Chemical Water Injection [PDF]

Zitiervorschau

CHEMICALS TREATMENT FOR WATER INJECTION BONY BUDIMAN OCTOBER 2021

https://www.linkedin.com/in/bony-budiman-39886031/

OBJECTIVES • Learn about purpose of water injection • Knowing water problem for water injection • Sharing method how to control and monitor water quality for injection • Discussion

OUTLINE

• INTRODUCTION • WATER TREATMENT FOR INJECTION • WATER QUALITY MONITORING • FIELD CASE • SUMMARY

PURPOSES OF WATER INJECTION Two majors purposes of water injection : • To enhance production or stimulate production from other wells • For disposal of fluids produced along with oil or gas

SOURCE OF WATER FOR INJECTION • Source of water for injection are comes from : • Produced water • Surface water (usually seawater) • Produced water is the best since it has same composition with formation water but for quantity reason sometime the O&G company should add from the surface water

SOURCES OF WATER INJECTION WATER TYPE LAKE OR RIVER

AQUIFER

COASTAL WATERS

DEEP SEA WATER

PRODUCED WATER

PROPERTIES LOW SALINITY / TDS HIGH BACTERIA HIGH SUSPENDED SOLIDS (POSSIBLY) LOW SALINITY / TDS HIGH OXYGEN HIGH SUSPENDED SOLIDS (POSSIBLY) MEDIUM SALINITY / TDS HIGH SUPHATE LEVELS HIGH SUSPENDED SOLIDS MEDIUM SALINITY / TDS HIGH SUPHATE LEVELS LOWER SUSPENDED SOLIDS RANGE OF SALINITIES / TDS VARYING SUSPENDED SOLIDS BACTERIA IF WELLS SOURED

HIGH OXYGEN COMPATIBILITY? HIGH HARDNESS

HIGH BACTERIA HIGH OXYGEN LOW BACTERIA LOWER OXYGEN NO OXYGEN OIL

TYPICAL COMPOSITION OF SEAWATER VS FORMATION WATER • Formation Water

• Seawater 400 ppm

100 – 1,000 ppm

> 1,200 ppm

< 100 ppm

> 2,500 ppm

SO42 -

< 50 ppm

+/- 150 ppm

> 500 ppm

+/- 7 ppm

< 0.05 ppm

> 35,000 ppm

+/- 15,000 ppm

15 – 30 oC

> 150 oC

CONCERNS OF SEAWATER • High sulphate • Could form scale : CaSO4, MgSO4, and BaSO4

• As nutrient for SRB (sulphate reducing bacteria), a microorganism that reduce SO42- to a corrosive gas, H2S.

• High dissolved oxygen • Increase corrosion rate

• High TDS • Increase corrosion rate or scaling growth • Plugging at downhole

PRODUCED WATER

PRODUCED WATER DISPOSAL There are two way of produced water disposal : • Dispose to the river, sea, lake • Limited by amount of water disposal and contaminant concentration

• Re injection to the formation • Has minimum issue to environment, but shall consideration regarding the reservoir acceptance.

ENHANCE PRODUCTION • An enhanced recovery injection well may be a formerly productive well whose production has decreased over time or a well specifically drilled as an injection well. • This type of injection well is used to inject fluid into the oil producing rock displacing oil towards a second well where the oil is extracted.

WATER DISPOSAL • The second type of injection well is for disposal of fluids produced along with oil or gas. These fluids may be nearly freshwater or, more frequently, water high in chloride called "brine". • This water, or brine is produced with oil and gas and is pumped back into the ground into rocks that can contain these fluids. In this way there is no discharge into the land surface or into nearby surface water way and environmental impact is reduced.

OUTLINE

• INTRODUCTION • WATER TREATMENT FOR INJECTION • WATER QUALITY MONITORING • FIELD CASE • SUMMARY

WATER INJECTION DESIGN APPROACH(5) • Generally, produced water may be injected with minimal treatment when injection under fracturing conditions or into (thermally) fractured formations. • Occasionally (e.g. under conditions of matrix injection) the quality of the produced water may require modifications prior to its injection, and so consideration should be given to the treatment and injection facilities. • A step by step approach to facilities design is given beside.

PROBLEMS OF WATER INJECTION • Plugging  problem in facility and formation • Scale

• Oil wettability • Dissolve and suspended solid

• Corrosion  problem in facility • CO2 • O2 • Bacteria • H2S

SUMMARY EFECT OF WATER QUALITY FOR INJECTION NO

PARAMETER

EFFECT

1

Salinity

The injection water must be compatible with the reservoir clays. Lower salinity will cause clay swelling and blockage

2

Oil

Usually oil will pass into the formation. However oil wet solids will cause blockages at reservoir face.

3

Solids

Suspended solids can cause plugging at formation face or pass into the rock and block pore throats.

4

Oxygen

Dissolved oxygen (and temperature & flow) will significantly affect corrosion.

5

Bacteria

Bacteria form biomass that, if removed by changing flow rates, will block formation face.

