Sulphide Scale Co-Precipitation with Calcium Carbonate

Identifying effective sulphide scale squeeze inhibitors has been a major challenge in the production of oil and gas from deeper, higher temperature reservoirs. Managing sulphide scales of zinc and lead (ZnS and PbS) that commonly occurs in deep, hot reservoirs poses a significant challenge because of their very low solubilities. In general, for scaling problems applying chemical scale inhibitors or dispersants is the preferred solution to most challenges. However, to date no effective sulphide inhibitors/dispersants have been available which can deal with severe lead, zinc and iron sulphide problems at high salinity (HS Ͼ200, 000TDS) and high temperature (HT Ͼ180°C) conditions. It is a particularly difficult task to find sulphide inhibitors which can also be "squeezed" successfully since they must return to the wellbore at relatively high concentrations. This paper describes various sulphide inhibitor testing techniques which have been applied to many candidate products for the management of ZnS and PbS in a gas condensate field with a known relatively severe ZnS/PbS scaling problem. The paper presents sulphide static and dynamic test measurements along with thermal ageing results that show some encouraging results in terms of ZnS/PbS sulphide inhibition. The paper extends our knowledge and ability to test effective sulphide inhibitors for severe ZnS/PbS scaling conditions in high pressure/high temperature (HPHT) reservoirs.

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Development and Qualification of New Zinc and Lead Sulphide Scale Inhibitors for Application under Harsh Conditions

Baraka-Lokmane

Hurtevent

Tillement

et al. 2015

SPE International Symposium on Oilfield Chemistry

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The paper will describe the challenges facing sulphide scale control in the challenging environment found in Totals Elgin and Franklin Fields. It will present the advances made in developing new thermally stable and compatible chemical inhibitors able to withstand the extreme conditions in these fields. The paper will then describe the test methodologies and experimental approach developed to examine the performance of various prototypes or candidate chemicals followed by more detailed testing on selected chemicals under the more challenging field representative conditions as well as application specific testing for both squeeze treatment and downhole continuous injection at temperatures of 196°C/282 °F. In collaboration with University of Lyon Total has developed a range of new inhibitor types specifically designed to inhibit sulphide scales and remain stable under the harsh conditions of these fields. The chemicals have been qualified independently using recently developed test methodologies for lead and zinc sulphide and show better performance against these unconventional scales comparing to the other chemistries examined. In addition, a new method was developed for scale inhibitor residual analysis. This method based on time resolved fluoroscopy allows a quick and very sensitive measurement. The work concludes that a new range of Zn/Pb sulphide specific chemicals have been developed for field application with selected species also being suitable for application under the extreme conditions of the Elgin and Franklin Fields. Zinc and lead sulphide scales became an increasing challenge in oil and gas production. More specifically when formed from wells producing under very severe conditions of high temperature (196°C/282 °F) and high salinity formation waters such as those experienced in Central Graben Fields, their prevention by conventional scale inhibitors has proved challenging. To date after extensive chemical qualification over several years, no conventional scale inhibitor has been found which can both inhibit lead and zinc sulphide and survive under the extreme conditions of these fields. Therefore, the results in this paper represent a significant advance in the ability to control sulphide scales and test the inhibition under appropriate conditions.

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Sulphide Scale Co-Precipitation with Calcium Carbonate

Cited by 10 publications

References 18 publications

Control of composite oilfield scales and deposits

Control of composite oilfield scales and deposits

Sulphide Scale (PbS/ZnS) Formation and Inhibition Tests for a Gas Condensate Field with Severe Scaling Conditions

Development and Qualification of New Zinc and Lead Sulphide Scale Inhibitors for Application under Harsh Conditions

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