SPT Gas Condensate vs Oil Wax Deposition

Gas Condensate vs Oil Wax Deposition Lauchie Duff Olga Users Group 11 November, 2009

OUTLINE q

Recap from Previous Olga Users Presentation

q

Gas Condensate Misconceptions

q

Fluid Characterisation Introduction Using Oil M

q

Fluid Characterisation Using A & B Gas Condensates

q

Wax Introduction

q

Wax Precipitation vs Wax Deposition

q

Waxy Condensates vs Waxy Oils Deposition

q

References

Recap Summary: Olga Wax Attack q

Non Newtonian Rheology & How to Model in Olga

Recap: Olga Wax Attack on Non Newtonian Flow Steady State Shear & Thermal History Effects Oil Cooldowns : SCDP vs CCDP

Apparent Viscosity (mPas) 4500 4000

S 1.20 BT 90C: 2kppm PPD, SCDP

3500 83% Delta at Final T

3000

S 1.20 BT 90C: 2kpp PPD, CCDP

2500 2000 1500 1000 500 0 20

22

24

26

28

30

32

34

Temperature (oC)

36

Recap: Non Newtonian Flow: Restarts Shear & Thermal History Affects on Restarts Shear Stress (Pa)

Restarts Ramps after Shut Down at 16oC: Shear History Effects

80 70 60 50 No ramping

40

after cooldown ramping

30 20 10 0 0

10

20

30

40

50

60

70

80

90

100 -1

Shear Rate (s )

WAX / Condensate Misconceptions q q q q q q q q q q

Condensate colour determines “contamination” Subsurface hydrocarbons are homogeneous fluids with no spatial variation, unlike petrophysical variations. Waxes are n alkanes only Measured WATs and wax contents are more accurate than simulated Wax Precipitation equals Wax Deposition Reported GC / HTGC compositions must be right. The lab has surely integrated the areas and mass %s correctly? Condensate compositions terminate around C30-C40 Long compositional heavy tails (of condensates), if they exist, are very insignificant (compared to oils) Reported compositions and associated EOSs are matched to measured dew points by regression of critical properties Condensate near well bore banking of heavy ends does not occur in high permeability formations

Fluid Characterisation is First (and very big) Step in Wax Deposition Concepts and Wax Primer: 1MComposition Measurements Oil HTGC vs GC Wt%

16.0

C30+ = 15.047 % 14.0

HTGC

12.0

GC 10.0 8.0 6.0 4.0

C52+ = 1.828%

2.0 0.0 0

10

20

30 SCN

40

50

60

M Oil Composition Lets take the HTGC and extend power and exponential laws

q

M Oil HTGC & Manual Extrapolations

Wt%

Measured HTGC

10.0000

HTGC: Manual Extrapolations Exponential

C52+ = 1.828%

Power

1.0000

Power (HTGC: Manual Extrapolations)

y = 29992290.385621x

0.1000

-4.827528

2

R = 0.974967

y = 78.1118e-0.1220x R2 = 0.9583 C52+ = 1.525%

C52+ = 2.189%

0.0100

0.0010

0.0001 5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

SCN

85

90

95 100 105 110 115 120 125 130 135 140 145 150

M Oil Composition q

Lets take the HTGC and extend using PVTSim Characterisationsie Log Wt% vs Molec Wt is Linear M Oil HTGC & Manual Extrapolations

Wt%

Measured HTGC

10.0000

HTGC: Basis for Manual Extrapolations Exponential Extrapolation

C52+ = 1.828%

Power Extrapolation

1.0000

PVTSim C100+ Characterisation 0.1000

C100+= 0.0785%

y = 78.1118e-0.1220x R2 = 0.9583 C52+ = 1.525% 0.0100

y = 29992290.385621x-4.827528

0.0010

R2 = 0.974967 C52+ = 2.189%

0.0001 5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

SCN

85

90

95 100 105 110 115 120 125 130 135 140 145 150

WAX: Composition incl n Alkanes qDoes the n alkane a/c for all the wax? M Oil HTGC

Wt% 6.0000

5.0000

HTGC: PVTSim Characterised C100+

4.0000

n alkanes 3.0000

2.0000

1.0000

0.0785

0.0000 5

10

15

20

25

30

35

40

45

50

55

SCN

60

65

70

75

80

85

90

95

100

M Oil Composition incl n Alkanes Wt%

Wax% ?

