Wells – Processes – Chemical inter-reaction of two or more introduced materials
Reexamination Certificate
2001-07-06
2002-10-15
Suchfield, George (Department: 3672)
Wells
Processes
Chemical inter-reaction of two or more introduced materials
C166S310000, C166S371000, C175S065000, C175S072000, C507S103000, C507S145000, C507S203000, C507S277000, C507S902000, C507S904000
Reexamination Certificate
active
06464009
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to methods and compositions for the controlled release of agents and components downhole in an oil recovery operation, and more particularly relates, in one embodiment, to emulsions for the controlled release of agents and components downhole.
BACKGROUND OF THE INVENTION
Drilling fluids used in the drilling of subterranean oil and gas wells as well as other drilling fluid applications and drilling procedures are known. In rotary drilling there are a variety of functions and characteristics that are expected of drilling fluids, also known as drilling muds, or simply “muds”. The drilling fluid is expected to carry cuttings up from beneath the bit, transport them up the annulus, and allow their separation at the surface while at the same time the rotary bit is cooled and cleaned. A drilling mud is also intended to reduce friction between the drill string and the sides of the hole while maintaining the stability of uncased sections of the borehole. The drilling fluid is formulated to prevent unwanted influxes of formation fluids from permeable rocks penetrated and also often to form a thin, low permeability filter cake which temporarily seals pores, other openings and formations penetrated by the bit. The drilling fluid may also be used to collect and interpret information available from drill cuttings, cores and electrical logs. It will be appreciated that within the scope of the claimed invention herein, the term “drilling fluid” also encompasses “drill-in fluids”.
Drilling fluids are typically classified according to their base material. In water-based muds, solid particles are suspended in water or brine. Oil can be emulsified in the water. Nonetheless, the water is the continuous phase. Oil-based muds are the opposite. Solid particles are suspended in oil and water or brine is emulsified in the oil and therefore the oil is the continuous phase. Oil-based muds which are water-in-oil emulsions are also called invert emulsions.
It is apparent to those selecting or using a drilling fluid for oil and/or gas exploration that an essential component of a selected fluid is that it be properly balanced to achieve the necessary characteristics for the specific end application. Because the drilling fluids are called upon to do a number of tasks simultaneously, this desirable balance is not always easy to achieve.
It would be desirable if compositions and methods could be devised to aid and improve the ability of drilling fluids to accomplish these tasks by delivering agents and components downhole, which could be released controllably to accomplish one or more jobs.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a method and composition for delivering an agent downhole in a hydrocarbon recovery operation, particularly during a drilling and/or completion operation.
It is another object of the present invention to provide a method and composition for delivering an agent downhole where the agent is released at a controlled time and place.
In carrying out these and other objects of the invention, there is provided, in one form, a pumpable multiple phase composition, also called a multiple phase emulsion drilling or completion fluid, for carrying an agent having a first phase, a second phase, and a third phase. The first phase is suspended in the second phase to form a first pumpable emulsion, and next the first pumpable emulsion is dispersed in the third phase to form the final pumpable multiple phase composition. The pumpable multiple phase composition may be an oil phase-in-aqueous phase-in-oil phase emulsion, or an aqueous phase-in-oil phase-in-aqueous phase emulsion. The agent is present in the first phase.
Additionally, there is provided in one form, a method for releasing an agent downhole beginning by forming a first pumpable emulsion for carrying an agent. The first pumpable emulsion has a first phase containing the agent, and a second phase. The first phase is suspended in the second phase to form a first pumpable emulsion. The first pumpable emulsion may be an oil phase-in-aqueous phase emulsion, or an aqueous phase-in-oil phase emulsion, where the agent is present in the first phase or is the first phase. Next, the first pumpable emulsion is injected into a fluid which may be either a drilling fluid or a completion fluid, such that the external phase of the drilling or completion fluid is immiscible with the second phase of the first pumpable emulsion thereby forming a pumpable multiple phase composition (multiple emulsion). Finally, the pumpable multiple phase composition is broken downhole to release the agent. The pumpable multiple phase composition may be broken by shear, for example, by pumping through drill bit nozzles.
DETAILED DESCRIPTION OF THE INVENTION
Pumpable multiple phase compositions (emulsions) are anticipated as being useful to organize a liquid phase to isolate one miscible phase from another. An oil-in-water emulsion could be used in an invert emulsion, hydrocarbon-based or ester-based or other water immiscible, non-aqueous-based system (forming an oil-in-water-in-oil system), while a water-in-oil emulsion could be used in an aqueous system (forming a water-in-oil-in-water system). In short, the multiple emulsion compositions of this invention and methods for their use may be applied to any two immiscible phases that form stable emulsions. The phases need not be “oil” and “water”, although such phases are likely to be the most common implementation. One non-limiting example is the combination of a water soluble, relatively high molecular weight glycol that forms an emulsion with brine.
One important application of this kind of organization would be the controlled release of the internal phase contents, such as an agent within the innermost (first) phase. A non-limiting example of such an application would be the emulsion of, for instance, a polyglycol, potassium salt, aluminum salt, calcium salt, a silicate salt, chelate or other shale stabilizer, or an aqueous solution thereof, as a first, internal phase in a hydrocarbon or hydrophobic carrier (second phase) optionally containing an emulsifier and/or stabilizer, and then adding the emulsion to a water-based drilling fluid. The polyglycol, potassium salt, aluminum salt, etc. or other shale stabilizer, alone if liquid, or in solution, e.g., is isolated from the water in the external phase of a water-based drilling fluid. Dilution is prevented, suppressed, or delayed until the emulsion is broken intentionally. A likely area for breakage of the emulsion is the high shear environment of and below the drilling bit, where the shale stabilizer is released to the borehole and cuttings in concentrated form on a localized basis. While the invention does not contemplate, as a preferred embodiment, making the multiple emulsion so stable that it is not broken in a drilling fluid or completion fluid application, such stable multiple emulsions are anticipated and may find utility.
Of course, emulsifiers, viscosifiers, or other structural stabilizers may also be added to increase the mechanical stability of the first pumpable emulsion in some cases to delay release of the contents (agent).
In more detail, the agent to be delivered as the contents of the internal phase or the first phase, may be any conventional agent, including, but not necessarily limited to, a shale stabilizer, as noted above, a filtration control additive, viscosifier, suspending agent, dispersant, thinner, an anti-balling additive, a lubricant (particularly in the oil-in-water-in-oil multiple phase compositions), a wetting agent, a seepage control additive, a lost circulation additive, drilling enhancer, penetration rate enhancer, corrosion inhibitor, acid, base, buffer, scavenger, gelling agent, cross-linker, catalyst, and the like, and mixtures thereof. Specific useful shale stabilizers include, but are not necessarily limited to, polyglycols, potassium salts, aluminum salts, calcium salts, silicate salts, chelates, amines, alkanolamines, alkanolamides, ampho
Bland Ronald G.
Quintero Lirio
Baker Hughes Incorporated
Madan Mossman & Sriram P.C.
Suchfield George
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