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"Cupiagua Sur XN1Z - Drilling Experience. Response and Uncertainty Management for Unexpected Overburden Sections"

Castillo, Jaime1; Castro, V.; Ramirez, A.; Mora, C.; Blanco, P.; and Ceballos, C.
1[email protected]

The geological environment of the Colombian Foothills is among the most complex and difficult in the world due to thrust faulting in an active tectonic setting. Compounded by the depth of the reservoirs, drilling new wells becomes very difficult, requiring close cooperation between geologist, geophysicist and drilling engineers.

The case in point for this article is the XN1Z appraisal well which was targeting a narrow and deep anticline (less than a 0.7 km wide at 15000 ft MD) with associated high overburden complexity. The highly faulted sections above the reservoir, combined with the relatively narrow structure, make it difficult to image and position the target with existing seismic data. When unexpected anomalous stratigraphic sections were encountered above the reservoir levels, the well started to deviate significantly from the original prognosis in the intermediate section.

The difficult decision to sidetrack early was made after integrating new drilling and seismic information to build and consider several potential subsurface models and their remaining uncertainties.

The final result was a successful geologic sidetrack that reached the original target optimizing the cost compared to other potential options.


AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013