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Eustasy Recording Potential of an Isolated Devonian to Pennsylvanian Carbonate Platform in a Foreland Basin Setting (Tengiz, Pricaspian Basin, Kazakhstan)*

By

J.A.M. Kenter1 and P.M. Harris2

 

Search and Discovery Article #20047 (2008)

Posted May 20, 2008

 

*Abstract prepared for oral presentation at AAPG Annual Convention, San Antonio, Texas, April 20-23, 2008.

Click to view list of articles adapted from presentations by P.M. (Mitch) Harris or by his co-workers and him at AAPG meetings from 2000 to 2008.

 

1 ETC, Chevron, Voorburg, Netherlands ([email protected])

2 ETC, Chevron, San Ramon, CA, USA ([email protected])

 

Abstract

Research drilling of continental margins over the last decade has validated a significant number, as well as the timing, of EPR sea-level events for the past 100 My. However, for the older geological record diverging sea level estimates (EPR curve, continental flooding records, planktic evolutionary records) still exist and the extraction of reliable eustatic records remains problematic.

Tengiz field is an isolated carbonate buildup in the southeastern Pricaspian Basin, containing a complete Late Famennian to Early Bashkirian platform succession that was deposited in a relatively stable but rapidly subsiding foreland basin setting facing a thrust belt to the south. Since the Famennian, the platform aggraded and periodically back-stepped, resulting in approximately 1400 m (4480 ft) of relief above the Famennian platform, followed by up to 2 km (1.2 miles) of Serpukhovian progradation. Vertical trends in relative shoaling and deepening, recorded exposure and/or erosional events, and biostratigraphy provide a relative sea level record of punctuated sea level falls and rises that is made up of 2nd and 3rd order sequences which are superimposed by higher (4-5th order) frequency platform cycles.

Though several of the observed sea level lowstands correspond to 3rd order eustatic sequences on the EPR curve, the influence of rapid changes in the paleobathymetry of the foreland basin, which caused significant thickening of sequences and drowning in the Late Devonian elsewhere in the basin, appears to have a strong influence on the regional sequence stratigraphic framework. This article addresses the interplay between subsidence and recorded sequences in such foreland basin settings.

 

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Paleozoic Carbonates in Foreland Basin Settings: Northern Pricaspian Basin (Kazakhstan) and Cantabrian Zone (Spain)*

By

J.A.M. Kenter1 and P.M. Harris2
With contributions by Oscar Merino-Tomé, Juan Bahamonde, Juan Colmenero, Tom Heidrick, and Kairat Jazbayev

 

Search and Discovery Article #20047 (2008)

Posted May 20, 2008

 

*Adapted from oral presentation at AAPG Annual Convention, San Antonio, Texas, April 20-23, 2008.

 

1 ETC, Chevron, Voorburg, Netherlands ([email protected])

2 ETC, Chevron, San Ramon, CA, USA ([email protected])

 

Outline

  • Rationale
  • Carbonate systems in foreland basin settings
  • Tectonic setting Pricaspian Basin
  • Tengiz Field accommodation history
  • Outcrop analog from northern Spain: platforms and thrust-top buildups in a foreland basin setting
  • Conclusions

 

uOutline

uFigures

uRationale

uNorth caspian basin

uCantabrian zone

uSummary

uReference

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

uOutline

uFigures

uRationale

uNorth caspian basin

uCantabrian zone

uSummary

uReferences

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

uOutline

uFigures

uRationale

uNorth caspian basin

uCantabrian zone

uSummary

uReferences

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

uOutline

uFigures

uRationale

uNorth caspian basin

uCantabrian zone

uSummary

uReferences

 

 

Rationale

  • Sedimentation in tectonically active settings controlled by 1) structural grain, 2) timing and rate of deformation, and 3) eustacy.
  • Many carbonate hydrocarbon reservoir systems formed in foreland basin settings.
  • Generally difficult to extract geometry and timing from outcrop BUT
  • Outcrop analog from northern Spain shows variation of depositional style in time and space.
  • May assist understanding/interpretation of carbonate system evolution in such tectonic regimes and in Pricaspian, in particular.

 

North Caspian Basin--Background

  • Produces oil from subsalt Devonian-Carboniferous carbonate platforms.
  • Pricaspian Basin holds 46 BBOE (56% gas).
  • Four supergiant carbonate fields: Tengiz, Karachaganak, Astrakhan and Kashagan.
  • Complex tectonic history of:
    • Thermal subsidence and rifting until Late Carboniferous
    • Collision and thrusting starting in Permian
    • Separation from Tethys Ocean and formation of salt basin in Kungurian.

 

Cantabrian Zone: Marine Foreland Basin
(after Merino-Tomé, Bahamonde, Fernandez, and Colmenero, in press)

  • Complex arc-shaped collision/deformation system.
  • Nucleation of Serpukhovian to Moscovianisolated platforms in foreland basin.
  • Highly variable subsidence rates caused by advancing thrust belt.
  • As a result, local drowning of buildups and variable depositional styles and internal geometries across basin.
  • Development of local basins at –and on top of frontal part of thrust belt.
  • Filled by (Moscovian-Ghzelian) alternating clastics and carbonate ramps and low relief platforms.
  • Angular unconformities and thickness variations reflect tectonic deformation rates but 3rdorder (and higher) eustatic SL signal preserved.

 

Summary and Conclusions

  • Northern Pricaspian has 46 BBOE and 4 supergiant isolated platforms in Paleozoic foreland basin settings.
  • Highly complex and variable system.
  • Both un-and deformed isolated buildups and thrust-top platforms have reservoir potential.
  • Cantabrian Zone (Spain) provides well-studied outcrop analogs of arc-shaped system.
  • Spain provides mosaic of carbonate buildup styles in space and time and as a result of tectonic deformation and eustatic sea level.

 

Reference

Bosence, D.W.J., 2005, A new, genetic classification of carbonate platforms based on their basinal and tectonic setting in the Cenozoic: Sedimentary Geology, v. 175, p. 49-72.

 

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