The chemical removal and dissolution of deposited wax has been described and proven in a variety of applications. This paper describes in detail the removal of wax deposits from a major subsea flowline with the use of a chemical dissolver. The following stages were key to the successful wax removal operation; selection and design phase of the chemical application, the chemical environmental selection criteria, the development of the work scope, as well as the mobilisation and logistics of the chemical application. This paper will illustrate the challenges faced as well as the novel monitoring and analysis techniques used in the field to determine the level of wax dissolution in situ. The wax removal process was deemed successful and offered the client significant benefit in terms of increased oil production. Reduced pipeline differential pressure and increased fluid arrival temperatures also indicated that the wax restrictions in the flowlines had been significantly removed. In addition, the impact on the platform processing facilities during final fluid displacement was much less than anticipated and occurred with no major concerns. A chemical dissolver application of this magnitude is thought to be unique, indeed a world first. The application was conducted in the Gannet D Field in the UK sector of the North Sea to remove wax deposits from two 16 km 6″ subsea production flow lines. Introduction The control and mitigation of wax deposition and its concurrent problems is rapidly becoming one of the critical challenges facing the oil and gas development and production industry. As the industry explores and develops in ever more challenging environments, such as deepwater and sub arctic conditions, the control of wax deposition and its subsequent remediation is becoming a critical technical challenge. Wax deposits can occur widely in the production process and are often considered as the organic equivalent of scale formation. This interpretation is misleading and belittles an important source of refined products from motor oil to jet fuel1. This definition also wrongly simplifies and implies equivalence to inorganic and organic "scales". We would refute this over simplification and take the view that organic and crude oil waxes have considerably different fundamental chemistries in particular in terms of their chemical bonding and the number of factors effecting their deposition1. Our approach to wax dissolution is exemplified in this paper which does not simply treat a deposited wax as a solid to be solvated and dissolved but involves an understanding of at least some of the complex solvent / solute interactions between the dissolver and the deposited wax 2. This paper therefore describes the selection of a wax dissolver and its full field application. The paper also considers the improvement in production rates in the Gannet D field by the application of a wax dissolver to remove restrictive deposition along a sub sea flow line. Field location and characteristics The Gannet field lies some 180km east of Aberdeen in a water depth of approximately 90m. Since the field was originally discovered in the 1970's, several satellite fields have been tied into the Gannet facilities. Gannet D is an oilfield located 16km northeast of the Gannet Alpha (Figure 1). Production is from five wells with oil being transported back to the Gannet Alpha facilities via two looped 6″ subsea flowlines referred to as Riser 31 and Riser 32. The crude from these reservoirs typically has an API of 41, a wax content of approximately 7%, and a wax appearance temperature in the region of 35.5oC. The Gannet G field is also produced via this system with a single 6″ flow line tied in at the base of Riser 32, half a kilometre from the Gannet Alpha platform. Therefore Riser 31 carries Gannet D crude only and Riser 32 carries Gannet D and G crude topsides onto the Gannet Alpha processing facilities where the oil is co-mingled with other Gannet fluids before being exported to the Fulmar platform.

Continuous Foam Injection is a proven deliquification technique in gas wells, but the technology typically struggles to perform in wells with high fractions of liquid hydrocarbons. For gas-lifted oil wells operating at high water cut, continuous downhole foam injection via the gas-lift system may prove feasible and open-up a whole new area of production enhancement. To establish if this technique could deliver sustainable and cost effective production enhancement in the field, Shell Malaysia Exploration & Production (SMEP) successfully conducted a trial in October 2016 in a mature oil field where a liquid foamer was injected into the gas lift system of an oil well. The project team took 10 months to conduct candidate well screening, comprehensive lab testing for chemical selection, well performance modelling, procurement, site visit, plant change requirements and finally site execution. Although the candidate well was located in an aging facility with limited production monitoring facilities, the available surface pressure/temperature transmitters and fluid sample points were sufficient to ensure a robust assessment of the trial results was possible. Over the trial period, a 22% increase in the gross production rate was seen in the candidate well, with downhole foamer and surface defoamer being applied on a continuous basis. Throughout the trial, the fluid properties were closely monitored to ensure secondary effects such as excessive surface foaming or untreatable emulsification did not occur and this strategy proved successful with the trial being completed without any downstream system upset. The trial being described in this abstract was the first time a foamer had been applied in this manner in Shell Malaysia.

