7. Waste Options: Deep well injection

Question 1

Deep Well Injection history

Answer 1

-in use since the 1950s by oil and gas for disposal of oil field brines

Question 2

2 Reasons for injecting fluids into the subsurface formations

Answer 2

-increase pressures i oil and gas reservoirs that have been on production for some time
(P increases, production rates of Oil and Gas Increase)
-Disposal of LIQUID hazardous wastes

Question 3

5 Classes of injection/disposal wells in Alberta

Answer 3

-based on type of fluid injected
Class IV
Class III
Class II
Class Ib
Class Ia

Question 4

Class IV injection wells

Answer 4

• direct injection into a reservoir (not a disposal well) –> SAGD
  eg. potable water, steam from potable water

Question 5

Class III Injection well

Answer 5

• injection of hydrocarbons, inert gases or other gases
• purely used for storage of liquids in enhanced oil and gas recovery systems
• Fluid types include solvents for enhanced oil recovery, sweet gas storage, emergency fuel supply

Question 6

Class II injection well

Answer 6

• injection or disposal of produced waters (mainly brines)

- brines originate from water produced during oil and gas production operations, water produced from solutions mining

Question 7

Class Ib Injection well

Answer 7

• disposal or produced water, specific oilfield waste streams and waste streams meeting specific criteria
• regs provide liquids which can be disposed here

Question 8

Class Ia Injection well

Answer 8

• disposal of oilfield or industrial waste fluids
• only waste to accept waste that’s not oil field waste
• liquids must be tested prior to disposal and must meet all criteria in ERCB directive 50

Question 9

Fluid Waste Criteria for DWI

Answer 9

• pH between 4.5 and 12.5
• substance doesn’t meet surface water discharge criteria
• has a non-halogenated organic fraction of less than 10% by mass (except untreatable sand or crude oil/water emulsion, antifreeze or dehydration fluid)
• has one or more halogenated organic compounds in a total combined concentration less than 1000 mg/kg
• PCB concentration less than 50 mg/kg

Question 10

Deep Well Injections regulated by:

Answer 10

ERCB directive 51, not Alberta Environment and Water

Question 11

ERCB Regulations focus on 4 key areas

Answer 11

• Wellbore integrity
• Formation suitability for the disposal of fluids
• Waste stream suitability
• Reporting and manifesting

Question 12

Wellbore Integrity

Answer 12

• both initial and ongoing containment of the injected fluids in the disposal/injection zone
  
  • protection of ground water
  • conservation of hydrocarbons

Question 13

Formation suitability for the disposal of fluids

Answer 13

-make sure injection/disposal zone will continue to confine the injected fluids with that single zone

Question 14

Wellbore Design

Answer 14

must result in complete isolation of the disposal zone from all other formations and especially from useable groundwater aquifers

Question 15

Well head

Answer 15

includes well head and casing pressure gages

Question 16

Surface Casing

Answer 16

Must extend below all useable ground water aquifers

Question 17

Production Casing

Answer 17

Extends from surface to the base of the well

Question 18

Annulus

Answer 18

Between casing and injection tubing

Question 19

Packers

Answer 19

Isolates the annular fluids from the disposal/ injection fluids

Question 20

Wellbore Integrity is ascertained by logging/testing the well:

Answer 20

• Prior to any fluids being injected into the disposal formation (if don’t meet this application will be denied)
• During the life of the disposal well (ongoing monitoring to ensure hydraulic isolation of the injection/disposal zone from other zones)

Question 21

Initial logging/testing requirements include:

Answer 21

• cement on top location logging
• hydraulic isolation logging
• casing integrity logging
• initial pressure tests

Question 22

Cement top location logging

Answer 22

• cement is used to hold the casing in place

- isolate various zones from one another

Question 23

Hydraulic isolation logging

Answer 23

-ensures isolation of disposal zone

Question 24

Casing integrity logging

Answer 24

-full length casing inspection to determine if corrosion is becoming an issue which can weaken the casing

Question 25

Initial pressure tests

Answer 25

• test pressures up to about 7000 kPa for 15 min for all classes of wells
• ensures no leaks will occur once injection starts

Question 26

Monitoring logging/testing requirements include (Class Ia wells):

Answer 26

• recording of annular and injection pressures daily
• hydraulic isolation logging every 5 years
• formation pressure surveys yearly
• packer isolation tests yearly

Question 27

Requirements for the disposal zone of fluids (relating to formation suitability):

Answer 27

• porous (storage) and permeable zone (waste can flow)
  
  • sandstones/conglomerates
  • carbonates
  • unconsolidated sands
• not fractured- may not be able to get hydraulic isolation
• below useable groundwater zones
• want formation waters to be saline
• confined
• deep

Question 28

Waste Stream Suitability

Answer 28

Injection fluids must be chemically compatible with both the formation fluid and the rock matrix

Question 29

Problems associated with deep well injection

Answer 29

• Contamination of ground water aquifers if hydraulic isolation of the disposal zone is not maintained
• Localized earthquakes because of increased subsurface pressure as fluids are injected