5.00

0.5

4.50

0.45

4.00

0.4 HTGC: PVTSim Characterised C100+

3.50

0.35

n alkanes as % SCN

3.00

0.3

2.50

0.25

2.00

0.2

1.50

0.15

1.00

0.1

0.50

0.05 0.0785

0.00 5

10

15

20

25

30

35

40

45

50

55

SCN

60

65

70

75

80

85

90

0

95 100

M Oil Properties: WAT / WDT q q

Pour Point = 24oC WAT by 3 different DSCs(45->75oC) / CPM (39-48.8oC)/ Rheology / oC) CWDT (51Heat M Oil DSC (Heating Cycle) Capacity O

J/g C 5

o

4.5

Still Melting at >100 C

WDT 2 = 44OC

4

O

WDT 2 = 55 C

O

WDT1 = 67 C

3.5

3

2.5

2 0

20

40

60

80 o

Temperature ( C)

100

120

M OIL WAX: WDT vs WAT q

Note endothermic melting curve vs exothermic xlln curve. Ie end of melting approx at beginning of Xlln. This is a very significant result as it reveals the effect of kinetics on WDT / WAT ie WDT-WAT almost zero

M WAT SIMULATION BASED ON HTGC o

Simulated M WAT: 52 C

Wax Wt% 25

Tulsa WAT to C52+

20

15

10

5

0 -30

-20

-10

0

10

20

Temperature (oC)

30

40

50

60

M OIL WAX: Conclusion

q We

have simulated WAT of 52oC vs DSC measured WAT of 63oC & WDT of >100oC. Is this Robust and we can now characterise to these measurements?

WAX: M Oil Composition incl n Alkanes qDoes wax content go down as SCN increases? Wt%

Wax% ?

5.00

0.5

4.50

0.45

4.00

0.4 HTGC: PVTSim Characterised C100+

3.50

0.35

n alkanes as % SCN

3.00

0.3

2.50

0.25

2.00

0.2

1.50

0.15

1.00

0.1

0.50

0.05 0.0785

0.00 5

10

15

20

25

30

35

40

45

50

55

SCN

60

65

70

75

80

85

90

0

95 100

M OIL : PVTSim Charactersation qPVTSim characterises zero wax after last measured plus fraction-but is this correct? PVTSims PARAW Characterised Fractions

Fraction 0.7 0.6 0.5

Paraffins Napthenes (Branched & Cyclics) Aromatics

0.4

Waxes Asphaltenes

0.3 0.2 0.1 0 0

10

20

30

40

50 SCN

60

70

80

90

100

WAX: Composition incl n Alkanes qPVTSim characterises zero wax after last measured plus fraction Wt%

Wax% ?

5.00

0.5

4.50

0.45

4.00

0.4 HTGC: PVTSim Characterised C100+

3.50

0.35

n alkanes as % SCN PVTSims Heavy Characterised Wax %

3.00

0.3

2.50

0.25

2.00

0.2

1.50

0.15

1.00

0.1

0.50

0.05 0.0785

0.00 5

10

15

20

25

30

35

40

45

50

55

SCN

60

65

70

75

80

85

90

0

95 100

My favourite PhD on WDT vs WAT Audrey Taggart 1995, Univ Strathclyde “Nucleation, Growth and Habit Modification of n Alkanes etc” Ref [3] qTerminology: Meta stable zone width = WDT-WAT q WDT approaches WAT in the limit of slow cooling

My favourite PhD : WDT vs WAT MSZW Associated with Crystallite Dissolution & Precipitation from Cooling Rate C18H38 Melt o

( C/min) 0.8

WAT

0.7

WDT

0.6 MSZW 0.5 0.4 0.3 0.2 0.1

T sat (at b =0oC /min)