6

Temperature

Temperature has a significant effect on scale formation, corrosion & bacterial growth and reservoir porosity.

7

Flow

Water velocity will affect biomass removal, corrosion and transportation to the formation

.

SO, BOTH SEAWATER AND PRODUCED WATER MUST BE TREATED BEFORE REINJECTION

PRODUCED WATER TREATMENT F lo ta tio n C e ll S u rg e T ank

F lo c c u la to r

S cale Inhibitor

S lo p O il D e a e ra to r T ower

D e Oiler

F ilte rs

Vacuum

Wa te r fro m AP I S e p a ra to r

B iocide

Oxygen S cavenger

B o o s te r P u m p s

C oagulant

In je c tio n We lls

OIL CONTENT REMOVAL FROM PRODUCED WATER 1

2

3

4

SOME METHODS OF WATER SEPARATION

1. Gravitation

2. Floatation 3. Filtration 4. Membrane filtration 5. Chemical Treatment

SEAWATER TREATMENT

CORROSION MITIGATION REMOVE MICRO PARTICLES

REMOVE MACRO PARTICLES

SCALE INHIBITIO N

REMOVE MICRO AND MACRO PARTICLES • Seawater contains many substances, from something that could be seen by naked eyes (like sand, a part of animal and plant, rubbish etc) to micro particles (such as dust colloid, crystal of scale, cation and anion). • Those particles should be removed before the water ready for injection since could cause damage for facility equipments (by macro particles) and cause plugging at formation (by micro particles).

TYPICAL SEAWATER TREATMENT Flash Mix

Hyper Filters

Long Stop Filters

Antifoam

Polyelectrolite Oxydator Biocide

Oxygen scavanger

Surfactant Backwash

Coarse Filters

Cl2 Analyzer

Corrosion/scale coupon Turbidimete r

Corrosion/Scale coupon

Scale Organic Inhibitor Biocide

Booster Pumps Sea Water Lift Pumps

Process Coolers

Corrosion inhibitor

Injection Wells

Chemical injection points Chemical& corrosion monitoring points

FILTRATION • Filtration is a method to remove unwanted material by adsorb them. • Filtration usually used for remove Total Suspended Solid (TSS) • Some filtration equipment could also adsorb oil content such as membrane filtration • Types of filters : • Coarse filter (to adsorb particles > 60 µm) • Fine filter

CORROSION

• Internal corrosion in water injection may occur in the pipeline from water treatment plant to water injection plant until injection line to downhole. • Corrosion caused by dissolved oxygen, SRB-H2S, and rest of dissolved CO2. • Water Corrosion Inhibitor could be used to reduce the corrosion rate. With dosage rate up to 20 ppm.

• The specification could be maximum 5 mpy or refer to the corrosion allowance and shelf life design.

DISSOLVED OXYGEN Chlorine

Deaerator

Gas

Coarse Filters

Lifting Pumps

Filters

• It is also responsible for creating plugging agents through oxidation of ferrous iron and hydrogen sulfide

Oxygen Scavenger – 10 ppm

• Seawater has more problem in dissolved oxygen, the concentration is in ppm level.

Biocide - Injected at 300 ppm / 3hr/week

Injection Wells

• Produced water has low dissolved oxygen, usually below 20 ppb, but when it processed at top side. Oxygen from atmosphere may ingress and increase the concentration.

Corrosion Inhibitor – 10 ppm

Booster Pumps

• Combination of mechanical (deaerator) and oxygen scavenger required to reduce the oxygen below 50 ppb.

BIOLOGICAL TREATMENT • Depend on the water source, some chemical treatment are as below • Chlorine : used to control seawater organism. Chlorine is oxidation biocide but chlorine not too effective for SRB

• Organic biocide : used especially used to control SRB in produced water.

Courtesy picture : https://www.intechopen.com/media/chapter/68149/media/F3.png

ORGANIC BIOCIDE • Bacteria especially SRB may cause problem in water injection for some reasons : • Plugging when sessile SRB deposited • Increase H2S concentration

• Organic Biocide is a chemical method to control the bacteria growth. • The limit for bacteria growth shall be low, due to it may grow later in the formation. Some fields put 102coll/cc as the specification

SCALE INHIBITION • Scale is deposition of soluble inorganic salts from aqueous solution • Scale will reduce inner pipe diameter and causing plugging in the reservoir • Scale Inhibitor used to minimize the scaling growth. • The specification could be as low as 20 mgsqftdd

TYPICAL CHEMICAL FOR WATER INJECTION Type of Water Chemicals

Produced

Sea / Lake

ppm Injected Corrosión Inhibitor

5.0 – 10.0

10.0 -20.0

Biocide

300 - 500 *

300 - 500*

Oxidising Biocide (Cl2)

0.2 **

Oxygen Scavenger

1.0 - 3.0***

4.0 - 6.0***

Scale Inhibitor

12.0 - 20.0

10.0 - 15.0

Water Clarifier

4.0 - 6.0

Filter Aid

1.0 - 2.0

Surfactants

5.0

*

300 – 500 ppm / 3-5 hours / weekly

**

0.2 ppm residual

1.0 - 2.0

• Table beside is an example of chemicals used in water injection system

• Dosage may adjusted depends on the severity for each parameter.

