BABY, PATRICE, ORSTOM, Santa Cruz, Bolivia, MARTIN SPECHT, Institut Francais du PEtrole, Rueil-Malmaison, France, EDGAR MENDEZ, YPFB, Santa Cruz, Bolivia, BERTRAND GUILLIER, IFEA, Santa Cruz, Bolivia, BERNARD COLLETTA and JEAN LETOUZEY, Institut Francais du PEtrole, Rueil-Malmaison, France

ABSTRACT: Development of Transfer Zones and Location of Oil and Gas Fields in Frontal Part of Bolivian Andean Fold-and-Thrust Belt

The frontal part of the Bolivian Andean thrust belt consists of a thick series of paleozoic to cenozoic sedimentary rocks (5 to 8 km thick) which are folded and thrusted towards the east on a sole thrust at the base of paleozoic series. The front of this tectonic wedge is characterized by transfer zones of various scales and geometries. The main oil and gas fields are located in these transfer zones. A study realized from YPFB (Yacimientos Petroliferos Fiscales Bolivianos) seismic data shows that in all the cases, the deformation is controlled by the geometry and thickness variations of the paleozoic basin. The most spectacular transfer zone appears at the bolivian orocline scale and corresponds to the famous bending of the andean thrust front close to Santa Cruz. More to the south (1 to 22 degrees S) the southern foreland fold and thrust belt is characterized by a set of local right lateral offset transfer zones ("en echellon" folds). The difference of geometry and scale of the transfer zones seems to be related to the variation of the angle value between the shortening direction and the direction of the paleozoic basin borders. In order to test our interpretation, to constrain the boundary conditions and to study the thrust propagation sequence, we performed a set of analog model experiments whose 3D visualization was analyzed by computerized X-ray tomography.

AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.