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

Statoil's ambition is to recover 55% of the STOOIP from subsea fields. To obtain this, extensive R&D efforts are required on all technology areas involved. Statoil's policy has been to establish strategic research partnerships with major suppliers and service companies, ideally with a 50/50 cost split between the parties. The partner selection process has normally been based on combined tender and architect competition, with a broad range of selection criteria. Implementation of the new technology is secured as far as possible by early commitments from the potential users among our assets. The users are also kept involved in all phases of the project, on an engineering level as well as on the management level. This both helps ensure the project is heading in the right direction and makes people responsible for implementation familiar with the new technology. Statoil subsea R&D efforts have already led to significant results. Several technologies are now being taken into operation according to plan. The most important being:A new ship for low cost subsea intervention (USD 150 000 per day) is in orderEquipment for subsea low cost TTRD sidetracks (USD 10 mill per drainage point) is ready for operation autumn 2007A complete subsea process plant is under installation in the Tordis field and will be in operation before the end of the year Introduction Comparing the present ultimate oil recovery of subsea fields with fields based on dry wellheads we see a significant difference in favor of dry wellheads. For Statoil operated offshore oil fields the average recovery levels are close to 45% and 60%, respectively. Even though these numbers are high in comparison with a world wide average, the ambition is to increase the recovery by another 10% points (Ref. 1). In Statoil's effort to reach this ambition the R&D portfolio addresses all the relevant technology areas. The different focus areas are:Ability to identify more accurate where the oil is located and its volumeImprove modelling of the production process and thereby the production strategyReduce cost of well construction and well interventionReduce cost and increase flexibility of subsea InstallationQualify pumps, compressors and other process equipment for sea bed installationImprove sensor technology, data transmission and data handling in order to make improved decisions There are no obvious inherent factors like reservoir properties or drilling challenges responsible for the gap in recovery between subsea and platform developments; it is solely a consequence of the economic reality operating subsea versus from a fixed installation. Our experience is that, all other parameters the same, recovery is a function of reservoir infrastructure (i.e. total number or density of drainage/injection points during the life of the field), access to well intervention and ability to minimize the wellhead pressure. Today the cost of a subsea well, all infrastructure included, is in the range 4-6 times the cost of a platform well.

Modeling of gas injection into an undersaturated oil reservoir using current simulation technology relies on the validity of assuming instantaneous equilibrium between the oil and the gas phases. This assumption makes the calculated performance highly sensitive to the size of the grid blocks. In particular, the calculated breakthrough time of the injected gas is underestimated. This is primarily due to the equilibrium assumption that requires the gas to saturate the oil in each individual grid block before flowing to the next block. A method is presented that treats the transient resolutioning of gas in oil within the framework of a practical reservoir simulation model. The inclusion of nonequilibrium mass transfer requires that the simulator include one mass balance equation for each component in each phase. A heuristic mass transfer model that governs the amount of gas transfered the oil phase is described. Parameters to the heuristic mass transfer model are determined from considerations of formation geology and the diffusion-convection characteristics of the hydrocarbon reservoir system. The results from the simulation model were compared to solutions obtained by conventional variable bubble-point models, and it was found that the performance, as estimated by the conventional simulators, is highly sensitive to the thickness of the blocks used to represent the reservoir. In order to verify the solutions obtained by the proposed model, comparisons were made to runs made with a high resolution reservoir model including both diffusion and convection effects. It was shown that the heuristic model relating the interphase mass transfer to the composition of the phases, is capable of efficiently simulating the gas injection process.

Statoil, as a major offshore operator, has established demanding ambitions with respect to increased oil recovery from our subsea fields. We see a large gap, appr. 15%, in recovery from our fields produced from fixed platforms relative to the subsea developed fields, even though the quality of the reservoirs is basically the same. To a large extent this gap is related to the high cost in subsea operations in general and well operations in particular. This paper includes:A listing and brief introduction to the technologies being developed and implemented.A generic evaluation of how the technologies will influence on the recovery from Statoil's existing subsea fields The paper will act as a bridging document between the other presentations and papers in the joint Statoil/FMC session at OTC 2007. Background Statoil envisages fulfilling the demanding requirements to significantly improve the oil recovery from subsea fields. Statoil's current average oil recovery from subsea fields is 45,1%, which is high compared to other operators. The recovery from our platform developed fields is close to 60%. The ambition is to increase the recovery from subsea fields to 55% by 2008, meaning that by 2008 the 55% ambition should be reflected in the resource plans for each individual asset summing up to 55% as an average within the company. Statoil has its current focus on the Norwegian Continental Shelf (NCS), the applicable technologies however are highly relevant also for other parts of the world, such as in deep waters and arctic areas. The current cost level in subsea drilling and well operations is determined as probably the main obstacle to increase the oil recovery. Consequently, the efforts are to a large extent focused in this area. Statoil has incorporated Riser less Light Well Intervention (RLWI) as a corporate service across asset borders. We intend to do the same with Through Tubing Rotary Drilling (TTRD) in subsea wells, the operations will commence in 2007 utilising the dynamically positioned rig Stena Don. The next step will be to develop the next generation of subsea wells (Subsea MMX) to significantly reduce the cost of a new well together with sufficient flexibility to tie in new wells over time. Along with the subsea system itself, it is essential to focus on the drilling and well solution and ultimately the rig solution (light unit). Other technologies such as Subsea Processing and Wet Gas Compression are also very important technologies that are being developed. The ambitions and deliveries General Based on experience from platform operations Statoil has established goals and ambitions within the subsea segment. The R&D focus areas are shown in figure 1. Figure 1: Statoil R&D focus areas within the subsea segment(available in full paper) There are ambitions linked to each of the focus area, these are:Identify drainage points and intervention needsLow cost drainage pointsLow cost well interventionIncreased fluid handlingReduced wellhead pressureIntegrated operations