Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
  • C09K8/02—Well-drilling compositions
  • C09K8/32—Non-aqueous well-drilling compositions, e.g. oil-based
  • C09K8/34—Organic liquids
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
  • C09K8/02—Well-drilling compositions
  • C09K8/04—Aqueous well-drilling compositions
  • C09K8/14—Clay-containing compositions
  • C09K8/18—Clay-containing compositions characterised by the organic compounds
  • C09K8/22—Synthetic organic compounds
• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B21/00—Methods or apparatus for flushing boreholes, e.g. by use of exhaust air from motor
  • E21B21/08—Controlling or monitoring pressure or flow of drilling fluid, e.g. automatic filling of boreholes, automatic control of bottom pressure

Definitions

• this pressure drop has a very unfavorable effect on drilling progress, which, for instance, may be expressed in the increase in drilling hole depth obtained per revolution of the drilling bit.
• This unfavorable effect is disclosed, among other things, by the fact that, when drilling at shallow depth, drilling progress is usually better than when drilling at a great depth under otherwise similar conditions as regards, for instance, the nature of the formation, bit load, and the speed at which the bit rotates, since when the hole increases in depth there is usually also an increase in pressure difference between the drlling fluid and the liquid in the formation, and consequently an increase in the said pressure drop.
• This phenomenon may be explained by the fact that when there is a high pressure drop over the filter layer the bit force required to loosen a particle or cutting from the drilling hole bottom is considerable owing to the difference in liquid pressures acting on this particle on the side of the drilling hold and the side of the formation; this pressure difference keeps the particle pressured close against the formation or held against the bottom of the hole, and hinders the separation of this particle from the rest of the formation by the rotating drill bit.
• a further object of the present invention is to reduce and preferably substantially equalize the pressure exerted on a formation being drilled by a circulating column of drilling fluid in the well, the pressure reduction or equalization taking place in the formation to a depth about the size of bit cuttings.
• Another object of the present invention is to provide a method of drilling wells wherein a temporary substantially impermeable barrier is formed below the formation surface.
• the formation is not or substantially not sealed at the boundary between the formation and the hole, viz., at the wallet the hole, but as much as possible in the formation itself at some distance from the said wall.
• the pressure prevailing in the formation near the wall of the hole then becomes the same or substantially the same as in the hole. Consequently, a particle loosened by the bit from the wall or bottom of the hole is exposed to substantially the same pressure from all sides, so that no additional force is required by a pressure difference to break the connection of the particle with the solid formation.
• the drilling fluid should penetrate into the formation without forming an impermeable layer on the wall of the formation, but that the pores are not clogged until the liquid has permeated into the formation, thus preventing further penetration of the liquid into the formation.
• the sealing barrier should be formed in the formation a distance from the face of the well borehole at least equal to about the average bit cutting size.
• the drilling fluid should not form a plastering layer on the drilling hole wall as is the case with the conventional drilling fluids.
• the aqueous constituents of presently known drilling fluids penetrate into the formation, most of the solid particles of different sizes are left behind on the wall of the drilling hole where they soon build up a filter layer which is impermeable or substantially impermeable to liquid.
• the drilling used according to the invention should not contain an amount of solid particles of the kind capable of forming a substantially impermeable filter layer, but the presence of non-sealing solid particle-s or cuttings may be permitted.
• the pores in a barrier may be formed or a formation may be clogged with drilling fluid. It is possible, for instance, to make use of the fact that in some formations the pores are filled with a liquid containing dissolved salts, especially sodium chloride, and to cause the drilling fluid to contain a dissolved substance which, together with the salt in the formation liquid, produces a precipitate or flocculation which narrows or even completely seals off the passage in the pores a distance away from the face of the hole.
• Suitable substances for dissolving in the drilling fluid are lead salts, such as lead acetate, and sodium soaps (e.g., sodium stearate).
• a drilling fluid When drilling through salt layers, a drilling fluid is generally used which has a high salt content in order to prevent leaching out of the salt layers. In such a case the above-mentioned substances are obviously practically useless.
• a substantially nonaqueous drilling fluid which forms a precipitate when diluted with salt or fresh formation water.
• a suitable drilling fluid for example, is one which consists of a solution of bitumen in pyridine, or of paratfin wax in methyl ethyl ketone. In an experiment with the latter system, carried out under the same conditions as specified above for the experiment with sodium soap, the quantity of filtrate Was found to be 10 cc. per minute after 120 seconds.
• Methods other than the one by which a precipitate is formed may be used for clogging formation pores.
• use is made of a great increase in viscosity of the drilling fluid after it has penetrated into the formation.
• a possible example is an aluminum carboxymethyl cellulose, dissolved in an alkaline liquid, which solution shows a great increase in viscosity with such decreasing alkalinity as results from dilution with formation water. It is essential that the cellulose material be of the type that will dissolve completely and go into the formation and not one that forms a sheath or filter cake on the wall of the well borehole.
• the presence of solid particles of great size in the drilling fluid does not give rise to the formation of a plastering layer. If the particles are so large that the interstitial pores are of the same order of magnitude as those present in the formation, the flow pattern is not essentially changed by a layer of such solid particles on the wall of the formation. But the presence in the drilling fluid of solid particles with a complete range of dimensions is detrimental to the object envisaged by the invention since in this case the pores remaining between the larger particles in the layer deposited are filled with particles of smaller dimensions until a substantially impermeable layer is formed. Hence, the drilling fluid should not contain an amount of solid sealing or plastering particles which would form an impermeable sheath on the wall of the formation.
• permeable formations When drilling a well, permeable formations will not usually be drilled over the entire depth; impermeable and very slightly permeable formations will also be encountered. If, however, permeable formations are anticipated over the depth to be drilled through, a drilling fluid according to the invention will usually be employed for the entire drilling operation. Although the effect described for permeable formations will not occur when drilling through impermeable or only very slightly impermeable formations, the absence in the drilling fluid of solid particles which can form a dense layer or compact mass may also be of advantage in this case.
• the zone of pressure difference normally at the face or wall of the well, is maintained at a point substantially at or below the depth of the chips or cuttings to reduce the hold-down force normally exerted on the bottom hole formation by the column of fluid in the well.
• the pressure drop front is continually moved below the area in which a bit is forming chips or cuttings.
• the substantially impermeable barrier just below or into the face of the borehole wall may be removed at least in that portion of the borehole traversing the producing formation of the well.
• the previously induced barrier in the formation may be removed by any one of several methods depending upon the type of barrier employed and the characteristics of the formation. Many barriers are readily removed by back-flushing liquid from the producing zone or putting the well on production so that oil or gas from the formation forces the barrier back into the well.
• a barrier depending on the type used, may be dissolved or destroyed by an acid or a solvent, either organic or inorganic, depending on the material to be attacked. In other cases viscosity reducing agents may be employed.
• a method of drilling wells formed by a drill bit at the lower end of a drill string while employing a drilling fluid comprises (a) rotating said drill string with the drill bit bearing against the face of the formation being drilled,
• drilling fluid contains solid particles of such dimensions that they do not form an impermeable layer on the wall.
• drilling fluid consists of a solution of paraffin wax in a solvent such as methyl ethyl ketone.
• the method of claim 1 including the step of increasing the viscosity of said drilling fluid within the formation at a point displaced from the face thereof by contacting said drilling fluid with formation liquid.
• the method of claim 1 including the step of subsequently removing the substantially impermeable barrier within the formation adjacent a producing formation traversed by said drill bit.
• a method of drilling wells formed by a drill bit at the lower end of a drill string while employing a drilling fluid comprises (a) rotating said drill string with the drill bit bearing against the face of the formation being drilled,
• a method of drilling wells formed by a drill bit at the lower end of a drill string while employing a drilling fluid comprises (a) rotating said drill string with the drill bit bearing against the faces of the formation being drilled,

