Caracterización de reservorios de hidrocarburos y acuíferos fluviales: Problemas y Soluciones Characterization of fluvial hydrocarbon reservoirs and aquifers: problems and solutions

Los depósitos fluviales son importantes reservorios de hidrocarburos y acuíferos en muchas regiones del mundo. A fin de valorar, desarrollar y utilizar estos recursos es necesario determinar la geometría tridimensional, la orientación, la distribución espacial y el volumen total de los reservorios y acuíferos. Generalmente, este tipo de caracterización de reservorios y acuíferos involucra, (1) el análisis de perfiles de pozos, cuttings, testigos corona y datos sísmicos, (2) la correlación de estratos entre pozos, y (3) el modelado tridimensional de los depósitos entre los pozos. Estos procedimientos requieren una elaboración del conocimiento geológico. Desafortunadamente, en muchos casos las propuestas actuales para la caracterización de los reservorios y acuíferos son problemáticas. Las formas fluviales de depositación (ejemplos: barras de canal, crevasse splays, deltas lacustres) son interpretadas comúnmente a partir de perfiles de pozo y testigos corona, ya que se piensa que los Fluvial deposits are important hydrocarbon reservoirs and aquifers in many parts of the world. In order to assess, develop and manage these resources, it is necessary to determine the three-dimensional geometry, orientation, spatial distribution and total volume of the reservoirs/aquifers. Such characterization of reservoirs/aquifers normally involves (1) analysis of well logs, cuttings, cores and seismic data (2) correlation of strata between wells, and (3) modeling of the three-dimensional volume between wells. These procedures require a great deal of geological knowledge. Unfortunately, current approaches to reservoir/aquifer characterization are problematical in many cases. Specific fluvial depositional forms (e.g., channel bars, crevasse splays, lacustrine deltas) are commonly interpreted from well logs and cores, because it is thought that deposits associated with particular depositional forms will have particular geometries and reservoir quality. However, it is very difficult to unambiguously interpret fluvial depositional forms from such one-dimensional data, and it is questionable that a particular depositional form will have a distinctive stratal geometry. In particular, it is not possible to distinguish braided river deposits from meandering river deposits based on their vertical facies sequences. Also, it is a common myth that there is a relationship between channel-belt width/thickness, channel pattern, grain size of sediment load, and bank stability. However, with very careful analysis, the lateral extent of subsurface channel-belt deposits and overbank deposits