Abstract: Kitina: A West African Intra-Albian Field
Francesco Cornaggia, Agostino Maccagni
Kitina field is located in Marine VII permit, offshore Congo. The field was discovered in 1991 by a joint venture composed of Agip Recherches Congo (operator), Hydrocongo and Chevron International Limited.
The field is a structural four-way dip closure trap shaped as turtle-back. Halokinetic movements are responsible for the structuring.
The seismic imaging of the reservoir is affected by strong lateral velocity variations caused by different sedimentation across the paleo-shelf edge in the post-Albian sequence. One pass 3D poststack depth migration, performed with a velocity field obtained by means of geostatistical integration of 2D seismic and wellbore velocities, achieved a good compromise between high dip reflector imaging and depths at well location.
Three main reservoirs of lower Albian age exist between -2100 and -3100 m. They are separated by tight mudstones which act as intraformational seal.
Seismic trace inversion improved the resolution of petrophysical variations in some of the field reservoirs, which have the following characteristics (from top to bottom):
-- reservoir 2A is composed of bioclastic and oolitic packstone-grainstone laid down during regional regressive phase in insulated offshore bars on the crest of structural high. Early diagenetic phenomena lead to the development of world class permeability framework.
-- reservoir 1A-1B are composed of sandstone bodies which were deposited as shoreface to offshore bars during short-term regressive pulse.
The 1A-1B reservoirs are embedded in mudstones deposited during long-lasting phases of relative high stand in relatively deep offshore setting characterised by high, halokinetic driven subsidence.
AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France