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Pore pressure prediction and monitoring 283

pore pressure before drilling, and correctly detecting and interpreting
abnormal pressures in the real time. Predrill pore pressure prediction can be
conducted by using seismic interval velocity in the planned well location as
well as using well logging and drilling data in the analog wells. In the cases of
new prospects and deepwater subsalt wells, high uncertainties and serious
challenges exist in the predrill prediction; therefore, real-time pore pressure
detection and analysis are highly needed to reduce drilling risks.
Pore pressure analyses mainly include three aspects: predrill pore pres-
sure prediction, pore pressure prediction while drilling (real time), and
postwell pore pressure analysis (e.g., Li et al., 2012). Predrill pore pressure
can be predicted using seismic interval velocity data in the planned well
location, as well as using geological, well logging, and drilling data in the
offset wells, as shown in Fig. 8.1. If a large uncertainty exists in the predrill
prediction, real-time pore pressure detection and updates while drilling are
recommended to reduce uncertainty. Real-time pore pressure detection
generally relies on the following measurements and data: logging-while-
drilling (LWD), measurement-while-drilling (MWD), measured pore
pressure and drilling parameters, and mud logging (Fig. 8.1).
It should be noted that the seismic interval velocity and well log-based
pore pressure predictions are based on the shale (mudrock) properties, and
the pore pressures obtained from these methods are the pressures in shales.

Figure 8.1 Schematic workflow for pore pressure analyses.