Navegante: Jewel in the Exploration Crown

“With the oil discovery at Bricol two years ago and the recent success at Navegante-1, we proved that we have not stopped attempting to incorporate more substantial onshore resources,” states José Antonio Escalera Alcocer, Subdirector of Exploration at Pemex E&P. While deepwater resources represent an important part of Pemex’s future, its diversification strategy allowed the E&P division to confirm an immediately exploitable reservoir 20km away from its headquarters in Villahermosa, Tabasco. According to Pemex o·cials, Navegante is expected to hold 3P reserves of around 500 million bbl of light oil, a volume that is expected to increase following the drilling of appraisal and delineation wells and through the search for field extensions.

The importance of the Navegante discovery is enhanced by the fact that pipelines for fast production and refineries plants in the region are already in place, but additionally, the oil in the reservoir is light crude. “Navegante gave us almost immediate production, with the first barrels being extracted in the beginning of 2013,” Escalera Alcocer confirms.

“Navegante has been the jewel in the crown this year: explorers have been pursuing this model for the last fifteen years, and this year it finally paid o†,” states Adán Oviedo Pérez Director General of Comesa. His company has been working with Pemex to acquire new seismic surveys of the region where Navegante was discovered in order to facilitate the development of a better geological model definition in this very complex thrust belt.

The Navegante project was challenging for Pemex. The well is deep, with high temperatures and high pressures, and presented substantial technological challenges while also environmental and social issues had to be considered given the well’s onshore location.

“It was a high-risk, high-volume project. The well is so complex that we could not fully evaluate the hydrocarbon column at first,” Escalera Alcocer explains. “We could just see the top 320m, while another 300m of the column were left unseen.” However, through the application of new 3D seismic technologies, Pemex was able to develop a model of the geological structure that provided the qualitative and quantitative information that encouraged the company to invest in the validation of the conceptual reserves.

Nagevante’s light crude oil reserves are located in the autochthonous block in the upper Jurassic kimmeridgian formations. “This represents an important upgrade from the four or five wells we drilled in the allochthonous block, which moved and displaced itself through inverse faults for 15km, below the inferior structure where we have been finding reservoirs,” Escalera Alcocer says. “The model we built indicates that the oil pocket moved south under the Antonio J. Bermúdez complex, a big onshore field. The confirmation of this theory could lead to finding more resources there, which is why we continue to do 2D seismic in the region.” Escalera Alcocer explains that as soon as 2D seismic acquisition is completed, Pemex will start structural geologic modeling through 3D seismic.

“Working in exploration usually means that we are more often wrong than we are right. The probability of discovering a commercial success averages at around 30%,” says Escalera Alcocer. “But we have learned how to take advantage of every single opportunity and learn from the information and knowledge that each well provides, while is allowing us to experiment with new concepts and designs that can be applied in other reservoirs. This has enabled us to reach a commercial success rate of around 40%.”

The current expectations for Navegante, according to Carlos Morales Gil, Director General of Pemex Exploration and Production, are to produce a volume of between 30,000 and 40,000 b/d. This number is anticipated as the initial production for the field as soon as the production wells are drilled. Escalera Alcocer, on the other hand, is more cautious when giving an outlook due to the complexity of the development wells that have to be drilled. “These are wells that take a long time to be drilled,” he says. “The original Navegante deposit was drilled in almost 450 days due to its complexity. We expect to lower the drilling time for the next wells to 280-360 days.”

Pemex E&P is determined to build on the Navegante discovery in the onshore Tabasco area. “We still believe there are several opportunities in this area, especially if we look for field extensions. Reserves related to these opportunities may not be as big as Navegante, and could be found at more profound depths, but we will continue to work by acquiring additional seismic information, model the reservoirs in their geological, geochemical, and structural characteristics to define which type of hydrocarbons we might be able to obtain,” Escalera Alcocer concludes. “The correct understanding of the imaging obtained with 3D seismic depth migration technologies and the implementation of 2D and 3D geological and geochemical modeling will help to define the areas where liquid hydrocarbons have bigger probabilities to be found in the future.”