Field Operations

Well Testing on Location: Setup, Flow and the Data That Pays

A production well test is one of the most repeated jobs in the oilfield. A crew hooks a well to a separator, chokes the flow, and measures what comes out. The numbers decide what the well is allowed to produce, how fast it declines, and what gets paid for. Here is the setup-to-report workflow that keeps the numbers honest.

Why wells are tested

A well test is not a formality. The operator and the state both use the results.

• Allowables. Regulators such as the Texas Railroad Commission set production limits for wells and fields, and reported test data supports those allowables.
• Decline analysis. Regular tests show how production falls over time and when a well needs attention.
• Reservoir data. Flow rate and pressure tell the engineer how the reservoir behaves and what the next step should be.
• Sales verification. The volume measured at the separator is the volume that should turn up at the sales point.

The test setup

The heart of the setup is the test separator. A three-phase separator splits oil, gas and water, and each stream is measured on its own. The crew rigs the hookup around it: the choke, the gauges, the sample points, and the dump valves that let each phase leave the vessel. The choke sets the rate. The gauges read the pressure on either side of it. The sample points let the tester catch a clean sample of each phase for the lab.

Safety before flow

Nothing flows until the hookup is proven. The order of checks matters.

• Gas test. The crew checks the hookup for leaks before any pressure gets near the well.
• H2S check. If the well can make hydrogen sulfide, the crew confirms the gas detection gear and breathing protection are on site and working, and the H2S contingency plan is current.
• Pressure test. The vessels and piping are tested to their rated pressure, so a weak connection shows up before it is asked to hold live flow.
• Exclusion zone. The area around the test equipment stays clear, and everyone on site knows the shutdown plan.

Running the test

The well is opened against the choke and the separator takes the flow. The first minutes tell a lot, but no numbers are taken until the flow stabilizes. Stabilized flow means the rates and pressures hold steady instead of climbing or falling. The flow period then runs for the agreed time, long enough for the separator to cycle several times.

During the period the tester watches the gauges, logs the rates, and keeps an eye on the dump valves. If the well is making water or sand, or the rates wander, the tester calls it before anything gets logged. A short, clean flow period is worth more than a long one that never settles. A well that just came off a wireline or coiled tubing job often gets tested right away, so the crew can confirm the intervention did what it was supposed to do. The same discipline carries over to flowback after a frac, when the recovery crews handle water and bring the well back on production.

Measurement

Measurement is where the test is won or lost. Oil and water volumes come off the separator dump counters, and sampling or a meter sorts the water cut between them. Gas goes through the meter at the separator outlet, and the reading is corrected for pressure and temperature. The tester takes samples at the sample points, labels them, and sends them with the run data. Where the well produces to a tank, the tester gauges the tank before and after the run, because the tank level should agree with the separator counters.

Measurement practice in the United States follows the American Petroleum Institute's Manual of Petroleum Measurement Standards. It covers everything from tank gauging to meter proving, and it exists so two people measuring the same oil get the same answer. When the numbers disagree, the test is run over. It is never patched.

Recording and reporting

The test report is written on location, not back at the office. It carries the well identification, the choke size, the flow period, the measured volumes, and the samples taken. The tester signs it and the operator keeps a copy. Where the state requires production reporting, the reported numbers should match the test reports on file, because the state report is built from them.

From test report to job ticket

The paperwork is where a good test pays. The report becomes part of the field ticket for the job, and the ticket drives the volumes, the billing, and the state report. When the test report rides with the ticket, the office and the state report see the same numbers. Software such as OpsFlo tracks field tickets, dispatch, approvals, timesheets and documents for oilfield service companies, so the report, the ticket, and the paperwork stay together from the location to the office.

A test that is measured well but written down badly is a lost test. A test that is measured well and recorded well is money in the bank.

Sources and further reading

• Texas Railroad Commission: Oil and gas (allowables and production reporting)
• API Manual of Petroleum Measurement Standards (MPMS)