﻿ In Situ Impacts

In Situ Impacts


Some bitumen has a low enough viscosity to flow to wellbores on its own and can be recovered through primary methods requiring no heat or injection of fluids. Most in situ bitumen recovery, however, uses steam to heat the bitumen in the reservoir, which reduces its viscosity and allows it to flow to wellbores. This is referred to as thermal in situ recovery. Sometimes small amounts of solvent are injected along with the steam to further reduce the bitumen viscosity and increase recovery.

There are currently two main thermal in situ oil sands technologies: steam-assisted gravity drainage (SAGD) and cyclic steam stimulation (CSS). SAGD injects steam into a horizontal well to deliver heat to the bitumen in order to reduce its viscosity so that it can flow more easily. Gravity then causes the bitumen to flow down to a second horizontal well positioned below the injector so it can be produced to surface.

CSS injects steam into a vertical or horizontal well with sufficient pressure to fracture the reservoir, allowing the steam to move rapidly out into the reservoir to deliver heat to the bitumen and reduce its viscosity, allowing it to flow more easily. During the production cycle, the bitumen is produced to surface using the same well.

The impacts of in situ oil sands development are different from mining operations and are managed and mitigated accordingly, including water use and ensuring reservoir containment.

Water Use

Water is heated to create steam at the surface and then injected into a reservoir to heat bitumen and reduce its viscosity so that it can flow to a wellbore. Water use is, therefore, a critical environmental impact that must be managed carefully.

The objective in regulating thermal in situ water management is to ensure efficient and sustainable in situ oil sands operations.

Directive 081: Water Disposal Limits and Reporting Requirements for Thermal In Situ Oil Sands Schemes consolidates various aspects of water management requirements for thermal in situ oil sands schemes. The directive sets out water disposal limits, which require operators to recycle produced water efficiently and ensure that all make-up sources are effectively used.

To support transparency to all stakeholders, the Thermal In Situ Water Publication provides monthly and annual water use information from January 2012. The dashboard is an interactive tool, allowing users to filter and analyze the information in different ways.

The publication includes the following monthly and annual water-use data, on a scheme basis:

  • maximum annual water disposal limits and actual water disposal
  • water productivity ratios (fresh water, brackish water, and disposal)
  • make-up water use (fresh and brackish)
Reservoir Containment

In thermal in situ recovery, steam is injected into a reservoir at high pressure to heat the bitumen and reduce its viscosity so that it can flow to a wellbore. The rock above and around the reservoir - known as cap rock - must act as a barrier to ensure containment of fluids and safe operations, which is critical to protecting the environment and ensuring bitumen is not inadvertently wasted.

Operators who apply for an approval for thermal in situ oil sands projects must show in their application to the AER that they have assessed the cap rock geology and that it will prevent steam and reservoir fluids from escaping. As well, legacy wellbores in the area must be examined for thermal compatibility as they are a potential conduit to the surface.

The AER conducts a detailed technical assessment of the project application, including the integrity of the surrounding geology, geomechanics (understanding of how the rocks, pressures, and temperatures will interact), and the engineering behind the project itself.

Given the relatively new technologies being used in thermal in situ development, reservoir containment is still an emerging issue and is being assessed on a project-by-project basis. Currently, the AER is engaging technical experts both internally and externally as we continue to analyze what constitutes a good cap rock and safe operating pressures for thermal in situ schemes in Alberta.

The AER is currently developing regulatory requirements that will apply broadly to all thermal in situ development so that operators have more certainty regarding what steps to take and what information to provide in developing their project applications.