A. Edwards, A. Selnes, D. Cameron, J.K. Welford, R. Wright, I. Atkinson, S. Green, W. Busuttil and S. O’Connor
In shale formations, the amount of pore space is representative of porosity and permeability, which are highly dependent on mineralogy, depth of burial, and the history of diagenesis. In the case of cemented shales, the overburden pressure can decrease permeability further than mechanical compaction such that the porosity and permeability are not proportional to the depth of burial. The impact of this process is that the cemented shales appear ‘artificially’ fast for any given depth such that the true pore pressure can be underestimated. Moreover, the uncertainties in the pore pressure model, as a direct function of the cemented shales, not only propagates into the well planning and well design stages but also into the overall de-risking of any prospect as these effective stress relationships are used as input for both rock physics modelling and geomechanical modelling. This paper demonstrates the importance of building robust pore pressure models in areas affected by cementation, such as offshore Newfoundland and Labrador. We will demonstrate the importance of identifying these intervals in rock physics modelling by integrating temperature and pore pressure data. Finally, we will attempt to explain the formation of these cemented shales by viewing the local data on a regional scale.
This paper was presented by Dr Alex Edwards, Ikon Science, at the EAGE 2015.