Stimulation of Sandstone and Carbonate Reservoirs Using Chelating Agents

Amin Ameri amin.ameri@akzonobel.com October, 2016

Introduction StimWell™ References Conclusions

Major problems with carbonate acidizing

Introduction StimWell™ References Conclusions

Major problems with sandstone acidizing

Introduction StimWell™ References Conclusions

Chelates ▬ StimWell Portfolio

Dissolvine StimWell is a chelate based product series

– Dissolvine StimWell HTF (pH 3.8): •  CaCO3 •  Iron scales

– Dissolvine StimWell DGH (pH 11.5): •  CaSO4

– Dissolvine StimWell DDH (pH 14): •  BaSO4 •  SrSO4

Introduction StimWell™ References Conclusions

Summary

GLDA ASDA EDG MGDA HEDTA MSA HCl Solubility pH<4 ++ + - - +/- ++ ++

Calcite dissolution + +/- - - + ++ ++

Carbonate (300°F, 2cc/min)

++ + - - + -* -*

Sandstone ++ +/- - - + n.d. -

Thermal stability + - ++ ++ + ++ ++

Corrosion L-80 + +/- +/- +/- +/- - -

Corrosion Cr-13 ++ + + + +/- - -

Health ++ ++ ++ ++ ++ - -

Biodegradability (OECD 301D)

++ ++ ++ ++ - ++ n.a.

Solubility in 15% HCl

++ - + +/- ++ n.d. n.a.

Iron control + + ++ +/- ++ n.a. n.a.

* Dependent on T and flow rate conditions

Introduction StimWell™ References Conclusions

0.0009 0.0011

0.0318 0.0900

0.5253

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

20wt% GLDA

10wt% Citric acid

10wt% Acetic acid

20wt% MGDA

20wt% HEDTA

10wt% Formic acid

15wt% HCl

6-ho

urs

met

al lo

ss (l

bs/s

q.ft)

•  Cr-13 •  300°F •  N2 head space •  6 hour metal loss at

temperature

Coupons fully dissolved GLDA HEDTA

Low corrosion profile

Introduction StimWell™ References Conclusions

•  L-80 carbon steel •  300°F •  N2 head space •  6 hour metal loss at

temperature

0.1956

0.0394

0

0.2

0.4

0.6

0.8

1

1.2

GLDA 20wt% HEDTA 20wt% MGDA 20wt% Acetic acid 10wt% Citric acid 10wt% Formic acid 10wt% HCl 15wt%

6-ho

ur m

etal

loss

(lbs

/sq.

ft.)

No CI

0.001v% CI

Coupons fully dissolved

GLDA Acetic

Low corrosion profile

Introduction StimWell™ References Conclusions

• Acids are used to create wormholes to connect the formation to the wellbore

• Success depends on how deep this acid will penetrate into the formation creating uniform wormholes

Stimulation in carbonate reservoirs

Introduction StimWell™ References Conclusions

Lab Study

9

1.0 mL/min Coreflood @ T and P

Introduction StimWell™ References Conclusions

• Acids are used to dissolve the soluble materials

• Solubility tests in the lab (samples from TU Delft - W-1)

– 100°C for 6 hours

Stimulation in sandstone formations

Solvent Dissolved [%] SW HTF 50% 9.87 SW DDH 50% 7.55 HCl 15% 14.34

Introduction StimWell™ References Conclusions

Stimulation in sandstone formations

Bandera core (10% illite)

• Coreflood tests with Bandera cores

Introduction StimWell™ References Conclusions

Case Histories - Overview

Formation

Geometry Temperature

Stimulation

Descaling

Pickling

Applications

150

200

250

300

Chalk

Calcite

Sandstone Dolomite

Materials

Carbon steel

Ni-Cr Cr

ESP 0  

50  100  150  200  250  300  350  400  

°F

400

Introduction StimWell™ References Conclusions

Descaling using StimWell HTF

De-scaling

Introduction StimWell™ References Conclusions

Field application I: Tight, sour gas well

Post treatment

target

Pre-treatment

5.25

4.2

3.15

0

Prod

uctio

n R

ate

(M

MSC

FD)

2.1

1.05

Expected fracturing

result

+110%

2.1

3.4

4.4

5

GLDA treatment

SPE 163332

•  325°F •  20% H2S •  9% CO2 •  Carbonate (calcite

and dolomite) •  Porosity: 11.5% •  Permeability: 4 mD •  CRA and carbon

steel •  20wt% GLDA at

pH=3.4

Introduction StimWell™ References Conclusions

Field application I: Tight, sour gas well

No after treatment required

0

10

20

30

40

50

0 5 10 15 20

Con

cen

trat

ion

(p

pm

)

Sample nr

Fe in stimulation fluid Mn Fe Cr

0

2000

4000

6000

8000

10000

0 5 10 15 20

Con

cen

trat

ion

(p

pm

)

Sample nr

Ca

Mg

All flowback samples pH>6

Effective dissolution of calcite and dolomite

No corrosion SPE 163332

•  325°F •  20% H2S •  9% CO2 •  Calcite and

dolomite •  Porosity: 11.5% •  Permeability: 4 mD •  CRA and carbon

steel •  20wt% GLDA at

pH=3.4

Introduction StimWell™ References Conclusions

Field application II: Horizontal well

•  271°F •  200 ppm H2S •  6mol% CO2 •  Permeability: 50

mD •  L-80 tubular •  >4500 feet

horizontal section completed within 4 hydraulic sliding sleeves

•  20wt% GLDA at pH=3.4 at 0.25 bbl/ft

Effective residual filtercake removal and stimulation from heel to toe due to slow reaction rate

Before stimulation After stimulation

Liquid rate (bbl/day)

PI (bbl/day/psi)

Liquid rate (bbl/day)

PI (bbl/day/psi)

Well 1

680 0.8 1215 1.8

Well 2

350 0.4 900 1.6

Introduction StimWell™ References Conclusions

Field application III: Descaling ESP

•  160°F •  FeCO3 and

CaCO3 around ESP

•  20wt% GLDA at pH=3.4

The oil production increased from 400 to 512 STB/day and the PI improvement sustained for 6 months SPE 166335

Introduction StimWell™ References Conclusions

Field application III: Descaling ESP

Analysis of flowback samples proved dissolution of the scales, without any adverse impact on the ESP or well tubular

SPE 166335

0

500

1000

1500

2000

2500

0 10 20 30 40 50 60

Con

cent

ratio

n (p

pm)

Sample nr

Ca

Fe

Mn

Zn

•  160°F •  FeCO3 and

CaCO3 around ESP

•  20wt% GLDA at pH=3.4

Introduction StimWell™ References Conclusions

Subject Reference Year

Field applications SPE 163332: SPE P&O (2013) 28-3, pp277-285 SPE 166335 SPE 168163: J. of Can. Pet. Tech., 54-5, pp289-297 SPE 173774

2012 2013 2014 2015

Carbonate coreflood SPE 127923: SPEJ (2011), 16-3, pp559-574 SPE 133497: SPEJ (2011), 16-4, pp968-980 SPE 140149

2010 2010 2011

Sandstone coreflood SPE 139815 SPE 143301 SPE 147395: SPE P&O (2015), 30-1, pp43-51

2011 2011 2011

Corrosion SPE 152716 SPE 160849

2012 2012

HSE SPE 157467 SPE 168145

2012 2014

Reaction rates SPE 139816 SPE 164480

2011 2013

Filtercake removal SPE 155426 2012

References

Thank you for your attention

Questions?