Control of the produced water scaling potential: an example from the Halfdan field (North Sea)
Author
Godinho, Erica dos Santos
Term
4. term
Education
Publication year
2018
Submitted on
2018-06-07
Pages
87
Abstract
Mineraludfældning (skalering) er et stort problem i olie- og gasindustrien. Når opløste mineraler bliver til faste aflejringer, kan de tilstoppe både produktionsudstyr på overfladen og strømningsveje i undergrunden, især i reservoiret og tæt på brønden. Det kan reducere produktionen og i værste fald føre til tab af en brønd. I dette studie undersøgte vi, hvor stor risikoen for skalering er, når en offshore-prøve af produceret vand fra Halfdan-feltet i Nordsøen bringes i kontakt med to forskellige formationsvande (Ekofisk og Valhall) ved 70 °C. Vi udførte kerneflow-forsøg med konstant gennemstrømningshastighed, hvor væsker blev pumpet gennem bjergartsprøver for at efterligne forholdene i reservoiret. Forsøgene viste et fald i porøsitet (ca. 1,3 % i ét af tilfældene) og et fald i permeabilitet på omkring 0,017 D (Darcy) i begge tilfælde. De kemiske målinger indikerede desuden mulig udfældning af barit, en tendens til tilbageholdelse af kalium-, karbonat- og bikarbonat-ioner, samt lokal opløsning af fosfat.
Mineral scale is a major challenge in the oil and gas industry. When dissolved minerals precipitate as solid deposits, they can clog production equipment at the surface and block flow paths underground, especially in the reservoir and near the well. This reduces production and can even lead to loss of a well. In this study, we examined the potential for scale when an offshore produced water sample from the Halfdan field (North Sea) was brought into contact with two different formation waters (Ekofisk and Valhall) at 70°C. We ran coreflooding tests at a constant flow rate, in which fluids were pushed through rock cores to simulate reservoir conditions. The tests showed a reduction in porosity (about 1.3% in one case) and a decrease in permeability of approximately 0.017 D (Darcy) in both cases. The measurements also indicated possible barite precipitation, a tendency for potassium, carbonate and bicarbonate ions to be retained by the rock, and localized phosphate dissolution.
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