Sulphate Removal for Barium Sulphate Scale Mitigation a Deepwater Subsea Production System

Abstract

Sulphate Removal for Barium Sulphate Scale Mitigation a Deepwater Subsea Production System I.R. Collins; I.R. Collins BP Exploration Operating Company Limited Search for other works by this author on: This Site Google Scholar R. Stalker; R. Stalker Scaled Solutions Limited Search for other works by this author on: This Site Google Scholar G.M. Graham G.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 2004. Paper Number: SPE-87465-MS https://doi.org/10.2118/87465-MS Published: May 26 2004 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Get Permissions Search Site Citation Collins, I.R., Stalker, R., and G.M. Graham. "Sulphate Removal for Barium Sulphate Scale Mitigation a Deepwater Subsea Production System." Paper presented at the SPE International Symposium on Oilfield Scale, Aberdeen, United Kingdom, May 2004. doi: https://doi.org/10.2118/87465-MS Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll ProceedingsSociety of Petroleum Engineers (SPE)SPE International Oilfield Scale Conference and Exhibition Search Advanced Search AbstractScale control is conventionally achieved by use of chemical inhibitors, introduced to the production system either by squeeze treatment into the reservoir or continual injection into the well. However, as new field developments encounter more challenging production environments or when the associated economic impact of chemical intervention is large (e.g. subsea completed wells with poor chemical placement by bullhead treatments, or limited access to wet subsea wellheads), other methods of scale control such as sulphate removal must be considered during the front end engineering design (FEED) stage.The Greater Plutonio development, lying in deep water (500 - 1600 metres) off the coast of Angola, will be produced via multi-well subsea facilities tied back to a floating production vessel, with reservoir pressure support being provided by seawater injection. Owing to the complex and inaccessible nature of the subsea production system, chemical control of sulphate scale was considered economically unfeasible. Scale control will therefore be achieved by means of sulphate removal prior to seawater injection. However, following conventional sulphate reduction towards 40 ppm there remains a residual scale potential, the impact of which on production is difficult to assess using thermodynamic scale prediction packages or normal laboratory conditions. Periodic squeeze treatments were however still anticipated. A detailed laboratory testing programme of dynamic and static scale formation tests coupled with dynamic core-blocking tests was undertaken to determine the effect of varying production conditions, organic acid content, flow regime and the nature of the underlying substrate on scale formation under field specific conditions for this mildly oversaturated system. The ultimate goal of the laboratory test programme was to define an optimal sulphate level in the injected seawater to prevent scale formation throughout the production lifetime of the field. By comparison of laboratory test results with predicted scale formation tendencies, an acceptable level of sulphate in the injected seawater was determined which would allow pressure support without causing scale formation. This allowed further detailed analysis of the costs associated with a residual scale risk at 40 ppm sulphate (or above) with the costs associated with upgrading the SRP facility to achieve lower levels of sulphate in the injection water. The laboratory work allowed an optimal sulphate concentration to be determined which was achievable through modification of the current design facilities and resulted in a significant cost saving in the development phase.IntroductionScale management in deepwater subsea fields is recognised as a particular technical and economic challenge facing petroleum production chemists. This means that scale management and its impact on field economics is generally considered in a pro-active manner at the front end engineering (FEED) design stages for such fields rather in a reactive manner following first production. The current case examined scale management for the Greater Plutonio project, a subsea development lying in deepwater (1400–1600 meters), offshore Angola. The pre-FEED design cases showed that scale management was a significant cost to the development (reduced PI owing to uncontrolled scale build up, coil tubing squeeze treatment interventions or scale removal operations). The cost of reactive scale management was so high that it had a significant impact on the project economics (reduced net present value (NPV) and rate of return). The costs associated with scale treatments were particularly significant owing to the anticipated requirement for coil tubing intervention at wet subsea wellheads in deepwater.1,2,3 Keywords: remediation of hydrates, ppm sulphate, squeeze treatment, sulphate level, production chemistry, scale formation test, hydrate remediation, concentration, injection, wax inhibition Subjects: Production Chemistry, Metallurgy and Biology, Improved and Enhanced Recovery, Inhibition and remediation of hydrates, scale, paraffin / wax and asphaltene This content is only available via PDF. 2004. Society of Petroleum Engineers You can access this article if you purchase or spend a download.