In situ stress state estimation in reservoirs using an inverse approach

Antoine Mazuyer. ( 2018 )
University of Lorraine

Abstract

Initial stress state is the stress state before any human activity. Its knowledge is essential when dealing with scientific (understanding of plate tectonics), preventive (earthquake prediction) and industrial (understanding reservoirs before their exploitation) purposes. We present a method to estimate the initial stress state in a 3D domain from sparse data. This method relies on an inverse approach which uses the finite elements method to solve the elastic mechanical problem. The model parameters are Neumann conditions, which are defined as piecewise linear functions. The data parameters are stress state observations, such as intensity and orientation at a few points. An ensemble optimization method is used to solve the inverse problem. The method is tested on a synthetic case where the reference solution is known. On this example, the method succeeds in retrieving the stress state at data points as well as in the whole domain. The method is enriched with a mechanical criterion which imposes mechanical constraints in the domain under study. The method is then applied to a real case : the Neuquèn basin in Argentina where borehole stress data is available. This application reveals some of the limits of the presented method. Then, the effect of faults on the stress state is investigated. Different modeling strategies are presented : the objective is to reduce the computing cost, which can be very high when dealing with such complex structures. We propose to model them using only elastic properties. Finally, we present the integrative software which were developed to run mechanical simulations. RINGMesh handles the structural model data structure and RINGMecha runs the mechanical simulations on the model. RINGMecha is interfaced with several simulators. Each of them can be called separately, depending on the problem to be solved. The interface of RINGMecha with third party simulators is done in a user friendly manner. RINGMecha was used for all the computations presented in this thesis. It was built in order to be extended to other problems, with other simulators.

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BibTeX Reference

@PHDTHESIS{,
    author = { Mazuyer, Antoine },
     title = { In situ stress state estimation in reservoirs using an inverse approach },
      year = { 2018 },
    school = { University of Lorraine },
  abstract = { Initial stress state is the stress state before any human activity. Its knowledge is essential
when dealing with scientific (understanding of plate tectonics), preventive (earthquake prediction) and
industrial (understanding reservoirs before their exploitation) purposes. We present a method to estimate
the initial stress state in a 3D domain from sparse data. This method relies on an inverse approach
which uses the finite elements method to solve the elastic mechanical problem. The model parameters are
Neumann conditions, which are defined as piecewise linear functions. The data parameters are stress state
observations, such as intensity and orientation at a few points. An ensemble optimization method is used
to solve the inverse problem. The method is tested on a synthetic case where the reference solution is
known. On this example, the method succeeds in retrieving the stress state at data points as well as in the
whole domain. The method is enriched with a mechanical criterion which imposes mechanical constraints
in the domain under study. The method is then applied to a real case : the Neuquèn basin in Argentina
where borehole stress data is available. This application reveals some of the limits of the presented method.
Then, the effect of faults on the stress state is investigated. Different modeling strategies are presented :
the objective is to reduce the computing cost, which can be very high when dealing with such complex
structures. We propose to model them using only elastic properties. Finally, we present the integrative
software which were developed to run mechanical simulations. RINGMesh handles the structural model
data structure and RINGMecha runs the mechanical simulations on the model. RINGMecha is interfaced
with several simulators. Each of them can be called separately, depending on the problem to be solved.
The interface of RINGMecha with third party simulators is done in a user friendly manner. RINGMecha
was used for all the computations presented in this thesis. It was built in order to be extended to other
problems, with other simulators. }
}