steam floods from around the world - petro water...

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


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


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


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

Low salinity

Low alkalinity

Low hardness

Bakersfield (CA) Water Analysis

slide 18

396

853

183

305-609

305

Depth (m)

Shallow – like Alberta & CA counterparts

Low API – "" ""

Low kh – "" ""

API: oil gravity



Middle East Steam Flood Parameters

slide 20

(NL)

California Steam Flood Parameters

slide 24

T = 24 to 43 C

h = 11 to 27 m

API: oil gravity



California Steam Flood Parameters

slide 25

Recent Projects (in development & starting up)

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