Paraffin deposition in oil export pipelines can prove problematic during "intelligent pigging" operations, when hydrocarbon deposits on pipe walls are not removed sufficiently during the cleaning phase. This gives rise to sensor clogging and lift-off causing inaccurate and in some cases complete loss of data from the inspection tool.In pipelines where paraffin deposition has caused problems, specific wax dissolvers in tailored treatments have been applied during pigging programmes to aid the removal of deposits from pipe walls and to prevent further wax deposition. This paper will discuss the selection and application of these wax dissolvers and the results obtained on applying the products in field. The laboratory methods used to evaluate and select a wax dissolver and the process of modifying the amount of chemical required will be discussed in this paper. The paper will also discuss the interaction of these dissolvers with specific hydrocarbon deposits. Furthermore, we will compare the characteristics of wax deposits retrieved from pigging programmes prior to and during dissolver application. This paper will demonstrate that in certain North Sea fields the physical characteristics of pig waxes altered when dissolver was applied, allowing hydrocarbon deposits to be removed more effectively from the export pipeline and enhancing the cleaning phase of the pigging programme. The application of wax dissolvers prior to and during export pipeline cleaning programmes, in preparation for intelligent pig runs, has proven beneficial where waxy crudes are being exported. The introduction of such chemical injection regimes has improved the removal of hydrocarbon wax deposits from export pipelines and has allowed meaningful data to be retrieved during intelligent pig runs. Introduction Paraffin waxes are a normal component of crude oil and should therefore be viewed as a valuable source of potential refined products, however their deposition can lead to many process problems1. The presence of paraffin waxes in crude oils can deliver a number of problems to the producer, transporter and refiner. These problems can vary from minor to severe depending on the nature and quantity of the wax deposited. Therefore the assessment of wax deposition is extremely important in the oil and gas industry. An application where wax deposition may cause problems is in the use of "intelligent pigging" for data collection in transport pipelines2, 3. Here, although the quantity of wax deposited may not be significant, the nature of the wax deposited and the location of wax deposition can lead to severe and frustrating problems in the collection of data and subsequent interpretation as to the internal condition of critical transportation lines. This occurs when insufficient mechanical cleaning (pigging)3 results in the remaining waxy hydrocarbons depositing on the intelligent pig sensors, which leads to incomplete collection of data from the inspection tool. In some cases wax deposition can even cause removal of the sensors from the inspection tool and therefore a total loss of data4, 5. It is estimated that the costs associated with an intelligent inspection run in the North Sea basin are on average $50,0006 and that to receive little and / or inconclusive data makes this an expensive and wasteful exercise. More importantly the internal condition of the transportation pipe is still unknown. We have proposed and shown that the selective use of specific wax dissolvers in tailored treatment programmes can minimise and completely eliminate this problem.

This paper describes the production chemistry management process undertaken during the design, commissioning and start-up phases of the Schoonebeek redevelopment. Challenging separation issues, saline water, together with a multitude of other process conditions, resulted in complex, but robust application portfolio. This was established during the design stages of the project. Early involvement of the production chemistry discipline aided this process. Chemical selection was conducted in adherence to HSSE directives and focusing on unique produced fluid properties. Since start-up, the success of chemical performance has been due to the availability of chemical treatment programs and surveillance/sampling plans. No contingency chemicals have so far been needed at the facilities since start-up. Export oil and water key performance indicators have been for the majority of the time met. Further optimization of chemical applications is an ongoing process which will follow the life of the field.