Carboniferous Carbonate Reservoir Geomechanics (CCRG)
PhD thesis I. Nugmanov
3D geomechanical characterisation of Carboniferous carbonate reservoir in Tatarstan, Russia
In the Republic of Tatarstan, Russia, about 20,4% of proven oil reserves are contained in carbonate reservoirs. However, only 10-15% of the oil-in-place can be currently recovered. Economically significant carbonates reservoir units are concentrated in the Lower Mississippian and the Lower Pennsylvanian, with the Bashkirian units being one of the main carbonate target intervals in the Volga-Ural region. From a production point of view, significant portions of the Devonian clastic reservoirs rocks are in a late production stage and consequently, the main focus of oil exploration in this region is now on the Carboniferous reservoir rocks. Application of horizontal drilling and acid fracturing are the most effective approaches for complex carbonates exploration from both economical and technological point of view. Thus, reservoir geomechanics become of paramount importance for successful and safe oil field development with regards to solve problems of wellbore instability, pore pressure prediction, reservoir depletion and fault reactivation. Research activities of the PhD project consist of the three main parts shown in Fig. 1.
The first part of the research work is related to acquiring in situ stress data on the regional scale, particularly on the orientation of the maximum horizontal stress. This information will be obtained by processing acoustic and resistivity wellbore image logs. Observed structures in the image logs will be ranked according the world stress map project ranking system. WellCAD software (ALT, Luxemburg) has been chosen for image log processing.
On the local scale our focus is on developing 1D and 3D mechanical earth models (MEM) of the Akan oil field in the Melekess depression. 1D MEM’s integrate well logging data, lab tests on core and well testing information by constructing the rock mechanical stratigraphy, pore pressure and near-well stress distribution. Computed rock properties, pore pressure, and horizontal stresses will be used for borehole stability analysis. The workflow for 1D MEM will be performed using Techlog software.
Finally, a 3D MEM of part of the Akan oil field will be build using finite element techniques. The structural model including existing faults will be derived from interpretation of 3D seismic surveys and the spatial distribution of the mechanical properties from seismic AVO inversion. Results from the preceding regional stress analysis will be used as boundary conditions for modelling. The numerical simulation will provide the full stress and strain tensors for each part of the model domain which are relevant for a wide range of practical applications.
Research work partly funded by the German Academic Exchange Service (DAAD) according to German-Russian Interdisciplinary Science Center grant.
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