Impact of Results from Complex Data-Intensive Wells on Understanding Fault, Fracture and Clinoform Geometry: Examples from a Maturing Carbonate oil Field in Abu Dhabi, United Arab Emirates
Yousuf S.W. Fahed Al-Mehairi
In an effort to accelerate field redevelopment, opportunities have been identified to re-activate wells through horizontal sidetracks and acquire geological data to evaluate potential discontinuities, irregular water front advance and uneven pressure distribution. The studied reservoir has been producing mainly from the south of the field, from platform interior and margin deposits. The north of the field is complicated by the presence of clinoforms and common faulting. Progradational clinoform belts in the north show rapid alternations of reservoir properties. Lack of crestal pressure support and uneven waterfront advance confirmed high reservoir complexity, with the main uncertainties being: (1) up-dip extension of barriers (dense limestone) related to third- and fourth-order transgressions within clinoforms; (2) continuity and sealing capacity of NW-trending faults; (3) connectivity between poorer quality clinoform bottomsets and the topsets of unit 1; (4) NS-trending discontinuities impacting pressure dissipation from flank-to-crest; and (5) detection and characterization of fractures (spatial extent, orientation and transmissibility). Recent drilled wells have included: (1) pilot holes with cores, borehole image logs and pressure/fluid measurements to evaluate the up-dip extension of dense units within clinoforms; (2) horizontal drains crossing several clinoforms and faults aimed at resolving complex structural and sedimentary geometries (distance to boundary logging and borehole imaging); and (3) borehole image logging in pilot holes and horizontal sections to characterize facies, fault and fracture distribution The integration of results from these wells with complementary studies (e.g. seismic attribute analysis, sequence stratigraphy, core studies, dynamic modelling) forms the foundation for optimizing the development scheme, extending field plateau life, and maximizing recovery.
AAPG Search and Discovery Article #90077©2008 GEO 2008 Middle East Conference and Exhibition, Manama, Bahrain