Development of capillary flow technique to investigate the mechanism of barium sulfate deposition

Abstract

Barium sulfate (BaSO₄) deposition is a significant and costly problem in oilfields which can occur when two incompatible waters mix. The precipitation of barium sulfate normally occurs in the bulk solution but for the deposition, it is not clear how barium sulfate deposits in the pipelines. In this research two possible mechanisms were proposed. First, since barium sulfate nucleation and before growth has completed, barium sulfate can deposit in pipelines. Second, after barium sulfate has completed their growth, barium sulfate can deposit in pipelines. To elucidate the possible mechanism, barium sulfate deposition experiments were conducted by flowing barium chloride and sodium sulfate solutions through a smooth and rough capillary. Results show that barium sulfate deposition is non-uniform and most of the deposition is observed at the beginning of the capillary. Moreover, the deposition is almost the same on both smooth and rough surfaces. In order to investigate the second mechanism, precipitated barium sulfate solution was flowed through a capillary. Results reveal that barium sulfate particles will not deposit on either of the surfaces after they precipitated and grew in the bulk solution. However, after a capillary was pre-scaled and precipitated barium sulfate solution was flowed through it, barium sulfate particles would slowly deposit inside the pre-scaled capillary.