In Situ method of producing oil

There are 2 different methods of producing oil from oil sands: open-pit mining and in situ (latin, meaning «in place») technology.
Bitumen close to the surface is mined.
Bitumen deep within the ground is produced in situ using specialized extraction techniques.

In Situ refers to the oil sands technologies used to recover bitumen that lies too deep beneath the surface to be mined (more than 75 meters deep) and too viscous to flow on its own.
At this depth, extracting oil sands is only workable using what is referred to as in-situ methods, which combines drilling and steam injection.
In situ production is required for approximately 80% of the bitumen found in the oil sands.
About 80% of the oil sands in province of Alberta in Canada lies too deep beneath the surface for mining.
The Canada Energy Regulator (CER) expects in-situ oil sands production to grow almost 70% between 2018 and 2040, from 1,6 to 2,7 million barrels per day (bbl/d). The main reason for this growth is that in-situ plants are cheaper than oil sands mining plants because they are smaller and don’t need processing plants and tailings ponds and dams.

The cost of in-situ projects is lower than oil sands mining projects.
In-situ projects:

• require 10 - 15% of the size of an oil sands mining operation,
• 1 or 2 wells,
• a separation plantб
• less expensive to maintain and operate.

Mines usually require more labour, equipment and supplies in all stages of the project.

In 2019 an in-situ project was profitable when the oil price was around US$60 per barrel, while the break-even oil price for new oil sands mine was US$75 - US$85 per barrel.
The oil price required for an oil sands in-situ expansion was cheaper, around US$52 per barrel.

In-situ projects can be even cheaper and faster with the help of modular construction methods.
According to the Alberta Energy Regulator (AER), in-situ operators have reduced the time between the start of construction and the start of oil production from 5 to 3 years by using off-site module prefabrication.

The most commonly used technology for in-situ production is Steam Assisted Gravity Drainage (SAGD).
Therfore, more emphasis in the article is placed on this technique.
There are 3 other techniques also in use:

• Cyclic Steam Simulation (CSS) - uses a single vertical well and the injection of steam to recover bitumen.
• Toe to Heel Air Injection (THAI) - involves igniting air and injecting it into a vertical well to melt bitumen and recover it.
• Vapour Extraction Process (VAPEX) - uses solvents to increase the viscosity of oil sands for recovery.

Cyclic Steam Simulation

In Cyclic Steam Stimulation (CSS), high-pressure, high temperature (350°C) steam is injected into a vertical wellbore in the oil sands deposit, which is fractured by the stream pressure.
As the steam soaks through the oil sands, the bitumen melts and flows to a producing well, from which it is pumped to the surface.
Each cycle of this process can take from 4 months to 2 years, and several cycles can be completed in a formation.

Steam Assisted Gravity Drainage

SAGD was invented in 1978.
SAGD is currently the most commonly used in situ recovery method. Water is injected into the deposit to maintain stability after the bitumen is removed.

SAGD works by drilling two horizontal wells beneath the surface, parallel to each other, about 4 to 6 meters apart.
Heated steam is injected into the upper well, where the build-up of pressure and heat melts the bitumen and causes it to flow downward to the second horizontal well, from which it is pumped to the surface.
This is the Steam Assisted (SA) part of the name.
The less-viscous bitumen then drains into the bottom well with the help of gravity and is pumped to the surface.
This is the Gravity Drainage (GD) part of the name.
The produced bitumen is mixed with hydrocarbons to further reduce its viscosity and is then stored in storage tanks for transportation and further processing

SAGD has several advantages over oil sands mining.
SAGD production has less land disturbance and does not result in the creation of tailings ponds.
However, SAGD requires large amounts of thermal energy to produce steam.
Currently the vast majority of this energy is provided by natural gas, a non-renewable and hydrocarbon fuel source, making greenhouse gas emissions a key concern.

Other in situ methods

Other in situ methods have been developed but are not yet used commercially, although these methods have numerous potential benefits, including higher resource recovery and lower energy costs, over current technologies.
The Toe to Heel Air Injection (THAI) system involves igniting air injected into a vertical well (TND 2007).
The Vapor Extraction Process (VAPEX) involves injecting solvent into the oil sands.
Both technologies rely on the reduced viscosity of the bitumen that allows it to flow to additional wells for pumping to the surface.