Investion of additives on drilling mud performance withTønder geothermal drilling as case study.
Translated title
Investion of additives on drilling mud perfomance with Tønder geothermal drilling as case study
Author
Nwaoboli, Awele
Term
4. term
Education
Publication year
2014
Submitted on
2014-01-06
Pages
128
Abstract
Denne afhandling vurderer fem boremuddertyper til mulig brug i Tønder geotermiske boring. Vi udførte laboratorieforsøg ved varierende temperaturer og tryk, forskellige aldringstider og med forskellige mængder af almindelige tilsætningsstoffer. To vandtyper blev brugt som basisvæske: frisk vand fra hanen og havvand fra Fanø strand. Vi analyserede også den væske, der filtrerer gennem mudderet (filtratet), for at se, hvordan den kan påvirke den omgivende formation. Undersøgelsen omfattede viskositetsforøgere (Duo Tec NS, bentonit og carboxymethylcellulose, CMC), som fortykker væsken; væsketabsadditiver (MI PAC Elv, bentonit, CMC og stivelse), som hjælper med at tætne formationen og begrænse vandtab; tyndere (polyfosfaterne SHMP og SPP), som reducerer viskositeten ved behov; hæmmere (glykol og kaliumklorid, KCl), der begrænser svulmen af ler/skifer; samt soda ash til at reducere opløst calcium og barit til at øge væskens densitet. Resultaterne viste, at alle fem mudder svulmede godt og kunne danne en belægning på borehullets vægge. Begge tyndere sænkede viskositeten, men SPP var mere effektiv end SHMP. Prøve 4 og 5 havde det laveste sandindhold, mens prøve 2 havde det højeste. CMC og Duo Tec NS øgede viskositeten effektivt; Duo Tec NS gav højere flydegrænse (yield point) og gelstyrke—egenskaber, der hjælper med at transportere borekaks og holde partikler svævende—og var dermed den stærkere viskositetsforøger i dette studie. Svulmehæmning skyldtes primært kaliumioner fra KCl; glykol alene forhindrede ikke vandoptag effektivt, men virkede i kombination med KCl. CMC viste meget gode væsketabsegenskaber; MI PAC ydede tilsvarende. Begge anbefales til at danne filterkager med ønskede egenskaber. Filtratanalyser viste acceptable niveauer af calcium, magnesium og klorider, så yderligere behandling var ikke nødvendig. Alkalinitetsforsøg bestemte mængden af karbonater og bicarbonater samt den syre, der skulle til for at nå standard endepunkter. Effekten af aldring var ikke entydig, men generelt reducerede den de reologiske egenskaber. At hæve temperaturen fra rumforhold til 74°C reducerede også typisk reologien. Øget tryk dannede filterkage, og forsøg bekræftede balancen mellem hydrostatisk tryk og formationstryk (balancerede, overbalancerede og underbalancerede forhold). Tilsammen giver resultaterne et praktisk grundlag for at vælge vandtyper og tilsætningsstoffer til boremudder i Tønder-geotermisammenhæng.
This thesis evaluates five drilling fluids (drilling muds) for potential use in the Tønder geothermal drilling project. We performed laboratory tests under varying temperatures and pressures, different aging times, and with different amounts of common additives. Two water types were used as the base liquid: fresh tap water and seawater from Fanø beach. We also analyzed the water that filtered through the mud (the filtrate) to assess how it might interact with the surrounding formation. The study examined viscosifiers (Duo Tec NS, bentonite, and carboxymethyl cellulose, CMC) that thicken the fluid; fluid-loss control additives (MI PAC Elv, bentonite, CMC, and starch) that help seal the formation and limit water escaping; thinners (the polyphosphates SHMP and SPP) that reduce viscosity when needed; inhibitors (glycol and potassium chloride, KCl) that limit clay/shale swelling; soda ash to reduce dissolved calcium; and barite to increase fluid density. Findings showed that all five muds swelled well and could form a coating on borehole walls. Both thinners lowered viscosity, but SPP was more effective than SHMP. Samples 4 and 5 had the lowest sand content, while sample 2 had the highest. CMC and Duo Tec NS both increased viscosity effectively; Duo Tec NS produced higher yield point and gel strength—properties linked to carrying cuttings and suspending solids—making it the stronger viscosifier in this study. Swelling inhibition was mainly due to potassium ions from KCl; glycol alone did not prevent water uptake effectively, but worked when combined with KCl. CMC showed very good fluid-loss control; MI PAC performed comparably. Both are recommended to produce filter cakes with desirable properties. Filtrate tests showed calcium, magnesium, and chloride at acceptable levels, so no additional treatment was needed. Alkalinity tests identified carbonate and bicarbonate levels and the acid required to reach standard endpoints. Aging effects were inconclusive overall but generally reduced rheological properties. Raising temperature from ambient conditions to 74°C also typically reduced rheology. Increasing pressure formed a filter cake, and tests confirmed the expected balance between hydrostatic and formation pressures (balanced, overbalanced, and underbalanced conditions). Together, these results inform the selection of water types and additives for drilling muds suited to the Tønder geothermal context.
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