"New Exploration Plays: a Modification of a Traditional Exploration Approach in Colombia"
Date: Monday, June 18, 2001
Place: Westchase Hilton, 9999 Westheimer
Time: Social 5:30 p.m., Dinner 6:30 p.m.
Cost: Click here
Abstract:
Despite its extended exploratory history, some plays in Colombia remain either in their early stages of exploration or unexplored. Simple surface structural features of considerable size remain undrilled because they are located outside of traditional basin geographic and topographic boundaries and because explorers have focused ourselves on rigid and traditional models. The perception of technical exploratory risk is generally higher outside of productive basin outlines and this detracts explorers from deep evaluations of potential frontier areas and from strongly promoting these ideas to management. Although the risk perception is higher the potential for opening and capturing a new play is significant, it is well-known that in the early stages of basin or play exploration most of the reserves are encountered rapidly by drilling the best and least complicated structures. In this presentation the general petroleum geology of Colombia will be outlined and four under-explored to unexplored plays in Colombia will be discussed. Some of these plays have large reserve potential but targets might be at considerable depths; others have less reserve potential but targets are shallower and seismic imaging is more reliable. All, however, require a considerable amount of exploratory effort and risk money expenditure. The new association contract in place today presents favorable economics, IRR and NPV, that covers the risk involved in exploration.
Why is there oil in Colombia?
The La Luna source rock is the primary component of the exploration puzzle in Colombia and is shared with other countries such as Venezuela, Trinidad and Ecuador. The deposition of the La Luna Formation (and many other names for similar coeval facies) was caused by above-average submarine volcanism that lead to the formation of a Large Igneous Province (LIP). The LIP volume raised sea level and its formation process injected tons of CO2 into the atmosphere heating the Earth. The rise in temperature and sea level led to a marine oceanic anoxic event that is exceptionally expressed in the Cretaceous of northern South America. This source rock has generated more oil than any other and is the main reason for the occurrence of oil in Colombia. Paleogeographic maps of the La Luna interval, the main reservoir units, seals and traps, will consolidate the geological history of oil through the presentation.
The Llanos Foothills play.
Although in Colombia the Llanos foothills play is considered proven and working, primarily because Cusiana and Cupiagua are amongst the major fields of the country, there are large trends or structural bands that remain untouched. One of such bands is the subthrust environment immediately below the frontal thrusts that bring Eastern Cordillera Cretaceous and Paleogene to surface. This structural domain has exploratory potential on a play area that is more than 1000 km long, structures of considerable size have been identified and one of them is currently being drilled. Canadian Rockies analogues to these structures and play concept are abundant and represented by many productive fields.
The frontal structures of the Llanos foothills with targets underneath faults that involve the reservoirs and expose Neogene strata to surface; e.g., Cusiana and Cupiagua fields, form part of an underexplored play. There are very few true exploratory wells along this trend, approximately 12, and the length of the prospective structural band is 1000 km. A play area such as this one in Canadian or US Rockies would have many more wells.
The western foothills of the Eastern Cordillera and the eastern foothills of the Central Cordillera plays.
The La Luna source rock of the Middle and Upper Magdalena valleys is excellent in character; TOC average values are very high and HI numbers more than appropriate. Reservoirs have been producing for a long time within the Valley and the petroleum system in general is fully proven with fields such as the La Cira Infantas (900 mmbo). Areas within traditional basin boundaries might be considered as mature using Colombian standards. Explorers have focused on subtle features on these obvious places and on the utilization of new technology for imaging deeper and seismically-complicated zones. Explorers have recently extended the boundaries of the mentioned basins with ideas that have turned into plays, into prospects and recently into a field. The Guando field, 200 mmbo, discovered by Petrobras and Nexen proves that the boundaries of the petroleum province can be extended up towards the western foothills of the Eastern Cordillera. Only three wells in that 75 km-long trend are producing in Guando which is a large surface feature that can be readily observed in aerial photographs. Along the western foothills of the Eastern Cordillera but in regions to the North of Guando there is a 100 km-long structural band in which Tertiary reservoirs could be encountered in the subthrust environment below the La Luna Formation and equivalent units. This structural domain has only one well and the well did not reach the target. South of Guando, in the Southern Upper Magdalena Valley, there is a large structural band in which lower Cretaceous reservoirs, proven in flat regions, are present underneath faults that bring basement to surface. This play will be tested for the first time at the end of this year by TotalFina ELF.
The fractured Cretaceous play.
The La Luna Formation and the rest of the Cretaceous system in the Middle Magdalena Valley and along the western foothills of the Eastern Cordillera adjacent to the Valley is susceptible to fracturing. The Eocene or Pre-Andean Orogeny has structurally affected in a significant manner the pre-existing Cretaceous rocks. Additionally, the Miocene or Andean orogeny has affected post Paleogene strata and "re-affected" pre-unconformity Cretaceous. These two major events affected calcareous and siliceous units that are potential fractured reservoirs. The play produces but is in the earliest stages of exploration.
Offshore Tertiary petroleum system (multiple plays unexplored and underexplored).
