A pioneer application of downhole tracer injection in geothermal production wells

Abstract

The principles of tracer flow testing were implemented to test the assumption of a down flow within a geothermal well bore’s open hole section in Ngawha geothermal field.
The production well had a pre-existing anti-calcite dosing system, however it had lower than expected calcium returns compared to those typical with the fluid chemistry in the geothermal field. The possibility of a small down flow existing above the dispersion head needed to be eliminated as one of the possible causes, prior to investigating other hypotheses.
To verify this possibility, a downhole tracer injection test was planned and conducted in conjunction with a standard surface tracer flow test. The test results show that both downhole tracer injection and standard surface tracer flow tests achieved almost the same flow rate and total enthalpyresults. These tests have proven that full returns were taking place at the current dispersion head set depth.
In addition, these tests have also proven that even with a lessthan-optimal tracer mixing distance, a homogeneous tracer flow in the two-phase pipeline can be achieved.