Field Testing the Polysaccharide Schizophyllan - Single Well Test Design and Current Results
D. Prasad, B. Ernst, G. Incera, B. Leonhardt, S. Reimann, E. Mahler and M. Zarfl
Event name: IOR 2017 - 19th European Symposium on Improved Oil Recovery
Session: Pilot & Field Cases
Publication date: 24 April 2017
Info: Extended abstract, PDF ( 1.57Mb )
Price: € 20
A bio-polymer pilot flood is ongoing in Bockstedt, a mature oilfield in northern Germany. Bockstedt is a highly saline, moderately viscous, moderate temperature and darcy sandstone reservoir and is on waterflood since 1959. Previous results of Schizophyllan properties in lab and field have been published by Leonhardt et. al. (SPE 169032) and Ogezi et. al. (SPE 169158). The polymer has shown very good injectivity and even though positive response was observed in a producer, no breakthrough of polymer has been observed so far in the producer. To understand this fact, multiple single well tests (SWT) have been conducted in the field by injecting, incubating and back-producing, to check the biopolymer performance especially in terms of mechanical/biological/chemical stability. Single well tests were designed considering several factors. Based on ability to produce/inject from/into the well, representative condition like temperature, shear, microbes and ability to acquire production/injection log data, an injector well in the pilot block was selected. Additionally injection rates, biocide concentration/type were varied to check the mechanical/microbial stability. The injected and produced volume were designed in a way to minimize dilution and mechanical stressing of biopolymer. Progressive cavity pump was used to avoid shear in the wellbore during back-production. A very extensive lab surveillance plan was set up to understand dilution of samples from wellbore/reservoir, mechanical and microbial degradation. Viscosity, microbial growth, chemical analyses and structural analyses of biopolymer conformation were performed on baseline injection samples and back produced samples at different times. Chemical tracers assisted in quantifying dilution of the injected polymer slug while back-producing. Special sampling procedures (e.g. anaerobic, sterile, high pressure sampling) were developed to ensure representative reservoir sample and its preservation in order to avoid incorrect conclusion. This paper presents the lab and field initial test design, important learnings during testing and the main outcome of the multiple single well tests.