The Colombian Caribbean offshore can be divided into two large regions with geological differences as well as differences in their exploratory history. The south-western region is approximately 12.5 million acres; it contains one of the largest deltas and submarine fans of South America and a cumbersome and poor exploration history. The last wells were drilled in 1980 and 1984 prior to acquisition of large seismic programs. 4,000 km of 2D seismic were shot in 1983 and 11,000 km were shot after drilling the last well. This area remains unexplored with recent technological advances. Amoco´s study calculated a potential of 13 billion boe with possibilities of encountering 30% liquids and 70% thermo- and biogenic gas. This study is based on seismic interpretation and on a significant sea bottom coring program in which samples of oil and gas were recovered. North-eastern Caribbean regions are approximately 12.5 million acres in size. 30,000 km of 2D seismic data have been acquired. The area has an unrisked gas potential of 50 TCF to be discovered and Chuchupa and Ballena gas fields with a total of 5 TCF recoverable. The Caribbean offshore has been in an exploration lag because of restrictions in market and a contract that did not cover all the risks of exploring in these areas. Currently, however, Ecopetrol has a new contract in place and is working towards improving the risk-reward ratio of exploring for gas in offshore Colombia, this includes generating potential markets and decreasing the price risk.
The new and underexplored plays mentioned above are only a few of many. Stratigraphic traps in the Llanos basin, the offshore Pacific coast and deep turbidite systems in the Lower Magdalena Valley will only be briefly mentioned during the presentation.
Biographical Sketch:
Tomas Villamil is a geologist from the National University of Colombia; he obtained his Ph.D. at the University of Colorado at Boulder under the supervision of Erle Kauffman. Afterwards, he was a postdoctoral researcher at TAI-Dartmouth College and Research Associate at the University of Colorado. Tomas worked in Conoco´s new ventures group for four years and joined Ecopetrol last year where he currently holds the position of Exploration Vice President and is responsible for exploration activities in Colombia. Contact: Tomas Villamil; Exploration Vice President ECOPETROL, Colombia; Email Tvillami@ecopetrol.com.co Phone: 011 571 234 5041.
Date: Wednesday, June 13, 2001
Place: The Petroleum Club, 43rd floor of the Exxon Building downtown Houston, 800 Bell Ave., 713-659-1431
Time: 11:30 a.m.
The eastern offshore marine province (EOM) of the eastern Maturin Basin (Columbus Basin of Leonard, 1982) is one of the most prolific hydrocarbon provinces in the world, having proven reserves of more than 486 MMbbl and 21.5 Tcf of natural gas. Some workers estimate exploration potential to total 50 to 70 Tcf of gas in a country where companies experience an 80% success rate for wells. With only three wells currently drilled in water depths exceeding 200 m much potential remains within deeper water provinces, a target of current exploration.
The eastern East Maturin Basin is filled with more than 12,000 m of deltaic, fluvial/estuarine and deep-marine sands and shales deposited in a rapidly subsiding basin along the triple junction of the westward-subducting Atlantic plate and the obliquely colliding Caribbean and South American plates. In a regional framework, the basin can be divided into three tectonomorphic provinces that are extensional, monoclinal, and compressional in a relative west-to-east direction. Each province exhibits its own unique interplay of structure and sedimentation, which control locations of accommodation, which in turn influence every aspect of the sedimentation system.
Primary structural elements in the extensional province of the basin include (1) a series of transpressional, northeast-southwest-trending, thrust-cored ridges and (2) northwest-southeast-oriented, down-to-the-northeast normal faults. Strata in this part of the basin can be divided into 11 third-order megasequences, each bounded at the base and top by major basinwide unconformities. Each of these megasequences steps basinward and contains several fourth-order sequences, giving each an overall southwest-to-northeast progradational pattern. Hydrocarbons are trapped within these megasequences in a series of downthrown, four-way, bow-tie anticlinal structures bounded proximally by a penecontemporaneous down-to-the-northeast fault and distally by shale diapirs. East-west closure is formed by two-way, subsidence-driven rollover, and north-south closure is formed by uplift along the thrust-cored ridges. Major hydrocarbon fields trend along four principle ridges: the Samaan-Galeota Ridge and the Poui-Teak-Omega, Ibis-Pelican-Oilbird, and Cassia-East Mayaro anticlinal trends. Normal faults young to the northeast, as do hydrocarbon traps and reservoir ages.
The monoclinal province (basinward of the present-day 100-m bathymetric contour [shelf-slope break] and extending approximately 120 km to the northeast) is characterized by mud diapirs and toe-thrust-bound basins that are both asymmetric -to -the -basin, as well as asymmetric -to -the shelf. Hydrocarbons may migrate along the diapir-flank faults or within the overpressured and fractured diapir itself to charge these basins at depth and continue migration updip until limited by lithology pinch-out.
The most outboard province, the compressional province, occurs approximately basinward of the 2,000-m bathymetric contour and extends to the front of the modern accretionary prism. Asymmetric-to-the-basin, piggyback basins form and fill under conditions of episodic thrusting. Depocenter axes migrate landward as the sediment fill becomes younger. Deep-marine, basin-floor turbidites show mounded and shingled offlap geometries on seismic. Hydrocarbons can migrate into piggyback basins along deep, bounding thrusts and associated down-to-the-basin normal faults. Updip migration of hydrocarbons in the back-rotated basin may result in traps formed in perched, basin-floor turbidite deposits by stratigraphic pinch-out along basin margins.
Biographical Sketch:
Dr. Lesli J. Wood , is a Research Scientist at the University of Texas Bureau of Economic Geology. Her expertise is in basin analysis, risk assessment, clastic sedimentology and sequence stratigraphy, and evolution of tectonically active basins. After completing her PhD at Colorado State University, Dr. Wood worked for six years in the hydrocarbon industry, first with ARCO then Amoco. Her other research interests include Caribbean plate tectonics and hydrocarbon systems, Quaternary stratigraphy, shale diapirism, deep marine sedimentation and seismic sedimentology.