*** for dissolved oxygen < 100 ppb

WATER COMPATIBILITY • In case sources of water injection are mix from different source (such as seawater and produced water) compatibility are critical

• Potential compatibility problem of mixing different source of water is deposition due to ions reaction. • Seawater may contain thousand of sulphate ion (SO42-) meanwhile produced water could contain hundreds of calcium ion (Ca2+), when they meet each others, CaSO4 is likely formed. • A laboratory test and modelling shall be conducted to evaluate the CaSO4 deposition risk.

• Compatibility with the formation clay also important to ensure no swelling issue. Courtesy Picture : https://c8.alamy.com/comp/C299BR/selenite-caso4-2h2o-hydrous-calcium-sulfate-form-of-gypsum-mt-gunson-C299BR.jpg

WATER COMPATIBILITY : EXPERIMENT • Table beside is result of laboratory experiment to study CaSO4 deposition when mix the produced water (PW) with the synthetic sea water (SSW) • The CaSO4 deposit has low tendency in PW but it will increase when mixed with the SSW.

• • • • • •

PW = Produced Water SSW = Synthetic Sea Water PW1SSW1 = PW : SSW in proportion 1 : 1 PW1SSW2 = PW : SSW in proportion 1 : 2 PW1SSW4 = PW : SSW in proportion 1 : 4 PW1SSW8 = PW : SSW in proportion 1 : 8

• The deposition also depend on temperature, higher temperature will increase the deposition tendency

Courtesy Picture :Energy & Fuels 2009, 23, 2527–2536, Coinjection of Seawater and Produced Water to Improve Oil Recovery from Fractured North Sea Chalk Oil Reservoirs, Tina Puntervold,* Skule Strand, and Tor Austad, 2009

OUTLINE

• INTRODUCTION • WATER TREATMENT FOR INJECTION • WATER QUALITY MONITORING • FIELD CASE • SUMMARY

PROCEDURE TO DETERMINE WATER QUALITY FOR INJECTION • Refer to NACE TM 0173 Methods for Determining Quality of Subsurface Injection Water Using Membrane Filters(2) there are two methods for evaluating water quality for subsurface injection : • Rate versus cumulative volume test (for water-quality monitoring) • Suspended solids test (for diagnosis or monitoring). In expansion the suspended test known as analysis of index number (IN) or relative plugging index (RPI)

RATE VS CUMULATIVE VOLUME(1) • The cumulative volume through the filter is recorded as a function of time, and the flow rate for each time increment is calculated from the data. • Flow rate is plotted versus cumulative volume throughput on a semilog plot. The slope of the line indicates the "quality," or degree of plugging which occurred with that particular water sample

• The curve 1 : Excellent. No plugging occurred since the flow rate remained constant throughout the test. • The curve 3 : Poorest of the three curves. The flow rate dropped much more rapidly indicating faster plugging.

INDEX NUMBER / RELATIVE PLUGGING INDEX

IN = TSS + ESN • TSS = Total Suspended Solid • ESN = empirical slope number

QA = Flow rate (ml/s) QB = Second Flow rate (ml/s) CVA = Cumulative volume (ml) CVB = Final cumulative volume (ml)

• IN/RPI is s quantitative number that indicate the water will plug the formation or not • The concentration of suspended solids in a water is determined by passing a known quantity of water through a membrane filter and determining the weight of solids collected on the filter(1) • Higher IN/KPI indicate higher suspended solid that may plugged the reservoir

IN/RPI INTERPRETATION • There are some classification that indicate the water quality. The rating specification may different as well. • The empirical water quality rating guide is described here for information only. • The application of it is left to the user’s discretion

HALL PLOT(3) • Another method of monitoring the water quality during injection known as Hall Plot Graph

• Hall plot shows pressure multiplied by duration of injection versus the injection volume • A straight line is expected for constant infectivity

• A curving upwards indicates loss of transmissivity (eq : plugging is happened) and the downward curve shows the containment fracture

CORROSION MONITORING • To check effectiveness of corrosion mitigation we should monitor some parameters as below : • Corrosion rate using corrosion coupon or corrosion probe

• Bacteria (especially SRB) using rapid check or serial dilution method • Dissolve Oxygen Analysis • Fe content using spectrophotometry method.

• The best monitoring point is near the well head of WIW, but if technically difficult we may choose as long as possible from chemical injection point

SCALE MONITORING • Scale monitoring is to get description of how scale is grow at our system • The most popular method is by using scale coupon.

• Other complimentary test is by check the Phosponate Residual Content (PRC) since most of the active content is phosponate.

TYPICAL SPECIFICATION

Parameters

Specification

Cumulative Volume Graph

Constant rate

Index Number