Lake Maracaibo Bachaquero Area, Bloque IV Field: A Sparse Logged Area with Additional Reserves?

Manfred Frass, Carolina Coll, Helena Gamero, Luis Rondon, Seyd Tariq, and Ian Bryant

The results of the high resolution logging throughout the Lagunillas Inferior reservoir, in the VLD-1112 and VLD 1152 wells in the Bloque IV area of Lake Maracaibo, Venezuela, are described in this work.

Parts of the reservoir were previously overlooked due to the use of simple petrophysical evaluation using very sparse old logs (SP, Gr, Res.) which show high water saturations (Sw>0.5) and very low porosity's (^phgr <0.1). In the intervals with thin laminations, the use of microresistivity images define the clean sands of the shaly section, where pressure tests were taken. With these logs, was possible to define local vertical permeability barriers, which separate the productive well known high permeability zones from other zones which could represent additional reserves. A new sedimentological model was defined using core information and the high resolution microresistivity images, subdividing the reservoir into 12 layers, replacing the old simple 3 layer model. Open hole evaluation of the new wells and cased hole measurements using a saturation log indicate that gas has preferentially moved into high permeability zones, leading to bypassing of oil in moderate to low permeability layers.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California