Sequence Stratigraphic Framework, Miocene Laguna Member, Lagunillas Formation, VLC-52/VLD-192 Reservoirs, Blocks III/IV, Maracaibo Basin, Venezuela
Ernest Gomez, Helena Gamero de Villarroel, and Robert A.
The Laguna Member of the Miocene Lagunillas Formation consist of interbedded clastic sediments deposited in a tidally-dominated lower delta plain and delta front setting. The Lagunillas Formation is comprised of three members; Lower Lagunillas, Laguna and Bachaquero, in ascending order. Within the VLC-52/VLD-192 reservoirs the Laguna has produced over 297 MBO since its discovery in the late 1950s. This reservoir had traditionally been interpreted as coastal bars comprised of three individually developed flow units.
A sequence stratigraphic framework was developed from the sedimentological interpretation of eight cored wells and the integration of 210 wireline logs and 3D seismic data. Two third-order sequences bounded by three Type 1 sequence boundaries were identified within the Lower Lagunillas and Laguna members. In the Laguna Member 16 individual, mappable sedimentary units were recognized (units XIII-XXVIII). A mid-Laguna type 1 sequence boundary divides the Laguna into upper and lower submembers. The lower submember is the highstand system tract (HST) of the lower third-order sequence, with the upper submember being the upper third-order sequence.
Paleosols caused by subaerial exposure and weathering have developed along the Type 1 sequence boundary between the Laguna and overlying Bachaquero Member. These paleosols reach over 100 feet in thickness and form a very effective reservoir seal. Also, thick incised channel sandstones develop along this sequence boundary and are an inviting development target.
Development of the sequence stratigraphic framework within this mature field a better definition and predictability of the reservoir units and will lead to increased recoveries. It also provides an effective model that can be extended outside the field boundaries into exploratory areas.
AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California