On the Universality of Rock Physics Trends — An Integrated Approach to De-Risking Frontier Basins

Abstract

Rock physics models attempt to establish a link between the seismic and the petrophysical properties in the subsurface; this requires prior knowledge and understanding of geophysics, petrophysics, geopressure and geomechanics, which can vary dramatically in basins around the world. However, if a simplistic view is taken then all rock physics models can be simplified to their reliance on an accurate understanding of three important parameters: temperature, pressure and gravity. While we assume that gravity is a constant parameter around the world, both temperature and pressure can vary significantly such that these variations impact the elastic properties of a rock. With a view to constraining these uncertainties we present in this paper a method of accurately building a rock physics model by integrating temperature and pore pressure data. Further, we demonstrate, by use of analogues, how universal these rock property models are at predicting the elastic properties of a rock with application to un-drilled areas. There is a wide range of rock physics models out there, ranging from theoretical, empirical, heuristic and bound filling models (Avseth et al, 2010). Our focus here is using a hybrid approach, where we combine theoretical, empirical and heuristic models to describe medium to high porosity clastic sediments. Looking at well log data from offshore Newfoundland and offshore Norwegian Sea, we see a clear correlation between the two datasets, which suggests that sorting and/or diagenetic trends are somewhat universal, regardless of distance or geology. The use of analogues for geopressure in Labrador was highlighted in a recent conference paper by Green et al. (2013). In this work the authors demonstrate that by integrating recent seismic data has revealed the similarity between Labrador and basins such as the Voring Basin in Mid-Norway. As there are no deep-water wells drilled in Labrador, we have shown that by using observations from an analogue basin such as, the Voring Basin Mid Norway, due to the abundance of shallow and deep water well penetrations, we can usefully predict the likely characteristics of the rock properties. Furthermore, by using known effective-medium models, we're in a better shape to make that specific trend general for the area of interest by bringing in geology and depositional settings.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015