--> Abstract: Sand Injectites: Aature and Hydrocarbon Implications; #90063 (2007)

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Sand Injectites: Aature and Hydrocarbon Implications. Outcrop Analogues From Santa Cruz, California and Tabarka, Tunisia

 

Scott, Anthony1, Mario Vigorito1, Andrew Hurst1, Joe Cartwright2 (1) Aberdeen University, Aberdeen, United Kingdom (2) Cardiff University, Cardiff, United Kingdom

 

Sand injectites have become increasingly important in the oil and gas industry. They have been identified in oil fields of the North Sea, west Africa and US Gulf Coast. Key to understanding the influence of sand injectites in hydrocarbon reservoirs is capturing the variation in geometry and petrophysics.

 

Sand injectite geometry and petrophysics are extremely variable even though they may have been initiated by a similar event. The reason for this variation is due to the influence of the mechanical properties of the host sediment. Outcrops of Tabarka in Tunisia and Yellow Bank Creek Complex (YBCC) in California represent sand injections into two contrasting types of host sediment.

 

Injectites in Tabarka suggest that sand injection occurred before significant compaction and lithification of surrounding host sediment. The abrasion and incorporation of mud (>10%) into the injection results in an irregular geometry with low porosity (<7%) and permeability (<120mD). In contrast, YBCC sand injection occurred when the host sediment was compacted or lithified. The contact margins indicate that the sand was injected into distinct fracture planes. The reduced mud content (<1%) results in a high porosity (>25%) and permeability (>2000mD).

 

Accurate and quantitative description of sand injectites in the subsurface is essential for providing models for reservoir simulation. Using sand injectite outcrop analogues helps to understand the influence of host sediment compaction and lithification on sand injectite geometry and petrophysical variation in the subsurface. This improves the accuracy of predicting fluid flow behaviour in sand injectite reservoirs.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California