0 25

26

27

28

29 Temperature

30

WDT / WAT and Wax Xtal Effects MSZWs vs Carbon Chain Lengths

Meta Stable Zone o

Width ( C) 3 TRICLINIC 2.5 2 1.5 1 MONOCLINIC 0.5 ORTHORHOMBIC

0 12

14

16

18

20

22

24

26

28

30

Carbon Chain Length

32

My favourite PhD on this subject WATs for Normal Alkanes (Measured at 5oC /min) Enthalpy of Crystallisation (J/g)

o

Temperature ( C) 105

240

TRICLINIC

95 85

210

75

180

65 150

55

MONOCLINIC ORTHORHOMBIC

45

120

35

90

25

WAT Enthalpy of Crystallisation

15

60 30

5 -5

0 10

15

20

25

30

35

40

45

50

55

Carbon Number

60

WAX PRIMER q

q q q

q q q q

Wax is not just n alkanes but many other species. eg Ref [2] determined microxlline waxes (mpts>60C) to be 20-40% n alkanes,15-40% iso alkanes and approx 35% cycloalkanes. Macro and microXlline waxes. Microxlline waxes average 1-2 microns. MicroXlline waxes MWts from 300 to 2500 (C21-C179). Relatively poorly measured and limitations of measurements not widely understood. For example UOP 46 measures wax content at –30C after filtering cold extract through GF filters that retain 1.5 microns (at best) in liquid. CPM measures down to 2 microns at best. Kinetics of cooling affects WAT measurement. WAT is defined as 2 ppm most insoluble (highest MWt) species. No lab measurements capable of measuring to this level. Recent project: Oil. CPM WAT 39-48oC. DSC WAT at least 63oC. GC / HTGC Measurements. Lack of resolution as Mwt increases and Xllinity changes from macro to microXlline. Recommend best GC / HTGC merged to provide overall fluid composition.

WAX PRIMER q q

Investigation of n alkane content of macro & microXlline waxes: AW 034 AND AW050 were microxlline and OFM/CFA macroxlline

Must Understand that Micro / Macro Relationship

WAX: Simulated WAT of Oil M Simulated WATs 52oC-85oC

q

o

Simulated M WATS: 52-85 C

Wax Wt% 25

PVTSim WAT to C52+

20

Tulsa WAT to C98+ PVTSim (Heavy) WAT

15

10

5

0 -30

-20

-10

0

10

20

30

40

Temperature (oC)

50

60

70

80

90

PVTSim: Melting (WDT) vs SCN PVTSim SCN vs Melting Points of n Alkanes

o

TM ( C) 140 120 100 80

If sample contains no more than

60

C52, then require heating sample

40

o

to 90 C in order to melt.

20

If sample contains C100, then

0

require heating sample to 125oC

-20

in order to melt.

-40

Equally, if sample contains C100,

-60

WDT - WAT = 125-96= 30 C

-80

If sample only contains C52:

o

WDT-WAT = 90- 52 = 38oC

-100

10 0

97

C

C

91

88

94 C

C

C

85 C

82 C

79 C

76 C

73 C

70 C

67 C

61

58

64 C

C

C

55 C

52 C

49 C

46 C

43 C

40 C

37 C

31

28

34 C

C

C

25 C

22 C

19 C

16 C

13

C

10 C

C

7

-120

GAS CONDENSATE FLUID CHARACTERISATION

Reasons why your gas condensate fluid characterisation is probably wrong. q q q q q

q

Sampling below dew point if MDT, sample contamination Compositional gradients DST-well conditioning / poor separator control = gas / liquid entrainment Subsampling losing fractions Laboratory GC vs HTGC Measurements-improper measurement heavy fractions: condensate PVT very sensitive to the small amounts heavy fractions EOS characterisation issues: Heavy fraction extension

GAS CONDENSATE FLUID CHARACTERISATION

Choosing Representative Samples q

Is there such a thing? ie how do reservoir compositional gradients affect sample colour for example? Ref [4]

GAS CONDENSATE FLUID CHARACTERISATION

Condensate colour q Ref [6] from onshore Canada describes the asphaltene production as varying from well to well and the condensate colour varies from clear to black between wells in the same field. Ref [6] further describes the condensate discolouration changing from pale yellow at low flow to black at high flow and back to pale yellow when flow is lowered again. Serious asphaltene emulsion and asphaltene fouling occurred during high flow periods. Other wells experienced a permanent shift from clear to dark condensates after absolute open flow tests with compression. q Ref [7] from an onshore Austrian lean gas condensate field also describes the same colouration issues as above being flow related. This reservoir was dew pointed at reservoir conditions (285 bar and 78oC). Plant asphaltene deposition was an issue and the estimated asphaltene content was 5 ppm of the produced liquid phase. The produced, dark coloured condensate streams showed through production testing to have increased colouring at the higher rates, attributed to increased asphaltene uptake.

