Sampling is always a vital procedure for conducting interwell tracer tests and timely sampling is most important in ensuring that a test is successful. The automatic sampler shown in Fig. 20 is designed to be installed at the well head. It can automatically collect seven samples within a planned period, e. g. over one day, one week or two weeks. The automatic sampler consists of a separator (A), a control unit (B), a mini-pump (C), seven water sample containers (D1-D7) and electromagnetic valves (V1-V12) (see Fig. 20). In many cases, the electromagnetic valves should be substituted with pneumatic valves due to the probability of gas leakage and the danger of an explosion caused by the electronic circuits.

The functioning of the automatic sampler is as follows:

(1) The multiphase flow enters through valve V1 into the separator.

(2) The produced fluid will charge the separator A and the oil and water separate continuously by gravity.

(3) The separated ‘oil’ phase on top of the separator is pumped back to the bypass pipeline through valve V2 when keeping valve V3 (drainage) and valve V4 closed.

(4) At the end of a set collection time, ‘old’ water from previous samplings is removed from the manifold by drainage through valve V5.

(5) The fresh ‘water’ sample from the lower phase inside the separator is transferred to the sample container (D1) by gravity by opening valve V5.

(6) After sampling, the remaining water in the separator is pumped back to the bypass pipeline by opening valve V4.

(7) Sequences 2-6 is then repeated for the remaining sampling bottles.

(8) Valve V3 is used for pressure release and drainage when replacing the separator equipment. Oil samples can be taken manually through valve V3 as needed.