THE ROLE OF THE "CHASER" IN "PUSH-PULL" TEST
However, the role of the chaser on the shape of the acquired tracer breakthrough curves during the pull-phase is unknown. Also the determination of the right volume for the chaser is a difficult task. The volume should be enough to fill the whole well and gravel pack volume, but should not reach the aquifer. In most cases the exact effective porosity of the gravel pack and accordingly its volume is unknown and therefore has to be estimated.
In our project, push-pull tests are investigated for their applicability as single-well tracer test method. One target is its method development and standardization. Therefore, also the role of the chaser was investigated by conducting six individual tests, each with different injection volume. By testing different chaser volumes, conclusions can be drawn about the optimal volume for the later field test campaigns. Furthermore, it seems to be possible to draw conclusions about the quality of the gravel pack and about potential dead volumes within the flow system. It was shown that a chaser test campaign prior to the main push-pull test is a very fast and easy method, which significantly helps to improve the results of the main test.