Anhydrite deposition in Cawayan wells, Bacman geothermal field, Philippines : prediction and possible remedies

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dc.contributor Jarðhitaskóli Háskóla Sameinuðu þjóðanna is
dc.contributor.author See, Fidel S. is
dc.date.accessioned 2020-05-12T13:58:17Z
dc.date.available 2020-05-12T13:58:17Z
dc.date.issued 1995
dc.identifier.issn 1670-7427
dc.identifier.uri http://hdl.handle.net/10802/23292
dc.description Myndefni: kort, línurit, töflur. is
dc.description.abstract The anhydrite mineral deposition inside the wellbores of Cawayan wells is investigated in order to predict its occurrence and come up with possible remedies. The chemistry of the fluids is thoroughly evaluated and some geochemical indicators of deposition such as Ca2+, SO42-, Mg2+, SiO2, and Cl- are established. The behaviour of various calcium and sulphate species during deposition, and the effects of temperature and pH are determined using the SOLVEQ and WATCH 2.1 chemical speciation programmes. Results show that with increasing temperature, the activity of sulphate and calcium species in solution decreases and consequently anhydrite supersaturation is increased. At low pH, sulphate activity is significantly reduced by the formation of bisulphate ions, and anhydrite undersaturation is attained; at high pH, undersaturation is also predicted because of decrease in calcium activity. However, the solution becomes supersaturated with respect to calcite at high pH. The CHILLER programme is utilized to simulate fluid-fluid mixing, and determine the effects of NaCl addition, Na2HPO4 addition, acid treatment, and CaCl2 injection on anhydrite deposition. Results show that NaCl, Na2HPO4 and HCl are possible inhibitors of anhydrite deposition. Increasing the salinity of production fluid before mixing with high-sulphate waters tends to retard deposition and increase the amount of mixing fluid necessary to initiate formation of anhydrite. Na2HPO4 prevents anhydrite deposition by significantly reducing activity of calcium through association with phosphate ions. However, the solution tends to become supersaturated with respect to apatite, which may be deposited. CaCl2 addition can induce deposition in acid zones and thus seal them off but this further lowers the pH of the high-sulphate acid fluid as bisulphate dissociates into sulphate ions and releases hydrogen ions. is
dc.format.extent 1 rafrænt gagn (28 bls.) is
dc.language.iso en
dc.publisher United Nations University is
dc.publisher Orkustofnun is
dc.relation.ispartofseries United Nations University., UNU Geothermal Training Programme, Iceland. Report ; 1995:13
dc.relation.uri http://www.os.is/gogn/unu-gtp-report/UNU-GTP-1995-13.pdf
dc.subject Jarðhiti is
dc.subject Jarðhitarannsóknir is
dc.subject Steinefni is
dc.subject Jarðefnafræði is
dc.subject Filippseyjar is
dc.title Anhydrite deposition in Cawayan wells, Bacman geothermal field, Philippines : prediction and possible remedies en
dc.title.alternative Geothermal training in Iceland en
dc.type Bók is
dc.identifier.gegnir 001516362


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