The bond between casing and cement placed in the annulus is an important aspect to wellbore construction. Bond is inferred after the cement has cured using acoustic methods well-known in the industry. This evaluation is dependent on the acoustic coupling between the cement and the pipe. If acoustic coupling exists, proper evaluation allows for a subjective assessment of the cement sheath behind casing. However, if the acoustic coupling is weak, non-existent, or has been damaged by operations such as pressure testing or stimulation treatments, the cement may be present but cannot be properly evaluated, leading to ambiguous conclusions and ultimately unnecessary remedial cementing. Enhancements to the casing/cement bond is achieved by use of surfactants, expansion agents, and other chemicals added to the cement slurry and/or spacer. Modification to completion practices is sometimes practiced to prevent bond disturbance. Modifications to the mechanical properties of the cement sheath are also done in an attempt to prevent or limit the permanent deformation to the cement sheath that occurs during these load events. All have varying degrees of success and cost. Attempts to modify the surface of the steel pipe have been practiced for several decades with varying results. The simplest and most effective has been to grit-blast the casing to remove mill varnish, as varnish highly hydrophobic and not conducive to cement bonding. Grit blasting also leaves the surface slightly roughened, which has been proven to improve both shear bond and acoustic transmittance. Coatings have been attempted in the past, usually based on altering the surface roughness by adhering grit using an adhesive. None of the afore-mentioned methods practiced to date have addressed two fundamentals: (1) carbon steel is naturally hydrophobic, and (2) cement and steel do not form a chemical bond. The purpose of this project was to address these short-comings by developing a method to modify the external surface of oil well pipe making it super-hydrophilic, and at the same time attempt to create a chemical bond to cement. Through a collaborative working relationship between this major operator and a small innovative technology company, a successful nano-technology treatment process has been developed and field tested in both unconventional and Deepwater environments. This paper will chronicle the project from concept development to lab proof-of-concept, several field trials, and provide a review of the lessons learned along the way. Comparative cement evaluation logs will be reviewed that show a significant improvement in some cases between the treated pipe and pipe that is either unmodified or grit-blasted.

Corrosion and biofouling control is an important consideration for offshore oil structures. Corrosion rates for steel exposed to seawater immersion and brine air can easily exceed 10 mils per year if left unprotected in the splash zone, while barnacles which attach in shallow tidal zones can similarly induce heavy, accelerated microbiological pitting corrosion. The subsequent deterioration of the ferrous substrates leave these structures at risk for mechanical failure, as the effects of particle impact, abrasion, wear, and erosion combine with the weakened surface structure to accelerate the loss of material. Maintenance of these critical assets often proves a logistical nightmare, when considering the limited accessibility, remote locations, and the huge expense of any interruptions in rig production. Attempts to contain the effects of corrosion are widespread, including strategies such as the introduction of chemical inhibitors to change the environment, sacrificial anodic and cathodic protection, and utilization of new highly alloyed materials. However, by far the most widely used technique is the application of specially engineered surface coatings to provide a physical and chemical barrier between the substrate and the surrounding corrosive media. Coatings can range between extremely simple hot-melted tar and liquid epoxy, which inherently have no chemical bonding to the substrate, and some slightly innate hydrophobicity, to engineered advanced systems including polytetrafluoroethylene (PTFE) and zinc silicates with specially paired primers for maximum surface adherence and broad chemical compatibility. None of the existing coating solutions practiced to date has been able to a key fundamental: coatings cannot be used as part of a refurbishment strategy to restore performance and production to existing structures after fouling. The purpose of this project was to develop a multifunctional, omniphobic coating with superior substrate adhesion such that it could fill in and plug surface crevices and pits stemming from corrosion. Additionally, unlike most other coatings, this surface adhesion could be attained through in-field application, either on exposed surfaces through aerosolized spray, or on the interior of transport pipelines via an in-line coating method. This paper will highlight various applications of the coating system on platform fixtures and supporting infrastructure, and how it can improve operational efficiency and extend the usable lifetimes of the selected assets. Offering abrasion resistance and an extremely low surface roughness finish, the coating has been demonstrated to actively repel both water and oil-based mixtures, as well as prevent the attachment and growth of typical marine biologicals such as barnacles and microbial algae. Suitable for nearly any substrate, this paper shall describe multiple ways in which the coating was deployed to combat not only corrosion on the platform itself, but also reduce drag in inspection underwater unmanned vehicles (UUV), and in offering flow assurance when used to refurbish a transport pipeline.

It is well understood that deposits such as corrosion and scale can greatly reduce the flow efficiency and throughput of a transport pipeline system. Regular intervention activities to promote flow assurance such as frequent mechanical pigging, introduction of chemical corrosion inhibitors, and introduction of drag reducing agents all require consistent operational expense, or significant pipeline downtime. Use of interior pipeline coatings and liners are potential long-term solutions which would represent a way to provide long-term refurbishment benefits. This work describes a novel material designed to interact specifically with highly corroded and weathered pipe, enabling in-place application and refurbishment. The material is applied extremely thinly on the pipeline interior, such that it might be considered a surface treatment, yet it is designed for permanence and for strong adhesion to even severely corroded surfaces. This water-and-oil compatible, chemically resistant material shows extreme resistance to corrosion, particle abrasion and delamination under operational conditions, and is specifically designed to reduce surface roughness by several orders of magnitude. By reducing surface roughness, losses due to frictional drag can be minimized, together with the chance of forming deposits of iron scale and black powder that can constrict pipeline flow and overall production. A case study is presented in this work which describes application of the coating to a fluid transport system, including a variety of different "challenge" features including: 90° 1.5D bends, valves, weld seams, flanged connections, and heavily corroded surfaces. The pipeline systems were all treated via an in-situ methodology and evaluated for flow performance both through modeling and experimental observation. The study of the practical effects of utilizing a low surface energy, low surface roughness coating that can be effectively applied to severely corroded pipelines with a minimum of surface preparation demonstrates how new material breakthroughs can allow for revitalization of previously mature intervention techniques.