AAPG GEO 2010 Middle East
Geoscience Conference & Exhibition
Innovative Geoscience Solutions – Meeting Hydrocarbon Demand in Changing Times
March 7-10, 2010 – Manama, Bahrain
Using Geomechanical and Fluid Flow Models to Predict Hydrocarbon Accumulation Zones
(1) Hydrogeology & Engineering Geology, National Mining University, Dnepropetrovsk, Ukraine.
(2) Geophysics, National Mining University, Dnepropetrovsk, Ukraine.
(3) Calculating Mechanics, Dnepropetrovsk National University, Dnepropetrovsk, Ukraine.
Location and redistribution of oil and gas deposits resulted by geologically long seepage of liquid and gaseous hydrocarbons are determined significantly by the stress-deformed state of the Earth in upper strata of 3-5 km thickness. Lithostatic and tectonic components make a decisive contribution to the total stress field, with the tectonics effect changing stress essentially. So that accounting for the stress anomalies of tectonic origin using geomechanical and fluid flow models enables characterizing reservoirs and determining accumulation zones of hydrocarbons more precise and reliable.
The proposed approach to estimate palaeotectonic stresses within the framework of the elastic medium theory includes the successive stages: (1) creation of the 3D structure velocity models of sedimentary deposits using the seismic prospecting data; (2) estimation of boundary conditions to calculate tectonic stresses by modeling of point displacements on layer boundaries due to long time deformations of the sedimentary cover; (3) development and identification of 3D geomechanical models based on FEM algorithms to calculate the tensor of tectonic and lithostatic stresses; (4) hydrodynamic evaluation and contouring of hydrocarbon accumulation zones.
The tectonic stress analysis allows revealing variations of the lithostatic stress field related to deformations of sedimentary deposits. The way to determine tectonic stress were proposed and discussed by M.M. Dovbnich et al. (2008). Geomechanical calculation of the stress tensor determines the sum of normal and shear stresses. Their combined analysis allows contouring condensed-stretched and tangent stress zones, which is especially important for geological interpretation.
Geomechanical and hydrodynamic models are coupled by the linear relationship between the stress in solid phase and the porous liquid pressure (Skempton A.W., 1954). This will enable approximate estimating the zones of high oil and gas content using Darcy’s low. Numerical modeling of oil and gaseous liquid flow in the heterogeneous layer makes hydrocarbon zone contours more precise.
The outlined approach was applied to predict locations of the areas perspective for oil and gas in the north of West Siberia. The maps of probable oil and gas accumulations were built by numerical modeling. The essential differences were found between predictions made for the lithostatic stress field only and the total stress field taking into account the tectonic component.