Basin modeling of Late Cretaceous / Mio-Pliocene (.) petroleum system of the deep-water eastern Colombian Basin and South Caribbean Deformed Belt

摘要

Previous interpretation of 2D and 3D seismic reflection data have shown widespread, direct hydrocarbon indicators from deep-water successions of the eastern Colombian Basin (ECB) and adjacent South Caribbean Deformed Belt (SCDB) that suggest the presence of an extensive - but poorly defined - petroleum system. We integrate Rock-Eval analysis, seismic interpretation, and 1D/2D thermal and basin modeling to better understand the origin of gas chimneys and bright spots identified in the ECB. Our dataset consists of 36 Rock-Eval samples of Coniacian to Santonian source rocks from the DSDP well sites 153, 151, and 146 located in the Beata Ridge tied to a 270 km-long composite 2D seismic line covering the ECB. Rock-Eval analyses reveal intervals of immature source rocks containing 1) kerogen types II and III; 2) an average TOC of 3.70% with a maximum TOC of 11.4%; 3) an average HI of 241; and 4) an average OI of 124. Seismic interpretation reveals: 1) wedging of post-Coniacian, organic-rich successions from the Beata Ridge (35-73 m thick) towards the ECB (500-1700 m thick); 2) Late Cretaceous to Eocene slow sedimentation rate of 38 m/my, followed by faster Oligocene to Recent sedimentation rate of 149 m/my from the Magdalena River; and 3) Late Oligocene to Recent thrusting and propagation of the SCDB. Thermal and basin modeling show: 1) mature Cretaceous source rocks in the SCDB and ECB; 2) Miocene to Pliocene, Magdalena Fan-derived deltaic and turbiditic reservoir and seal rocks, and Plio-Pleistocene sealing mass transport deposits.; 3) Late Oligocene to present-day trap formation related to thrust front structures, compaction folds, and stratigraphic traps; 4) hydrocarbon expulsion since Pliocene times; 5) vertical and lateral up-dip seaward migration occurs in the ECB while a secondary landward migration takes place toward the SCDB; and 6) hydrocarbon accumulation and preservation may be affected by remobilization due to biodegradation in the ECB and trap breaching in the SCDB.