IS THE COLOMBIAN CARIBBEAN MARGIN AN UNDEREXPLORED ANALOGUE TO THE PROVEN HYDROCARBON PROVINCE OF THE NORTHERN BORNEO MARGIN (MALAYSIA-BRUNEI)?

ROSSELLO, E.A., WANNIER, M.

Santa Marta

Congreso; XVIIº Congreso Colombiano de Geologia; 2019

XVIIº Congreso Colombiano de Geologia

The Baram Basin and the Sabah Trough of the Northern Borneo Margin(NBM), and the Colombian Caribbean Margin (CCM) witnessed similar geologicalconditions, which were dominated by deposition of thick late Tertiaryprograding sequences related to the Baram/Champion and Magdalena deltas, respectively.The first oil field in the NBM was discovered in 1910 in Miri (onshoreSarawak basin), followed in 1929 by the discovery of the giant Seria field inBrunei. Limited further exploration was done until the mid-1960?s whenexploration moved offshore. There, giant oil fields and large gas fields havebeen discovered in deltaic, shelfal and deep-water clastics. Source rockscomposed of terrigenous organic matter yield oils exhibiting highpristane/phytane ratios. Maturation occurred from Middle Miocene to Present asthe area is still undergoing subsidence. Faults act probably as main migrationroutes though many could act as seals as well. Hydrocarbon migration alsooccurred along porous sedimentary facies, updip from condensed intervals. Mainreservoirs include fluvial and tidal sandstones filling incised valleys cutduring lowstand periods, deltaic & shoreface sandstones, as well assiliciclastic turbidites. Anticlinal features associated with growth faultingor resulting from transpression affecting wrench faults, form the main traps.Additionally, fault, unconformity and stratigraphic traps are also present.Regional seals correspond to transgressive marine shale intervals, whichfrequently develop shale diapirs and mud volcanoes. In the case of CCM, many authors describe thesubduction of the Caribbean plate under the South American plate with suturesand other related tectonic phenomena, such as the subsequent development of anaccretionary prism. However, there is no clear surface morphological evidencesuch as a trench or onshore mountains to support this hypothesis. Nor is thereany subsurface evidence such as a magmatic arc, dipping seismicity orconvergence data that is typically seen in other known subduction margins (e.g.Chile-Peru, Indonesia, Aleutians, etc.).For this reason, it is proposed that the CCM is a result of the dynamicbalance of an early extensional margin related to a Mesozoic to Cenozoicpassive margin style where the continental platform progrades by gravitationalgliding onto the oceanic plate and is affected by a late dextral transpresionalinversion associated with oblique convergence. Taking inaccount this extensional tectonic setting present at regional and local scalesin the CCM, the tectonostratigraphic history strongly resembles that of theNBM. This analogy may extend to the petroleum systems present in the twobasins. The big and non-geological difference, however, is that in the NBM,exploration has been intense with over 50 fields discovered to date, whichproduce approximately 100,000 BOPD and with reserves estimated at 5.0 BBO and22 TCFG.Resolving the controversy over thetectonic setting of the CCM isextremely important because it impacts the petroleum potential of the region.Incorporating detailed tectono-sedimentary and 4D deformational analyses withrecent surface and subsurface data would provide a framework to address thiscontroversy.