This article describes the sampling analysis procedure for sand control: conventional and side stream filtration method.
1 Conventional procedure
By passing the oil sample through a sieve of a given size the sand particles can be separated from the oil and collected. The sand particles collected can be measured and related to the size of the sample to produce a sand production rate for the producing well.
1.1 Apparatus/chemicals
ASTM sieve 325 mesh (44 um or 0.045 mm)
Hand centrifuge with 10 mL graduated centrifuge tubes
Pail or bucket - for collecting crude oil filtrate
Measuring jug or cylinder (2 Litres)
Plastic wash bottle
Collecting beaker
Glass or metal rod
Demulsifier (currently in use
Detergent (e.g. Teepol concentrate)
Distilled water/clean tap water
1.2 Method
1. Sample from the well bean box 4-8 litres of crude oil in a suitable container. Note: Flush the sample point prior to sampling to eradicate any possible particle accumulation.
2. Add 4 - 5 drops of demulsifier to the sample (see note).
3. Shake sample container vigorously before sieving to ensure all sand is suspended while decanting.
4. Sieve the oil sample with constant agitation/stirring through a clean ASTM sieve 325 which is placed on top of a collecting bucket.
5. For viscous crude or stable emulsion, which do not sieve through easily, add a known amount of detergent concentrate or demulsifier to the sample and continue sieving with constant stirring.
Upon completion of step 5 note the total volume of oil filtrate after sieving collected in the bucket.
6. The volume of detergent used must be subtracted from the total volume of oil filtrate measured after sieving to give the actual crude oil sample being filtered. If detergent volume is small enough, it can be ignored.
7. On completion of sieving, wash the sieve containing sand particles with detergent solution to remove traces of oil.
8. Finally wash the sand particles carefully into a clean beaker with distilled water or tap water in wash bottle.
9. Transfer all the sand particles from the beaker into a graduated 10 mL centrifuge tube via a funnel.
10. Fill to 10 mL mark with distilled or tap water. Hand centrifuge for 2 minutes.
11. Note the mass of sand collected at the bottom of the tube.
Remark: With the availability of precision electronic weighing machines, it is less cumbersome and more accurate to dry the sand and weigh it.
2 Side stream filtration method
2.1 Principle of the Method
A sample of produced fluid is passed through a series of three sieves. The residue is washed with solvents to remove excess oil, wax and water. The volume of the residue is measured after drying. A density factor is applied and the weight of sand produced is related to a unit volume of produced fluid.
For the results obtained by this method to be meaningful, the well being sampled must be in a stable flow state. It is important that no sampling be done until five hours after a bean change.
2.2 Apparatus
Sieve holder. 100 mesh sieve complete with dispersion plate. 200 mesh sieve. 325 mesh sieve. 3 "0" rings 2 gaskets. 1/4" metal support ring. find brush. graduated centrifuge tube.
2.3 Chemicals
Toluene. Acetone.
2.4 Sampling
1.Aassemble the sieves in the holder with the steel ring at the base and each sieve separated by an "O" ring.
2.From the top the order of assembly is:
a)100 mesh sieve complete with dispersion plate
b)200 mesh sieve
c)325 mesh sieve
d)metal support ring.
3.The seal at either end is completed with gaskets.
4.Referring to Fig. 760 connect the sieve holder to the flow line by means of the snap couplings.
5.Close valves A, B, C, D.
6.Open valve A fully.
7.Open valve B fully.
8.Use valve C to direct the flow to dump.
9.Continue to dump until the line at C feels warm.
10.Redirect the flow to the sieve holder through C.
11.Over a period of 10 seconds gradually open valve D fully. This gradual operation of D helps to prevent wax deposition on the sieves.
12.Sample through the sieve holder for three minutes into the container.
13.Record the THP.
14.Close valves C, B and A.
15.Remove the sieve holder.
16.Cautiously remove the sieves from the holder so as not to lose their contents.
17.Determine the volume in litres of produced fluid passed through the sieve holder during sampling.
18.Install clean sieves.
2.5 Analysis
Wash the sand in each sieve with toluene. Wash the sand in each sieve with acetone. Allow the sand to dry. Brush the dry sand from each sieve into the same graduated centrifuge tube. Measure the volume of sand in cm3.