steam floods from around the world - petro water...
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Steam Floods
from Around the World
John M. Walsh
Shell Technology
Amsterdam, NL
What can we learn about
Best Practices
in Water Treating for Steam Flood
by comparing steam floods
from different regions of the world?
Objective of Paper
slide 2
We are looking for similarities and differences in parameters such
as:
Availability & quality of feed water
Waste water disposal options
Extraction strategy (CSS, SAGD, SOR)
Hydrocarbon reservoir (depth, kh, sat, comp)
Hydrocarbon fluids (API, viscosity, comp)
Produced water characteristics (over time)
and how these parameters impact the choices in project
parameters such as:
Equipment selection
Process configuration
Chemical treating programs
Operating practices
Strategy / Approach of this Paper
CSS: Cyclic Steam Stimulation
SAGD: Steam Assist Gravity Drainage
kh: permeability x reservoir thickness
Sat: saturation, i.e. percent of pore space w/ oil in it
API: oil gravity = 141.5/sg – 131.5
slide 3
Crude Oil Reserves – billions of barrels
slide 4
We will focus on heavy oil extraction by steam flooding in
Alberta (see above), Oman, and California
Oil sands:
20 % surface
80 % subsurface
Alberta Heavy Oil / Bituminous Sands –
General Background:
Refs: N. Edmunds, JCPT (2001); Albahlani, SPE 113283 (2008).
World Heavy Oil/Bitumen reserves:
1,100 billion m3
Canadian bitumen reserves:
50 billion m3
roughly 20 % of Canadian HO/B
reserves can be surface mined, the
remainder must be extracted with steam
“Bituminous sands (oil sands) contain naturally
occurring mixtures of sand, clay, water, and a
dense and extremely viscous form of petroleum
technically referred to as bitumen. Oil sands
are found in large amounts in many countries
throughout the world, but are found in
extremely large quantities in Canada and
Venezuela.” Ref: Wikipedia.
Ref: http://environment.alberta.ca/01729.html
Typical Water Management Trend for Alberta Steam Flood
slide 6
All three regions can be considered "arid" from the
standpoint of water availability.
Fresh
water use
is limited in
Alberta
and is
essentially
unavailable
in CA &
Oman
Overview of Typical Steam Flood
Shallow
oWater chemistry – meteorological sweep
oLow reservoir pressure (low steam T)
High steam volumes
oSOR from 2 to 5 m3/m3
slide 7
OTSG: Once Through Steam Gen
PWRU: Produced Water Re-Use
SOR: steam oil ratio (v/v)
TH: total hardness
ZLD: Zero Liquid Discharge
CSS: Cyclic Steam Stimulation
SAGD: Steam Assist Gravity DrainageRef: aquateam
Heavy oil
oHigh oil viscosity (high steam T)
oDifficult oil/water separation
Scarce water resources
oPWRU w/ 300 mg/L silica
OTSG requirements:
oTH < 0.5 mg/L as CaCO3
oSilica < 50 mg/L
oTDS < 10 kmg/L
oOil < 10 mg/L
Limited disposal options
oImprove waste water quality
oZLD
Water handling and steam generation is 50 % of project costo therefore SOR is important to economics
Well cost is between 20 % to 30 % of project costo many wells are required due to low productivity
Considerations in Selecting the Operating Steam Pressure:o higher pressure results in higher well productivity and higher oil revenue
due to higher steam chest temperature and therefore lower oil viscosity;
o steam pressure does not significantly affect the ultimate recovery;
o higher steam pressure results in higher water treating CAPEX and
OPEX due to higher pressure rated system, and due to higher quality
feed water requirement (silica and hardness removal);
o higher steam pressure results in greater energy losses to surrounding
rock which increases the SOR and increases the operating cost due to
less efficient use of steam.
Ref: N. Edmunds, JCPT (2001)
Overview of Water Treating & Steam Generation Processes:
slide 8
Steam T for Various Steam Floods
Project Oil API Steam T (C)
Carmon Creek (AL) 351
Cold Lake (AL) 11 340
Various AL 320 to 330
Fire Bag (AL) 12 320
Kern River (CA) 9 to 16 310
Mukhaisna (Oman) 16 280
Amal (CA) 17 to 20 275
Belridge (CA) 14 270
QA (Oman) 16 250
slide 9Ref: Edmunds, JCPT (Dec 2001) PETSOC-01-12; various other
Steam saturation T vs steam pressure
Oil viscosity (for a particular oil)
Oil flow rate through porous media vs
steam P (T)
Oil flow rate through porous media
determines:
Number of wells, their length, spacing
Steam T (P) (assuming no back-pressure)
Steam / Oil Ratio
Project economics
Steam Flow Rate (SOR) for Various Steam Floods
y-axis: Oil / Steam Ratio
x-axis: kh:
permeability x thickness (reservoir
quality)
OSR = 1/ SOR
SOR depends on the quality of the
reservoir (kh, p, sat).
