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Oilfield Chemistry
Sludge and Soaps
 
All oilfield production systems, at one time or another, will generate certain amounts of interface sludges, 'bad oils', slop oils and other wastes.   Such materials if not properly identified, understood and handled, will reduce the cost efficiency of a number of critical oilfield operational activities.   These would include oil dehydration, produced water treatment and disposal, oil storage and export.    The presence of such materials in production systems can have a number of consequences, all of which can impact greatly on system OPEX.
 
  • Off specification export oil
  • Reduced export oil storage capacity
  • Increased frequency of production shutdowns
  • Emulsion pads in separators inhibiting separation
  • Semi-solid sludge/scale deposition
  • Production wells formation damage
  • Off spec produced water
  • Produced water facilities shutdowns
  • Damaged controls facilities


Electrostatic coalescer naphthenate scale
 
One particular type of sludge that is becoming more prevalent  is the family of naphthenate and fatty acid soaps that can manifest as emulsion sludges or as deposited solid scales.   As the extracted crude oil comes from increasingly heavy (low API gravity) naphthenic  and light fatty acid rich sources the problems from naphthenate sludges become very critical, severely impeding the production process.   Oil Plus has extensive experience as a leading oil industry consultant on the diagnosis of such materials, in setting up monitoring programs for them and in determining the most effective operational and chemical treatment solutions, for control and mitigation of problems caused by such naphthenate sludges .

Identification

Full production system audits are recommended as a detailed on-site system survey, including fluids characterisation (novel analysis techniques employed on-site), identification of emulsion stabilising agents, solids types and related production chemistry aspects.   This is combined with a process engineering review of all operational and chemical treatment activities, to define a mass balance in the system of all the waste materials and the  waste sources.   This is even more critical for oilfields with suspected soap sludge/scale problems, as the understanding of the fluids and sludge chemistry is absolutely crucial to successful and timely identification of the most suitable treatment and control option for a specific facility.

Waste Management and Mitigation

From the detailed characterisation of the system fluids and the waste streams, the sources of problem streams, incompatible streams, and process units that create waste materials are identified.   All the available data is analysed to troubleshoot and optimise the processing system and also modify/upgrade as required.

Short-term recommendations are made to improve operational practices that will reduce the volumes of wastes formed. An audit of the chemicals treatment system will identify improvements that can quickly be made on-site.   For the long-term, new treatment facility wastes/slops process options will be developed and the optimum option recommended.   This approach can be taken through the feasibility study and conceptual design phases, then on to the detailed engineering, procurement, handover and operational support phases of the project.   Suitable fluid quality monitoring programs are set up during commissioning.

Plant trials of speciality chemicals are developed for sludge handling (minimising as well as processing of the waste streams generated).   These are properly managed and fully monitored trial runs of chemicals from different vendors and provide an objective assessment of the sludge mitigation options available for the specific application.   Based on the knowledge gained, process designs are developed for handling of the waste and slop streams in the facility to complement the main production process.