Pore pressure is an important driver in many aspects of petroleum exploration and production including prospect screening, drilling, completion, and production. However, in low permeability unconventional reservoirs it is only possible to sample reservoir pressure one point at a time. This leads to the question of how we interpolate between these pressure measurements to derive a 3D pore pressure model that can be predictive for drilling operations, and useful for completions and reservoir engineering models.
In this paper we will discuss a workflow to integrate point data pressure measurements such as the Diagnostic Fracture Injection Test (DFIT), with pressure indicators like mud weight (MW), and multiple empirical log based pore pressure prediction methods into one 3D model of the basin. For log based pore prediction, the Eaton-Yale, and Eaton methods were used to calculate continuous pore pressure profiles across the entire stratigraphic section logged. These pore pressure prediction methods were calibrated to DFIT measurements were the data was available. Next, the calculated 1D pore pressure logs were imported into a fine grid 3D stratigraphic model and geostatistically interpolated throughout the model. Then after rigorous quality control, drill stem test (DST) and MW measurements from thousands of wells were incorporated into the 3D model to validate the petrophysical based pore pressure calculation. The result of this workflow is a 3D model populated with pore pressure and pore pressure gradients at each discrete cell.
The resulting model can be used to understand different aspects of the reservoir by different disciplines. Geoscientists can use this model to understand the geological causes of overpressure, hydrocarbon maturation, or sealing stratigraphy. When combined with 3D rock property models, the pressure model could help us to identify the overpressured geological zones.
In addition to the geological uses, this information can be used by other disciplines in their workflows. Drilling engineers can use the estimated pressure as an input for wellbore stability models to enhance well planning. Completions engineers can use the outputs in their hydraulic fracture models, and reservoir engineers can import this data into their production models. Most importantly having everyone using the same pore pressure model fosters better integration, communication, and understanding of the reservoir.