Abstract

Deposition of inorganic and organic solids in production systems impacts throughput and can cause other operational and safety issues. Once formed, remediation of deposits is costly, often resulting in lost production. Solids management strategies involve a combination of chemical injection, thermal management and periodic chemical or mechanical remediation operations specific for each depositing species. A novel diamond-like carbon (DLC) coating, which exhibits extreme hydrophobicity in oil water systems, has been developed to control deposition of most common solids including asphaltenes, inorganic scale, wax and potentially hydrates under flowing conditions in production tubing and flowlines. This molecularly bonded, multifunctional coating may simplify solids management strategies and lower field development costs by reducing chemical injection, eliminating chemical injection systems, reducing insulation and eliminating the need for active heating. In this paper, we build on previous published data further refining the performance envelopes of the coating for inorganic scales.

Previously published work has shown that this coating is effective in managing wax and asphaltene depositions. Over forty tests in a 2-inch flow loop were used to define an operating envelop as a function of wall shear and δT in which little or no wax deposition occurs. This envelop covers much of the operational range of typical production systems. A Couettte shear cell, Organic Solids Deposition and Control (OSDC) [Zougari et al, 2006], was used to test the deposition tendency of asphaltene on the coated surface at wall shears representative of field conditions. Both live oil and dead oil tests showed a significant reduction of deposits on the coated surface for the two oils tested.

Initial testing for calcite deposition tendency was performed using a benchtop Rotating Cylinder Electrode (RCE) device. Also, small scale flow loop tests were done to determine the impact of the coating on halite and barite deposition. The coating resulted in a reduction of deposition rate for both calcite and halite. For barite, there was a significant reduction in adhesion force between the scale and the coated tubing resulting in an easily remediated deposit. In this paper, we further refine the performance envelopes for calcite and barite with a systematic study investigating the impact of brine composition, wall shear rate and the presence of oil on both deposition tendency and adhesion force.

Based on the positive results of the performance testing, a commercial-scale application facility has been designed and constructed. Plans are underway to deploy the coating, where conditions are applicable, throughout the industry.

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