Fluid Circulation in the Llanos (Colombia) and Diagenese

The Colombian Llanos constitute the current foreland of the Eastern Cordillera, HC exploration is active near the compressive front (thrusted anticline structures) as in the plain (affected by small normal faults) or eastward near the wedge of the basin. Petroleum systems are known to be efficient but their complete understanding is far to be simple. The role of the water flow within the HC migration and maybe trapping needs especially to be better defined. The water production is very high in many HC fields (up to 75% of the fluid production) and the handling of such a huge quantity of water is a major environmental and economic issue. Question marks are numerous about the origin of this water (compaction, meteoric, other). The water sampled in the HC field is often fresh (not salted). Within this general context, the goal of the presented study is to test a single idea: can this unusual water flux be for a part due to diagenetic processes, namely to the dehydration of the smectite since the tertiary deposit are for large part shales.