Measurement of Subsea Produced Water Quality the Importance and Challenges Dr. Ming Yang, NEL, UK
Content Background What is subsea separation & PWRI / discharge? Subsea raw sea treatment? Benefits? Status of developments and applications? Why subsea water quality measurement? Challenges Potential technologies Tests and qualifications Projects at NEL and elsewhere Concluding remarks
Background Subsea Separation
Background Subsea Raw Seawater Treatment (1)
Background Subsea Raw Seawater Treatment (2)
Background Benefits Economic Potentially eliminating surface facilities Increased oil production and oil recovery Enabling marginal field developments Saving on flow lines / chemicals Operational Easier O/W separation Less flow assurance issues Environment Less produced water for discharge
Background Status: Subsea Separation and PWRI Troll Pilot (Statoil) (1999) PWRI for disposal Water depth: 340 m API 37 o Tordis Statoil (2007) Water & sand re-injection in a disposal well Water depth: 210 m API 37 o Increased oil recovery factor from 49% to 55% 26 million bbl extra oil Marlim (2012) PWRI for pressure maintenance Water depth: 900 m API 22 o Water spec: OIW<100 ppm; solids<10 ppm
Background Status: Subsea Raw Sea Water Treatment - Development C-FAST: Combined Filtration and Seawater Treatment (1990 s) JIP led by CAPACIS (UK) SWIT: Sea Water Injection & Treatment (2000 s) Developed by Well Processing AS in Norway Now under the name of Seabox SPRING (Subsea PRocessing and INjectin Gear) JIP by Total, Saipem and Veolia from 2007
Background Status: Subsea Raw Sea Water Injection - Applications Field Water Depth Flow Rate (m 3 /hr) Start Treatment Technology Columba E 145 m 331(at 320 bar) 2007 Filter (80µm) Tyrihans 270 m 580(at 205 bar) 2009 Strainer (7mm) Albacora 440 m 688 2012 Filter (50µm) Note: All of them use simple filtration, no electro-chlorination, no sulphate removal technologies have been included in these applications.
Why Subsea Water Quality Measurement? Current practice ROV / sampling / surface analysis Problems Time consuming and costly Huge time lag Not-continuous No good for process operations Definite technology gap Therefore the need!
Challenges Extremely tough environment Water depth: - up to 3000m Process fluids in the case of produced water: High temperature / pressure Need to measure oil and / or solids Few measurement technologies Lack of regulator s involvement Lack of well established standards for tests and qualifications Lack of testing facilities for testing subsea instruments?!
Potential Technology - Requirements Produced Water Discharge Subsea Minimum: oil-in-water (OIW), discharge volume Subsea PWRI Content of oil and solids Particle size and size distribution of oil and solids Subsea Sea Water Injection Content of particulates Particle size and size distribution Free chlorine? Content of sulphate?...
Potential Technologies Laser Induced Fluorescence (LIF) Light scattering Ultrasonic acoustic Microscopy imaging LIF combined with imaging Laser reflectance, e.g. FBRM Sand detector and monitor Acoustic or erosion based Potentiometric / amperometric OIW Conc. Solid / Oil Conc. & Sizing Particle Sizing only Solid Particle Conc. Free residual chlorine
Laser Induced Fluorescence (LIF) UV is induced by laser, aromatic HCs in PW absorb and emit fluorescence light, that is detected and linked to total or dispersed HCs in PW
Focused Ultrasonic Acoustic
Microscopy Image Analysis Basic principle: passing fluids between a gap of high intensity light source and microscopic camera. Images captured are then analysed to provide size, shape and concentration data
Residual Free Chlorine Potentiometric ORP / Redox: measure an aqueous system s capacity for releasing or accepting electrons from chemical reactions Amperometric Measure the change in current resulted from chemical reactions as a function of the analyte concentration
Potential Technology - Summary For OIW concentration Laser Induced Fluorescence (LIF) For oil & solid in water concentration Ultrasonic acoustic For both concentration and particle size of oil and solid in PW Image based systems Combination of LIF and image analysis For Residual Free Chlorine Amperometric / Potentiometric
Tests and Qualifications Objectives To demonstrate functional requirements To screen out faults and defects To improve robustness and reliability Types Environment Performance Duty
Tests and Qualifications Environment Pressure Temperature Shock / vibration EMC Performance - Duty Accuracy / Repeatability / Stability Responses
Test and Qualifications - Key Documents Recommended Practice DNV-RP-A203 Qualification procedures for new technology, September 2001 ISO 13628-6 Petroleum and natural gas industries Design and operation of subsea production systemssubsea production control systems, 2006 API RP17Q: Subsea Equipment Qualification, Rev. 1 January 2010 ISO 15839: Water quality online sensors / analysing equipment for water specification and performance tests, 2003
Projects at NEL NEL JIP (2009-2010) Develop Operating Envelope(s) and Test Protocol for Subsea Water Quality Measurement Devices Objectives Market assessment Technology review Operating envelope Test requirements / protocols Test organisations
Projects at NEL NEL JIP (2011-2013) Independent Evaluation of the Technology of Subsea Water Quality Measurement Devices Objectives Further review of technologies Performance evaluation tests Gap analysis
Projects at NEL NEL JIP (2014-2016) Development of Subsea Water Quality Measurement Technology Up To TRL 5 Objectives: To develop at least one subsea water quality measurement technology to a TRL5.
Other Projects On-going or Planned Statoil & Petrobras Aim: to develop and qualify a subsea oil-in-water monitor in 2015/2016 Pressure range: 20-100 barg; OIW: 10-3000 ppm RPSEA RFP: issued in July 2013 Aim: To develop sensors reaching TRL 3 to 4 Approach: Part 1: technical spec & gap analysis Part 2: design, develop and test Status: Proposals in Sept 2013. Project starts in July 2014
Concluding Remarks Subsea separation offers many benefits Subsea water quality measurement: a key technology gap There are many challenges in developing subsea water quality measurement devices Potential technology candidates LIF, image analysis, ultrasonic and or combination for oil and solids potentiometric / amperometric for free chlorine Testing and qualification plays a key role Real R&D efforts on-going to close the technology gap
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