Wireless Onshore Seismic Acquisition

Wed, 01/22/2014 - 16:47

PEMEX’s South Region, which encompasses production assets such as Samaria-Luna, Bellota-Jujo and Cinco Presidentes, is one of the oldest onshore oil producing areas of the country. The South Region stretches from the state of Tabasco to the southern part of the state of Veracruz, but both of these states are covered in dense rainforests and rivers with an unfortunate tendency to seasonally overflow and flood neighboring communities as well as oil and gas facilities. In this context, the acquisition of geological data through seismic methods in this region can be a risky and expensive proposition when using traditional, cabled technology. Personnel that are tasked with carrying and laying cable, geophones and assorted equipment over kilometers of dense jungle are taking considerable risk. Footing is uneven and significantly unstable in the muddy ground below the rain-drenched canopy, and most of the territory lacks clear or even remotely identifiable pathways. These operations represent a substantial expense for PEMEX or future private operators, not only because of the price tag that a team of exploration professionals might place on so arduous a job, but also because impenetrable terrain sometimes leads to the use of helicopters to lay cable, which is a costly measure. There is also the presence of certain unexpected issues that could arise when relying on cabling. For example, people could cut or steal them, if possessed of a social or criminal incentive to sabotage oil and gas operations.

A current technology trend in the seismic data acquisition industry appears to be close to making this problem disappear. As exploration engineer Javier Nuñez, President of Grupo Nuñez, points out, “the current technological focus of the global seismic industry is on wireless systems. Cable might still be considered the traditional method but it is becoming more and more obsolete by the day.” Wireless seismic acquisition systems, such as Sercel’s UNITE system, are usually composed of little more than a small plastic unit no bigger than a shoebox. These boxes can safely and easily be transported to any location, regardless of the remoteness or inhospitable nature of the survey site. Therefore, all expenses, risk and downtime related to the wear and tear of cables laid in adverse conditions and rough terrain disappear if the cable is no longer necessary. In the specific case of Sercel’s UNITE system, wireless seismic acquisition technology possesses a total possible battery autonomy that ranges from 200 to 256 hours and memory autonomy from 310 to 480 hours. In other words, these devices can store up to twenty days’ worth of data, which they can transmit to any receiver up to 1,500 meters away at a rate of 11 Mbps. They can operate in temperatures ranging from -40°C to 60°C while also withstanding high amounts of humidity. 

They also conveniently include Lo-Jack protection in case of loss or theft. Nuñez says that such devices were expressively designed to work under extreme conditions, not unlike those present in the South Region of Mexico.

The fact that seismic acquisition teams no longer depend in the physical integrity of a cable also increases the quality of the information itself as Nuñez explains. “These new wireless systems allow us to acquire information with less noise and more frequency content. In this way, the companies dedicated to seismic data processing receive better information in order to build more comprehensive models of the seismic sections with more events, thus improving their image of the subsurface.” Sercel also offers a tie-in package of software solutions that can be used to verify the quality of the data being acquired and execute all related computations, such as stacks or correlations, before recording the data into the physical format of the operator’s choice.

Together with the Northeast Marine Region and the Southwest Marine Region, the South Region currently remains one of the most important pillars of PEMEX’s overall production, and the most productive of the onshore regions. The entire region averaged more than 480 million b/d during 2013, comparable to the 592 million b/d average of the Southwest Marine Region in that same year. However, it is unfortunate that some people tend to regard the South Region as one that is slowly sliding towards irrelevancy. “Due to the advanced age of most of the region’s wells and the antiquity of its available geological information, a common myth is that its geography no longer holds any surprises. But the new possibilities created by wireless seismic acquisition technology might help change the general perception of the South Region,” says Nuñez. He is quick to point out that PEMEX and COMESA are already making considerable investments to use this technology “in areas where data had already been acquired many years ago with analogue methods. These areas are being studied anew through these modern technologies that provide more information and more clarity. Beyond this, wireless technology can also help seismic teams enter areas that were previously inaccessible, such as certain sections of the Nanchital Hill. This can all contribute towards creating and promoting new opportunities in the South Region and changing its image as a declining territory.” Grupo Nuñez, as a representative of this technology in Mexico, will continue to bet on wireless seismic acquisition products as a cornerstone of its collaborations with PEMEX, COMESA and other possible operators in the near future for all onshore regions, with a special focus on the South Region.