The project aimed to describe the dependency of seismic velocity in anisotropic siliclastic rocks as background for interpretation of seismic data with respect to effective stress and lithology. We use the tensorial porosity-deformation approach for anisotropic rocks (originally piezo-sensitivity theory, Shapiro 2003; Shapiro and Kaselow 2005) and give an adapted formulation for vertical and horizontal transverse isotropic rocks under uniaxial and triaxial loading conditions. By using the porosity-deformation approach the number of free parameters is reduced compared to phenomenological fitting of data. With this theory we explain literature data of compliances measured in a shale sample during a multistage pseudo triaxial experiment. The obtained model parameters from fitting the hydrostatic part are used for the prediction of the compliances describing the S-waves in the triaxial part of data. Furthermore, we developed further an experimental setup and are now able to measure complete sets of velocity for the description of transverse isotropic and orthorhombic rocks. The new data reveal new aspects of the stress dependency of anisotropy parameter. The applicability of the theory on the new data and on previously obtained incomplete datasets is shown, including the reconstruction of velocities.

Abstract: The present study aims to summarize the state of knowledge concerning the effects of sulphur compounds and odorants in underground gas storage facilities (UGS). It is motivated by increasing amounts of biogas in the German gas grid, potentially followed by residence of mixed odorized gases in UGS. The effects of these compounds on reservoirs are heterogeneously described by theoretical geochemical publications, laboratory results and the experiences of operating French and German UGS. An increase of the formation of H2S that coincide with risks for storage integrity, capacity and well productivity is not known from operation practice. Pore blockage and reduction in permeability in consequence of mercaptans or THT contaminations are not published. The same can be stated for any increased flow resistance, blockage and corrosion processes in well completions. However, increased technological requirements are expected during injection of odorized gas concerning the processing or disposal of reservoir fluids charged with sulphur compounds and odorants as well as contaminated brines during releaching. Thus, no immediate safety requirements to UGS arise due to the storage of odorized biogas. However, technical operation must be surveyed for additional effects. The number of relevant publications available on the topic is limited so that a significant number of questions related to particular storage sites remains unclarified.

The focus of this R&D project is the development of a new integrated workflow using state of the art optimization techniques combined with the adjoint method for history matching. The integration concept is aimed at developing a robust workflow supporting decision processes for evaluating alternative production scenarios of oil and gas fields. For this purpose, SenEx, which is an advanced sensitivity computation tool capable of modifying rock properties on grid-block level, has been linked to the existing optimization framework MEPO. The Hotlink thus developed has been tested, reviewed and enhanced. Within the framework of this re-search project, the developed workflows have been applied to a spectrum of history match-ing problems with varying complexities. In general, multiple geological realizations were used to capture existing uncertainty in an extended optimization workflow, including history matching and production optimization. Us-ing this method, history match is typically achieved with significantly less number of iterations compared to existing methods. The workflow applied is useful for evaluating alternative re-development scenarios, quantifying uncertainties and generating realistic history matched models. Benchmarking work performed provided better insights into benefits and limitations of the adjoint method.