In the oil and gas industry, tests of all sorts are a regular part of running an operation. Running tests are the only way to discover important information.
Production tests are run to obtain an indication of well productivity and are carried out to determine its flow capacity at specific conditions of reservoir and flowing pressures. Testing on oil and gas wells may be performed at various stages of drilling, completion, and production for a variety of different purposes.
Each test is designed to reveal specific information about a well and how it is behaving.
Gas Well Testing
Originally wells were tested utilizing the “absolute open flow” technique which was highly undesirable within the industry since there were conservation and safety risks associated. The oil and gas industry then began testing with controlled flow rates to reduce these risks and started with the “conventional back pressure test” method. Then came the more practical testing methods such as “isochronal testing” and “modified isochronal testing”.
Isochronal testing is a multi-rate test designed as a series of drawdown and buildup sequences at different drawdown flow rates, with each at the same duration and each buildup reaching stabilization at the same pressure as at the start of the test (Definition from the Oilfield glossary).
Recently, testing has been made up of a combination of flow and shut-in periods and with greater complexity for well testing providing greater accuracy for volumes and understanding.
Today, there are two types of acceptable well tests conducted on gas wells:
- Tests for deliverability
- Tests for knowledge of the reservoir
Well testing is typically performed by directing well production through a three-phase separator as indicated in figure 1 or if hydrocarbon liquids are too small to be measured during typical well test durations then a two-phase separator may be used.
The test must begin only after a liquid level stabilization period.
- The test duration must be a minimum of 12 hours;
- After production begins at the proration battery, all wells must be tested within the first month, then again within six months, and thereafter annually. New wells added to the battery must be tested within the first month of production, then again within six months, and thereafter annually;
- Consistent testing procedures must be used for consecutive tests to identify if a change in a well’s flow characteristics has occurred;
- These wells are typically tested by directing flow from the well through a test separator. If the initial testing with a separator shows a liquid-gas ratio (LGR) of less than 0.01 m3 liquid/ 103m3 gas, other testing methodologies, such as a smaller separator or a single test meter without separation, could be used for the next test. If the total liquid volumes at the group measurement point exceed a ratio of 0.05 m3 liquid/ 103m3 gas in any month, a test separator must be used to test all the wells within the battery for the next round of testing to determine where the liquid originated;
- The gas, condensate, and water volumes must be measured;
- The condensate must be sampled during every test and subjected to a compositional analysis, which is to be used to determine the gas equivalent factor (GEF). The sample may be taken from the condensate leg of a three-phase separator or the liquid leg of a two-phase separator (The water must be removed from the condensate before conducting the analysis);
- The GEF must be used to convert the liquid condensate volume determined during the test to a GEV, which will be added to the measured test gas volume to determine the total test gas volume if the condensate is not delivered for sale at the group measurement point (see section Directive 017 7.3.2);
- The WGR, CGR, and OGR (if applicable) must be determined by dividing the test water, condensate, and oil volume respectively by the total test gas volume; and
For orifice meters, the test gas meter must use 24-hour charts for a test period of 72 hours or less, unless electronic flow measurement is used; for testing periods longer than 72 hours, 7-day charts may be used, provided that good, readable pen traces are maintained (see section Directive 017 4.3.4).
Financial Impacts of Improper Testing
Business processes and field level procedures often introduce significant business risk; specifically with respect to regulatory compliance and enforcement, business reputation and potential financial loss. Some financial impacts of improper testing may result in:
- Over-sizing of gas gathering equipment (compressors, pipelines, etc.)
- Over-payment of royalties due to over-reporting of gas production volumes
- Potential for over-payment of carbon taxes
- Test frequencies exceeding regulatory requirements for low gas producing wells
- Enforcement action resulting in facility suspension
Energy companies in Alberta must test their wells on a regular basis to
- measure each well’s productivity and performance over time,
- manage oil and gas reservoirs,
- identify resources that are trapped beneath the surface, and
- meet reservoir production and pressure requirements.
After performing high-quality well tests, companies must follow the technical procedures listed in AER requirements. When each test is over, they are required to submit the results for regular compliance with Directive 017, 034, 040.
If you are seeking well testing services, consider an energy services provider such as Intricate with their leading expertise and equipment to get the job done.
Intricate’s Gas Production Testing Solution
Through the implementation of the AER’s Enhanced Production Audit Program (EPAP), Intricate has identified many instances where current business processes and field procedures for periodic updates of gas production from oil wells does not meet the requirements set out by the regulator.
Intricate has designed, manufactured and fully integrated an automated gas production testing solution for conventional and heavy oil production facilities.
This production testing solution consists of accurate gas measurement equipment with current capabilities of:
- Gas Rate Testing (Without separator / conversion to GOR)
- Oil Well Testing (Gas Rate / GOR / With or without GIS)
- Integration with corporate initiates and production auditing
- Multi-level approval of tests (can be customized to your specific needs)
- 100% digital workflow
- Compliant with regulatory measurement uncertainty requirements for Western Canada
- Efficient data connectivity
- Production audit trail report delivery
Since Production tests are an essential part of any operation, and the key to obtaining an indication of well productivity we suggest you be sure find a provider with accurate reporting!