[First Hit]

AAPG Middle East Region Geoscience Technology Workshop

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Five Reasons for Carbonate Oil Production at High Previous HitArchieNext Hit Calculated SW


Water free oil production from carbonates at high Previous HitArchieNext Hit calculated SW may occur when: (1) The calculated SW is not correct. (2) The calculated SW is correct but the water is immobile. (3) A combination of the previous two. High SW is generally considered above 50%. Five reason for water free oil production at high Previous HitArchieNext Hit SW are: (1) Layer formation – Stacked layers of small pore size rock (micritic Wackestone) with coarse pore system rock (Grainstone) below the resolution of the resistivity tool. (2) Dual porosity system – Large pores surrounded by micritized grains. The large pores flow oil while the capillary bound water in the micrite grains is immobile. (3) Fractures – Fine grained matrix with capillary bound water combined with fractures flowing oil and a lowering of Previous HitArchieTop’s cementation exponent. (4) RT lowered due to deep conductive mud filtrate invasion. (5) Conductive minerals such as pyrite. Whether a porous rock at a given saturation produces water free oil depends on the assemblage of pore and pore throat sizes and the rock wettability.