Range of RACOS^® services, advantages and unique features

 

RACOS^® is a comprehensive procedure for determining from core samples 3D values of important in situ parameters such as stresses, elasticity and deformability, as well as the effects of pore pressure change on these values¹.

 

The basic laboratory measurements are made on samples taken from core from the zone of interest. These measurements determine the spatial seismic anisotropy and the 3D dynamic elastic parameters. From the measured data the 3D effective in situ stresses are derived directly. They are essential for stability analysis and sanding evaluations².

The determination of the pore pressure effectiveness (3D Biot coefficient) is necessary for the calculation of the total in situ stresses. The 3D in situ total stresses³ are required for frac planning. The 3D pore pressure effectiveness (also derived from the laboratory measurements) can be used to evaluate preferred in situ flow directions.

Supplementary investigations can be made to determine in situ stress conditions after the pore pressure has changed and/or under paleo conditions, to evaluate recent tectonic stress components and (if not already available) for the geographic reorientation.

On the basis of the laboratory measurements, without additional stress-strain tests, 3D elastic and total deformation parameters can be determined for relevant loadings. The measured propagation velocities of elastic waves can be used to correlate sonic log data with in situ parameters. The orientations of the 3D parameters can also be used to define principal directions for plug preparation for further investigations of 3D properties (permeability, strength).

 

The determination of the complete 3D magnitudes of in situ stresses and important rock parameters is offered on the basis of RACOS^® core analyses. No work is required at the drilling site, and the analyses can be carried out at any convenient time. No assumptions are necessary about parameter values or constituitive laws for the rock.

 

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1	3D strength parameters can be determined with on additional laboratory testing.
2	The total stress is the external loading against which the internal loading (the pore pressure) acts. Its vertical component corresponds to the total overburden pressure and the minimum total stress component corresponds to the closure pressure of a hydraulic frac.
3	The total stress is the external loading against which the internal loading (the pore pressure) acts. Its vertical component corresponds to the total overburden pressure and the minimum total stress component corresponds to the closure pressure of a hydraulic frac.