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Stratigraphic Traps as Exploration Targets Examples From Petrotrin's Soldado Acreage, Gulf of Paria, Trinidad

Abstract

To date, most of the exploration and development drilling in Petrotrin's Soldado fields have targeted accumulations associated with anticlines and updip fault closures, usually with good success. After fifty nine years of exploitation all of the simple (easy) structural targets have been identified and tested. As part of a re-evaluation of exploration leads, existing 3D seismic data was re-interpreted and four major stratigraphic surfaces mapped. Interval RMS amplitude maps for the Forest interval revealed meanders, channels, point bars never before seen in the area, the unconformity at the base of the Morne L'Enfer was also seen in areas to erode deeply into the underlying Forest, truncating the reflectors and associated stratigraphy. This unconformity and its overlying claystone dominated sediments have created a stratigraphic trap on the southern flank of the Erin Syncline. The occurence of a flat spot within the Forest Formation strongly suggests a fluid contact within the (Forest) interval. Traditionally the Lower Cruse interval has been mapped as being dominated by basin floor fans, however a re-examination of the paleobathymetries and log motifs suggest a slope setting. Spectral Decomposition was used to further understand the stratigraphic setting of the Lower Cruse. Various tuning cubes were generated for the Lower Cruse interval at a low frequency of 10 Hz and a time window of 100 ms illustrated a channelized system with a sand trend from SW – NE and source direction from the SW. A south to north trending progradational feature was mapped on seismic, which internally exhibited bidirectional downlap that created potential closures in an updip direction. A second deeper feature was also mapped. This extraction illustrated WSW – ENE trending high amplitude that parallels the interval thickness map. It was infered that the amplitude variation reflects a change from claystone to sand. Within this study area no structural traps were identified, however the data shows that stratigraphic traps exist within all of the formations mapped. Two explorations wells have been proposed to be drilled to test the validity of these stratigraphic concepts.