GAS CONDENSATE FLUID CHARACTERISATION

q

Examples of GC vs HTGC and how GC misses heavy fractions Ref [1]

GAS CONDENSATE FLUID CHARACTERISATION

q

Examples of GC vs HTGC and how GC misses waxes and other high MWt species

GAS CONDENSATE FLUID CHARACTERISATION `

North Sea Gas Condensate Example Ref [5]: HTGC inset

GAS CONDENSATE FLUID CHARACTERISATION

1. Condensate A GC vs HTGC

n n n

Company A HTGC C100+ = 3.5 wt% Company B GC C36+ = 0.384 wt% Company C GC C35+ = 0.03 wt%

GAS CONDENSATE FLUID CHARACTERISATION 1.

2. PVT Consequences of Gas Condensate A GC / HTGC Measurements n

n

GC based EOS underpredicted two measured dew points by 344 and 690 psi HTGC based EOS exactly matched one and underpredicted the other by 190 psi

P Condensate Case History

P Condensate Properties n

API 46.7 (0.794 g/cc)

n

Pour point 21oC

Cloud Point 41oC by AMS 259 (CPM cooling at 0.2oC /min (= WAT?)

n

n

CWDT 45oC

n

Wax content ?

P Condensate Case History: PVT P Gas Condensate VLE (Company X) PSIG 8000 7000 6000 5000 4000

Measured Dew Point

3000

Co X Characterisation

2000

PVTSim C20+ Characterisation

1000 0 0

50

100

150

200 o

Temperature C

250

300

350

P: Reservoir Fluid & TBP Given Wt%

Reported Compositions: Reservor Fluid P & TBP P

100.00

Condensate TBP Reservoir Fluid

C20+ = 6.055 %

10.00

1.00

C38+ = 0.36% 0.10

N 2 C O 2 C 1 C 2 C 3 iC 4 nC 4 iC 5 nC 5 C 6 C 7 C 8 C 9 C 10 C 11 C 12 C 13 C 14 C 15 C 16 C 17 C 18 C 19 C 21 C 24 C 28 C 3 C 2 38 +

0.01

SCN

Flash P Reservoir Fluid to STP n

Why stop at C59+?

"Normal Characterisation" Options: Reservoir STP Flash to C59+ with 55 C7+ Pcs

Wt% 100.00

10.00

STP Condensate Reservoir Fluid

6.055

C62+ = 1.2324% 1.00

0.10

62

60

-C

57

54

C

51

C

48

C

45

C

42

C

39

36

C

C C

SCN

C

33

C

30

C

27

C

24

C

21

C

18

C

15

C

12

C

9 C

6 C

4

nC

2 C

N

2

0.01

STP P Condensate Composition n

Lets go to C80 being Max PVTSims “Normal Characterisation” " Normal Characterisation" Options: Reservoir STP Flash with 74 C7+ Pcs to C80

Wt% 100.00000

STP Condy Characterised to C80 STP Condy Characterised to C59+

10.00000

Reservoir Fluid

1.2324%

1.00000

0.39% 0.10000

C80+ = 0.0339%

0.01000

0.00100

0.00010

N

2 C 1 C 3 nC 4 nC 5 C 7 C 9 C 11 C 13 C 15 C 17 C 19 C 21 C 23 C 25 C 27 C 29 C 31 C 33 C 35 C 37 C 39 C 41 C 43 C 45 C 47 C 49 C 51 C 53 C 55 C 57 C 59 C 61 C 63 C 65 C 67 C 69 C 71 C 73 C 75 C 77 C 79

0.00001

SCN

STP P Condensate Composition

n Why

stop at C80? C80+ is still 339 ppm n We want to go to 1-2 ppm. n Why?

