Waste disposal options: DWI

Question 1

2 main reasons for injecting fluids into the subsurface

Answer 1

1. increase the pressure in O+G reservoirs

2. Disposal of liquid HW

Question 2

5 Classifications of wells based on type of fluid

Answer 2

4. direct injection into a reservoir – not for disposal, SAGD
5. injection of HC, inert gases or other gases – storage of liquids and enhanced oil recovery
6. injection or disposal of produced waters (brines)
   1b. disposal of produced water, specific oilfield waste streams
   1a. only well to accept liquid waste other then O+G

Question 3

Fluid waste criteria for DWI

Answer 3

1. PH: 4.5 to 12.5
2. does not meet surface water discharge criteria
3. has a non-halogenated organic fraction < 10% by mass
4. has one or more halogenated organic compounds in a combined [ ] of < 1000mg/kg
5. PCB concentration < 50mg/kg

Question 4

Alberta regulations focus on 4 key areas

Answer 4

1. wellbore integrity
2. formation suitability for disposal of fluids
3. waste stream capability
4. reporting and manifesting

Question 5

Wellbore design

Answer 5

Once the wellbore is completed, it must result in complete isolation of the disposal zone from all other formations–especially usable GW aquifers. TDS < 4000 mg/l

Question 6

Surface casing must…

Answer 6

Extend below the base of all usable GW wells

Question 7

Wellbore integrity is maintained by…

Answer 7

Logging and testing the well:

1. prior to any fluids being injected - req’s must be met
2. during the life of the well - ensure hydraulic isolation is maintained

Question 8

Initial logging and testing requirements include:

Answer 8

1. cement top location logging
2. hydraulic isolation logging - temp log, radiactive tracer log , oxygen activation log, cement integrity log
3. casing integrity log - check for corrosion
4. initial pressure tests - 7000 kpa for 15 min

Question 9

Monitoring logging/testing requirements:

Answer 9

1. recording of annular and injection P
2. hydraulic isolation logging
3. formation pressure surveys
4. packer isolation tests

Question 10

Formation suitability for the disposal of fluids

Answer 10

1. n- enough space for fluids
2. K - fluids need to flow into FM - best sed rx SS
3. No fractures
4. Below GW aquifer
5. Confined n + K zone
6. Deep

Question 11

Waste stream suitability

Answer 11

See if fluids will react with the aquifer matrix or the FM

Question 12

Problems associated with DWI

Answer 12

1. Contamination of GW aquifers if hydraulic isolation not maintained
2. Potential for localized earth quakes