Subsurface Observations of Deformation Bands and Their Impact on Hydrocarbon Production within the Holstein Field, Gulf of Mexico, USA
S.J. Naruk, S. Wilkins, R. Davies, J. Bikun, O. Uzoh and L. Jensen
Event name: 2nd EAGE International Conference on Fault and Top Seals - From Pore to Basin Scale 2009
Session: Fault and Top Seals in Research
Publication date: 21 September 2009
Info: Abstract, PDF ( 840.44Kb )
The Holstein Field in the Gulf of Mexico consists of Pliocene, poorly lithified turbidite sands deposited in a ponded basin above an allochtonous salt tongue. Dense arrays of cataclastic deformation bands have been observed in core from wells that penetrate the K2 reservoir sand. The highest density of bands is located near the hinge of a monoclinal fold that divides the field into an up-dip terrace and a down-dip, steeply-dipping ramp. The predominant set of deformation bands strike parallel to the fold axis, and dip at both high and low angles to bedding. Their orientation, and offset of marker beds where present, suggest reverse shear. Restorations indicate that the deformation bands formed early during the burial process, and an inferred stress path suggests that high fluid pressures during the initial phase of burial was an important component. Reservoir permeability estimates from PTA well tests indicate a bulk permeability approximately one third of the reservoir core permeability. In comparison, the reservoir bulk permeability calculated on the basis of the deformation bands' actual permeabilities, thicknesses and densities, exceeds the well-test permeability by a factor of two. Additional factors are required to account for the well test results.