The use of moored structures in ice infested waters is of relevance for the exploration or the exploitation of hydrocarbon fields in arctic waters. The assessment of the impact of ice actions in the design process is challenging as the ice actions and the structural response will differ for a moored structure. Further, design criteria may be given by severe and complex scenarios resulting from the interaction with intact level ice and ice ridges in variable ice drift.Ice model testing is an important part in the design process of a moored structure designed to operate in ice infested waters. The ice basin tests allow the measurement of the structure response to complex ice interactions. However, the conditions achieved in the ice tank can deviate from the target full scale scenario. Some structural parameters may not be replicated fully (for instance mooring forces on the structure), and the achieved ice conditions at the instant of the testing may deviate partially from the target ones (it is challenging to scale several ice parameters at the same time resulting in distorted ice properties).A numerical model was developed to simulate the response in real time of moored structures to drifting level and ridged ice. The engine simulates ice actions of the structure including sub-surface ice transport of broken ice around and under the structure. The response of the structure is computed accounting for non-linear effects in the time domain.The most promising use of these modeling capabilities is the possibility to correct and update ice basin measurements for the deviations between the achieved and target interaction scenarios: The tests performed in the ice basin are simulated numerically. A numerical model of the test setup needs to be built (of the structure, the mooring and the achieved ice conditions). By comparing the simulated and measured response, the numerical model can be calibrated and validated.  Numerical simulation of the target scenarios: A numerical model of the target design setup is built, and the response of the structure to full-scale target ice interactions is then estimated. The numerical simulation of the target scenarios represents then the corrected ice basin measurements accounting for all deviations. The simulated response will be used further in the design process, with a confidence based on the quality of the calibration exercise.Examples from two ice basin campaigns are presented where numerical simulations are compared with ice basin measurements, and where full-scale responses to target scenarios are then simulated numerically: Turret moored Offloading IceBreaker (OIB) vaning in level ice (Breivik et al., 2007),  Turret moored Arctic Shuttle Barge (ASB) interacting with drifting ice ridges (Jensen et al., 2000a,b). BackgroundMoored structures are a promising alternative for the development of fields in areas which present sea ice intrusions. Ice actions and the corresponding structural response have to be assessed in the design process. Both extreme and operational aspects are of...

Declining oil production and increasing water cut in mature fields highlight the need for improved conformance control. Here we report on a successful in-depth water diversion treatment using sodium silicate to increase oil recovery at the Snorre field, offshore Norway, utilizing a new operational concept of using a stimulation vessel as a platform for the large-scale injection into a subsea well. A custom modified 35,000 DWT shuttle tanker was employed for the field pilot. This paper describes the vessel preparations and the large-scale interwell silicate injection operation. The operational aspects of the large-scale interwell silicate injection include; identification of injection vessel requirements, major vessel modifications, chemical logistic, general logistics to site, major equipment set-up on vessel, subsea connection, mixing and pumping schedules, onsite QC, and real time monitoring. Experience from these operations and lessons learned are included in this paper.After the injection of approximately 400,000 Sm 3 (113,000 Sm 3 preflush, followed by 240,000 Sm 3 of sodium silicate gelant and 49,000 Sm 3 of postflush fluid) at injection rates up to 4,000 Sm 3 /d, the injection from the vessel was stopped and the well was put on regular seawater injection. Following more than two years of regular production, transient pressure measurements, tracer testing and water cut data are presented from the ongoing comprehensive data acquisition program. These results demonstrate clearly the achieved in-depth flow diversion through a delayed breakthrough of injected tracers and lower water cut in the relevant production well.