Putting pressure on productivity

29 October 2019

Carefully selected measurement instrumentation and a suitable inventory management system help avoid the health and safety risks associated with the necessary chemical injections in the oil and gas industry and can also help reduce costs.

In oilfield services chemicals are often used to coat the side of a wellbore to improve stability. In pipelines they prevent build-up and keep the infrastructure healthy. So, in the oil and gas industry chemicals are regularly injected, in many different forms, into process lines and fluids. They protect the infrastructure, optimise processes, assure flow and in general improve productivity. 

Unfortunately, their use is not without risk – too little chemicals may lead to downtimes or process fluid clogging, while too much chemicals may damage the infrastructure and lead to empty supply tanks or may complicate the regeneration process. Measuring the correct density and the correct blending of multiple chemicals is vital. If too much pressure is used for the injection, production may need to shut down which can be very costly. 

Plant operations typically involve the interaction and coordination between different stakeholders, each looking after their own responsibilities and targets but sharing a common goal – to improve operations and to make them safer. Maintenance managers have to take single systems out of line for periodic maintenance checks, quality managers check the implementation of new safety rules, well managers seek to reduce chemicals density to prevent damage to the well and operations managers often want to use more viscous materials to minimise the risk of build-up. 

To align all of these demands requires a clear automation concept which offers a future-proofed solution. Inventory management systems support the operator by improving regeneration processes and assisting with optimal fluid orderings. This leads to additional cost-savings and answers the demands of different stakeholders. 

But how does it work? Take, for example, the injection skids for the oil and gas production and for the pipeline infrastructure. Every injection line is typically equipped with a flow meter – usually mass flowmeters – a pressure transmitter, temperature control and a pressure regulator to control the pressure of the injection. An inventory management system compares the tank level measurement of the skid with the main inventory measurement, derives trends and optimises the just-in-time principle of inventory management. Future requirements can be matched with current inventories and supplies are ordered in good time to avoid running out of chemicals to inject. 

By processing injection rates and level measurements in one system, operators are able to detect differences in measurements. When comparing in mass, the sum of injections should be equal to the levels measured in the tanks. In case of discrepancies, system connections need to be checked for leaks or erroneous injections. Measuring the individual tank level and the injection rate also helps optimise blending volumes. A backup or safety system ensures the correct blending, based on the density or tank level compared to plan. During pressurisation and flow injections the infrastructure is facing a higher risk of damage. Reliable pressure and flow measurement instruments are crucial to optimize injection performances and contribute to resource conservation.

Among the most important selection criteria are liquid compositions, temperature and pressure ranges, flow rates, the location of an installation and specific certificate requests. Weight is also important as chemical injection skids often are used on offshore platforms. Since the risk of over-pressurisation is minimal, a compact pressure transducer with a 4 to 20 mA analog signal is generally a good choice for single line use. The signal goes to the system DCS, where the operator monitors the individual line pressures. 

Device data is provided via software interfaces and webserver technologies. It is crucial to ensure flexible and to the data for everyone who needs it for decision making. As data now is available in electronic form, the reconciliation between inventory management systems and ERP systems is becoming increasingly efficient.

Going one step further: if data relating to the chemical inventories is shared between operators and suppliers, proactive resupply of raw materials is improved as part of an integrated supply chain management. With proper data monitoring about current product consumption and inventories, suppliers are enabled to plan just-in-time shipments, resulting in higher production continuity while keeping inventories to a minimum. 

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