A single well polymer injection and back-production test has been performed at Heidrun, an offshore oil and gas field in Norway. The objective of the test was to verify at field conditions the properties measured in the laboratory for the biopolymer Schizophyllan. This test was part of a polymer qualification program. This paper will give an overview of the single well test and lessons learned.
To ensure high quality data from the test, all elements in the test required detailed planning and following up, including an extensive quality check. The successful execution of the test was possible through a joint active collaboration between the operator, the biopolymer supplier and the service providers. The first focus was on the logistical chain from production of biopolymer, transportation and quality checking prior to injection. The second focus was on the injection, including qualifying polymer mixing equipment for offshore use and preparation for using an injector for both injection and back-production. The third focus was on sampling and analysis where high quality sampling and analysis was a prerequisite for getting conclusive results.
The test was an operational success with no HSE incidents and delivery of an extensive data set, including pressure, temperature and flowrate data as well as of fluid samples. A total of 3,500 m3 of polymer solution including biocide was injected as planned, followed by a short back-production period of 195 m3 for baseline sampling. The remaining polymer solution was shut-in for 39 days before final back-production of 365 m3. Both during injection and back-production samples were taken for later analysis and evaluation of results.
The data confirms that the biopolymer is not being biodegraded during the shut-in period due to efficient application of the biocide injected simultaneously with the biopolymer. The rate and pressure data also supports that the injectivity is maintained during the test compared to water injectivity.