Topic last reviewed: 10 April 2013
Sectors: Downstream, Upstream
Commissioning and start-up are the phases of a project when gas is introduced into new facilities and equipment to test the production of the sales products (oil, gas, LPG, condensate, etc). Start-up follows an extensive pre-commissioning phase involving thousands of individual systematic tests to ensure that the newly-installed equipment can be safely operated. Some of the activities that typically occur during this time are testing of the power systems, pipelines and tank integrity, and the checking of offshore production platforms and lines which bring gas from offshore, as well as the testing of safety systems. Generally, the gas introduced during the commissioning phase is disposed of by flaring. Following the successful completion of commissioning, the plant is started and begins production.
Some examples of good practices to reduce flaring during pre-commissioning, commissioning and start up for new projects or expansion projects are provided below.
During the project phase, identify critical instrumentation (sensors, valves, etc.) and systems that could, if they malfunction, induce operational flaring, and ensure that all devices are of adequate quality. For valves connected to the flare, the appropriate valve type and valve trim should be selected to ensure that they can provide a tight, long-term shut-off. Selecting the incorrect valve for the purpose may result in leakage as there is a large performance difference between different types of control valves. Cage-guided globe valves with hardened trim will ensure low valve leakage over the long term. This kind of control valve can be specified by default, and hardened trims are mandatory for certain differential pressure thresholds.
Before commissioning the project, the project team should issue a ‘plan’ to reduce initial start-up flaring, that includes: the schedule for commissioning; flaring and venting profiles including well drilling, testing and workovers; and mitigation measures. The efficiency of such a plan will be improved if start-up flaring minimization objectives have been given to the engineering, procurement and construction (EPC) contractor at the project definition phase.
During commissioning, several tests and avoidance measures can be taken to avoid start-up flaring, including:
- Testing of the power generation system and main energy consumers using diesel (before fuel-gas in) or fuel-gas (coming from another facility or a network). If the power generation system has not been tested with product quality fuel prior to start-up, there is a risk that any issues encountered during start-up may lead to the flaring of significant volumes of process fuel-gas. The testing of the power generation system prior to start-up can help to avoid this risk of start-up flaring.
- Always perform a high pressure (HP) test of the larger valves connected to the flare system (pressure control valves, blowdown valves, etc.) to check for internal leaks (see the template for Passing valves (leakage)).
- Replace all control valves with spool pieces before flushing and leak testing. Many control valve trims can be damaged—even before initial start-up—from solid particles that stick inside the trim during flushing and leak testing. This trim surface damage may lead to continuous valve leakage during production operations.
- Ensure that all production equipment is in place and fully operational prior to testing process units with a high potential for start-up flaring (e.g. perform well completions only when the separator and gas pipeline infrastructure are in place).
|Years experience in the industry:||21+|
Range of application:
|Process units routed to flare system|
|Efficiency:||Losses due to start-up flaring can be significantly reduced by implementing good practice measures|
|Guideline capital costs:||Insignificant|
|Guideline operational costs:||Cost savings from gas recovery|
|Typical scope of work description:||The typical scope of work to avoid start-up flaring would entail the development and execution of a Flare Minimization Plan that: identifies potential flaring events, causes and abatement measures; establishes goals and performance indicators; and integrates root cause analysis and continual improvement concepts.|
|Technical:||Infrastructure availability for production|
|Operational:||Start-up plan to minimize flaring|
Training of operators
|Commercial:||Saving energy and fuel cost|
|Environmental:||Reduction in air emissions of nitrogen oxides, sulphur dioxide, mercury, particulate matter, and greenhouse gases (GHGs).|
The following are technologies that provide similar benefits and may be considered as alternatives to start-up flaring minimization:
- Passing valve inspections
Issues and risks are few and known. Flare reduction technology has been used for many years. If good practices are not followed, the risk of significant flaring during start-up may lead to environmental and safety concerns.
- CAPP (2006). ‘Best Management Practices for Facility Flare Reduction’. Publication no. 2006-0018, Canadian Association of Petroleum Producers, Dec. 2006.
- OGP (2000). ‘Flaring and venting in the oil and gas exploration and production industry: An overview of purpose, quantities, issues, practices and trends’. Report no. 2.79/288, International Association of Oil and Gas Producers, January 2000.