MUSTAFA

ABDOLMOTA

LLEB

JAVA

D ANSARI N

ASAB

SAMAN MOHAMMADI

SAGD PROCESS AT PORE SCALE:

1.What is SAGD?

2.What does “pore scale” mean?

3.What are the aspects of “SAGD process at pore scale”?

4.conclusion.

SAGD PROCESS

Steam Assisted Gravity Drainage (SAGD) is an enhanced oil recovery

technology for producing heavy crude oil and bitumen by steam injection. The concept of

SAGD was initially proposed by Butler and his colleagues (Butler et al., 1981; Butler and

Stephens, 1981). In this process, two horizontal wells are placed close to the bottom of a

formation, with one above the other at a short vertical distance. Steam is continuously

injected into the upper injection well with slightly above reservoir pressure. As the steam

rises, moving both upward and sideward, it conducts its latent heat to the cold heavy oil

and bitumen. As the reduction of the bitumen viscosity continues due to heat conduction,

the heated oil together with the condensed steam drains into the lower production well.

WHAT DOES “PORE SCALE” MEAN?

Pore=An opening or channelway in rock or soil.

Scale= in weights and measures

MICROMODELS RELATED TO PORE SCALE:

HINTS:

1.The glass micromodels were initially saturated with heavy oil.

2.All the pore-level SAGD experiments were carried out in a vacuum

chamber in order to reduce the excessive heat loss to the surrounding

environment while steam was injected under different superheating levels.

3.Local temperatures along the model's height and width were recorded on

a real time basis.

4.The pore-scale events were recorded using digital photo capturing techniques.

 

MECHANISTIC INVESTIGATION OF THE SAGD PROCESS USING PORE-SCALE EXPERIMENTAL STUDIES:

The interplay between gravity and capillarity forces results in the drainage of the

mobile oil near this pore-scale mobilized region.

Mobilization of the bitumen was found to be as a result of both conductive and

convective elements of the local heat transfer

PORE-SCALE EVENTS ANALYSIS WITHIN THE MOBILIZED REGION

The mobilized region contains thermally-mobilized oil, droplets of water condensate,

and also steam phase which are flowing simultaneously parallel to the apparent

interface.

Different acting forces are contributing to the simultaneous fluid flow within this

mobilized region, namely gravity, capillarity, and buoyancy forces in the absence of

excessive viscous force. This region is formed due to the presence of temperature

gradient at the pore-scale and it clearly has an oriented structure, in which three

different fluid phases are flowing parallel to the apparent SAGD interface.

The mobile oil, as well as the water condensate within the mobilized region, would

drain by the action of gravity when gravity forces overcome the capillary and possible

viscous forces.

This phenomenon, which is supported by the temperature gradient, could be seen in

two successive pictures shown as Figures. Mobile oil drained out of these pores and

steam invaded through them following the sequential behaviour of pore drainage

during an immiscible displacement process .

MICRO-SCALE CHALLENGES OF THE SAGD PROCESS :

a) Local fluid mixing at the pore bodies,

b) Snap-off mechanism of the invading fluids,

c) Local conduction-convection heat transfer,

d) Steam Fingering Phenomenon

f) Micro-scale emulsion formation and flow along the drainage path.

 

 

STEAM FINGERING PHENOMENON

The conceptualized Butler’s theory of rising steam fingers during the vertical

encroachment of the steam chamber is schematically shown in Figures. It is believed

that the steam fingering phenomenon during the vertical encroachment of the steam

chamber happens as a result of buoyancy forces. Although the steam chamber is

stable at its bottom part near the injection well due to continuous nature of the steam

injection, buoyant steam phase near the topside of the steam chamber has an inherently

unstable interface with the thick, cold, and stagnant continuum of oil on the top.. It is likely

that the topside of the chamber would be dome-shaped, having a lot of steam fingers in it.

According to the literature, there is still doubt about the possibility of steam fingering in the

outward direction, i.e. spreading phase of the steam chamber.

 

 

EMULSIFICATION AT THE PORE-SCALE

presence of a gas phase, local enclosure of water droplets within the continuum of

the mobile oil behind the apparent SAGD interface would form the localized water in

oil emulsification. In Figure , three snapshots are shown regarding the state of in-

situ emulsification in the SAGD process. Figure a shows the local entrapment of

a large number of water micro-droplets within the continuum of the mobile oil at the

pore-scale. The selected area is one pore-body-dimension distance away from the

apparent SAGD interface. Figure b presents the engulfment of two individual

water droplets inside the pool of oil with a distance equivalent to three-pore-

dimensions from the apparent SAGD interface. Figure .c also demonstrates the

microscopic enclosure process of a number of small condensate droplets at the left side of

the picture which were detached from the bulk column of the condensate phase formed at

the top of the oil-filled pores.

+ condensate droplets would be trapped within the reduced-viscosity oil continuum.

In

addition, they should overcome the associated film pressure of the tiny mobile oil

films in between in order to be able to coalesce to each other. Due to the convective

nature of the drainage process within the mobilized region, it was observed that both

condensate droplets and also small steam bubbles become entrapped within the

continuum of the mobile oil just behind the apparent SAGD interface. One of the

mechanisms responsible for small steam bubbles being trapped within the bulk of the

mobile oil is the snap-off phenomenon at the pore-scale.

REFERENCES:

1. A thesis presented to the University of Waterloo in fulfilment of the

Thesis requirement for the degree of Doctor of Philosophy in Chemical Engineering

Waterloo, Ontario, Canada, 2012,Omidreza Mohammadzadeh Shanehsaz

2. Pore-Level Investigation of Heavy Oil and Bitumen Recovery Using Solvent –Aided

Steam Assisted Gravity Drainage (SA-SAGD) ProcessO. Mohammadzadeh,* N.

Rezaei, and I. Chatzis

3.My own efforts(saman mohammadi)

4. Pengrowth Energy Corporation Lindbergh SAGD Project .