The Blane Field, North Sea, has one injection well and two production wells and is tied back to the Ula Field platform. The original scaling risk assessment was based on injection of platform produced water (PW) with minor seawater (SW) (~90:10 PW:SW). However, after injection of 25:75 PW:SW for only 6 weeks, a change in operational circumstances on the Ula Field meant that only 10:90 PW:SW injection water could be supplied for the next 18 months. There was a risk that this might result in unmanageable BaSO4 scaling conditions in the production wells but the alternative would be to cease injection, leading to reservoir pressure decline and loss of oil revenues. The need for a rapid decision negated the use of reactive transport reservoir simulations to predict the future BaSO4 scaling risk under the new injection scenario so a novel, alternative approach was adopted. A history matched ECLIPSE model served as the basis for predicting the types of water entering the production wells over time and their rates. A 1-D reactive transport model was then used to predict the Cl, Ba and SO4 composition of these waters after accounting for the effects of reservoir reactions. These results were integrated in a spreadsheet to provide predictions of Cl, Ba and SO4 concentrations in the produced water from each well over time. The results for future injection water scenarios indicated that the scaling risk would increase over time in the wells but, due to deposition of BaSO4 and CaSO4 in the reservoir, the BaSO4 scaling risk would be manageable even allowing for uncertainties associated with this approach. Based on these results, and those of associated studies, a decision was made to continue water injection resulting in avoidance of loss in oil revenues. This novel scaling prediction approach may be useful on other fields where reactive transport reservoir simulations may not be possible.

In recent years, Aker BP has explored and developed a number of digital improvements to optimize production. The underlying business drivers are meant to improve efficiency, increase production and reserves, decrease costs, and reduce the carbon footprint from operations. The example described in this article has innovative elements of digitalization and automation of workflows which provide a new approach for better handling of slugging in subsea developments with long tiebacks. The new solution has a potential for optimizing production and limiting the amount of flaring. Flow Instabilities in the Vilje Field The Aker BP-operated Vilje field in the Norwegian Continental Shelf has occasionally experienced production-flow instabilities in the production pipelines and risers due to slugging. The company worked with Turbulent Flux to develop a software solution, the FLUX Stability Adviser, to continuously and precisely monitor production in real time. Field Description and Outline of Problem The Vilje field is a subsea development with three horizontal producers tied back to the Alvheim floating production, storage, and offloading (FPSO) facility through a production line longer than 20 km. The inlet separator at Alvheim is shared with other third-party developments. After an initial period of dry-oil production at the field, which started production in 2008, the oil rate has gradually decreased as a result of increased water cuts (WC) over time. Gas lift has been used to sustain production. The occasional slugging at the inlet separator had been controlled by increasing the backpressure to the production line and/or shutting in one of the producers. However, this practice affects production potential and may lead to production losses or deferral. Explanation of the Solution The two companies developed a Stability Adviser application to advise operators of the settings to optimize production in real time while lowering the risks related to slugging at any point in time. The developed solution runs on a cloud infrastructure with an interactive web-user interface. The main user interface contains a 3D heat map which is based on output from a series of pre-run transient simulations and a statistical analysis of the associated slugging severity. The model quality of the pre-run simulations was benchmarked with field data, and a similarity index was introduced to evaluate the degree of matching. Transient multiphase flow simulations represent the state of the art in the prediction and analysis of slugging behavior in multiphase transport pipelines (both terrain-induced and hydrodynamic slugging). These simulators capture and follow slugs as they are forming along the pipeline. That said, these simulations are time consuming, which limits their usefulness in a real-time operational context.

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