Wells – Processes – Dissolving or preventing formation of solid oil deposit
Reexamination Certificate
2001-07-16
2003-05-20
Tsay, Frank (Department: 3672)
Wells
Processes
Dissolving or preventing formation of solid oil deposit
C166S305100, C507S246000
Reexamination Certificate
active
06564869
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to cleaning and inhibiting deposited solids and viscous fluids (including bitumin and other hydrocarbons) in and on well equipment, such as flowlines, injection lines, shakers, and other equipment having metal surfaces. More particularly, the present invention relates to the use of terpene additives in water based well fluids to clean and inhibit solids, bitumin tar, and viscous fluids deposited in such well equipment.
2. Background Art
When drilling or completing wells in earth formations, various fluids typically are used in the well for a variety of reasons. For purposes of description of the background of the invention and of the invention itself, such fluids will be referred to as “well fluids.” Common uses for well fluids include: lubrication and cooling of drill bit cutting surfaces while drilling generally or drilling-in (i.e., drilling in a targeted petroleum bearing formation), transportation of “cuttings” (pieces of formation dislodged by the cutting action of the teeth on a drill bit) to the surface, controlling formation fluid pressure to prevent blowouts, maintaining well stability, suspending solids in the well, minimizing fluid loss into and stabilizing the formation through which the well is being drilled, fracturing the formation in the vicinity of the well, displacing the fluid within the well with another fluid, cleaning the well, testing the well, implacing a packer fluid, abandoning the well or preparing the well for abandonment, and otherwise treating the well or the formation.
Environmental regulations governing the use and disposal of these well fluids have become increasingly restrictive. With the increase in regulation, many well fluids, which had been “oil-based” (having hydrocarbon as a principal component) are now “water-based.” Further, certain types of wells will suffer formation damage if an oil-based well fluid is used. While water-based well fluids are generally superior from an environmental perspective, and often from an economic perspective, the water-based well fluids have some disadvantages as well. Most notably, it has been found that the deposit of heavy hydrocarbonaceous materials and finely divided inorganic solids on the inner surfaces of the piping (and, in general, on all of the metal surfaces present) used in well drilling applications is more significant when using water-based well fluids than when using oil-based well fluids.
The deposits discussed above typically comprise finely divided inorganic particles, such as solids produced from the formation, which may include hydraulic fracturing proppant, formation sand, clay and various other precipitates. These particles become coated with hydrocarbonaceous materials and subsequently accumulate additional quantities of heavy hydrocarbonaceous material in flowlines, settling tanks, and other surfaces on and in well equipment, both metal and ceramic.
The deposits are slimy, oily substances which strongly adhere to metal and ceramic surfaces, as well as other surfaces of the well equipment, and serve to inhibit fluid flow throughout a drilling or production system. Other areas susceptible to deposit build-up, not explicitly referred to above, include shakers, screens, and the other filtration systems used in a drilling system. Common apparatus for mechanically removing solids from drilling mud include shale shakers and vibratory screens, desanders, desilters, and centrifuges. Again, as deposits form on these devices, fluid flow through the devices is curtailed, thereby causing operating problems.
Much of the prior art deals with mechanical attempts to clean drilling equipment. However, mechanical cleaning is not practicable with respect to all of the drilling equipment. Another method of cleaning has been to include potassium sulfate as an additive to the well fluid.
What is needed, therefore, is a simple, low-cost system for cleaning and inhibiting the accretion of tar an other fluids or solids in and on drilling equipment in water-based well fluid applications.
SUMMARY OF THE INVENTION
In one aspect, the present invention relates to a method for cleaning and inhibiting deposits in and on well equipment used in conjunction with a water-based well fluid which comprises mixing an effective amount of a miscible terpene in the well fluid.
In another aspect, the present invention relates to a method for cleaning and inhibiting deposits in and on well equipment used in conjunction with a water-based well fluid which comprises mixing an effective amount of d-limonene into the well fluid.
In another aspect, the present invention relates to a water-based well fluid which comprises an effective amount of miscible terpene in the well fluid.
In another aspect, the present invention relates to a water based well fluid which comprises an effective amount of d-limonene into the well fluid.
Other aspects and advantages of the invention will be apparent from the following description and the appended claims.
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PCT Search Report dated Oct. 25, 2002, 7 pages.
Ewanek John
McKenzie Neil
M-I L.L.C.
Rosenthal & Osha L.L.P.
Tsay Frank
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