1 -Classification: Internal Painting the pores Gullfaks Diverging Pilot Well A-35 Author: Rune Instefjord,

2 -Classification: Internal Outline Introduction to the Chemicals. How does the chemicals work. Planning of pilot on Gullfaks −Selection of pilot area −Simulation Implementation Summing up

3 -Classification: Internal Introduction to Abio gel Abio gel is compound, consisting primarily of Sodium silicate. When Abio gel is brought into contact with divalent cations (i.e. Ca and Mg) in formation- or seawater it reacts to form a microcrystalline suspension which may become a stiff gel if concentration of divalent cations exceeds about 1 %. Otherwise it behaves as a cement paint coating the rock matrix. Abiogel coat narrow the flow channels gradually keep certain permeability in favor of indepth fluid diversion The following text and illustration is provided by CNPC Abiogel is actually a gel used in chromatography and is also a brand name for cement paint

4 -Classification: Internal Gullfaks flow diversion project Bypassed oil 1000 ton chemicals (silica based) injected into the injector A-35. The chemicals is environmental classified as yellow. It is environmentally acceptable and unproblematic to use. The chemicals shall move into the reservoir and form micro gel particles, which will stick to the surface of the pores and thereby reducing the permeability in invaded zones. The water will be forced to find new paths and invade less water flooded areas. Hit bypassed oil and increase the oil recovery.

5 5 Illustration of water diverging Important issues: - Improve the volumetric sweep efficiency. -Reduce permeability and reduce flow of water in existing water channels. Divert water into unswept areas. - Alternative to drilling of new wells into areas with very uncertain flooding pattern.

6 -Classification: Internal Illustration of water diverging

Classif ication: Interna l Status: Draft layer36layer38layer40 layer42 layer44 layer46layer48layer49  Plane remaining oil mainly distributes out of the main water streamline region and in the bottom low permeability formations Remaining Oil Distribution

8 -Classification: Internal Introduction to Gullfaks  Discovered: 1978  Start production: 1986  STOOIP: 599 MSm³  Base oil reserves: 365 MSm 3  Produced to date: 351 MSm 3 Recovery of base reserve: 96% Overall expected recovery: 61% Overall recovery pr. 2011: 59%  Current daily production: 14 kSm 3  Current average water cut: 84 %  Initial pressure/temperature: bar/ 71 o C at 1850m TVD MSL  Bubble point pressure: ~ bar at 1850m TVD MSL  GOR: ~ 100 Sm³/Sm³  Oil viscosity: ~ 0.5 – 1 cp Gullfaks Norway Iceland Ireland UK North Sea Sweden Denmark Germany Finland Russia

9 Pilot area: Lower Brent, segment H1 Segment selected for a water based chemical method. STOOIP in lower Brent is 20,3 MSm³ oil. Lower Brent in H1 has ”only” 57 % recovery factor. Potential MSm³ mobile oil left. Relatively isolated segment. A lot of data is collected in this area. It was the first production area and therefore a lot of good, initial data. 2 active wells in lower Brent, A-35 (injector) and A- 39A (producer). 2 active producers in upper Brent, B-37 and A-38A. Pressure communication between B-37 and lower Brent. No communication with A-38A? Problem with H 2 S in A-39A. B-37 may also give a H 2 S problem.

10 -Classification: Internal One-dimensional model to simulate sand pack experiment Parameter adjustment Simulation −Establish a History Matched (HM) simulation model for the H1-segment −Understand the mechanism of the chemicals and find the relevant parameters −Make predictions using the optimal simulation tool and – method using restart from the HM model

Classification: Internal Operation, offshore setup Scandi Flora at the North Shaft (NS) Hose BOP deck NS Connection to Chicksan 2” line KillWing WellHead

Classification: Internal Events each batch Mixing chemicals at CCB, Ågotnes outside Bergen % wt. solution mixed in Fresh Water. Mixed max 800 m³ of solution due to regulations by the government. Scandi Flora transported and pumped the chemicals into A-35. Start injection m³ KCl preflush and postflush, rate: m³/d in the 2 first batches. Injected m³ solution with chemicals at rate: m³/d. Density of the liquid was Viscosity around 3.5 cP. PH around 13. End injection Restrictions on wave height. Maximum 3 m due to hook up between vessel and platform.

Classification: Internal Batch 1 Before 1st Batch treatment DHP for inj. rate 2000 sm3/d was 296bara, after treatment DHP stabilized around 280bara. This effect was interpreted as stimulation of the well.

Classification: Internal Pressure details batch 1 Start chemical injection End chemical injection Start KCl postflush Start KCl preflush Stop KCl preflush Start SW injection

15Classification: Internal Well shut in Start chemical injection Drop due to density Start SW injection Increase due to density Pressure 4th batch (part 1)

Classification: Internal SW inj. pressure after each batch

Summary Successful operation but used some more time than planned due to weather conditions. It is to early to see any IOR in the producers, so we do not know the answer on the questions! We expect increased oil production in the producers after around 1 year. Have technical problems in one of the wells per today and the well are therefore shut in. This may worsen the interpretation of the pilot. First multi well diverging project in the North Sea. If success it may give a lot of increased oil for more fields than only Gullfaks. 17 -Classification: Internal

18 -Classification: Internal Presentation title Presenters name Presenters title address, tel: Thank you