Abstract

Underground gas storage Lauchstaedt (East Germany) is represented by fractured reservoir. For adequate representation of considered deposit, an idea of two-layered reservoir has been chosen. One layer was responsible for the system of fractures, whereas another one corresponded to matrix blocks description. For this storage an automatic history matching procedure has been implemented that was based upon optimal control theory approach. Objective function to be minimized included the sum of least square mismatches of observed and calculated well's reservoir pressures. A conjugate gradient method was implemented to minimize given objective function. Applied history matching algorithm implied solution of forward and adjoint boundary value problems. A set of control parameters contained porosity and permeability of fractures and matrix blocks.

The problem of reservoir petrophysical properties estimation was investigated in 3D statement. Developed history matching algorithm turned out to be very efficient. A very good fit of observed and calculated well's grid block pressures has been reached after 8 iterations of gradient search procedure, nevertheless 10 control parameters were introduced. The most sensitive parameter happened to be porosity. It resulted in initial gas in place overestimation by 15% comparing with registered one.

It was also obtained a good match of observed and calculated pressures after manual history matching procedure for reservoir described as dual porosity layer. Only two matching parameters have been introduced in this case, namely

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