Field Case Study #4

H2S Scavenging in Iron Bearing

Substrates

Mike Singleton

Flow Assurance & Scale Team: Scale Workshop

Treetops Hotel, Aberdeen, 29 January 2019

Background

Project with Petronas

Full findings published at First EAGE/IFPEN

Conference on Sulphur Risk Management –

2018

Objective:

• Understand the mechanism of H2S scavenging by Fe

bearing substrates

• Generate scavenging capacities (mg/g) for inclusion

into reservoir models

Scavenging Capacity – Static Tests

Brine of known [H2S] (aq)

T = 25ºC or 96ºC

Substrate – mix of sand

and Siderite (FeCO3)

Samples taken over time

Assay for H2S(aq)

Correlate H2S removal to

Scavenging Capacity

(mg/g)

GAS

WATER

H2S

H2S(aq)

H+

HS-

S2-

OH-

Fe2+?

Sand + FeCO3(s)

CO2

CO2(aq)

HCO3-

CO32-

Scavenging Capacity – Static Tests

0

2

4

6

8

10

12

14

0 2 4 6 8 10 12 14

Sca

ve

ng

ing

ca

pa

city (

mg

/g)

Initial pH

Scavenging capacities for 2 g of siderite at 25°C and 96°CParticle size 100-315 µm unless otherwise stated

25 °C 96 °C

<100 µm shaken

<100 µm unshaken

<100 µm unshaken

Scavenging Capacity – Dynamic Tests

Fluid Inlet

Fraction

Collector

Inlet Pressure

Transducer

Differential

Pressure

Transducer

Outlet Pressure

Transducer

UVWater

bath

Column

Flow rate = 10 ml/h

Initial [H2S] = 250 ppm

Porosity of columns ≈ 40%

Mass of siderite = 4 g in 50 g (8

wt%)

Mass of crushed field core = 25 g

Injector

Transfer

vessel

maintains

[H2S]

Scavenging Capacity – Dynamic Tests

Crushed Field Core

Scavenging Capacity – Dynamic Tests

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 10 20 30 40 50 60 70 80 90

Sc

ave

ng

ed

su

lph

ide

(m

g)

Cumulative volume (PV)

25 °C 4 g siderite 96 °C 4 g siderite

25 °C Crushed core 96 °C Crushed core

25°C

Crushed core = 144 mg total (5.76 mg/g)

Siderite pack = 51.72 mg total (1.03 mg/g)

96°C

Crushed core = 145 mg total (5.80 mg/g)

Siderite pack = 87 mg total (1.74 mg/g)

Scavenging Capacity – Dynamic Tests

Inlet

Outlet

Scavenging Capacity – Dynamic Tests

0

5

10

15

20

1.2

0

1.6

1

2.1

7

2.9

2

3.9

2

5.2

7

7.0

8

9.5

2

12.8

17.2

23.1

31.1

41.8

56.2

75.6

102

137

184

247

332

446

600

%

High size (µm)

Particle size distribution (1.2 - 600 µm range)

Column Blank

0

5

10

15

0.1

0

0.1

4

0.1

9

0.2

6

0.3

6

0.4

9

0.6

8

0.9

3

1.2

8

1.7

5

2.4

1

3.3

2

4.5

6

6.2

7

8.6

2

11

.80

16

.30

22

.40

30

.80

42

.30

58

.20

80

.00

%

High size (µm)

Particle size distribution (0.1 - 80 µm range)

Column Blank

Column Blank

Mechanistic Interpretation

Grains of siderite (FeCO3)

Fe2+

Direction of flow

Fe2+ Fe2+ Fe2+ Fe2+ Fe2+

Fe2+

Mechanistic Interpretation

Grains of siderite (FeCO3)

Direction of flow

Fe2+ + FeS +

H2S

Fe2+ + S2- → FeS

Grain of (FeCO3) +

FeS

Fe2+

Mechanistic Interpretation

Grains of siderite (FeCO3)

Direction of flow

Fe2+ + FeS +

H2S

Fe2+ + S2- → FeS

Grains of (FeCO3) +

FeS

Other Factors to be Investigated

Capacities for Consolidated Core

Presence of Oil

• H2S partitioning to oil phase

• Impact of Oil films

Impact of Kinetics

Other Fe bearing Substrates