Reservoir Development in Volcanic Provinces

Hartley, Adrian; Ebinghaus, Alena; Jolley, David; Hole, Malcolm; Barker, Aaron; Taylor, Ross; Millett, John

With exploration becoming progressively focussed into challenging geological terrains increasing attention is being paid to basins dominated by volcanic systems. Not only do these areas prove challenging from a seismic imaging perspective, but little or no information is available concerning the development of potential reservoirs and likely reservoir quality within these systems. To rectify this we have undertaken studies of drainage system development in two Large Igneous Provinces (LIPs), the Columbia River Plateau Basalts, Washington State, and the onshore extension of the Faeroe-Shetland Basin in the Hebridean Islands of NW Scotland. By combining field observations with analysis of remotely sensed imagery from modern volcanic terrains it is possible to develop predictive models for both reservoir development and reservoir quality within the lifetime of a LIP. Three phases are recognised:

1) Initial LIP development: significant volcanic activity and fault activity restricted to isolated volcanic centres. Local volcaniclastic input adjacent to volcanic centres but with small drainage networks. Existing (clastic) fluvial systems will be deflected away from volcanic centre, but be unaffected elsewhere. Pillow lavas and hyaloclastites in lakes and adjacent to shorelines. Faulting may result in deflection of drainage producing lake (continental setting) or depending on nature of shoreline may produce tidal or wave-dominated systems.

2) Mid LIP development: thermal uplift and main period of volcanic activity. Lavas swamp all drainage systems creating new topography and damming valleys. Isolated (diatomaceous ortuffaceous) lakes developed on and between lava flows. Pillow lavas and hyaloclastites in marine or lacustrine settings. Fluvial systems restricted to edge of the lava pile. Volcaniclastic dominated fluvial systems within the LIP.

3) Late LIP development: decrease in eruptive activity, dominance of erosional processes and thermal subsidence. Drainage systems largely sourced from volcanic edifices producing volcaniclastic material. Decrease in fault activity. Onlap of sedimentary systems onto volcanic edifices, likely to be a regional transgression so may move from fluvial to shallow marine environments.

Each phase has the potential for clastic reservoir development although distribution and reservoir quality will vary significantly between them.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013