Luis Montes

Utilizing the radiometric and seismic methods for hydrocarbons prospecting in the Rancheria sub-basin in Colombia

An onshore radiometric survey sampled in situ the isotopes U238, Th232, K40, and Rn222 to build maps of normalized values for each element containing negative and positive radiometric anomalies, which could associate with hydrocarbon deposits in the subsoil. The vertical migration of hydrocarbon, water or other gases would have generated the different isotope anomalies. In four 2D seismic sections of the study area, three on dip direction and another in strike direction, we interpreted unconformities, flooding surface, and maximum flooding surfaces, as well as Cretaceous tops. In structural contour maps made from aforementioned seismic sections, we observe structural highs and structures such as truncations of strata. These structures in-depth coincide with uranium, thorium, potassium and radon anomalies seen on the surface. This oil and gas exploration approach that integrates radiometric and emanometric integrated with seismic prospecting can help to reduce the risk in hydrocarbons projects (however, radiometric anomalies are not uniquely associated with hydrocarbons). This work shows a correlation between radiometric (uranium, thorium, and potassium) and emanometric (radon) data in the surface with structures in the subsurface suck like truncation, that could present hydrocarbon, however, on this sub-basin, there has not been found commercial hydrocarbon.

AVO analysis with partial stacking to detect gas anomalies in the GÜEPAJÉ-3D project

Resumen La tecnica AVO con apilados parciales se aplico en un campo gasifero para detectar presencia de gas al tope de la Formacion Cienaga de Oro (FCO) usando apilados parciales del programa sismico terrestre Guepaje-3D y apoyado con registros del pozo Ayombe-1. Mediante la tecnica de sustitucion de fluidos se simulo el reemplazamiento de gas por agua para conocer la sensibilidad de la respuesta sismica al cambio del fluido en un segmento del pozo Ayombe-1. Se observo una anomalia clase I al tope de la FCO, aun cuando las respuestas de sustituir gas por agua fueron muy similares al aplicar la tecnica AVO con apilados parciales se observaron anomalias AVO clase I al tope de la FCO en los pozos con gas Ayombe-1 y Guepaje-1 y ninguna en el pozo seco Guepaje-3. A pesar de tener gas, en el pozo Guepaje-2 los resultados permiten diferenciar entre una incipiente anomalia clase I y ninguna. Al usarse en el volumen sismico del Proyecto Guepaje-3D la tecnica suministra un mapa de indicador directo de gas que se correlaciona con estructura de la superficie al tope de la FCO. Pueden factores liticos como compactacion, cementacion y presencia de carbonatos supra yaciendo la FCO, asi como la variabilidad en el espesor variable de las capas parcial y totalmente saturadas al tope de la FCO, generar anomalias en zonas con baja probabilidad de tener gas.

Modeling And Removal of Back-scattered Noise From Rough Topography In Land Seismic Data

The seismic records of Colombian foothills are usually noisy and contaminated by coherent and high amplitude back-scattered associated with roughness topography, which obscure reflectors from deeper layers. To remove this back-scattered noise, filters have been applied getting satisfactory results for smooth topography and short offsets, but in general conventional methods yield unsatisfactory results. We applied an approach based in prediction and subtraction of the unwanted noise to attenuate it. The extracted source signature of each record and the shallow velocity model were input to the finite element software to model the acoustic wave equation, obtaining the back-scattered noise in each record. Each output was subtracted from its corresponding record, attenuating noticeably the noise. The procedure was applied in the shots records of a foothill seismic line providing an improved image of the stacked section after time processing. The software had been previously tested on synthetic data giving promising results.