Development of a Structurally Complex Field Without “Seeing”, Eastern Cordillera Fold and Thrust Belt, Colombia

Abstract

The initial wells in the Piedemonte area were drilled in an attempt to extend on prolific discoveries to the south. These exploration wells were drilled based on models similar to the observed geometry in the fields to the south. These wells showed significant productive potential and thus 3D seismic was acquired. The 3D seismic, even through several iterations of reprocessing, still does not yield much of an image of the thrust sheets at depth. This has made development of these resources difficult and with high uncertainty on position, extent and size. Structural modeling techniques, especially 2D and 3D restoration and balancing, based in large part on well data have allowed effective development of the area. An initial structural model was developed, based in large part on two sets of two wells, each set oriented in the dip direction. This model was extended to other sections, first including other single wells that encountered only the shallowest producing thrust sheet. Further expanding the network of sections allowed definition of a fault network, with extensive testing of the model via 2D restoration and balancing. The sections were then used as a template to build a full 3D model. Additional 3D restoration and balancing improved the sections and model. Drilling based on this model has proved successful, and has greatly extended the vision of the thrust sheets. As wells are completed, new data are incorporated in the sections and model, thus continuing to reduce uncertainty as drilling progresses. This area of Piedemonte, north of the earlier Cupiagua-Recetor discoveries, with the data from the new wells, has confirmed the initial, foreland verging, stacked thrust model and refined it. The structural style of an antiformal stack in this area is different than the observed backthrusted geometry to the south, and this impacts shape, extent and size of the thrust sheets. Uncertainty in these un-imaged thrust sheets remains high, but the structural model allowed developing the resources effectively. With ten new wells, the thrust sheets are now much better defined, with additional resources discovered and continuing to be developed. The ten wells are all producers or potential producers. With high drilling costs, ensuring that the structural uncertainty is minimized has been to key to effective development.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015