Abstract This paper presents field results and lessons learned from a North Sea field where a combined scale and corrosion inhibitor has been applied using a single formulation to control both the deposition of scale and associated corrosion. The Galley field is a subsea development within the UK sector of the North Sea. The use of a single product has facilitated a reduction in the number of umbilical lines to be used to provide flow assurance on the subsea flow lines and process of this facility.
The paper outlines the problems encountered when the initial formulation was deployed in the field and the steps taken to develop and monitor an improved formulation. Problems that can affect product application in a subsea environment, including deposition of suspended solids within the chemical, hydrate formation, incompatibility of the chemicals with umbilical material and produced fluid, will all be addressed. The laboratory methods used to select the product along with measurement methods used in the field are also discussed. The validation of the laboratory selection methods in the field required the development of a monitoring program to establish base line control and to assess the degree of protection from scale deposition and corrosion across the process.
The changing physical conditions within the flow lines and across the topside process will be described, as well as the changes in brine chemistry within the field, as injection water breakthrough occurred. The use of novel real time monitoring, as well as water chemistry tracking and analysis of suspended solids within the produced fluids across the process will prove vital to the understanding of the efficiency of flow assurance within the processes was and how treatment rates and products could be optimised.
This paper will outline in detail the particular issues associated with chemical injection to a subsea facility, many of which are currently being developed in the Gulf of Mexico and is a good example of lessons learned and sharing of best practice from another oil basin.
Introduction Scale and corrosion control in subsea facilities - the challenges and the prize. The development of subsea facilities to improve the economics of marginal oilfield developments has focused attention on the need to develop single and combination production chemicals that can function in subsea environments. The recent development of long (> 20km) subsea tie backs in the North Sea, Gulf of Mexico and West Africa has focused attention on long term product stability at seabed temperatures and the associated product specification required for this kind of service. The following short section outlines some of the technical challenges and current methods that can be utilized to eliminate or at least reduce the risk to flow assurance by using such chemicals.
Technical Issues Few umbilical lines. With fewer chemical injection lines being designed into subsea developments, the requirement for combination products has become increasingly important. In many cases these products involve the formulation of generic chemicals that would normally be considered to be incompatible or sparingly compatible when combined or mixed. To overcome this problem, multifunctional molecules (such as poly aspartic acid) have been developed which function as a corrosion inhibitor and scale inhibitor. Conventional water based scale and corrosion inhibitors can also be formulated together with the aid of mutual solvent systems.