Temperature, differential pressure, and porosity inversion for ultradeep carbonate reservoirs based on 3D rock-physics templates

Ultradeep carbonate reservoirs have high temperatures and pressures, complex pressure/tectonic stress settings, and complex pore structures. These conditions make their seismic detection and characterization difficult, particularly if the signal-to-noise ratio is low, as is the case in most situations. Moreover, the high risk of deep-drilling exploration makes it impractical to carry out normal logging operations. We have developed a temperature-differential pressure-porosity (TPP) rock-physics model based on the Biot-Rayleigh poroelasticity theory to describe the wave response of the reservoir. A preliminary analysis indicates that temperature, pressure, and porosity are well correlated with wave velocity and attenuation. On the basis of this theory, we have built 3D rock-physics templates that account for the effects of TPP on the P-wave impedance, V-P/V-S ratio, and attenuation. The templates are calibrated with laboratory, well-log, and seismic data of the S area (Shuntuoguole uplift, Tarim Basin, Xinjiang, China). Then, the template is used to obtain the properties of the reservoir at seismic frequencies. The predicted results are consistent with the field reports (high temperature, low differential pressure, and high porosity) indicating high production rates. The methodology will be useful for hydrocarbon exploration in ultradeep carbonate reservoirs.