Tail production: Choosing the right strategy for Produced Water Management K.I. Andersen

Produced Water Daily Volumes Statfjord m3/d Gullfaks m3/d Snorre m3/d Tordis/Vigdis m3/d Veslefrikk m3/d Heidrun m3/d Norne m3/d Åsgard 500 m3/d

m3/d of produced water..

Mars April 2004

Oil rate development 2003 vs 1998 All GF and SF wells

Water rates pr. well 2003 vs 1998 All GF/SF

Increased watercut : scale, reinjection, water shutoff, downhole separation

Environmental impact (EIF) at Statfjord C

Environmental impact (EIF) at Gullfaks A Gullfaks A 2002

Produced Water Management Water shut off Re-injection Produced water treatment

Authorities, Produced Water and Environment: Reduced Tolerance vs.

Produced Water Handling Principles 1. Improve use of chemicals 2. Reduce at source Isolate water producing zones (plug, patch, gel) Intelligent completions Downhole separation 3. ReinjectProduced water reinjection in active reservoir 4. StoreUtsira or depleted/non active areas of field 5. Purifiy before dischargeCTour, EPCON etc

§1. Reduce chemical consumption or change to non-toxic

H2S-removal by use of scavenger

Environmentally friendly H2S removal ProPure C100 installed at Åsgard B May 2001 –Low capital cost Performance test in 2002 –30 % reduction in chemical consumption –Low pressure drop (0.2 bar) Installed at Huldra, Veslefrikk, and Gullfaks B in 2002 Installation at Gullfaks A and C in 2003

§ 2. Shut off waterproduction at source

Well completion type dictates water shutoff complexity Horizontal, screen Horizontal, cased Cased Screen

Main Well Categories in Statoil (total wells) Perforated,cement deviated Openhole, deviated Perforated, cemented, horiz. Openhole horizontal Complexity, zonal isolation 60 % 5% 25% 10 %

- Cumulative annual water shut off m3/d

Ongoing R&D : Revisiting chemical route to water shutoff

Chemical water shutoff/Emulsified gel technology DPR- ”Classic” i.e. polymer ”Strong gel” e.g. H2Zero

Rate effects of changing PI and WC

R&D continued: Downhole separation - ’light’ version Objective : Research of slip gravity separator concept for downhole separation. By controlling the stratified layers between oil and water in an inclined tube, the layers can be controlled to segregate through specially designed slots in the tubing wall. Demo 2000 project - ABB, Statoil, Shell Technology and NTNU.

Future : Subsea Separation and PWRI

§3. Reinject water (PWRI)

A-43 PWRI performance

Statfjord field map pilot well

- Today reinjecting m3 of water

R&D - PWRI Fracture growth : improving our modelling capability

§3. Dispose into aquifer

Utsira – a shallow saltwater reservoir

Extent of Utsira aquifer

- Kvitebjørn to dispose all produced water into Utsira

§4. Purify and discharge

Distribution of organic components in produced water WAF= Water accommodated fraction

The CTour process

Results from CTour test at Statfjord B These component groups are together with our corrosion inhibitor the largest contributors to EIF Blue line system performance (with hydrocyclones), red line effect of condensate and mixers only

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