Berbice Submarine Canyon Guyana's Basin, Possibly Jurassic through Cretaceous-aged Deepwater Sediment Delivery System, Offshore Guyana
Allan E. Kean
Atlantic Basins Exploration Manager, Repsol
This presentation is the results of Repsol's exploration activities in the Guyana's Basin. Repsol originally, through the acquisition of Maxus Energy and through the acquisition of YPF, acquired operatorship in the Georgetown Block. Subsequently, the Jaguar-1 well was drilled followed by relinquishment of the Georgetown Block. The new Kanuku Block was subsequently licensed, and the focus has now shifted from the less confined toe of slope/basin floor depositional environment to the more proximal portion of the canyon in a shelf/slope setting.
The results of the Jaguar-1 well is another story that compliments this presentation. In summary, the Jaguar-1 well was drilled offshore Guyana, SA with a proposed TD of 21,450' in 2012 with a deep-water depositional environment, clastic objective. However, this presentation is primarily focused on the updip Berbice submarine canyon where Repsol and partners Tullow Oil and RWE shot a nearly 3,200 sq km 3D seismic survey which was completed in mid-December 2013.
The Guyana's Basin is located in a unique geologic area where there exists two distinct Break-up and Drift episodes in this overall passive margin setting. The first episode is related to the North Atlantic rifting that began in Triassic/Jurassic time, followed by the second episode related to the Mid-Atlantic rifting of West Africa from South America. This second episode of rifting was preceded by a counter-clockwise rotation of the West African plate into the northern South America plate as a result of the opening on the South Atlantic margins when South Africa and South America began to rift and drift in late Aptian to early Albian time, which resulted in a compressive event resulting in the accentuation of the Demerara Rise. Subsequent to this compressive event, the margin began to drift and develop into what we now know is a passive margin.
The Berbice submarine canyon is also a unique geologic phenomenon in this margin, that I will show in some detail, to be the result of a possible failed triple junction associated with the older north Atlantic rifting. This Berbice submarine canyon exhibits dimensions as great as or greater than the USA's Grand Canyon, however, that is where the similarities end. Ten third order Sequence Boundaries have been seismically mapped within the updip Berbice canyon with drainage and deposition to the north northeast of sediments believe to be of Cretaceous age.
The Jaguar-1 well was drilled in the now expired Georgetown Block in 2012 in a down dip position of the Berbice submarine canyon at the toe of slope for the interval of interest. The well encountered high temperatures as prognosed and ultra-high pore pressure, much higher than prognosed. The pre-drill "worst case scenario" parameters for which the well was designed were a bottom hole temperature >450 degrees F and a pressure situation where the reservoir rock was actively being charged by currently generating source rock, whereby the reservoir section in situ existed at the fracture gradient.
The Jaguar-1 fan complex is sediment sourced through the Berbice submarine canyon by erosion of the quartz-rich Guyana Shield. The closest offset well Abary-1 reached a 13,000' TVD before being P&A'd due to mechanical reasons/fluid influxes. Observations from this offset well along with the calibration with 3D seismic data and a VSP constrained the correlation and prognosis for the Jaguar-1 well. This well was meant to be a basin opener for HPHT objectives in the deep-water depositional environments of offshore Guyana's Basin. The target objective was not reached due to even more extreme pore pressure encountered than what was predicted as the "worst case scenario" pre-drill. Geologic correlations predicted the lithologies and the presence of hydrocarbons which were all positive outcomes from this drilling campaign. These encouraging results now justify continued exploration here. The problem becomes predicting the expected pore pressure below 16,000', along with correlating this ultra-high pore pressure updip into the Berbice Canyon. The expectation is for lower pore pressures updip in Berbice, with a similar size hydrocarbon accumulation. The new 3D seismic data should help us determine if this is the case.
AAPG Search and Discovery Article #90203 © AAPG Geoscience Technology Workshop, Trinidad and Tobago Deep Horizon and Deep Water Frontier Exploration in Latin America and the Caribbean, March 9-11, 2014, Port of Spain, Trinidad