Numerical Simulations in Support of a Long-Term Test of Gas Production from Hydrate Accumulations on the Alaska North Slope: Reservoir Response to Interruptions of Production (Shut-Ins)

We investigate by means of numerical simulation a planned year-long field test depressurization-induced production from permafrost-associated hydrate reservoir on the Alaska North Slope at site recently drilled Hydrate-01 Stratigraphic Test Well. The main objective this study is to assess quantitatively impact temporary interruptions (well shut-ins) expected fluid performance B1 Sand stratigraphic Unit B during controlled depressurization over different time scales, as well other relevant aspects system response that have potential significantly affect design test. consider eight cases depressurization, including (a) rapid 60-day period terminal bottomhole pressure PW 2.8 MPa and (b) slower rate final 0.6 end test, in addition (c) multi-step regime (d) quasi-linear continuous strategy. results indicate shut-ins obviously reduce gas release immediately after their occurrence, but longer-term effects are strongly dependent observation, covering entire range outcomes. Shut-ins universally strong negative effect when involved regardless length period, positive schemes becomes apparent earlier for large initial drops, can also appear practically no slow stepwise lead reformation hydrates, even point disappearance free phase reservoir. Rapid regimes early maximum rates dissociation production, while occur depressurization. do not significant water cessation followed higher resumes. Similarly, fraction produced CH4 originating exsolution water, water-to-gas ratio, replenishment boundary inflows affected shut-ins, which seem be majority cases. confirmed superiority methods most effective strategies showed two observation wells (located distances 30 50 m well) appropriately positioned both able capture P, T, SG behavior any we investigated.