An SPE workshop held recently in Xian, China, examined effective and efficient development of fractured carbonate reservoirs. It was the third workshop sponsored by China’s Sinopec and attracted 80 attendees representing 13 organizations from seven countries.
The workshop reviewed experiences and challenges in the sector during seven interactive technical sessions with 58 technical presentations, including discussions on reservoir characterization, simulation, and steam/water flooding.
The opening was officiated by Yang Li, chief engineer of Sinopec, and the keynote presentation was given by Christine Ehlig-Economides, a professor at Texas A&M University and a member of the Committee on America’s Energy Future.
Development of fractured carbonate reservoirs is a world-class challenge and Sinopec’s Tahe oilfield is one of the most complex ones. Participants discussed state-of-the-art technologies and the most recent advances in petrophysics, geomechanics, flow mechanics, and numerical modeling. In the Tahe field, diffracted waves were used to characterize karst reservoirs. New well log techniques and modeling methods were applied to model fractures, caves, and vugs of different scales, while coupled simulation technology was used to identify residual oil. Another presentation centered on waterflooding carried out with a 3D well pattern. The on-site applications of these technologies showed that reservoirs with extreme complexities such as Tahe could be effectively developed.
The summarized major field experiences are:
- Crustal stress and type of karst reservoir usually carry essential information for reservoir characterization, which should be studied in addition to outcrops, cores, and logs.
- Low seismic imaging accuracy caused by overlying formations has brought uncertainties to reservoir identification, which may be bypassed by using karst-type-based modeling.
- A fluid flow study showed that coupled simulation has been proved to be a way to greatly improve simulation results.
- Successful applications of production engineering in this sector include use of advanced drilling technology, waterflooding/gas (nitrogen) flooding, and enhanced oil recovery.
- There is a need for more study of detailed characterization of karst holes, reducing uncertainties of modeling/simulation, effective flooding technologies, and multidirection acid fracturing.
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