Shrinkage Tester FAQ

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Shrinkage Tester FAQ
Q. What is a shrinkage tester? A. It is a device which allows well testers to easily determine the shrinkage rate of the freshly separated oil at the well site. This is important to know because oil shrinks over time; one BBL of oil at the wellhead may reduce to .9514 of a BBL after a few days due to cooling and the dissipation of gas and volatile compounds. Shrinkage makes buyers very unhappy since they receive less than they expect. Knowing the shrinkage value allows the sales rate to be adjusted; a buyer is charged for 1 BBL when in fact 1.05 BBL may be put into the pipeline at the wellhead.	Shrinkage Tester (behind ladder) Mounted in a Test Separator
Typical Shrinkage Tester	Q. How does a shrinkage tester work? A. The shrinkage tester includes a sight glass calibrated in percentiles to review current oil flows. Typically, a valve is opened that pressurizes the shrinkage tester to the same pressure as the separator, then oil is allowed to flow into the unit from the separator. The process is controlled by the well tester until 100% of scale is reached, then the oil flow is shut off, followed by shutting the pressure equalizing valve. This fresh sample is slowly opened to atmosphere allowing entrained gasses and volatiles to escape as well as cool. As the gas volume in the test chamber is reduced, the oil volume shrinks. Using an establish time factor against the oil's API density, a tester can determine the percent of error in the oil flow meter via the shrinkage percent scale.
Q. How accurate is a wellsite shrinkage tester? A. It is adequate for field calculations. Other factors, especially secondary and tertiary downstream separators will cause additional shrinkage -- after all, that's the reason they exist, to further remove undesired consituents from the oil. Typically, shrinkage tests are done after each separator in the pipeline to accurately determine the total shrinkage from wellhead through delivery.	Q. Does Mountain Equipment sell shrinkage testers? A. Yes we do. Well testers often ask us to include a shrinkage test unit built into the Test Separator. We also sell them separately. Q. How much does a shrinkage tester cost? A. Please call for price and delivery.
Q. How is a shrinkage tester operated? 1. Make sure valves E and Drain valve are closed then open valves B and C. 2. Slowly open valve D until the pressure in the shrinkage tester equalizes with the pressure in separator vessel. It is very important the pressure matches between the two *before* filling the shrinkage tester in step 3. 3. SLOWLY open valve A and monitor the rising fluid in sight glass until 100% is reached on the scale, then CLOSE valve A. 4. Open needle valve E very slowly to allow trapped gas in upper shrinkage tester chamber to escape to atmosphere. 5. At this time valves B, C and E should be the only valves open. 6. Allow 12-24 hours dependent upon oil API to achieve oil free of gas. 7. The final level taken from the adjacent scale is to be applied to the oil meter reading for accurate factoring -- this is commonly called the "shrinkage factor", here's how to use it: Number of BBLs from meter reading times percent from scale equals oil shrink factor, i.e., 200 BBL x 93% equals 186 actual BBLs through oil meter after shrinkage. 8. Open drain valve and allow oil to drain into a safe catch basin.