Optimizing Chemical Injection

Chemical injection on offshore platforms is used to control corrosion, hydrate formation, and wax/asphaltene/scale/emulsion buildup in the well or piping to the separation and finishing process. The cost of the chemicals used can add up over time. And problems with the injection can lead to excessive corrosion. Optimizing the use of these chemicals helps improve operational performance. Under injection can lead to the problems mention above and over injection wastes chemicals and money, not to mention the additional storage space and weight required on the platform.

Anthony Hartman and Wendell Love at Emerson ExchangeEmerson’s Anthony Hartman and Wendell Love presented on how to optimize chemical injection operations. Anthony shared an example of an offshore producer having hydrates forming costing lost production of a $1 million per day. For one 8-well platform, injected chemicals cost $175 million annually. Every platform and most every onshore well pad will have chemical injection processes.

Without optimized injection, most operators tend to over inject to avoid the corrosion and other issues. Some operators have technicians manually adjust the injection rates every four hours which is quite man intensive.

Wendell discussed one oil & gas producer who had an offshore corrosion inhibitor skid. The injection control valve plugged every few hours and maintenance was required to bypass and unplug the valve. There was no online monitoring or control of the skid.

The skid had 12-15 control valves per skid. Flow rates varied from 5 to 40 gallons per day at a pressure of 1350psi. Flow measurement was performed using Micro Motion Coriolis meters for each well.

The solution to the plugging involved replacing the manual devices with TESCOM 56 series flow control devices without any plugging issues. The need for dedicated operators to look in on the skid frequently was no longer required. System flow rates of the chemicals could also be tied to the actual well production rates saving the platform more than $350,000 in chemicals annually for the single platform.

The TESCOM devices handle the changes in downhole pressures to manage the rate of chemical injection required. The operator selects the flow rate setpoint for the TESCOM flow control device. It can provide active control from 0.04 to 37 gallons per minute, with an accuracy of 0.1%.

Given the accuracy of the Micro Motion meters and TESCOM flow control devices, the accuracy of the chemical injection control is great. Additionally by adding Roxar or Permasense corrosion sensors, closed loop control can be achieved to control injection based on corrosion levels seen by the sensors.

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