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New acquisition system handles harsh environments.
Geophysical service providers rely heavily on equipment manufacturers for integrated solutions that can support the smallest 2-D projects to the largest, most complex 3-D high-productivity Vibroseis (HPVS) operations. BGP, a subsidiary of China National Petroleum Co. (CNPC) and the world's largest land seismic contractor, continually seeks cutting-edge seismic technology to maintain its competitive edge for providing high-quality data acquisition services. BGP's numerous seismic crews operate across the globe in all types of challenging terrains and extreme weather conditions and require a stable, easy-to-use recording system that can perform in tough seismic programs.
Nearly two years ago INOVA Geophysical was launched as a new entrant in the land seismic equipment market. A strong working relationship between BGP and INOVA has combined operational excellence with technological innovations to develop advanced products to meet the growing demands of the seismic industry. In addition, BGP evaluates INOVA's new equipment and conducts extensive field tests to make sure the products meet its standards of excellence before making an investment in new seismic systems.
In 2011, BGP Domestic agreed to test INOVA's new G3i cable-based acquisition system in the Turpan-Hami (Tuha) basin in the eastern part of the Xinjiang Uygur Autonomous Region in China. The Tuha basin is the combination of the Turpan Depression and the Hami Depression and covers an area of more than 53,000 sq km (20,460 sq miles), with estimated natural gas volumes of 266 Bcm and oil volumes of 2.5 billion tons. BGP has been surveying the Tuha Oilfield for several years as one of CNPC's key exploration programs. Because field operations were already in process in the region and due to the BGP crew's familiarity with the arid desert environment, the contractor thought the oil field was an ideal location to extensively test the system.
With its ruggedized ground electronics manufactured from high-strength polycarbonates, aircraft-grade aluminum, and stainless steel, the G3i system easily can operate in harsh environments. Power-down-the-line technology eliminates the need for large quantities of batteries and provides seismic crews a significant reduction in the amount of ground equipment required. Using fiber-optic baselines, the system delivers more than 100,000 channels in real time.
The G3i system's architecture consists of a single software platform supported on multiple central recording system options for optimal operational flexibility. Its box-cable-box architecture also allows operators to easily locate and resolve field faults. In the event of a remote acquisition module, fiber tap unit, or power supply unit failure, trained crew technicians with proper equipment can repair the unit. Furthermore, the integration of INOVA's Vib Pro source controllers and Connex Vib navigation system with G3i provides greater efficiency during HPVS operations. Advanced Vibroseis techniques have been widely accepted by energy companies for achieving densely sampled, high-quality data acquisition more cost-effectively.
BGP planned to deploy approximately 5,000 channels to administer two separate tests, the first beginning in November 2011 and the second in February 2012. With a stringent test plan in place and new G3i equipment, INOVA was well positioned to start the joint field test program. Since the BGP crew was unfamiliar with the G3i system, INOVA field service engineers provided onsite technical training to their field support technicians, observers, and field crews to properly execute the tests.
Upon receiving the G3i system, BGP engineers completed floor commissioning of the equipment without issues in just a few days at their Zhuozhou facility and quickly mobilized the crew to begin field trials in the Tuha Oilfield. By mid-November 2011, the system was fully deployed in the field. A complete set of monthly tests were run on all channels and geophones, and communication was established between the G3i system and BGP's vibrators. With 501 stations on a 2-D line, the crew acquired more than 1,100 records using both dynamite and Vibroseis sources.
After the 2-D recording was finished, the crew moved onto 3-D testing. More than 3,600 shots were recorded using the 3-D spread, which consisted of 20 lines of 195 active stations. During this phase of the testing, the crew also conducted tests on real-time receiver line channel capacities using several different sample rates.
After successful completion of these tests, BGP picked up all line equipment, demobilized its personnel, processed the recorded data, and made recommendations for G3i system enhancements, which are currently being implemented by INOVA.
In February 2012, INOVA released a G3i software update to support HPVS techniques and many of BGP's suggested enhancements. BGP crews returned to the Tuha Oilfield to conduct the next field test, focusing on HPVS methods. The tests included slip-sweep, two-cluster and three-cluster distance separated simultaneous sweeping (DSSS), and DSSS with slip-sweep (DSSSS) using the 5,000-channel G3i system, Vib Pro source controller, and Connex Vib navigation system. Five separate slip-sweep tests were undertaken, ranging from 6-second to 28-second sweep times with 5-second to 6-second listen times and 5-second to 10-second slip times. Two-cluster and three-cluster DSSS and DSSSS operations of 12-second sweep time, 5-second listen time, and 10-second to 12-second slip time were tested using cluster distances from 10 km to 25 km (6 miles to 15 miles) with dynamic fleet grouping capabilities. Active patches within the super-patch were separated and successfully correlated during slip-sweep tests.
While performing aggressive slip-sweep with 28-second sweep time, 5-second listen time, and 5-second slip time, the G3i central system handled multiple overlapping shots without computing delays. In all, BGP executed more than 22,000 vibrator points and achieved 100% efficiency levels during the HPVS tests since there were no delays in vibrator starts or file output between vibe starts.
Collaboration pays benefits
This joint collaboration and successful testing of the G3i system benefited both companies. BGP engineers were pleased with the results of the field tests and acknowledged the performance of INOVA's G3i system. After completing the tests, the company formally accepted G3i and purchased 10,000 additional channels for its upcoming seismic projects in Western China later this year. Having INOVA's high-performance G3i acquisition system as part of its equipment portfolio offers BGP an advantage in winning project bids from global oil and gas exploration companies.