Analysis of Flow Mechanisms in a Faulted Carbonate Oilfield through Reservoir Simulation and Experimental Design

摘要

The limited ductility of carbonate rocks in general with regard to tensile or compressive stress results in a significant C_- if not predominant C_- proportion of carbonate oilfield showing static and/or dynamic evidence of fracturation. This natural fracturation can occur and have an impact on production mechanisms at different scale within the reservoir, from diffuse fractures to regional faults. Al Khalij field is located offshore Qatar in the Mishrif formation composed of Cenomanian limestones. The reservoir has a limited thickness and is made up of a layercake of high porosity/permeability oil bearing and low porosity/permeability water bearing layers affected by early and late diagenesis lying on an active aquifer. The field is essentially developed with long horizontal wells and peripheral water injection. Continuous reservoir monitoring acquisition, the resulting dynamic synthesis as well as borehole imagery logs and seismic imaging tend to bring into light the possible presence of dynamically active faults previously undetected that are deemed to link the aquifer with the reservoir and to result in observed water cut increases and production interferences. Decision has been taken to put a slant on locating and qualifying these events taking advantage of an integrated Geosciences and Reservoir study. On the one hand a comprehensive seismic and geological study as been carried out (See IPTC09 abstract proposal Fault detection workflow in a dimmed structural context: Al Khalij field in Qatar by B.Klein et al.); on the other hand authors dedicated themselves to describing complex flow mechanisms close to these faults in order to assess their impact in terms of oil production, reserve forecasting and relevance of current operating methods.