Novel Laboratory and Field Approaches to Control Halite and other Problematic Scales in High Salinity Brine from the Bakken

Abstract

AbstractScale formation during oil and gas production may cause formation damage, pump failure, blockage of tubing or annulus, and deposits in surface lines and equipment that can result in shutdowns or loss of production. Therefore, the prevention of scale is of considerable interest and concern to the oil and gas industry. Control of scale, particularly halite in high salinity Bakken brines (total dissolved solids > 250,000 mg/L), is challenging on two fronts: 1) laboratory evaluation of scale products by conventional dynamic tube-blocking tests or static bottle tests are not optimal for halite scale, and 2) halite formation and high tendencies for carbonate and sulfate scales characterize high-salinity brines, which are difficult to manage with conventional scale control strategies. This paper describes a novel laboratory testing procedure to better evaluate halite/scale inhibition and how to apply this method. Conventional testing is also included to provide a more robust strategy for effective scale control in the high-salinity Bakken brines.Currently, there is not an industry-recognized method for laboratory testing of halite due to difficulty controlling the amount of halite precipitation and reproducibility during the test. However, a test method was devised utilizing an ultraviolet-visible (UV-Vis) spectrophotometer to monitor dynamic scale formation during product evaluation. This kinetic turbidity test (KTT) uses the information on scale formation kinetics to differentiate various product performances with reproducible testing results. Halite inhibitors and combination products (halite inhibitor + common scale inhibitors) were screened with this method for potential use in field applications. The combination of products exhibited good scale inhibition performance for both halite and other common scales.The challenges of halite and other scales in Bakken brines cause typical scale inhibitors to be ineffective. Diluting brines with freshwater is the common field treatment to lower scaling ion concentrations and wash out salt deposits. However, this approach is restricted in the Bakken because of the limited fresh water availability, poor fresh water quality (i.e., high bicarbonates and high pH), and remote locations that can impede freshwater treatment. Therefore, more effective treatments are essential for economic oil and gas production.