Peter Gibson (Operations & Wellsite Geologist)
With increased focus on real time pore pressure evaluation it has become commonplace to utilise Pore Pressure Engineers to provide a “real time” quantitative pore pressure solution using LWD as the primary input. Whilst these LWD based pore pressure models are generally very good, it is vital to realise they have their limitations, particularly where offset well data is sparse or where the geology changes rapidly.
The LWD sensors that provide the input to pore pressure models can be located 5 to 10’s of metres behind the bit. In addition, the LWD pore pressure models take time to interpret and they rely on establishing trends and deviations from trends and therefore the “real time” quantitative LWD pore pressure solution is often tens of metres behind the bit. Because of these limitations, it is imperative that the Wellsite Geologist is cognisant of the primary indicators of pore pressure and incorporates these pore pressure indictors with the Pore Pressure Engineers quantitative interpretation to provide an integrated pore pressure solution.
This article discusses a number of tools that are available to the Wellsite Geologist and Pore Pressure Engineer to provide a qualitative assessment of pore pressure. I doubt that my list is all-encompassing and you are encouraged to add to the list. Be aware of false positives, any one of the primary pore pressure indicators used in isolation has the potential to provide a false indication of pore pressure. It is therefore essential to utilise all the qualitative and quantitative indicators of pore pressure to arrive at the best possible pore pressure solution.
The use of qualitative pore pressure indicators are an important part of any pore pressure evaluation plan. They provide essential barriers in the well control bow-tie and require ownership by several disciplines at the wellsite.