Biofilm activity, behaviour and our ability to control biofilms depends to a large extent on mass transfer phenomena in the biofilm, at the biofilm-liquid interface and in the bulk liquid. Biofilms respond to changing mass transfer conditions by adjusting morphology, thereby optimising the exchange of matter with their surroundings. Observing biofilm morphology and mass transfer in relevant fluid dynamic conditions can therefore yield essential information to understand and model biofilm behaviour. Lack of such knowledge, as the case is with regards to biofilm behaviour in various porous media, such as sandstone reservoirs, limits our ability to predict biofilm effects. A transparent porous media replica of a sandstone reservoir with cybernetic image processing has been designed to study biofilm related transport phenomena in porous media. The porous medium was inoculated with a mixed bacterial culture and fed a sterile nutrient solution in a once through flow mode. The biofilm was observed by microscopy with automated image analysis. This novel integrated software/hardware cybernetic design allows near real-time, essentially simultaneous, surveillance of several critical sites in the porous network and facilitates selective recording and compilation of observations as a function of the biological activity at each particular site. Biofilm biomass distribution in space and time (morphology and morphological changes) are thereby recorded at a representative selection of sites in the porous structure. Local in-pore flow velocity measurements were carried out by measuring the velocity of suspended particulate matter such as detached cells or clusters of cells. The influence of biofilm morphology on convective mass transport could thereby be observed and recorded. This effect, on a meso scale, was also monitored by sensitive, automated pressure drop measurements across the porous medium cell. Important observations so far include: • Bioweb; the biofilm morphology in porous media is very different from the “classical film”, as it appears more like a spider web where each strand varies in size and shape. • The biofilm maintains a large surface area and minimal biofilm depth, thereby minimising mass transfer resistance between the fluid and the biofilm phase, under the conditions tested. • The biofilm influences the convective flow through pores both locally within pores and effecting the flow distribution between pores. Pores with high initial permeability thereby become less permeable, diverting more flow to less permeable zones in the porous matrix. Large variations in this picture were observed, demonstrating the need for a sophisticated experimental apparatus with high sampling capacity to investigate such an intricate system. The observed biofilm behaviour in porous media has important theoretical and practical implications. Flow diversion and permeability effects are of immediate practical importance, improving the prospects for biological treatment of reservoirs. The information obtained in this study will be applied in mathematical simulations of ground water reservoirs, bioremediation and biological enhanced oil recovery.

Leif Hinderaker, SPE, Norwegian Petroleum Directorate, Rolf H. Utseth, SPE, Statoil, Odd Steve Hustad and Idar Akervoll, SPE, IKU Petroleum Research, Mariann Dalland, Bjorn Arne Kvanvik, Tor Austad, and John Eirik Paulsen, SPE, RF-Rogaland Research. Abstract RUTH (1992-1995) was a four year Norwegian research program on improved oil recovery funded by Norwegian authorities and 18 participating oil companies. This paper describes how the program was organized and highlights the main results. Research was performed within six main themes: Gas flooding, combined gas-water injection including WAG, foam, polymer-gels, surfactant flooding, and microbial method. Applications in Norwegian fields are discussed with special focus on field pilot tests. The program contributed to establish a pilot-activity on three new methods, WAG, foam, and polymer-gel, on the Norwegian continental shelf. Introduction An important goal for Norwegian petroleum policy has been to secure the best possible exploitation of the petroleum resources. The initiation and implementation of IOR R&D programs have been an essential part of the strategy to reach this goal. Several major Norwegian IOR programs have therefore been initiated since the nineteen eighties. These are listed on Table 1. The Joint Chalk Research program, dedicated to improving hydrocarbon production from Norwegian and Danish chalk fields, was launched in 1982 on the initiative of Norwegian and Danish authorities. The state sponsored SPOR program, which was carried out during 1985 through 1991, focused on IOR and EOR methods, and had as its main goal to build a national Norwegian IOR expertise. Two follow-up programs were initiated after SPOR: The PROFIT program, concentrating on "Reservoir Characterization" and "Near Well Flow", and RUTH. PROFIT was a collaborative program between 13 oil companies and the Norwegian Petroleum Directorate (NPD). About 50 million USD have been invested in these programs, including RUTH. RUTH (Reservoir Utilization through advanced Technological Help) was a cooperative IOR effort conducted by the Research Council of Norway, the Norwegian Petroleum Directorate, Norwegian research organizations, and 18 oil companies. The total program budget was 106 million NOK. The Research Council of Norway funded 55 million NOK, and 51 million NOK was funded by the participating oil companies (1 USD is about 6.50 NOK). The program lasted 4 years (1992-1995), and a total of 32 projects were performed. RUTH aimed at following tip the research topics included in the SPOR program which were not conducted by other programs, and to include new subjects of strategic importance. The main objectives were:–Contribute to increase oil recovery from sandstone and chalk reservoirs on the Norwegian continental shelf by 300 million Sm3.–Meet the authorities' specific and long-term requirements for research on advanced oil recovery.–Help Norwegian research groups to further develop an internationally recognized expertise that can be of use to the oil companies. Additional objectives were to concentrate on applied research that is related to advanced recovery methods and to help qualify advanced technology by means of field tests. Of the three main objectives, we believe the first objective will be reached through the use of the developed technologies, and that the other two objectives have been met. P. 251

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractDischarge of drill cuttings generated offshore while drilling with oil-based drilling fluids in the North Sea areas was banned in 1994. This paper outlines how oily drill cuttings may be used in soil, and presents results of a mesoscale growth experiment where fresh oily cuttings were used in plant growth media.Growth experiments were performed at meso-scale. A standard test species, Rye gras, was grown in pots containing oily cuttings mixed with different soils, and peat in varying ratios. The physical conditions of the oily drill cuttings were generally within current accept criteria for soil meant for agricultural purposes. Measured concentrations of heavy metals and organic components complied with current environmental standards. Analyses included crop yield, assimilation of heavy metals, soil chemistry, and toxicological tests in selected blends of materials. The collected data provide a basis in evaluation of alternative applications of the technology, and issues that should be addressed when environmental impacts in general are discussed.The experiments suggest that oily drill cuttings is applicable as a constituent of growth media, preferably used for cultivation of plants used for other purposes than consumption. Cuttings may be added in significant proportions to natural soils. Thus it should be considered as a viable alternative for final disposal of oily drill cuttings.