Page 73 - Enhanced Oil Recovery in Shale and Tight Reservoirs

60 Enhanced Oil Recovery in Shale and Tight Reservoirs

2.15.6 Summary of gas huff-n-puff performance
Overall, some learnings from those gas huff-n-puff pilots presented above
may be summarized in the following.
• Gas injectivity did not seem to be a problem.
• Gas breakthrough was observed in some projects. The success of a project
required the confinement of the injection pattern.
• Later projects performed better than the earlier one.
• Tens of CO 2 huff-n-puff field tests including some large-scale field
projects have been carried out in Chinese low-permeability sandstone
reservoirs. Most of those tests were claimed to be successful. Some tests
were in tight oil reservoirs.
• One of the important economic parameters is gas utilization factor. The
above projects did not report this data. In conventional reservoirs, the
CO 2 utilization factors reported are 1.3 MSCF/bbl (Thomas and
Monger-McClure, 1991), and 0.3e10 MSCF/bbl for light oils and
5e22 MSCF/bbl for heavy oils (Mohammed-Singh et al., 2006). For
shale reservoirs, Gamadi et al.’s (2014a) simulation data showed to be
about 10 MSCF/bbl.