very tip of the salt, but what occurs where the salt is thicker? Conceptually, there are three possibilities: (1) subsalt basal shear, in which some of the advance is accommodated by shear in underlying strata (Harrison and Patton, 1995;Harrison et al, 2004); (2) base-salt detachment, where slip on the frontal thrust continues as slip on the base salt; and (3) intrasalt basal shear, with a zone of concentrated shear inside and near the base of the salt sheet. We see no field evidence supporting subsalt basal shear, and a base-salt detachment is incompatible with viscous drag near the boundary of a salt layer unless the boundary is somehow lubricated or highly overpressured, which is unlikely at the shallow levels of initial sheet advance.…”

Section: Advancementioning

confidence: 99%

“…These zones may contain locally repeated section, overturned strata, and blocks of mixed biostratigraphic ages. A number of theories have been proposed to explain these observations: (1) subsalt basalt shear, in which the advance of salt is accommodated, at least in part, by shearing and thinning of subsalt strata to form a subsalt shear zone (Harrison and Patton, 1995;Harrison et al, 2004); (2) imbricate thrusting to form an antiformal stack beneath salt that has already been emplaced (Jackson and Hudec, 2004;Alexander et al, 2004); (3) imbricate thrust faults ahead of the salt tip that are overridden when the salt advances on one of the more hinterland thrusts Jackson, 2006, 2009); and (4) debris-flow deposits, in which carapace slumps from the frontal scarp and is subsequently overridden by the salt sheet (McGuinness and Hossack, 1993;Kilby et al, 2008;Hudec and Jackson, 2009). However, subsalt rubble zones are not ubiquitous; some wells exit the base of salt sheets into undeformed minibasin strata, and others encounter coherent upturned or overturned strata (Kilby et al, 2008;Saleh et al, 2013).…”

Section: Introductionmentioning

confidence: 98%

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Allochthonous salt initiation and advance in the northern Flinders and eastern Willouran ranges, South Australia: Using outcrops to test subsurface-based models from the northern Gulf of Mexico

Hearon¹,

Rowan²,

Giles³

et al. 2015

Bulletin

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The northern Flinders Ranges and eastern Willouran Ranges, South Australia, expose Neoproterozoic salt diapirs, salt sheets, and associated growth strata that provide a natural laboratory for testing and refining models of allochthonous salt initiation and emplacement. The diapiric Callanna Group (∼850-800 Ma) comprises a lithologically diverse assemblage of brecciated rocks that were originally interbedded with evaporites that are now absent. Using stereonet analysis to derive three-dimensional information from two-dimensional outcrops of stratal geometries flanking salt diapirs and beneath salt sheets, we evaluate 10 examples of the transition from steep diapirs to salt sheets, 3 of ramp-to-flat geometries, and 2 of flat-to-ramp transitions.Stratal geometries adjacent to feeder diapirs range from a minibasin-scale megaflap to halokinetic drape folds to high-angle truncations and appear to have no relationship to subsequent allochthonous salt development. In all cases, the transition from steep diapirs to salt sheets is abrupt and involved piston-like breakthrough of thin roof strata, which permitted salt to flow laterally. We suggest two models to explain the transition from steep diapirs to subhorizontal salt: (1) salt-top breakout, where salt rise

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Section: Advancementioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Allochthonous salt initiation and advance in the northern Flinders and eastern Willouran ranges, South Australia: Using outcrops to test subsurface-based models from the northern Gulf of Mexico

Hearon¹,

Rowan²,

Giles³

et al. 2015

Bulletin

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show abstract

“…However, one point of geomechanical relevance will be commented upon here. At the Pompano field, a large number of sub-salt well penetrations have enabled good characterization of the basal shear zone and the pore pressure variations extending away from the salt 21 . At Pompano, this is greatly facilitated by several reservoir sands located immediately beneath the salt where pore pressures have been measured directly.…”

Section: Pore Pressure Beneath Saltmentioning

confidence: 99%

Geomechanics Considerations for Through- and Near-Salt Well Design

Willson

Fredrich

2005

Proceedings of SPE Annual Technical Conference and Exhibition

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractOver the next decade a significant amount of exploration and new field developments will take place in salt provinces around the world -in the deepwater Gulf of Mexico, and offshore Angola, Brazil, and North and West Africa. Salt formations provide both opportunities and challenges to the design and construction of the often complex wells to be drilled in these locations.An overview of the many geomechanical considerations necessary to ensure successful well construction when drilling in through-, sub-and near-salt environments is presented. The structural styles of deformed sediments adjacent to salt, combined with stress perturbations caused by the presence of salt, are used to assess the risk of encountering zones that might cause wellbore instability or lost-circulation problems. Well design examples are provided that show how near-and through-salt uncertainties may be included within a geomechanical well design for required mud weights while drilling.

