Base of Groundwater Protection
(BGWP)
Carrie Dickinson, P. Geol.
Oil Sands and Coal Branch
Tony Lemay, M.Sc., P.Geol.
Geology, Environmental Science and Economics
Branch - Alberta Geological Survey Group
Energy Resources Conservation Board
Acknowledgments
• Michael Bevan - ERCB
• Elena Zimmerman - ERCB
Outline
• History of the Base of Groundwater Protection
• Groundwater protection and the ERCB
• Groundwater protection regulations that involve the
Base of Groundwater Protection
– Drilling and completion activities
– Production operations
– Abandonment
• The process of defining the Base of Groundwater
Protection
• The administration of the Base of Groundwater
Protection
History of the BGWP
• BGWP was originally released by AENV in 1993, and
updated in 1995.
• The 1995 version of the BGWP was available through
Statistical Series 55: Alberta’s Usable Groundwater Base of
Groundwater Protection Information (1995).
• The original objective was to map to the base of the
deepest non-saline aquifer. Due to limited data availability,
some regions were mapped to the base of a specified
formation or a general depth for the township/range was
provided. Blank areas of the table required the user to
request a BGWP depth from AENV.
Groundwater Protection
and the ERCB
• Oil and Gas Act
– allowed for regulations “for the prevention of pollution of fresh
water supplies”
• Water Act
– defines saline groundwater as having >4,000 milligrams per litre
of Total Dissolved Solids (mg/L TDS)
• Base of Groundwater Protection (BGWP)
– identifies approximate depth where groundwater changes from
non-saline to saline, managed by ERCB
– enhanced ERCB requirements when working above BGWP
Groundwater Protection During
Drilling and Completion
a) Directive 036 - Drilling Blowout Prevention
Requirements and Procedures
– Section 19.1: “The use of oil-based drilling fluids (or any other
potentially toxic drilling additive) is prohibited when drilling
above the ‘base of groundwater protection’ depth.”
Groundwater Protection During
Drilling and Completions
b) Directive 009 - Casing Cementing
Minimum Requirements
– surface casing must be cemented to surface, and
if it does not extend below BGWP, next casing
string must be cemented full-length, to surface
– if cement not to surface, must notify ERCB for
guidance
Conductor Pipe
Surface Casing
Cement
BGWP
Production
Casing
Cement
Groundwater Protection During
Drilling and Completions
c) Directive 027 - Shallow Fracturing Operations
– Non toxic fluids above the BGWP, must be designed so no
non-saline aquifers could be impacted
– Restrictions in proximity to water wells and bedrock surface
200 m
Water
well
50 m
Bedrock surface
Gas well
NO FRACTURING
PERMITTED
Gas well
50 m
NO
FRACTURING
PERMITTED
Groundwater Protection During
Drilling and Completions
d) Directive 035 - Baseline Water Well Testing (BWWT)
Requirement for Coalbed Methane Wells Completed
Above the Base of Groundwater Protection (BGWP)
– Operationalizes AENV baseline water well testing standard
– Company must offer to test all water wells within 600m of
proposed CBM well; if none, must offer to test closest within 800m
– BWWT results must be sent to AENV and landowner
– “If a landowner/occupant perceives a change in water well
quantity or quality after CBM development, then the CBM
developers must retest the water well.” AENV Standard, 2006
Groundwater Protection During
Production
a) Directive 044 - Requirements for the Surveillance,
Sampling, and Analysis of Water Production in Oil
and Gas Wells Completed Above the Base of
Groundwater Protection (BGWP)
– Effective for all wells producing 5m3/month water or more.
– Water produced (>5m3/mo) from above the BGWP must be
measured, analysed and reported.
– Ensure no cross-flow of water between completion intervals.
– Ensure no non-saline water production from coal without
authorization from AENV
Groundwater Protection During
Abandonment
a) Directive 020 - Well Abandonment Guide
– all oil and gas zones must be isolated
– all non-saline groundwater zones above the BGWP must be
isolated, for wells drilled prior to current groundwater
protection requirements
The Process of Defining the Base
of Groundwater Protection
•Base of Groundwater Protection (BGWP)
– identifies approximate depth where groundwater changes from
non-saline to saline, managed by ERCB
– process began by attempting the map this interface
The Process of Defining the Base
of Groundwater Protection
Sample Depth (m)
• Changes in water chemistry with depth
TDS (mg/L)
The Process of Defining the Base
of Groundwater Protection
• Understanding the relationships of TDS and depth
Paired water well depth correlations, comparing different TDS ranges
Conclusions from the TDS and
depth work
• A relationship exists between TDS and depth,
however, the relationship is complex and
influenced by many factors. These factors
significantly increase the spatial variability of
TDS concentrations, making it difficult to
extrapolate expected concentrations to areas
with little or no data.
• Very few water well samples have a TDS
concentration > 4,000 mg/L.
A New Old Approach
• The BGWP as originally
defined was associated in
most parts of the Province
with a particular Formation
or Formations.
• A geological approach was
largely used to define the
BGWP and could therefore
be used to develop the final
surfaces.
• Various surfaces, picks and
geochemical information
could be used to constrain
this surface.
Data screening
Workflow for
the definition
of the BGWP
Data analysis
Statistical analysis
Mapping
of uncertainty
Presentation of the
results
Geostatistical mapping of uncertainty
p10
p50
p90
Presentation of the results
The results of the mapping are now being disseminated
electronically through a web tool available at
http://www.ercb.ca, under the “Quick Links” drop down menu.
Future BGWP Revisions
• Future changes to the BGWP will be managed jointly by
AENV and the ERCB.
• The ERCB stores water chemistry received through
application submissions and surveillance initiatives, which
will be used to assist with future revisions of the BGWP.
• Future revision of the BGWP will be done on a province wide
scale to avoid piecemeal changes to the database.
– Avoid discontinuity between regions
• Concerns with the depth of the BGWP at specific locations
are being handled on a case by case basis.
• Water chemistry received by the ERCB is compared to the
BGWP database to ensure groundwater protection is being
achieved. The ERCB feels the BGWP is adequately
protecting non-saline groundwater.