Abstract
A two-step method is described which enables the depositional history and the structural development to be simulated. The method is illustrated by simulation of a North Sea field containing a chalk reservoir with a large overpressure. The simulation is based on back-stripping techniques including decompaction calculations in which sediments are ``unloaded`` in successively older time steps. The first step involves 1D consolidation calculations in a number of wells in the area, implying coupling of compaction and flow of pore fluid. The compaction is solved by soil mechanics constitutive laws including time dependent deformations. These laws provide effective stresses, pore pressures, thicknesses and void ratios as functions of time. This makes it possible to model the behavior of overpressured shales. The computations are iterative forward modelling, and the results are compared to the present day situation. A decompaction factor is introduced. This factor describes the relative change of computed thickness for a given layer during a time interval. It is possible to include flow between the wells in a particular layer, such as a chalk reservoir, and thereby make the model partly three-dimensional. The decompaction factors for the wells can be interpolated, and thereby provide a field-wide description of the decompaction
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Citation Formats
Olsen, A, and Rasmussen, F O.
Numerical method to describe the deformation of chalk reservoirs.
Denmark: N. p.,
1992.
Web.
Olsen, A, & Rasmussen, F O.
Numerical method to describe the deformation of chalk reservoirs.
Denmark.
Olsen, A, and Rasmussen, F O.
1992.
"Numerical method to describe the deformation of chalk reservoirs."
Denmark.
@misc{etde_10156783,
title = {Numerical method to describe the deformation of chalk reservoirs}
author = {Olsen, A, and Rasmussen, F O}
abstractNote = {A two-step method is described which enables the depositional history and the structural development to be simulated. The method is illustrated by simulation of a North Sea field containing a chalk reservoir with a large overpressure. The simulation is based on back-stripping techniques including decompaction calculations in which sediments are ``unloaded`` in successively older time steps. The first step involves 1D consolidation calculations in a number of wells in the area, implying coupling of compaction and flow of pore fluid. The compaction is solved by soil mechanics constitutive laws including time dependent deformations. These laws provide effective stresses, pore pressures, thicknesses and void ratios as functions of time. This makes it possible to model the behavior of overpressured shales. The computations are iterative forward modelling, and the results are compared to the present day situation. A decompaction factor is introduced. This factor describes the relative change of computed thickness for a given layer during a time interval. It is possible to include flow between the wells in a particular layer, such as a chalk reservoir, and thereby make the model partly three-dimensional. The decompaction factors for the wells can be interpolated, and thereby provide a field-wide description of the decompaction during each time interval. In the second step - the back-stripping - the decompaction factors are used instead of the traditional depth/porosity relations. In this way geotechnical methods are introduced into the back-stripping technique. At the Danish Geotechnical Institute (DGI) the results of this modelling has been used in calculations of two or three dimensional stress fields, fracture directions and intensity at different times. These computations are described in the companion paper by K. Petersen et al. ``Natural stress field in a chalk reservoir predicted by spatial finite element analysis``. (au).}
place = {Denmark}
year = {1992}
month = {Dec}
}
title = {Numerical method to describe the deformation of chalk reservoirs}
author = {Olsen, A, and Rasmussen, F O}
abstractNote = {A two-step method is described which enables the depositional history and the structural development to be simulated. The method is illustrated by simulation of a North Sea field containing a chalk reservoir with a large overpressure. The simulation is based on back-stripping techniques including decompaction calculations in which sediments are ``unloaded`` in successively older time steps. The first step involves 1D consolidation calculations in a number of wells in the area, implying coupling of compaction and flow of pore fluid. The compaction is solved by soil mechanics constitutive laws including time dependent deformations. These laws provide effective stresses, pore pressures, thicknesses and void ratios as functions of time. This makes it possible to model the behavior of overpressured shales. The computations are iterative forward modelling, and the results are compared to the present day situation. A decompaction factor is introduced. This factor describes the relative change of computed thickness for a given layer during a time interval. It is possible to include flow between the wells in a particular layer, such as a chalk reservoir, and thereby make the model partly three-dimensional. The decompaction factors for the wells can be interpolated, and thereby provide a field-wide description of the decompaction during each time interval. In the second step - the back-stripping - the decompaction factors are used instead of the traditional depth/porosity relations. In this way geotechnical methods are introduced into the back-stripping technique. At the Danish Geotechnical Institute (DGI) the results of this modelling has been used in calculations of two or three dimensional stress fields, fracture directions and intensity at different times. These computations are described in the companion paper by K. Petersen et al. ``Natural stress field in a chalk reservoir predicted by spatial finite element analysis``. (au).}
place = {Denmark}
year = {1992}
month = {Dec}
}