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Synthetic well test modelling in a high net-to-gross outcrop system for turbidite reservoir description

Ewan Robertson, Patrick W. M. Corbett, Andrew Hurst, Nick Satur and Bryan T. Cronin
Synthetic well test modelling in a high net-to-gross outcrop system for turbidite reservoir description
Petroleum Geoscience (February 2002) 8 (1): 19-30


Synthetic well tests have been produced using a 3D model of an outcropping turbidite sandstone unit from the Cingoz region in southern Turkey. The model contains realistic sand sheet, tongue, lobe and background sand facies architecture (i.e. geometry and stacking) mapped from an outcrop study. The geometric information is useful as an analogue for high net-to-gross turbidite oil fields. The facies have been assigned petrophysical properties from a subsurface analogue. There is little shale in this system. Well test responses were then derived from the high net-to-gross turbidite model using various architectural, porosity-permeability scenarios and completion strategies. The impact on well test derivatives of various sand body geometries and permeability contrasts could then be determined. Two completion strategies--partial penetration and fully perforated intervals--were assessed for their applicability in the high net-to-gross system. The geological model is effectively a sandbox, and shows a very uniform testing response from the rather uniform property distributions. However, when the level of permeability heterogeneity is increased by populating the model with varying contrasts of permeability and porosity, the sand body geometry can be seen to influence the well tests. Partial completions in sand bodies are particularly effective in detecting sand body geometry. The geometry controls the flow regimes in a well test response despite variations in the permeability contrasts. The effect of varying geometry is illustrated and an external linear flow regime is identified. Where there is sufficient sand body thickness, partial perforation results in spherical flow, from which a vertical permeability can be obtained. In the model, the vertical permeability thus obtained is a local (to the volume investigated) effective permeability of stacked isotropic facies. This work was undertaken to give guidance on the description of hydrocarbon reservoirs by well testing. If well testing is to be used in high net-to-gross turbidite systems for the purposes of reservoir characterization, then partial perforation of the system should be planned. Interpreted vertical permeabilities should be applied with careful consideration of the stacked pattern of sand bodies.

ISSN: 1354-0793
EISSN: 2041-496X
Serial Title: Petroleum Geoscience
Serial Volume: 8
Serial Issue: 1
Title: Synthetic well test modelling in a high net-to-gross outcrop system for turbidite reservoir description
Affiliation: Heriot-Watt University, Department of Petroleum Engineering, Edinburgh, United Kingdom
Pages: 19-30
Published: 200202
Text Language: English
Publisher: Geological Society Publishing House, London, United Kingdom
Accession Number: 2002-024080
Categories: Economic geology, geology of energy sources
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Includes appendices
Illustration Description: illus. incl. block diags.
N35°49'60" - N42°00'00", E26°00'00" - E44°45'00"
Secondary Affiliation: Aberdeen University, GBR, United Kingdom
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 200209
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