Earth boring – well treating – and oil field chemistry – Earth boring – Contains organic component
Reexamination Certificate
2000-12-28
2003-10-07
Tucker, Philip (Department: 1712)
Earth boring, well treating, and oil field chemistry
Earth boring
Contains organic component
C507S204000, C175S072000
Reexamination Certificate
active
06630429
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention pertains generally to lost circulation materials and methods, and more particularly to a highly effective, environmentally safe loss circulation material and method use. The invention can be effectively employed in oil, gas, water, geothermal, offshore, and like drilling and excavation applications.
2. Description of the Background Art
During the drilling of wells for oil, gas and other materials, a drilling fluid is generally circulated through the well bore to the drill bit. The drilling fluid lubricates and cools the drill bit and removes cuttings from the drill bit. A common problem during drilling is lost circulation of the drilling fluid, which occurs when the drill bit encounters highly permeable or fractured subterranean formations during drilling. The drilling fluid can drain into the porous formations and thus be lost from circulation around the drill bit. The loss of drilling fluid in this manner can result in loss of the drilling structure, unwanted cavity formation, damage to the drill bit and interruption of the drilling operation.
In order to avoid such lost circulation problems, a variety of lost circulation miaterials or LCMs have been developed for addition to the drilling fluid. These materials form gels, slurries, colloidal dispersions when added to the drilling fluid, otherwise render the drilling fluid less susceptible to loss from circulation in porous or fractured strata. Typically, the drilling fluid is circulated from the drill bit back to the top of the well, via annulus return, where a “mud pit” is used to add the lost circulation material to the drilling fluid. The lost circulation material is agitated in the mud pit until a gel or slurry forms, after which it is pumped back down the hole for circulation through the drill bit. The lost circulation material and drilling fluid will typically have to withstand elevated temperatures associated with the drill bit. The ideal lost circulation material should also be able to bridge and cross-link across pores or fractures of varying sizes which are encountered during drilling, in order to prevent fluid loss. To achieve these ends, numerous types of natural and man-made fibers, gels, surfactants, clays, and mixtures thereof have been developed for use as lost circulation materials.
Previously used lost circulation materials have generally proved deficient in one or more respects. For example, lost circulation materials which are mixed directly in the mud pit often result in rapid increases in viscosity of the drilling fluid, and are difficult to pump or circulate back to the drill bit. Lost circulation materials based on natural and man-made fibers tend to be bulky and are inconvenient to store and transport. Many natural materials additionally are subject to decay, mildew and insect depredation during storage. Further, many lost circulation materials include one or more materials which may present an environmental problem which remains at the drill site after drilling and pumping operations are terminated. Various attempts have been made at mixing natural and man-made fiber materials with clays such as bentonite. However, lost circulation materials based on clays and cement often result in unwanted, irreversible clogging of the production zone of a well.
There is accordingly a need for a lost circulation material and method of use which is heat resistant, which provides effective bridging, which does not need to be mixed directly in the mud pit, which is compact and easy to transport and store, which avoids clogging of well production zones, and which uses environmentally safe materials. The present invention satisfies these needs, as well as others, and generally overcomes the deficiencies found in the prior art.
SUMMARY OF THE INVENTION
The invention is an environmentally safe lost circulation material and method of use which provides effective drill bit lubrication, over a wide temperature range, for drilling in a variety of porous or fractured subterranean structures In its most general terms, the invention is a lost circulation material comprising pelletized natural fiber material, preferably together with between approximately 0.001% and approximately 0.01% by weight of preservative. The preferred pelletized natural fiber material is pelletized cotton seed hulls, but may alternatively or additionally comprise pelletized nut shells, bean hulls, hemp, jute, or any other vegetable fiber or natural fiber.
In one preferred embodiment of the invention, the lost circulation material comprises of between approximately 98% and approximately 99.5% by weightof pelletized natural fiber, between approximately 0.5% and approximately 2.0% by weight of vegetable starch, and between approximately 0.001% and approximately 0.01% by weight of preservative.
In another preferred embodiment of the invention, the lost circulation material comprises of between approximately 98% and approximately 99.5% by weight of pelletized cottonseed hulls or other pelletized natural fiber material, between approximately 0.5% and approximately 2.0% by weight of corn starch or other vegetable starch, between approximately 0.001% and approximately 0.01% by weight of preservative, and between approximately 0.001% and approximately 0.01% by weight of surfactant.
In yet another preferred embodiment, the lost circulation material comprises of between approximately 50% and approximately 80% by weight of pelletized cottonseed hulls or other pelletized natural fiber material, between approximately 10% and approximately 40% by weight of pelletized wood, between approximately 0.001% and approximately 20% by weight of water-swellable cross-linked polymer, between approximately 0.5% and approximately 2.0% by weight corn starch or other vegetable starch, between approximately 0.001% and approximately 0.01% by weight of preservative, and between approximately 0.001% and approximately 0.01% by weight of surfactant.
The method of the invention comprises generally of providing a lost circulation material of the type described above in accordance with the invention, and adding said lost circulation material, in dry form, directly into the suction portion of the mud pit, without mixing with fluid in the mud pit. The lost circulation material is transported down to the “Kelly” in dry form, and mixes with fluid and undergoes swelling proximate to the bottom of the well to preserve the well structure.
An object of the invention is to provide a lost circulation material and method which utilizes only environmentally compatible materials.
Another object of the invention is to provide a lost circulation material and method which provides effective drill bit lubrication over a wide temperature range.
Another object of the invention is to provide a lost circulation material and-method which undergoes effective bridging and plugs pores and fractures of various sizes.
Another object of the invention is to provide a lost circulation material and method which does not need to be mixed directly in the mud pit.
Another object of the invention is to provide a lost circulation material and method which is compact form and is easy to transport and store.
Another object of the invention is to provide a lost circulation material and method which avoids clogging of well production zones.
Further objects and advantages of the invention will be brought out in the following portions of the specification, wherein the detailed description is for the purpose of fully disclosing the preferred embodiment of the invention without placing limitations thereon.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the following detailed description, it will be seen that the invention provides a new lost circulation material and method of use which provides effective bridging, which does not need to be mixed directly in the mud pit, which is compact and easy to transport and store, which avoids clogging of well production zones, and which uses environmentally safe materials. The invention is disclosed generall
Cremeans Jim G.
Cremeans Keet Stene
LandOfFree
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