Simulating Thermal Interaction of Gas Production Wells with Relict Gas Hydrate-Bearing Permafrost

Evgeny Chuvilin,Gennadiy Tipenko,Boris Bukhanov,Dimitri Pissarenko,Vladimir Istomin

doi:10.3390/geosciences12030115

Evgeny Chuvilin, Gennadiy Tipenko + Show 3 more

Open Access

https://doi.org/10.3390/geosciences12030115

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Abstract

The thermal interaction of a gas production well with ice-rich permafrost that bears relict gas hydrates is simulated in Ansys Fluent using the enthalpy formulation of the Stefan problem. The model admits phase changes of pore ice and hydrate (ice melting and gas hydrate dissociation) upon permafrost thawing. The solution is derived from the energy conservation within the modeling domain by solving a quasilinear thermal conductivity equation. The calculations are determined for a well completion with three casing strings and the heat insulation of a gas lifting pipe down to a depth of 55 m. The thermal parameters of permafrost are selected according to laboratory and field measurements from the Bovanenkovo gas-condensate field in the Yamal Peninsula. The modeling results refer to the Bovanenkovo field area and include the size of the thawing zone around wells, with regard to free methane release as a result of gas hydrate dissociation in degrading permafrost. The radius of thawing around a gas well with noninsulated lifting pipes operating for 30 years may reach 10 m or more, while in the case of insulated lifting pipes, no thawing is expected. As predicted by the modeling for the Bovanenkovo field, methane emission upon the dissociation of gas hydrates caused by permafrost thawing around producing gas wells may reach 400,000–500,000 m3 over 30 years.

Highlights

One of the key problems related to well completion in permafrost is the control of thaw subsidence and mechanic stability of wells
This, apparently, unexpected result may be due to the starting conditions of about −5 ◦C permafrost temperature and Sh = 20% chosen according to field and laboratory experimental evidence from the Bovanenkovo field
As shown by more detailed studies, the effect of the hydrate component on the thawing rate is controlled by thermal conductivity, which is inversely proportional to the hydrate saturation and initial permafrost temperature

Summary

Introduction

A great number of Russian oil and gas fields are located in the Arctic region, where vast expanses, harsh climate, geotechnical, logistic, and infrastructure issues pose problems to the production and transportation of hydrocarbons. The problem of thermal and mechanic interactions between production wells and permafrost was formulated in the 1970s, with the onset of development in the Russian Arctic petroleum provinces. One of the key problems related to well completion in permafrost is the control of thaw subsidence and mechanic stability of wells. The mechanic well– permafrost interaction has been modeled since the 1980s [32–36]. APtatrhame eBtoervsaonfeantkhoreveo-sgtrainsgfiperlodd[u6c1in].gTwheellt.emperature on the lifting pipe/permafrost interface within theOinustuelraDtioianminetteerrv,aIlnwnaesr aDssiaummeetderto, CbeemcoennsttaOnut taetr32 ◦C. It was estimated NtooproceCeadsifnrogm the resermvmoir temperaturem, lmocal geoDthiearmmeatel rg,rmadmient, anDdepgtahs,flmow rate. The gas was r2ecovSeurerdfaacet acadsa-ily flow 3ra2t4e of ~400,000–530004,000 m3, and 3it9s4pressure was ~41500MPa

Intermediate casing

Results and Discussion

Conclusions