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“…Humphris, 1978Humphris, , 1979Worrall & Snelson, 1989) and along the margin of West Africa (e.g. D 'onfro, 1988;Nelson & Fairchild, 1989;Wu et al, 1990); (ii) surficial glacial flow (McGuinness & Hossack, 1993;Fletcher et al, 1995); (iii) advance above subsalt shear zones (Harrison & Patton, 1995;Harrison et al, 2004); and (iv) and emplacement along leading-edge thrusts (Hudec & Jackson, 2006, 2009. Analysis of seismic data, well data and physical and numerical models have led to various models of allochthonous salt emplacement, including: (i) lateral injection (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…McGuinness & Hossack, 1993;Harrison & Patton, 1995;Harrison et al, 2004;Jackson & Hudec, 2004;Alexander et al, 2005;Kilby et al, 2008;Hudec & Jackson, 2009). This zone, when present, may contain overturned stratigraphy, mixed biostratigraphic ages and structurally repeated strata.…”

Section: Introductionmentioning

confidence: 99%

Geology and tectonics of Neoproterozoic salt diapirs and salt sheets in the eastern Willouran Ranges, South Australia

et al. 2014

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Allochthonous salt structures and associated primary and secondary minibasins are exposed in Neoproterozoic strata of the eastern Willouran Ranges, South Australia. Detailed geologic mapping using high-quality airborne hyperspectral remote-sensing data and satellite imagery, combined with a qualitative structural restoration, are used to elucidate the evolution of this complex, long-lived (>250 Myr) salt system. Field observations and interpretations at a resolution unobtainable from seismic or well data provide a means to test published models of allochthonous salt emplacement and associated salt-sediment interaction derived from subsurface data in the northern Gulf of Mexico. Salt diapirs and sheets are represented by megabreccias of nonevaporite lithologies that were originally interbedded with evaporites that have been dissolved and/or altered. Passive diapirism began shortly after deposition of the Callanna Group layered evaporite sequence. A primary basin containing an expulsion-rollover structure and megaflap is flanked by two vertical diapirs. Salt flowed laterally from the diapirs to form a complex, multi-level canopy, now partly welded, containing an encapsulated minibasin and capped by suprasalt basins. Salt and minibasin geometries were modified during the Late Cambrian-Ordovician Delamerian Orogeny (ca. 500 Ma). Small-scale structures such as subsalt shear zones, fractured or mixed 'rubble zones' and thrust imbricates are absent beneath allochthonous salt and welds in the eastern Willouran Ranges. Instead, either undeformed strata or halokinetic drape folds that include preserved diapir roof strata are found directly below the transition from steep diapirs to salt sheets. Allochthonous salt first broke through the diapir roofs and then flowed laterally, resulting in variable preservation of the subsalt drape folds. Lateral salt emplacement was presumably on roof-edge thrusts or, because of the shallow depositional environment, via open-toed advance or extrusive advance, but without associated subsalt deformation.

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Base of Salt Structure and Stratigraphy—Data and Models from Pompano Field, VK 989/990, Gulf of Mexico

Cited by 10 publications

References 0 publications

Allochthonous salt initiation and advance in the northern Flinders and eastern Willouran ranges, South Australia: Using outcrops to test subsurface-based models from the northern Gulf of Mexico

Allochthonous salt initiation and advance in the northern Flinders and eastern Willouran ranges, South Australia: Using outcrops to test subsurface-based models from the northern Gulf of Mexico

Geomechanics Considerations for Through- and Near-Salt Well Design

Geology and tectonics of Neoproterozoic salt diapirs and salt sheets in the eastern Willouran Ranges, South Australia

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