Day 2 2 acidizing placement and diversion techniques final

Placement defini9ons Engineering a good matrix acid job the treatment effectiveness depends on getting the fluids where they’re supposed to go!. Lower zone takes most acid High S zone to

techniques 

Placement defini9ons 

Engineering a good matrix acid job the treatment effectiveness depends on getting the fluids where they’re supposed to go 

!  Diversion ‐ methods and materials to appropriately distribute  fluids across the treatment interval 

!  Pumping Schedule ‐ injection method and rates to efficiently  place fluids 

!  Placement ‐ calculated end effect of combining fluid stages, 

diversion and pumping on formation interval 

Diversion, Pumping Schedule &

Placement and Diversion 

Diversion, Pumping Schedule &

Acid Placement in Heterogeneous  Forma9ons 

4 zones of different permeability

Name!

Top  Meas. 

Depth  (m)!

Bottom  Meas. 

Depth 

(md)!

Porosity  (%)!

Pressure  (bar)!

Inflow  (%)!

Skin!

Reservoir  Type 

zone 1 3726.0 3735.0 50.0 11.00 188.2 28.00 4.08 Carbonate zone 2 3736.0 3745.0 10.0 10.00 188.5 10.00 ‐1.57 Carbonate zone 3 3746.0 3756.0 100.0 10.00 188.7 2.00 390.46 Carbonate zone 4 3757.0 3765.0 200.0 12.00 189.1 60.00 12.54 Carbonate

Mineralogy Data 

Mineral!

zone 3 at  3752.0 m!

Average %  Content for Well 1!

Anhydrite 15.0 15.0

Calcite 35.0 35.0

Dolomite 50.0 50.0

Name!

Top  Meas. 

Depth  (m)!

Bottom  Meas. 

Depth 

(md)!

Porosity  (%)!

Pressure  (bar)!

Inflow  (%)!

Skin!

Reservoir  Type 

zone 1 3726.0 3735.0 50.0 11.00 188.2 28.00 4.08 Carbonate zone 2 3736.0 3745.0 10.0 10.00 188.5 10.00 ‐1.57 Carbonate zone 3 3746.0 3756.0 100.0 10.00 188.7 2.00 390.46 Carbonate zone 4 3757.0 3765.0 200.0 12.00 189.1 60.00 12.54 Carbonate

Mineralogy Data 

Mineral!

zone 3 at  3752.0 m!

Average %  Content for Well 1!

Anhydrite 15.0 15.0

Calcite 35.0 35.0

Dolomite 50.0 50.0

Lower zone takes most acid

High S zone

to be acidised

Coiled tubing (CT) 

!    

SpoΦng acid 

Maximum rate Maximum pressure 

Diversion, Pumping Schedule &

!    

!    

!     

Diversion, Pumping Schedule &

Par9culate diverters – film forming 

Par9culate diverters – cake forming 

Diversion achieved? 

Diversion, Pumping Schedule &

Gelled acid diversion 

!  Displace the acid with a suitable brine, diesel or other 

fluid. 

!  Close the well in for 12‐24 hours to allow for sufficient 

reaction time (depending on the type of acid and damage)  and proper breakdown of the viscosity or 

!  Use pH crosslinked stages 

Emulsified acids 

Diversion, Pumping Schedule &

Diversion, Pumping Schedule &

Diversion, Pumping Schedule &

Foamed acid 

OilSeeker (Schlumberger)‏

Divert acid away from water zone, into oil zone

Some good case histories published

high viscosity in water

viscosity break after mixing with oil

Viscosity develops as acid spends spents

stage

2

acid + visco-elastic surfactants

viscosity block

stage

3

plain acid

next acid stage into low

k zone

¥  acid is pumped through a jetting nozzle,

improving acid-rock contact and wormhole initiation

¥  while acid is pumped through the CT, an

inert fluid is pumped simultaneously

through tubing-CT annulus, with the

purpose to improve diversion and

placement

¥  Patented tool is run on coiled tubing

¥  Unique design of the tool causes the tool to oscillate as fluid is pumped through the tool

Ð  Fluid can be acid, water, diesel, nitrified fluids, etc

¥  Near wellbore mud removal, screen cleaning

Decision tree