Shale compaction modeling study in the South Caspian Basin

Shale compaction modeling study in the South Caspian Basin

The South Caspian Basin (SCB) is a young basin with a sedimentary rock column up to 25 km thick. During the last 5 million years, high sedimentation rates in combination with other factors resulted in abnormally high pore pressures, especially in shales. Understanding the nature and distribution of the overpressure is one of the most important issues for exploration and reservoir engineering concepts, as well as drilling and completion operations.

Figure 1: (a) Map of the South Caspian Basin showing different pore pressure regimes (modified after Javanshir et al. 2015);
Figure 1: (b) pore pressure-depth relationships for shales and sands in three areas (Bredehoeft et al. 1988).

Our approach investigated the relationship between the effective stress and porosity in shales of the Productive Series and how it is affected by the shale volume.

Porosity was calculated from the bulk density log and calibrated with X-Ray Diffraction (XRD) measurements. Effective stress was estimated by applying the Terzaghi principle. The shale volume was calculated from the Gamma Ray log and calibrated with XRD measurement points.

Two disequilibrium compaction models, one proposed by Aplin et al. (1995) and the other by Schneider et al. (1994), were tested in the SCB for the first time.

Figure 3. 1D compaction modelling results
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