Selection of Barium Sulphate/Barite Dissolver Chemical through Establishment of Standard Laboratory Screening Protocols

Abstract

Barium Sulfate (Barite, BaSO4) scale is the most difficult scale to remove due to its low inherent water solubility. After more than 10 years of production in Field A, barite scales are recently found deposited in the tubing and at the topside in one of the oil producer wells. In this case, barite scales are precipitated through mixing of formation water containing high concentration of barium ions and injection seawater with high sulphate concentrations. Successful method of removing barite scales is using chelant based chemicals i.e. EDTA/DTPA. The best possible way to reduce failure risks of the pilot removal application using these chemicals for Field A is through series of lab testing. This paper describes the selection of barite scales dissolver chemicals through establishment of standard laboratory screening protocols prior to field applications in PETRONAS. In the industry, there are various experimental methods to study the effect of barite dissolver chemicals on barite scales dissolution. Since PETRONAS has just recently encountered barite scales deposition issues, it is crucial to have a standardized protocol to ensure the effectiveness of the chosen chemicals to remediate the issue immediately. The protocol developed was based on various references and citations from other operators and chemical service provider. The protocols are divided into three (3) sections in series i.e. characterization of deposit samples mineralogy, barite dissolution and chemical compatibility testing. Prior to barite dissolution tests, deposit samples collected from the wells/topsides are characterized through XRD/XRF analysis, organic scale identification/analysis and acid solubility test. Finally, the most effective barite dissolver chemical will undergo chemical compatibility tests with production fluids, incumbent production chemicals and core samples. Barite scales deposits collected from Field A were found to be radioactive. Testing procedures were in-line with precautions taken to prevent risks exposure to these materials. Scale characterizations indicated samples are dominated by barium sulfate containing some small percentage of calcium carbonate scales and organic contents. Static disintegration and dynamic dissolution tests carried out shows significant results differences where application of barite dissolver chemicals in the well may require coil tubing assistance. Compatibility studies of the dissolver chemical with incumbent production chemicals shows suitability of the different chemicals when the well is flow back after treatment.