Test Separators for Well Testing FAQ

What is a well test separator?

A well test separator is a pressure vessel that uses gravity to separate sand, natural gas, oil and water from each other. It is rigged up to a new well by a well testing or flowback company soon after the well has been drilled and completed. In addition to separating the well stream into its constituent components, the well test separator records the volume of each component over time, allowing the flow rates to be calculated, most often as barrels per day or "MMSCFD" (million standard cubic feet per day). This allows the tester to figure out how productive the new well is and gain insight into the underground reservoir that holds the oil and natural gas into which the new well has tapped. A 3-phase test separator handles the separation of oil, gas and water while a 4-phase test separator can also separate sand and small particulates.

How is the flow data captured?

A well test separator is usually equipped with a recording device or devices that enable the gas, oil and water flow rates, pressure, and temperature to be recorded over time. The most common recording device is a chart recorder which is used to capture data about the gas flow rate. Turbine meters combined with digital displays called "totalizers" capture the flow rate data for the oil and water being produced. As technology evolves, the chart recorder and totalizers are being replaced with integrated “flow computers” that record gas, oil, and water flow rates in addition to pressure and temperature data in digital format. Flow computers can store the data locally or can be set up to transmit it — usually by cell or satellite — to a central server which can render and serve the data to web browsers anywhere in the world.

What sizes of well test separators are available?

Test separators typically range from small 24" OD (outside diameter) by 8' long s/s (seam-to-seam) to very large 60" OD x 20' s/s units. The bigger the unit, the larger the flow it can separate. For instance a 30” x 10’ x 1440# psi wp (working pressure) unit can separate 6,250 barrels of oil and water (combined) per day and 27 MMSCFD of natural gas at 1 minute retention time. If you are unsure what size separator you need, please contact Mountain Equipment and provide the projected flow rates you will need to handle for the reservoir you intend to test in. If you don’t know the projected flow rates, ask the Company Man, reservoir geologist, or well tester. Click here for In Stock test separators.

What is the difference between a 3-phase and 4-phase Test Separator?

A three phase separator separates the flow into natural gas, oil, and water while a 4-phase separator also will separate particulates, especially sand, from the flow. In a four phase separator the flow comes into the vessel and hits a heavy-duty plate that breaks up the flow. The sand and particulates drop out off the flow and settle on the bottom of them vessel and are contained behind a weir plate call the sand weir. In advanced 4-phased separators a special jet, called a "sparger", enables the well tester to purge the accumulated sand and mud from the bottom of the vessel without shutting in the well.

What are the flow rates for the Mantis Well Test Separators?

Test Separator Flow Rates
Product ID OD x Length x Pressure Oil & Water @ 1 Minute Retention Gas @ 1000 psi per Day
Mantis Test Separator TS-1 30" x 10' x 1440# 6,200 BBL/Day 27 MMSCFD
TS-2 36" x 15' x 1440# 13,200 BBL/Day 47 MMSCFD
TS-3 42" x 10' x 1440# 12,700 BBL/Day 54 MMSCFD
TS-4 42" x 15' x 1440# 18,150 BBL/Day 65 MMSCFD
TS-5 48" x 15' x 1440# 24,100 BBL/Day 83 MMSCFD
TS-6 54" x 15' x 1440# 27,500 BBL/Day 104 MMSCFD

What is retention time?

Retention time refers to how long the flow from the well is actually inside the well test separator and how long it takes the flow to transit from the inlet to the respective outlets (the gas, oil and water outs). The longer the retention time, the better the resulting separation into natural gas, oil and water. One minute is considered the minimum amount of time the flow should be in the test separator. Two and three minute retention times are considered better, but of course, each minute of retention reduces the daily output. For instance, the 30" x 10' x 1440# psi test separator mentioned above only produces 3,125 barrels of oil and water (combined) per day at two minutes retention time. That is why you may see larger test separators like 36" x 15' units being used on smaller wells. The other important thing to consider is vessel length; the longer the test separator, the greater the internal surface area and therefore the better the separation of gas from the liquids.

What does "coded" or ASME certification mean?

Test Separator ASME TagA "coded" vessel is a vessel that is built to the exacting standards of the American Society of Mechanical Engineers (ASME) and inspected by an ASME inspector. The ID plate attached to the vessel will show a "U" stamp if it is a ASME coded vessel. Most company sites require the use of coded vessels to ensure the safety of the site as well as to meet insurance requirements. You may be asked by the Company Man to verify your vessels are ASME certified. Sometimes simply showing the ID plates will suffice, especially for vessels built in the last few years. However, you may need to supply documentation such as a U1A Data Form as well. This form is generated by the ASME inspector and is then given to the vessel manufacturer. Other items you may be asked for include a current hydro-test chart, a recent Ultra-sound (UT) test, MTRs (Material Test Reports), a vessel drawing, and NACE certification of all wetted parts including the vessel if the vessel will be used in an H2S environment. For more information about ASME and U stamps, see our Buyers Guide.

Is ASME a world-wide standard?

Unfortunately, no. Though many countries will accept a coded ASME pressure vessel, not all will. For instance, each province of Canada requires a Canadian Registration Number (CRN) for that province.

Do you build test separators for sour service?

Yes, we build to NACE MR-0175 (latest edition) standards. Please let your sales person know if you need NACE. Be aware that NACE costs more and adds time to the fabrication process.

Do you build well test separators for pressures other than 1440# psi?

We specialize in 1440# psi working pressure, ANSI 600, test separators. We can build to higher pressure, but the lead times will run longer since we do not keep the all the parts needed in stock.

Once an order is placed, when will the test separator be ready to ship?

It depends on the model of well test separator ordered. For instance, our Mantis TS-1 (30" x 10' x 1440# psi wp 3-phase) is a standard item; we may have some in stock or a short lead time. A larger unit like our Mantis TS-5 (48" x 15' x 1440# psi wp) model will take longer, since we may need to build the separator vessel first, before finishing it as a fully functioning test unit. Please discuss your requirements with your Mountain Equipment sales person.

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