EAGE/SEG Summer Research Workshop - Towards a Full Integration from Geosciences to Reservoir Simulation

In order to incorporate the size of reservoir grids into the seismic frequency scale, the standard Backus averaging method is used for upscaling. We propose to extend the Backus averaging method for the low-frequency case and introduce the dispersive Backus model using the Baker-Campbell-Hausdorff (BCH) series. The accurate description of velocity dispersion for effective medium is very important in seismic modelling and inversion of seismic data into effective reservoir properties.

Research has been done with the task of identifying structural and tectonic characteristics of the Čačak – Kraljevo basin, and the goal was to determine tectonic setting of the basin and it’s basement. Complex geophysical and geological data were used: gravity and geomagnetic maps, Landsat 7 satellite imagery and map of temperatures, derived from thermal bands of the satellite imagery. It was obtained that tectonic characteristics of the investigated area are complex, due to it’s complex geotectonic setting. Kinematic and dip angle of the ruptures were obtained from the combination of standard visual methods and map of vertical gradient of gravity acceleration. Map of temperatures can confirm existence of the ruptures, on the places which are not highly visible on any other set of data used. Geotectonic setting of basement of the basin was obtained from the combination of interpretation of the tectonic fabric and geological and petrological data.

Knowledge of the structure controlling the flow of fluids within a reservoir is critical in many activities, such as hydrocarbon extraction and carbon capture sequestration (CCS). To this end, surface deformation are important observations that help in relating the ground motion to flow-related processes at depth. InSAR data from satellite radar sensors are gaining increasing attention for their unique technical features and cost-effectiveness. These data provide accurate displacement measurements along the satellite line-of-sight (LOS) and high spatial density (typically exceeding 100 measurement points/sqkm) over large areas, especially when advanced InSAR technique, such as PSInSAR™ are applied. There are significant advantages in combining two or more data stacks acquired along different satellite orbits in order to estimate a 2D vectorial displacements (East-West and Vertical components). In this work we highlight the importance of using two components of displacement to better constraint an inversion for a distributed source model.

Time-lapse electrical resistivity tomography (ERT) represents a powerful tool for subsurface solute transport characterization since a full picture of the spatio-temporal evolution of the process can be obtained. However, the quantitative interpretation of tracer tests is difficult because of the uncertainty related to the geo-electrical inversion and the constitutive models linking geophysical and hydrological quantities. Here a new approach based on the Lagrangian formulation of transport and the ensemble Kalman filter (EnKF) data assimilation technique is applied to assess the spatial distribution of hydraulic conductivity K by incorporating time-lapse cross-hole ERT data. Under the assumption that the solute spreads as a passive tracer, for high Peclet numbers the spatial moments of the evolving plume are dominated by the spatial distribution of the hydraulic conductivity. The assimilation of the electrical conductivity 4D images allows updating of the hydrological state as well as the spatial distribution of K. Thus, delineation of the tracer plume and estimation of the local aquifer heterogeneity can be achieved at the same time by means of this interpretation of time-lapse electrical images from tracer tests.

We analyze the orientation of three-component borehole geophones by means of a walk-around VSP carried out in the proximity of the well. We propose a tomographic approach for improving the standard estimation based on hodogram analysis, using the 3D velocity field obtained from surface seismic and well logs. Taking into account the ray bending, the estimate dispersion due to local velocity anomalies can be reduced. This makes more reliable our estimates of fractures orientation and microseism hypocenters when borehole receivers are used in passive seismic surveys.

In order to improve the hydrate knowledge, it is very important to analyze the relationship between hydrate stability and overpressure condition. The overpressure condition in the free gas zone causes the disagreement between theoretical and seismic BSR depth. We model the effect of the overpressure condition versus sea water depth, geothermal gradient and hydrate stability. We introduce the following concepts: 1) hydrostatic BSR, which is the theoretical BSR evaluated supposing hydrostatic pressure in the pore space, and 2) the overpressure BSR, which is the BSR shifted with respect to hydrostatic condition because of the overpressure in the free gas zone. We draw the following considerations: i) the difference between the hydrostatic and the overpressure BSR depths is inversely proportional to water depth; ii) the geothermal gradient is inversely proportional to the difference between the hydrostatic BSR and the overpressure BSR depths. These results of this study are very useful in many fields. First of all, they should be considered in the environmental hazard. In fact, the hydrate present below the hydrostatic BSR is probably in meta-stable condition and more sensible to boundary conditions. Moreover, the effect of overpressure is important in shallow water, where human manufactures are located.

Abstract: This study was focused on calculating the geothermal gradient and checking it by thermal modeling in Asmari & Bangestan Reservoir in the Dezful Embayment, Iran. Temperature data are obtained in boreholes and then use for calculating the geothermal gradient. But sometimes determining of correct geothermal gradient due to some factors such as lithology variation and a little error in temperature readings is impossible. Also some wells show a geothermal gradient higher than others. For solving of these problems we utilized thermal modeling and organic geochemistry.

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