In one of the JIVE configurations, horizontal wells were used. What are horizontal wells and how do they work?

In traditional vertical wells (those drilled directly downward) the well accesses only a small section of the reservoir and the oil is drawn very slowly to the single extraction point. Some techniques (such as injecting water to ‘push’ the oil toward a well) have been devised to move the oil more quickly and readily toward the well’s location.

In a horizontal well, the drill curves as it goes down, producing a well shaped like a cross-section of a mixing bowl - a curve that flattens out to a horizontal line on the bottom of the reservoir.

Extremely long horizontal sections allow oil to drain into the entire length of the well. The oil is then rather easily pumped to the surface. Horizontal wells can produce up to five times the amount of oil that a vertical well can, in the same amount of time.
Horizontal well technology brought a major increase to production in Saskatchewan’s declining fields in the 1990s, and have allowed for the development of the Bakken Formation in southeast Saskatchewan.  It was also used in the JIVE project in some of the well configurations.

Horizontal wells have several advantages over vertical wells:
•    Large reservoir contact area
•    Facilitates high production/injection rate
•    Allows use of fewer wells – minimizes surface disruption
•    Lower reservoir drawdown – reduced water and gas coning
•    Improved productivity and recovery
•    Used for producing thin hydrocarbon formations
•    Used for connecting vertical fractures
•    Used for producing low-permeability reservoirs

What is Solvent Vapour Extraction (SVX) and how does it work?

In many heavy oil reservoirs, waterflooding to increase pressure and production is no longer effective because water tends to flow under much of the reservoir and reaches only the oil in the lower portions. Thus, a vapour is needed to reach the oil in the upper parts of the reservoir and thin it, which causes the oil to flow downward with the aid of gravity to lower production wells.

The solvent vapour process involves the injection of a vaporized solvent into a horizontal well located in the upper portions of the oil reservoir. The solvent dissolves into the heavy oil reducing its viscosity and creating an expanding solvent vapour chamber. The diluted oil then drains down the edges of the chamber by gravity to a vertically aligned lower horizontal production well where it is pumped to the surface.

What is the difference between Steam Assisted Gravity Drainage (SAGD) and Solvent Vapour Extraction (SVX)?

For heavy oil recovery to be effective, the viscosity of the crude oil must be reduced (it must be made thinner and more fluid). This can be accomplished by either heating the oil (steam injection – Steam Assisted Gravity Drainage or SAGD) or by blending the oil with a solvent (Solvent Vapour Extraction, SVX).

In the ’80s and ’90s, development of a specific solvent-based process that exploited gravity drainage was carried out at the University of Calgary under the leadership of Dr. Roger Butler. He coined the term VAPEX (Vapour Extraction) for this process. Different forms of vapour extraction now exist, not just the patented VAPEX method, and these collectively are referred to as solvent vapour extraction (SVX) methods.

SAGD is often used for heavy oil extraction because it provides both a vapour and heat to reduce the viscosity of the oil. However, using solvent vapour extraction has certain additional advantages and differences. Whereas the production of steam uses considerable amounts of energy, which produces greenhouse gases, and uses enormous amounts of water, Vapex uses no heat and water. The solvents (butane, propane, methane, and in some cases CO2) are made of hydrocarbons that originally came from oil reservoirs so they are not harmful to the reservoir. The solvents are recovered with the oil and recycled, so they are not released to the atmosphere.

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