Online Journal for E&P Geoscientists

Moscariello, Andrea ^*2; Janszen, Adriaan ³; van der Vegt, Paul ⁴; Huuse, Mads ⁵; Moreau, Julien ⁵; Gibbard, Philip ⁴; Jedari-Eyvazi, Farid ¹; Guasti, Elisa ¹
(1) TNO, Utrecht, Netherlands. (2) University of Geneve, Geneve, Switzerland. (3) Delft University of Technology, Delft, Netherlands. (4) University of Cambridge, Cambridge, United Kingdom. (5) University of Manchester, Manchester, United Kingdom.

Glaciogenic sedimentary successions represent important exploration targets and developing reservoirs in the Paleozoic series both in the Middle East and in North Africa. However, these reservoirs pose a number of challenges primarily related to understand the sedimentary facies distribution hence the predictability of reservoir connectivity and properties.

The depth of these reservoirs (below 3-4 km) does not allow obtaining sufficiently reliable seismic images of the reservoir for mapping the internal sedimentary architecture and facies model. Paleozoic glaciogenic reservoirs are often identified in seismic by the presence of large incised valleys (tunnel valleys) cutting down the pre-glacial sedimentary record.

In order to assist exploration and development of these reservoirs we have carried out an extensive study of several analogues sedimentary systems developed in North Europe and North America where these large tunnel valleys formed underneath the Pleistocene ice-sheets.

We will present the key results of a four year industry-sponsored research project (GRASP: Glaciogenic Research Analogue Studies Project) on several aspects of geological analogues of Pleistocene age. In particular this study focused on the description of morphologic and sedimentary characteristics of tunnel valleys infill and their impact for geo-modeling approach.

This study highlighted the importance of subglacial erosional processes and their relationships with the bedrock and the type of sedimentary infill. Sedimentary features of large dimensions such as gently upstream dipping clinoforms have been described inside the tunnel valleys and are coinciding with subtle changes in lithological composition, possibly leading to changes in reservoir properties.

The high resolution modeling of a data set from Germany was used to develop 3D geological models, which helped us to unravel key ‘rules’ of glacial deposition such as thickening and thinning of sand and gravel deposits in correspondence of tributary valleys.

The learnings obtained from this project can be applied to the exploration and development of older glaciogenic reservoirs and are aimed to assist geologist in understanding better the complexity of these sedimentary systems. The results will help to reduce uncertainties of Palaeozoic reservoirs and to better evaluate the potential of these Quaternary reservoirs, which from a first examination, seem to contain considerable amount of (exploitable?) biogenic shallow gas.