P Condensate Composition n We

now need to use PVTSim Heavy Characterisation to go beyond C80. n But this condensate is not heavy. API = 46.7 n Problem # 1 with PVTSim: Many normal waxy fluids have carbon numbers in excess of C100 n We continue with Heavy Characterisation

STP P Condensate Composition n

Lets go to C200 being Max PVTSims “Heavy Characterisation” " Heavy Characterisation" Options: Reservoir STP Flash with 74 C7+ Pcs to C80

Wt% 100.0000

STP Condy Characterised to C200 STP Condy Characterised to C80 10.0000

STP Condy Characterised to C59+ Reservoir Fluid

C61+= 1.2324%

1.0000

C100+= 0.0874%

0.1000

0.0100

N

2 C 1 C nC3 nC4 5 C 7 C C 9 1 C 1 1 C 3 1 C 5 1 C 7 1 C 9 2 C 1 2 C 3 2 C 5 2 C 7 2 C 9 3 C 1 3 C 3 3 C 5 3 C 7 3 C 9 4 C 1 4 C 3 4 C 5 4 C 7 4 C 9 5 C 1 5 C 3 5 C 5 5 C 7 5 C 9 6 C 1 6 C 3 6 C 5 6 C 7 6 C 9 7 C 1 7 C 3 7 C 5 7 C 7 7 C 9 8 C 1 8 C 3 8 C 5 8 C 7 8 C 9 9 C 1 9 C 3 9 C 5 9 C 7 99

0.0010

SCN

P Condensate Heavy vs Normal Charact n

Normal

Heavy vs Normal Characterisation P Condensate 20 C7+ PCs

Wt % 14.00 12.00 10.00

Normal Characterisation Heavy Characterisation

8.00 6.00 4.00 2.00

N 2 C O 2 C 1 C 2 C 3 iC 4 nC 4 iC 5 nC 5 C 6 C 7 C 8 C 9 C 10 C 11 C 12 C 13 C 14 C 15 C 16 C 17 C 18 C C1 20 9 C C2 22 1 C -C2 25 4 C C2 29 8 C -C3 34 3 C -C3 40 9 C -C4 49 8 -C 80

0.00

P Condensate Heavy vs Normal Charact n

Heavy

Heavy vs Normal Characterisation P Condensate 20 C7+ PCs

Wt % 14.00 12.00 10.00

Heavy Characterisation Normal Characterisation

8.00 6.00 4.00 2.00

N 2 C O 2 C 1 C 2 C 3 iC 4 nC 4 iC 5 nC 5 C 6 C 7 C 8 C 9 C 10 C 11 C 12 C 13 C 14 C 15 C 16 C 17 C 18 C C1 20 9 C -C2 22 1 C -C2 25 4 C -C2 29 8 C -C3 33 2 C -C3 4 9 C 0 -C 50 4 -C 9 20 0

0.00

P Condensate Characterisation Summary

Characterisation Summary Fluid Characterisation C7+ PCs C20+ C38+ C59+ TBP1 None None 10.96 0.36 TBP2 None None 20.8 GC Normal 20 26.23 GC Heavy 20 24.65 GC Normal 55 26.227 8.771 1.779 GC Normal 74 26.231 8.776 1.784 GC Heavy 94 24.644 8.164 1.875

C80+

C100+

0.000 0.034 0.390

0.000 0.000 0.087

P Condensate HTGC : What is this saying? n

Wax content decreasing as SCN increases? " Normal Characterisation" Options: Reservoir STP Flash with 74 C7+ Pcs to C80

Wt% 10.00000

1.00000

0.10000

0.01000

0.00100

STP Condy Characterised to C80 0.00010

HTGC (n alkanes) of Condy

SCN

C 80

C 78

C 76

C 74

C 72

C 70

C 68

C 66

C 64

C 62

C 60

C 58

C 56

C 54

C 52

C 50

C 48

C 46

C 44

C 42

C 40

C 38

C 36

C 34

C 32

C 30

C 28

C 26

C 24

C 22

C 20

0.00001

Simulated P WAT v1 based on HTGC n

V1 Simulated WAT =36oC vs CPM 41oC or CWDT 45oC? o

P Condensate Simulated WAT v1 = 36 C Wax Content % 100

10

1

0.1 v1 WAT

0.01

0.001

0.0001 -30

-25

-20

-15

-10

-5

0

5

10

Temperature oC

15

20

25

30

35

40

P Condensate Distillates Properties n

49.2 % Wax for C22+

Boiling Range

°C

Yield Range

wgt %

84.1 - 100

Yield

wgt %

15.9

g/ml cSt cSt °C

31.8 0.866 8.697 4.736 21

Conradson Carbon Residue Ash

wgt %

0.48

wgt %

0.045

Asphaltenes Wax Content

wgt % wgt %