Acquisition Model that Fits the Exploration Challenges

Wed, 01/25/2012 - 16:43

Deepwater in the Gulf of Mexico presents a considerable technological challenge for Pemex. One of the main problems is seismic acquisition, because the Gulf of Mexico is principally constituted of potentially productive fields underneath large salt structures. “The Gulf of Mexico needs a seismic model leading to an acquisition that can pass through the salt structures and get the subsalt seismic information,” says Alma América Porres Luna, Commissioner at the CNH, as normal seismic techniques cannot get through the salt. “Pemex has put a lot of emphasis on new acquisition techniques and depth migration,” she says.

Another technological challenge is producing geologicgeochemical models in the Gulf of Mexico, in order to assess the maturity and type of field. “In some of the wells that have been drilled, certain guidelines were brought from the onshore region, for example from Poza Rica, to the Gulf of Mexico. The thinking was that there could be a continuity of the basins, and they might have oil,” explains Porres Luna. “But it turned out that they didn’t. Instead, gas fields were found.” What is required, she says, is a detailed geologicgeochemical model of the Gulf of Mexico. The geochemical study can tell what fluid is likely to be found in the fields: the organic material transforms itself over millions of years and, depending on the temperature, becomes either gas, light oil or heavy oil, among other things. Geochemistry thus studies the maturity of the field, and makes sure that when drilling starts, there is a prognosis as to what will be found, according to Porres Luna.

“If all characteristics indicate that there should be light oil and you drill and find gas, that means you didn’t do your studies well,” she explains. According to Porres Luna, a simulation had to be done particularly in the Gulf of Mexico, estimating where the organic material deposited itself and, after millions of years, into what it transformed.

The model needed for the Gulf of Mexico must be an integral model including not just geology and geochemistry, but also 3D seismic (wide azimuth) and electromagnetic surveys. Most of these technologies are already used in Mexico. She explains that Pemex’s capacity is augmented by contracting international companies. “The exploration technology used is created on an international level and it is possible to obtain it,” Porres Luna says. For example, technology can appear in the North Sea and Pemex can either visit or the companies themselves can come to Mexico to showcase the potential benefits of the application of new technologies in Mexico’s exploration process, according to the CNH commissioner. “Pemex already has the human resource capacity and technological understanding to integrate these new exploration technologies.”

Pemex has access to the latest generation of seismic acquisition technology, even the new pre-salt methodology developed in Brazil. While the Gulf of Mexico’s geology diers from that of Brazil, it is perhaps possible that the Brazilian pre-salt technique can be of use in subsalt parts of Mexico, “we’ll have to see if it does or doesn’t behave in the same way,” Porres Luna says.

The three most important discoveries between 2006 and 2011 in terms of 3P reserves quantity were the Tsimin field (1.1 billion Boe) and the Xux field (836 million Boe), both of which contain light crude, as well as the Ayatsil field, with 596.1 million Boe of heavy crude. The Ayatsil-Tekel complex is located in the northern part of Ku-Maloob-Zaap, Mexico’s most productive region, and the Tsimin-Xux area is located in shallow waters 87km from Ciudad del Carmen.

In 2012, Pemex’s exploration priorities will be in shallow waters and deepwater areas, according to Carlos Morales Gil, Director General of Pemex Exploration and Production. “In shallow waters, we are focusing on three areas: the area of Tsimin-Xux, which we discovered two years ago, where we are looking for extensions of those reservoirs. We are also exploring in the continuity of the Ayatsil trends in the heavy crude area, and we continue also to explore in the coastal areas of Tabasco.” In deepwater, Morales Gil reveals that Pemex has already received some preliminary confirmations of liquid discoveries, but is waiting for more solid proof before making an announcement. Oil discoveries will continue to be the priority for the company, as these will be much more profitable deepwater wells than gas discoveries. In the middle of the year, the company intends to move north to its Perdido field and drill two deepwater wells, part of the six that the company is aiming for in 2012.