Piezo3 is an authoritative tool for validation of pore pressure predictions in deep water. It addresses the Amoco, Tau, Dutta, Bowers, Ham/Swarbrick, and Patchett prediction methods – the Ham/Swarbrick 1d method for bench marking acoustic-derived predictions and the Patchett CEC method for detecting illitization that can cause gross underprediction.. Click on any text box to view a description of that input, parameter, or calculation. The placeholders shown in the result boxes are equation numbers cited in 'book' and 'Durham'. To provide an example, data from the Deepwater Horizon Macondo have been preloaded.
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Click each textbox for a description of each calculation
Piezo3 is a supplement to 'Elements of Deepwater Geopressure Prediction'. That book is available for the cost of printing. A paperback copy of my Durham research is also available (in several languages) but that text can be downloaded 'here'. The references noted in Piezo3 are fully cited in those two texts. Send corrections and comments as a message to my LinkedIn page (Martin Traugott)
As a pore pressure validation example, consider the BP Macondo data. (Click to reset the inputs to that data.) Click 'Calculate' and examine the diagnostics. CEC values (Patchett or Qv derived) that fall out of a normal range are flagged as bad data, non-shale, or indication of illitization.
Not reported in the Piezo3 data set is a Geotap measurement that recorded a true pore pressure of 14.2 equivalent mud weight. Now consider for a moment that you yourself were on the Deepwater Horizon at a point in time that drilling was about to continue below 17,600 feet.
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Here is the conundrum you face. Do you re-calibrate the acoustic parameters such that the acoustic predictions match measured values; OR, do you validate the prediction and tell the drillers there is a likelihood of drilling ahead into a massive pressure regression - and into massive lost circulation if the fracture gradient predictions are correct. In onshore and shelf wells it is common to re-calibrate for fluid expansion effect caused by illitization. The temperature at 18,000 feet in the Macondo could be certainly in the illite window.
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The Macondo of course did drill below 17,600 feet into a two pound per gallon drop in pore pressure – pretty much in agreement with the acoustic prediction. Lost circulation compromised well completion - the blowout triggered when the riser was displaced with sea water in preparation for rig moveoff.
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For more prospective on geopressure prediction view a 1997 World Oil article or the proceedings from a 1970 with particular focus on page 12 and page 59 in the 1970 proceedings. Note in figure 2 on page 59, that Pennebaker's normal compaction line is plotted correctly as a log-log function, not as a semi-log function as commonly plotted.
Traugott, December 2023.