DRILLING FLUID AND A METHOD FOR PREPARATION THEREOF Russian patent published in 2004 - IPC

FIELD: drilling engineering.

SUBSTANCE: invention relates to boring wells, in particular to formulations and methods for preparing drilling fluids used for flushing-out of oil and gas boreholes, in civil constructions, in particular in directed and horizontal drilling, construction of underwater passages, and when completing wells. Drilling fluid is based on water-oil emulsion and contains, kg/m³: bentonite clay 30-72,;caustic soda 0.2-0.7; low-viscosity carboxymethylcellulose 0-3.5; multifunctional surfactants IKLUB and IKD, 3-8 and 0.5-3, respectively; polymers: high-molecular acrylamide-containing anionic polyelectrolyte IKSTAB or ampholite polyelectrolyte GRINDRIL, 2.6-4.5, low-molecular anionic polyelectrolytes IKPAN-SL and IKPAN-RL, 2.5-4.5 and 1.2-2.5, respectively; additionally soda ash, 1-2.5; and water - the balance. Drilling fluid may further contain attapulgite clay in amount no higher than 33 kg/m³ and up to 2.5 kg/m³ of high-viscosity carboxymethylcellulose. When reaming and calibrating holes with length above 600 m and diameter more than 1200 mm, fluid contains ampholite polyelectrolyte GRINDRIL and also bactericide IKBAK in amount 0.5-1 kg/m³, 0.1-0.25 kg/m³ of antifoaming agent, Palygoskite and/or kaolinite clay. Preparation procedure comprises mixing oil, multifunctional surfactants, caustic soda, carboxymethylcellulose, polymer, and bentonite clay. More specifically, hydrophilic clayey slurry is first prepared by mixing indicated clay with calcined soda and soda ash in water, after which low-viscosity carboxymethylcellulose and IKPAN in the form of fine reverse water-oil emulsion are successively added at stirring to form homogenous system. To the latter, IKSTAB with intrinsic viscosity 10-20 or GRINDRIL with intrinsic viscosity 10-18 is added in the form of fine reverse water-oil emulsion in amount 40-60% of its content in drilling fluid and then IKLUB and IKD. When apparent viscosity of resulting suspension reaches 50 s, the rest of IKSTAB or GRINDRIL is added. It is possible, that carboxymethylcellulose and IKPAN are introduced into above-indicated slurry when its apparent viscosity reaches at least 30 s, while bentonite and attapulgite clays are introduced separately in the form of lamellar- or scale-particulate powdered clay with bulk density 800-900 kg/m³, bentonite clay being added when addition of attapulgite clay is ended. Low-viscosity carboxymethylcellulose CMC-LV (degree of polymerization 500-550) has viscosity at least 50 mPa.s and high-viscosity carboxymethylcellulose CMC-HV (degree of polymerization 700-800) above 1000 mPa.s, both being in sodium salt form. IKPAN-SL and IKPAN-RL utilized have intrinsic viscosity 1.5-2.5 and 2.5-4.5, respectively. Acrylamide-containing polymers are synthesized using acrylamide monomer selected from amide series including acrylamide, methacrylamide, N-alkylacrylamide, N,N-dialkylacrylamide, and using, as monoaminomonocarboxylic amino acid, α-amino-γ-methylbutiric acid or methionine (feed or pharmaceutical grade). Mixture of fatty acids selected from oleic, linoleic, linolenic, and/or steric acid, resin acids, and/or tallow oil aid with triethanolamine and/or emultal is used as emulsifier to prepare dispersion phase of reverse emulsion of selectively purified distillate hydrocarbon oils with congelation temperature -40 to -70^оС and cinematic viscosity 2-16 mm²/s (at 50^оС). Blend and blend water-oil reverse emulsion is cooled, after its formation, to temperature by 2-3^оС exceeding cloud point temperature of blend solution when performing turbulent emulsifying with the aid of high-speed stirring device, turbine stirrer, or mixer providing preferably motion of liquid with Reynolds criterion at least 2.3·10⁵ , gap between stirrer blade and wall and bottom being no more than 2-3 mm. Acrylamide-containing polyelectrolytes serve to efficiently form a multitude of composite thickenings, gels, threads, or polymeric lattices, or their combinations.

EFFECT: enhanced efficiency of drilling and completion of wells.

24 cl, 6 tbl