AAPG Europe Regional Conference, Global Analogues of the Atlantic Margin

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Seal Capacity for Early Stage Exploration - multiple approaches reduces the uncertainty.


Seal assessment is one of the key elements of every petroleum system and its evaluation is fundamental from the early stage regional exploration to the individual prospect risking. Top seal capacity and integrity are two of the main components of the seal assessment and yet remains an uncertain area of science that is hard to constrain in the early stages of exploration especially in wild cat areas where the lack of data is a real challenge. Quantitative approaches are often difficult to constrain and empirical relationships of column heights vs depths are preferred instead. This presentation shows the application of number of different approaches to attempt to answer key aspects of the seal capacity and integrity to give a range of estimates on column heights for wells and prospects in a new area. Capillary seal capacity, hydrodynamic seal capacity, brittle and fracture seal failure are evaluated from the analysis of offset well pore pressure and fracture gradient interpretation, seismic velocity and basin modelling analysis. This process focuses on the present day trapping capacity but also has to address the potential through time to give a view of the seal risk of individual prospects. The conclusions after applying this variety of approaches in real cases, is that this area of science is multidisciplinary, and no single approach gives the right answer every time. Moreover, the analysis benefits from multiple methods to get a better understanding of the capacity and its uncertainty prior to finalizing the assessment of the seal risk. Also, the lack of data is not always such a limit when assessing the seal, the use of multiple approaches can often reduce uncertainty by ruling out some scenarios that are not consistent with all the different types of analysis. A multidisciplinary integrated workflow is also presented, which can help to enhance the seal assessment and reduce exploration risk.