A Placement Case Study for a Well in the North Sea Field

Abstract

This paper considers the placement challenge in selected wells in a North Sea Field and presents the importance of understanding reservoir properties such as relative permeability, mobility and fluid in place when attempting to simulate treatments in complex wells such as these. The work presents the challenges and solutions offered to minimise the scale risk in this mature field as a result of changes in the overall drainage strategy. Many wells in the North Sea Field are complex and produce from multiple heterogeneous formations which makes them difficult to treat, and so effective placement is vital to mitigate downhole scaling. The wells highlighted in this paper were originally planned for minimal interventions. However as the field development plan matured an increased (albeit mild) sulphate scaling risk became evident in several production wells. Therefore, pre-emptive squeeze treatments were planned to mitigate downhole barium sulphate scaling. Given the heterogeneity in the formation this resulted in potential risks in the event that squeeze treatments could not be designed to give effective placement. This paper presents the placement challenge that is seen in these wells in addition to potential methods of overcoming these challenges. Effective placement does not necessarily mean placement into all producing layers, but means placement of inhibitor into layers upstream of any potential mixing point of scaling brines. Therefore, this work highlights the necessary placement required for effective inhibition and the corresponding treatment designs that may achieve this. One treatment injection strategy to assist effective placement is the use of a staged diversion treatment which is simulated using a near-wellbore placement model. This paper documents a case study of modelling placement, and the corresponding squeeze return, in a mature North Sea Field. It highlights the important influence of reservoir properties such as relative permeability effects (in addition to permeability, porosity, fluid mobility etc.) and how these are used such that chemical treatments in complex heterogeneous wells can be readily simulated without the necessity of using complex full field reservoir simulators.