Poor reservoir quality can be
compensated by using higher
steam T (to lower the oil viscosity)
Project economics are strongly
dependent on the Steam / Oil Ratio.
Water treating system size depends
on SOR.
slide 10Ref: Edmunds, JCPT (Jan 1999) PETSOC-99-01
2.0
2.5
3.3
SOR
Alberta SAGD produced water:
produced water silica: 250 – 300 mg/L
hardness: 300 mg/L
TOC: 500 mg/L
fluorescence: high
Steam System water treatment equipment:
Deoiling
Warm Lime Softener
Filtration
WAC
Silica removal to levels between 50 mg/L and 150 mg/L
In some applications, operators are using evaporators + drum boilers in place of
Warm Lime Softener and associated equipment.
Alberta Environmental guidelines in Alberta require the recycle rate of Produced
water to be 90% or greater.
Waste management is a big issue. Some operators are implementing ZLD.
API: oil gravity
kh: permeability x reservoir thickness
PI: productivity index ~ BPD/well
Alberta Steam Flood Parameters
slide 11
Produced Water:
silica content:
increased from 70 mg/L initial
to 250 to 300 mg/L from 1975 to 1985
TOC: 500 mg/l
fluorescence: high
Steam System water treatment equipment:
Deoiling
Warm Lime Softener
Filtration
WAC
Silica reduction to levels less than 50 mg/L
OTSG
Steam Separators
TOC: Total Organic Carbon
CA Steam Flood Parameters
slide 12
Produced Water:
silica content:
50 to70 mg/L
Steam System water treatment equipment:
Deoiling
Warm Lime Softener
Filtration
WAC
Silica reduction to levels less than 50 mg/L
OTSG
Steam Separators
Early days of steam flooding. Thus, silica level in the produced water is relatively low.
Artificially low gas price affords cheap injection disposal.
In Oman, and other Middle Eastern countries, some of the steam floods are in fractured
carbonate reservoirs. Relatively low steam temperature is being used (250 C). A wide
range of SOG is encountered (from 2 to 5 m3/m3).
Oman Steam Flood Parameters
slide 13
Geochemical factors that control the
chemistry of shallow water:
Water chemistry of typical
oilfield brines:
Dominated by sea water
evaporation processes which
are fairly well understood, by
the presence of CO2 at high
pressure, biodegradation of
crude oil, and by contact with
mineral deposits through
migration which occurs over
millennia.
This leads to TDS in the range
of 100 to 250 k mg/L, pH in the
range of 4 to 5, silica in the
range of 30 mg/L, and to high
Total Acid, alkalinity, hardness,
and scaling potential.
Shallow water chemistry is
completely different.
Oilfield Brine vs Shallow Water:
slide 14
SOR ~3.5
Steam T, P, Quality
OTSG
silica
TDS build-up
due to ZLD
Salinity
TDS: Total Dissolved Solids
P50 & P90: project probabilities
SOR: Steam / Oil Ration (v/v)
OTSG: Once-Through Steam Generator
Carmon Creek (AL) Water Analysis:
slide 15
pH
Example
produced water
for feed to Steam
System.
Variation in feed
water quality
within each
region is greater
than variation
between regions.
ZLD by injecting
80 % steam.
Hardness/
alkalinity
Availability of feed water
oAll locations face similar severe limitations
Waste water disposal options
oAlberta: trend toward ZLD
oOman: deep disposal available / (artificially) cheap gas
oCA: trend toward ZLD
Extraction strategy (CSS, SAGD)
oAll locations SAGD/CSS
Hydrocarbon fluids (API, viscosity, composition)
oAlberta more viscous
Hydrocarbon reservoir (depth, kh, sat, comp)
oAlberta employing higher steam T w/ higher CAPEX & OPEX
Produced water characteristics (over time)
oAlberta & CA: mature floods w/ full effect of back-production
oOman: start-up, initial stage of back-production
Regional differences do exist. There are opportunities to learn more by
regional comparison but more detail is needed in the literature.
Initial Conclusions – What have we learned?
slide 16
17
Low salinity
Low alkalinity
Low hardness
Bakersfield (CA) Water Analysis
slide 18
slide 19
396
853
183
305-609
305
Depth (m)
Shallow – like Alberta & CA counterparts
Low API – "" ""
Low kh – "" ""
API: oil gravity
kh: permeability x reservoir thickness
PI: productivity index ~ BPD/well
Middle East Steam Flood Parameters
slide 20
21
slide 22
slide 23
(NL)
California Steam Flood Parameters
slide 24
T = 24 to 43 C
h = 11 to 27 m
API: oil gravity
kh: permeability x reservoir thickness
PI: productivity index ~ BPD/well
California Steam Flood Parameters
slide 25
Recent Projects (in development & starting up)
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