TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractA Self-Diverting-Acid (SDA) using a Visco-Elastic Surfactant (VES) has been developed. The viscosity of the solution does not develop until the acid reacts with carbonate in the formation. The increases in Ca 2+ ions and pH due to the HClcarbonate reaction cause in situ gelling of the acid. The high viscosity temporarily blocks the wormholes formed in the rock matrix, allowing the acid to cover the un-acidized area. The viscosity of the gelled acid can be completely reduced by post flush of solvent or by the hydrocarbon in the formation during flow back. Unlike the polymer based gelled acid systems , the new material does not leave any residue once it has broken. Multi-Core flood testing incorporating a post acidizing Computed Tomography (CT) scans showed that the VES based Self-Diverting-Acid successfully diverted acid from high permeability section into lower permeability sections. The rock face remained clean without any trace of residue. Rheology measurements showed the consistency of the viscosity development by the gelled acid upon reacting with carbonates.

Scale buildup can have serious operational consequences. Formation, Removal and Inhibition of Organic Scale in the Oilfield Environment gives an overview of the science and technology of scale formation, removal, and inhibition to a general technical audience, with emphasis placed on the basic chemical and mechanical principles for scale control. Learn about the environment in which damaging scales occur and the technical aspects of scale management from an upstream oil and gas industry perspective. The text and more than 100 illustrations describe aspects of inorganic scales, including the chemical driving forces for scale formation, methods for removing and preventing scale, and the mathematical methods behind engineering guidelines, along with a discussion of best practices and case histories for control of the various types of inorganic deposits.

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Two model compounds, n-dodecylpyridinium bromide (n-DDPB) and l-octyn-3-01, were tested in HCI acid as inhibitors for J55 oilfield steel. This paper describes the kinetic and chemical analyses conducted to arrive at inhibition mechanisms for these model compounds. These studies show that the pyridinium forms a weak bond with the chloride-covered surface and is sensitive to temperature and [HCI]. Octynol, however, chemisorbs and produces a film that contains a reaction product of the acetylenic alcohol. This film is quite insensitive to changes in temperature and [HCI].

Deposition of organic and inorganic solids is common in various areas of the oil and gas production operations that include pipelines, wellbores, and the reservoir and surface facilities. Precipitation is the first step leading to deposition and is a necessary but not sufficient step. Deposition must then occur on a susceptible surface to be detrimental. At this point the deposit may be called a "foulant". There is a large literature base on individual deposits (inorganic scales, wax, asphaltene and hydrates), but relatively little on "real" foulant that usually are much more complex. To maintain production (Flow Assurance-FA) it is not enough to control scale or wax or hydrates. Since these materials affect each other and form complex mixtures, the formation of them must be addressed and treated simultaneously. This paper will review the formation, inhibition and removal of complex inorganic/organic deposits. Practical multi-faceted techniques based on the most recent research and developments will be described and then illustrated using case histories to arrive at best practices for control.The scope of this paper is directed to issues of complex fouling deposition phenomena in the production ("upstream") oilfield environment. This includes the near well bore ("formation damage"), arterial deposits in flow lines, natural or artificial tubulars, subsurface devices, gathering lines and well site surface equipment. From a FA perspective, the biggest problem faced in the offshore developments is the formation of gas clathrate hydrates. The second most important problem is wax damage, followed by asphaltenes. Onshore and especially for low production ("stripper") wells, paraffin deposition is a major production problem. In reality, in both environments, these are usually mixed deposits since corrosion-susceptible steel surfaces are present in contact with unstable brines and mixed hydrocarbons.The first part of the paper will review current literature on the formation of complex mixtures including scales and asphaltenes in the near well-bore area, "Black Powder" deposits in gas lines and the effect of surfaces on wax and hydrate formation. Since the subject is multi-component deposits, control methods also must be multi-faceted. Chemical and engineering analysis techniques that will be highlighted include down hole/surface fluid (oil/ brine and gas) evaluation as well as methods to analyze the efficacy of remediation and prevention methods. Of particular interest are methods for treating multiple types of problems. These include simultaneous scale/organic removal/inhibition treatments and wax/asphaltene/corrosion control treatments. Application methods reviewed include matrix (squeeze) methods, pig trains and coil tubing placements. The case histories of multiple deposit treatments will be included. The conclusions result in a best practice that starts with fluid collection and ends with a comprehensive plan and implementation of multiple FA strategies.The economic impact of scales and organic deposits is in the mul...