--> Abstract: Simulation of N<sub>2</sub>/CO<sub>2</sub> Injection in Coal Beds: Lessons Learned from Tiffany Field Case Study ; #90055 (2006).

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Simulation of N2/CO2 Injection in Coal Beds: Lessons Learned from Tiffany Field Case Study

Wo, Shaochang1 (1) University of Wyoming, Laramie, WY


Methane (CH4) production from coal beds can be enhanced by injection of carbon dioxide (CO2), nitrogen (N2), or a mixture of both (flue gas) to accelerate methane production at sustained or increased pressures. However, the actual field performance of enhanced coalbed methane recovery (ECBM) processes is largely dictated by how effectively injected gases contact and interact with coal beds over the active project lifetime. By history matching the early nitrogen breakthrough time and nitrogen cuts in BP’s Tiffany Unit, simulation indicated that the injected N2 may only contact a small portion of the total available pay, which was evidenced by the spinner surveys conducted in some of the N2 injectors. As a possible explanation, the elevated pressure affected by N2 injection may expand the coal fractures on the preferential permeability trends in the Tiffany Unit. The field performance of N2-ECBM provides not only valuable knowledge of how the coal formation interacts with injected N2 while the coal swelling due to CO2 injection is absent, but also has important implications for CO2 sequestration via flue-gas injection. Simulation prediction of CO2-N2 mixed gas injections was performed following the history matching in the pilot area. Methane seepage has already been observed from many locations along the north and west Fruitland outcrops in the San Juan Basin. The concern is that injected CO2 could likely follow the methane seepage paths and leak from the outcrops. Scenarios of methane and CO2 seepage were simulated based on the geological setting of the Fruitland coal outcrop.


AAPG Search and Discovery Article #90055©2006 AAPG Rocky Mountain Section Meeting, Billings, Montana