Resumé
The liberated free-gas phase, generated due to reservoir pressure decline, can either be a
handicap or a benefit during oil production. The unfortunate scenario is that disconnected immobile
gas bubbles can block individual pore throats, lowering, thus, the effective permeability of the
reservoir. Unfavorable pore geometry, along with capillary forces/wettability balance are the main
contributors to that possibility. On the other hand, a favorable case is that the liberated gas bubbles
coalesce easily, forming a mobile gas phase, which can provide energy to the reservoir by a
competent gas-oil gravity drainage mechanism. For such an effective upwards gas migration,
though, crucial parameters are permeability and dip of the reservoir, layering/stratigraphy, as well
as the relative permeabilities of the fluid phases. The experimental study of this work aims to
determine the mobility of the formed gas bubbles and their effect on the effective (relative)
permeability of the oil. The experiments involve gas liberation in low permeability outcrop and
reservoir samples, induced by pressure decrease. The pressure varies from above to below the
saturation pressure, while X-ray computer tomography is applied to detect the in-situ gas liberation
and determine the gas saturation. Effective oil permeability versus pressure and saturation is
monitored. The onset of gas-phase production (the value of residual saturation) is monitored as
well. Along with the experimental work, the modeling part of the study is developed. For
calculating the amount of the produced gas, a previously developed thermodynamic model (DTU)
is adjusted and applied. The model involves oil and gas equilibrium under the action of capillary
forces. If the released gas stays in the pores in the form of bubbles, a correlation between the
amount of liberated gas and the reduction of oil permeability is provided. For the time being, the
correlation between the amount of liberated gas and the reduction of oil permeability is being
modeled and verified using date from the literature. The final experimental setup has been
determined, and the first results are obtained for model oils and outcrop or reservoir cores.
handicap or a benefit during oil production. The unfortunate scenario is that disconnected immobile
gas bubbles can block individual pore throats, lowering, thus, the effective permeability of the
reservoir. Unfavorable pore geometry, along with capillary forces/wettability balance are the main
contributors to that possibility. On the other hand, a favorable case is that the liberated gas bubbles
coalesce easily, forming a mobile gas phase, which can provide energy to the reservoir by a
competent gas-oil gravity drainage mechanism. For such an effective upwards gas migration,
though, crucial parameters are permeability and dip of the reservoir, layering/stratigraphy, as well
as the relative permeabilities of the fluid phases. The experimental study of this work aims to
determine the mobility of the formed gas bubbles and their effect on the effective (relative)
permeability of the oil. The experiments involve gas liberation in low permeability outcrop and
reservoir samples, induced by pressure decrease. The pressure varies from above to below the
saturation pressure, while X-ray computer tomography is applied to detect the in-situ gas liberation
and determine the gas saturation. Effective oil permeability versus pressure and saturation is
monitored. The onset of gas-phase production (the value of residual saturation) is monitored as
well. Along with the experimental work, the modeling part of the study is developed. For
calculating the amount of the produced gas, a previously developed thermodynamic model (DTU)
is adjusted and applied. The model involves oil and gas equilibrium under the action of capillary
forces. If the released gas stays in the pores in the form of bubbles, a correlation between the
amount of liberated gas and the reduction of oil permeability is provided. For the time being, the
correlation between the amount of liberated gas and the reduction of oil permeability is being
modeled and verified using date from the literature. The final experimental setup has been
determined, and the first results are obtained for model oils and outcrop or reservoir cores.
| Originalsprog | Engelsk |
|---|---|
| Status | Udgivet - 2019 |
| Begivenhed | Danish Hydrocarbon Research and Technology Centre Technology Conference 2019 - kolding, Danmark Varighed: 11 nov. 2019 → … |
Konference
| Konference | Danish Hydrocarbon Research and Technology Centre Technology Conference 2019 |
|---|---|
| Land/Område | Danmark |
| By | kolding |
| Periode | 11/11/19 → … |
Programområde
- Programområde 3: Energiressourcer