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DPS presents: QI and Geomechanics
20th September 2018 @ 3:30 pm - 7:00 pm UTC+1
Date & Time: September 20, 15:30-19:00 CET (click to add to calendar)
Venue: KIVI Prinsessegracht 23, 2514 AP Den Haag (click for map)
Please Click to email with RSVP to firstname.lastname@example.org before 19th Sep 2018
Gassmann equations (Gassmann, 1951) are used to calculate seismic velocity changes that result from variations in reservoir fluid saturation. These equations became predominant in the analysis of a direct hydrocarbon indication from seismic data through their use in analyzing the compressional to shear velocity ratio, Vp/Vs. This Vp/Vs ratio is used in many industry analyses, such as the amplitude variation with offset (AVO) analysis developed by Castagna et al. (1993). Multiple authors have since published a variety of Vp/Vs seismic interpretation techniques that use empirical relationships with Vp, Vs, and porosity terms. Unfortunately, however, there is a gap in the use of Vp/Vs relationships in petrophysical interpretation.
Recent years more and more complex wells have been drilled, quite often through depleted formations. NPT due to losses or stuck events can have significant impact on the project economics. Comprehensive geomechanical model can highlight potential hazards and allow to take early actions to mitigate issues.
Elasticity and particularly its anisotropy is a vital part of the comprehensive geomechanics model. As it will be shown, it has dramatic impact on the horizontal stresses profiles. Presentation demonstrates anisotropic elasticity modeling process.
The suggested workflow exploits Reuss, Upper and Lower Hashin-Shtrikman bounds for various cases of dispersed clay modeling. Each of the bounds corresponds to specific dispersed clay textures, like clay cementation, pore filling etc. These textures are classified and tied to the corresponding bounds.The rock anisotropy is modeled by Backus averaging of shaly sands with dispersed clay as a first component and laminated clay as a second component. The degree of anisotropy is controlled by the volume of laminated clay and its elastic moduli. The model is calibrated through several rock-physics cross-plots. The most optimal way is to calibrate model with measured velocities in vertical and horizontal wells. Other options like Stoneley wave driven horizontal shear velocity, calibration with core etc. and its pitfalls will be discussed as well. Typically, the strain response of the rock and the associated velocity changes is measured in pore depletion experiments. The velocity is determined by analyzing the first arrival of a transmitted ultrasonic wave. The relation between velocity changes and strain is generally well explored and understood. We propose a method for the monitoring of the deformation using the diffuse field, that is to say, focusing on the coda wave of the transmitted ultrasonic wave. Cross correlation analysis of the coda part returns higher order of information associated with inelastic changed in the medium. The applications are diverse and range from civil engineering, to seismology and reservoir monitoring.
As usual all have an opportunity to socialise with fellow petrophysical professionals over drinks and snacks.
Doors will open for registration and coffee at 3:30 pm and the talks will commence at 4:00 pm. The social hour will begin at 5:30pm.