Egil Sunde

Microbial response to reinjection of produced water in an oil reservoir

The microbial response to produced water reinjection (PWRI) in a North Sea oil field was investigated by a combination of cultivation and culture-independent molecular phylogenetic techniques. Special emphasise was put on the relationship between sulphate-reducing bacteria (SRB) and nitrate-reducing bacteria (NRB), and results were used to evaluate the possibility of nitrate treatment as a souring management tool during PWRI. Samples were collected by reversing the flow of the injection water, which provided samples from around the injection area. The backflowed samples were compared to produced water from the same platform and to backflowed samples from a biocide-treated seawater injector, which was the previous injection water treatment of the PWRI well. Results showed that reinjection of produced water promoted growth of thermophilic SRB. Thermophilic fatty acid oxidising NRB and potential nitrate-reducing sulphide-oxidising bacteria were also found. The finding of thermophilic NRB makes nitrate treatment during PWRI possible, although higher nitrate concentration will be necessary to compensate for the increased SRB activity.

Field Experience From a Biotechnology Approach to Water Flood Improvement

This paper is based on a field implementation in the United States of a biological process for improving waterflood performance. The Activated Environment for Recovery Optimization (“AEROTM”) System is being developed by Glori in collaboration with Statoil and derives its roots from a microbial enhanced oil recovery technology developed and successfully implemented by Statoil offshore Norway. Unique among IOR technologies, AERO implementation requires virtually no capital investment and achieves high performance efficiencies at low operational cost. The simplicity of setup allows pilot project implementation creating a very low risk entry point for the operator. A pilot project was selected for a controlled investigation of the performance and impact. Robust testing was done in both water and oil phases prior to treatment, confirming the potential for improved sweep and conformance from the project. Subsequent implementation resulted in decreased water cut and increased oil recovery observable both at the wellhead and allocated pilot levels. This paper summarizes a rigorous analysis of the pilot project‟s performance to date, concluding that the production improvement should be credited to the implementation of the AEROTM System. Introduction An AEROTM (Activated Environment for Recovery Optimization) System field pilot was initiated at the Stirrup Field in southwest Kansas (Figure 1) to evaluate the potential improvement in recovery from a waterflooded reservoir. The field is at a relatively mature stage of waterflood and following robust testing of the water and oil phases, it was believed that the AEROTM System could enhance performance through improved sweep and conformance. Figure 1: Location Overview for the Stirrup Field Morton County, Kansas

New gypsum/polymer mud system eliminates gumbo problems on Tommeliten field production wells

The Tommeliten field is located west of the Ekofisk area in Block 1/9 in the Norwegian sector of the North Sea. Six exploration wells were drilled between 1977 and 1983, and the Gamma and Alpha chalk reservoirs were identified (Fig. 2). The Gamma structure was developed by subsea installations. In 1986 and 1987 four of six subsea-completed wells were drilled through a template from the semisubmersible {ital Ross Isle}. This paper compares Exploration Wells 4 and 5 and the first four development wells. Exploration Well 6 took an inordinate length of time to drill for various operational reasons and is not sufficiently representative to be included in this comparison. The compared section in this study is from 3,280 to 9,515 ft (1000 to 2900 m). Exploration Wells 4 and 5 were vertical. One development well was vertical, with the others having an inclination of about 20{degrees} in the 12 1/4-in. (31.1-cm) section.