Scale Dissolver Application Under HP/HT Conditions - Use of a HP/HT "Stirred Reactor" for In-Situ Scale Dissolver Evaluations (2005)

Scale Dissolver Application Under HP/HT Conditions - Use of a HP/HT "Stirred Reactor" for In-Situ Scale Dissolver Evaluations Helen Williams; Helen Williams Scaled Solutions Limited Search for other works by this author on: This Site Google Scholar Rex Man Shing Wat; Rex Man Shing Wat Statoil ASA Search for other works by this author on: This Site Google Scholar Ping Chen; Ping Chen Champion Technologies Ltd. Search for other works by this author on: This Site Google Scholar Thomas Hagen; Thomas Hagen Champion Technologies Ltd. Search for other works by this author on: This Site Google Scholar Kjell Erik Wennberg; Kjell Erik Wennberg Statoil Search for other works by this author on: This Site Google Scholar Vigdis Vikin; Vigdis Vikin Statoil Search for other works by this author on: This Site Google Scholar Gordon M. Graham Gordon M. Graham Scaled Solutions Limited Search for other works by this author on: This Site Google Scholar Paper presented at the SPE International Symposium on Oilfield Scale, Aberdeen, United Kingdom, May 2005. Paper Number: SPE-95127-MS https://doi.org/10.2118/95127-MS Published: May 11 2005 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Williams, Helen, Wat, Rex Man Shing, Chen, Ping, Hagen, Thomas, Wennberg, Kjell Erik, Vikin, Vigdis, and Gordon M. Graham. "Scale Dissolver Application Under HP/HT Conditions - Use of a HP/HT "Stirred Reactor" for In-Situ Scale Dissolver Evaluations." Paper presented at the SPE International Symposium on Oilfield Scale, Aberdeen, United Kingdom, May 2005. doi: https://doi.org/10.2118/95127-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search nav search search input Search input auto suggest search filter All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE International Oilfield Scale Conference and Exhibition Search Advanced Search AbstractIn several high temperature and high pressure (HT/HP) production environments severe downhole carbonate scale formation is often anticipated and effective carbonate scale dissolvers are required. However for most cases the selection of scale dissolvers is conducted under much less severe conditions, involving simple bottle tests conducted at temperatures up to 95ºC and ambient pressure. These tests although generally accepted for screening purposes suffer a number of significant limitations. In addition to the moderate test conditions the low pressure means that carbon dioxide is readily released following the dissolution and results in changes in the test pH which may mean the efficiency of the dissolvers could be overstated.This paper describes the use of a novel a novel HP/HT "stirred reactor" test rig to more closely examine the relative performance of selected scale dissolvers including organic acids (formic and acetic acids), inorganic acids (16% HCl) and other more conventional scale dissolvers under typical field application conditions. The equipment is specially designed for the extraction and stabilisation of samples at or 'near' tested conditions and therefore allows the equilibrium dissolution level to be determined under more representative HP/HT conditions. In this work preliminary tests were conducted using 16% HCl under progressively more severe test conditions (RT & 1,500 psi; 150ºC & 1,500 psi and then 150ºC & 4,500 psi. Further tests were then conducted to compare the performance of organic acid based scale dissolvers (formic acid and acetic acid based products) together with other selected scale dissolvers at 150ºC and 4,500 psi and compared with the results obtained for 16% HCl. For these HP/HT tests, samples were collected and analysed after 2 and 20 hours equilibration time and results were compared with those obtained in more conventional "bottle tests conducted at less severe environmental conditions (90ºC and ambient pressure).In summary the results demonstrate the importance of conducting scale dissolver tests for field applications under more representative (HP/HT) conditions.Of particular significance was the impact of the cooling and pressure reductions.For one of the products tested, although very good dissolution was recorded under the HP/HT conditions, re-precipitation of a different polymorph of calcium carbonate occurred very rapidly resulting in a significant increase in the volume of carbonate precipitation within the reaction vessel and various sample lines. The paper will describe the details of the test equipment used in this work and present a mechanistic interpretation of the various results obtained.IntroductionThe development of HP/HT gas condensate fields in the North Sea has brought about a number of important oilfield scale control problems.These fields are often characterised by temperatures in excess of 150ºC, downhole pressures of greater than 10,000 psi and high salinity brines (TDS > 200,000ppm).1In several of these HP/HT fields severe downhole carbonate scale is anticipated during production due to changes in the temperature, pressure and pH which lead to changes in the supersaturation of calcium carbonate in the brine.Pressure reduction during production is one of the main causes of carbonate scale formation due to the evolution of carbon dioxide from the brine phase, which increases the solution pH (Equation 1) and the solubility with respect to carbonate declines rapidly, leading to precipitation (Equation 2). Keywords: asphaltene inhibition, bottle test, upstream oil & gas, reactor, hp ht condition, calcium concentration, dissolver, calcium, dissolution, test condition Subjects: Production Chemistry, Metallurgy and Biology, Unconventional and Complex Reservoirs, Inhibition and remediation of hydrates, scale, paraffin / wax and asphaltene, HP/HT reservoirs This content is only available via PDF. 2005. Society of Petroleum Engineers You can access this article if you purchase or spend a download.