A geomechanical property model of the Trattnach Oil Field in the Upper Austrian Molasse Basin

Katrin Schmid

Research output: ThesisMaster's Thesis

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Abstract

The Trattnach field was discovered in 1975 and produces oil from Cenomanian sandstones ever since. Multiple studies and investigations have been made for this area, concentrating mainly on the Cretaceous (Cenomanian) reservoir section. In this thesis a geomechanical model is established. It includes the crystalline basement and the entire basin fill reaching from Jurassic units to the Miocene sediments of the Innviertel Group. An existing reservoir model provided by RAG is extended and modified to fulfil the requirements to build a geomechanical grid. The geomechanical gridding is performed using the “Reservoir Geomechanics” plug-in from Schlumberger´s Petrel software package. The reservoir section and the additional under- and overlying horizons up to the earth’s surface are now embedded in a cube of side- and underburden cells. These allow a smooth simulation using the VISAGE simulator, a finite-element geomechanics simulator developed by Schlumberger. Running such a simulation requires a reservoir simulation model and a geomechanic grid which is populated with geomechanic parameters like Young’s-, bulk and shear modulus, as well as porosity and density data. These parameters are calculated using geophysical log data provided by RAG, including compressional sonic velocities, gamma ray and various resistivity logs. The compressional sonic velocities are used to calculate missing density, porosity and shear sonic velocity data. Density logs are created by using Gardner’s empirical relationship. Wyllie’s time average equation is used for the missing porosity logs and the vp-vs relationship developed by Castagna is used for the calculation of shear sonic velocities. With the shear-, compressional velocities and densities of a rock it is possible to calculate geomechanical parameters like Young’s moduli, Poisson ratios, as well as shear and bulk moduli. Additionally performed laboratory measurements on core plugs of the reservoir rocks provide the uniaxial compressive strengths. The Jurassic limestones are the stiffest material with an averaged Young’s modulus of 48 GPa, the seal rock of the CET1 formation has a averaged Young’s modulus of 36 GPa and the reservoir rocks formed by the CET2 and CET3 formations have a averaged Young’s modulus of 24 GPa. The grid has been been populated with all input data combined and represents a new basis for further geomechanical studies concerning the Trattnach oil reservoir.
Translated title of the contributionEin geomechanisches Model des Trattnach Ölfeldes im oberösterreichischen Molassebecken
Original languageEnglish
QualificationDipl.-Ing.
Awarding Institution
  • Montanuniversität
Supervisors/Advisors
  • Gruber, Wilfried, Supervisor (external)
  • Sachsenhofer, Reinhard, Supervisor (internal)
Award date19 Oct 2018
Publication statusPublished - 2018

Bibliographical note

embargoed until null

Keywords

  • Molasse Basin
  • geomechanical model
  • Petrel
  • reservoir geomechanics
  • VISAGE
  • elastic parameters
  • Castagna
  • Wyllie
  • Gardner

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