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Organic Chemistry (AREA)
• Materials Engineering (AREA)
• Geology (AREA)
• Mining & Mineral Resources (AREA)
• Fluid Mechanics (AREA)
• Geochemistry & Mineralogy (AREA)
• Environmental & Geological Engineering (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Physics & Mathematics (AREA)
• Mechanical Engineering (AREA)
• Dispersion Chemistry (AREA)
• Earth Drilling (AREA)
• Removal Of Floating Material (AREA)
• Consolidation Of Soil By Introduction Of Solidifying Substances Into Soil (AREA)
• Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
• Perforating, Stamping-Out Or Severing By Means Other Than Cutting (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=19752816

Family Applications (1)

Country Status (6)

Cited By (4)

Families Citing this family (1)

Citations (7)

• 0
  • NL NL260171D patent/NL260171A/xx unknown
• 1961
  • 1961-12-07 US US157814A patent/US3223185A/en not_active Expired - Lifetime
• 1962
  • 1962-01-16 DE DES77568A patent/DE1148953B/de active Pending
  • 1962-01-16 ES ES0273755A patent/ES273755A1/es not_active Expired
  • 1962-01-16 GB GB1570/62A patent/GB934165A/en not_active Expired
• 1964
  • 1964-10-28 OA OA50489A patent/OA00412A/xx unknown

Patent Citations (7)

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