SAND CLEANING STATFJORD C FIELD TEST Stavanger 18 – 19 January 2006 Henrik Dannström, MATOR AS

CURRENT PRACTICE ON THE NORWEGIAN SHELF Solids are normally handled in dedicated treatment units. In most cases jetting water and associated solids are treated separate from main produced water stream. Solids are reinjected, treated to achieve discharge quality or sent onshore for disposal.

BACKGROUND Discharge quality governed by REGULATIONS RELATING TO CONDUCT OF ACTIVITIES IN THE PETROLEUM ACTIVITIES (THE ACTIVITIES REGULATIONS) Section 59 discharge of cuttings, sand and solid particles Cuttings from drilling and well activities, sand and other solid particles shall not be discharged to sea if the oil content of formation oil, other oil or base fluid in organic drilling fluid is more than ten grams per kilogram of dry matter. Dedicated sand treatment not available on Statfjord C. Statoil therefore wanted in 2005 to investigate sand treatment methods utilising existing equipment (Flash Tank CD2015).

CONCEPT STAGES 1.Theoretical evaluation  optional cleaning methods (mechanical, steam, chemical)  suitability of CD2015 for selected method (pressure, temperature, materials, instrumentation etc)  sampling and analysing methods → Decision to investigate condensate wash 2.Laboratory test  washing of sand with condensate → Decision to proceed with field test

TEST SET-UP, PILOT SCALE Process and test separator jetting water and –sand routed batchwise in to CD2015. Excess water drained between jettings.

TEST CONDITIONS, PILOT SCALE  Volumetric flow rate to ensure fluidisation of sand in one of three jetting sections Fluidisation factor (F) to be higher than ) 1) Tippets, R Priestman G ”Liquid Jet Fluidisation and Solids Wash Out”

TEST CONDITIONS, PILOT SCALE  Operating pressure to ensure liquid phase condensate in wash section

TEST CONDITIONS, PILOT SCALE  Mixing of condensate and sand / water - in–line mixer used  Condensate flow rate to fit purpose - tested with 0.1 – 0.2 vol-% of water flow rate  Recirculation - until desired oil-on-sand concentration achieved  Disposal of hydrocarbons -flashing / disposal through flare and skimming to reclaimed oil sump

TEST SET-UP, PILOT SCALE

ANALYZING METHODS oSampling oConcentration and analysis oFiltering 1.2 µm / 5.0 µm oWeighing (correction for OiW) – washing – re-weighing oMethod accurate down to 0.2 wt%.  Method to be modified for floating installations oRetorte – accuracy down to 0.5 – 1.0 wt%, requires larger sample volumes oIR / Infracal for OiW

TEST RESULTS, PILOT SCALE

POSITIVE:  Promising results in terms of cleaning efficiency, although 10 g/kg not was achieved  CD2015 well suited for purpose  Full scale test may easily be carried out based on same principle NEGATIVE:  Mechanical failure (leakage) led to modifications on site and reduced capacity  Reduced sand concentration over time CONCLUSION: Results promising enough to proceed with full scale field test

TEST SET-UP, FULL SCALE Major changes to pilot test: -all three jetting sections utilised -larger flow rate (larger pump, hoses, lines, valves) -more instrumentation -longer test period -more analysing equipment

TEST SET-UP, FULL SCALE Pump 210 m3/h 10 barg Condensate feed to in-line mixer

TEST CONDITIONS, FULL SCALE  Volumetric flow rate to ensure fluidisation of all sand in vessel  Tie-in such that all water and sand in vessel are circulated  Operating pressure to ensure liquid phase condensate in wash section  Mixing of condensate and sand / water. In-line mixer used.  Water level 50% - 70% of vessel height  Condensate flow rate to fit purpose  Recirculation  Disposal of hydrocarbons

TEST RESULTS, FULL SCALE Results from 1:st sand batch circulation

TEST RESULTS, FULL SCALE Results from 2:nd sand batch circulation

TEST RESULTS, FULL SCALE Results from flow regime test

TEST RESULTS, FULL SCALE SUMMARY  Demonstrated ability to achieve discharge quality for oil wetted sand by means of condensate washing.  Associated water quality well below discharge requirements.  Overall condensate consumption to achieve cleaning of 1 week of accumulated jetting solids approximately 1 m 3, of which % reclaimed.

BATCH PROCESS REQUIREMENTS  Vessel with holding capacity for separator / process vessel jetting inventory  Pumparound system for vessel inventory, with pump discharge pressure above condensate flash point  Flow capacity and internal distribution arrangement to ensure fluidisation of solids  Suitable mixer and choke  Condensate with appropriate qualities  Means for discharge of flashed and gravity separated hydrocarbons

CONCLUSION Client objective of finding alternative means of solids treatment identified. Concept is oil extraction from sand using condensate. This can be achieved in several configurations. One batch configuration found suitable for Statfjord C. Technology qualification next step towards implementation as permanent installation. Implementation of concept on other facilities subject to feasibility evaluation.