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3-D and 4-D Visualization of Geochemistry and Production Data to Refine a Structural Model


Geological models are commonly framed using only geophysics and Geology data. Data from other disciplines can be extremely useful for fine tuning a model, to the point of sometimes completely altering the existing one. Thus geochemical data (e.g. specific gravity or isotopes) or production data such as pressure and GOR/yield can be extremely useful to refine a geological model; that is especially true in structurally complex compressional settings. New structural interpretations, sometimes only local, will be evoked with their respective revealing parameters. At the center of all of these visualizations of “production” data are various depth references that vary depending if we are dealing with rock, fluid or pressure data. Thus porosity barely change through the field production life whereas hydrocarbon may have resettled through gravity if tectonic activity post emplacement took place. Moreover, fluid and pressure data need to be studied through time and corrections need to be applied to visualize the data in four dimensions, i.e. time. For the latter, “at datum projections” are ideal to reveal compartmentalization not revealed by well or seismic data. The very large amount of engineering and geochemical data available during the production of a field should be systematically analyzed and integrated into the geological model in order to maximize infill drilling and identify the best intervals for recompletion. Most of the examples will dwell upon data from three giant fields in the Eastern Venezuelan Thrustbelt: the Santa Barbara, Carito and Furrial fields. Oil gravity has been analyzed in various ways; thus, some simple depth plots of wells with abnormal depth trends as far as 25km apart have revealed the existence of four thrust sheets not previously recognized. A different approach was the visualization of a chosen API gravity in 3-D through time (e.g. 32 degree API) or of the GOR through time; these studies clearly revealed compartmentalization unknown before. Three-dimensional stable carbon isotope analysis (the best being isobutane) from produced oil samples allowed the identification of a major fault not imaged by seismic and not understood before and even revealed the fault throw with outstanding precision. Such data integration should become the norm in geological modeling.