Biodegradable additive concentrate with pour point according to standard ASTM D 97 below −5° C., improving the lubricity of water-based muds, comprising at least one compound selected from the group consisting of: the diglycerol mono- and diesters, the acids and the ester derivatives of monocarboxylic fatty acids comprising from 16 to 22 carbon atoms per chain, the acids and the ester derivatives of resin acids, the monoesters of polyol comprising more than 4 hydroxylated groups and of carboxylic fatty acids comprising from 6 to 12 carbon atoms, saturated and unsaturated by at least one unsaturation, and the mono- and polyalkoxylated esters of saturated and unsaturated dicarboxylic acids comprising from 6 to 12 carbon atoms. The use of this concentrate in a water-based mud and the water-based mud containing said concentrate that can be used for drilling.

Biodegradable additive concentrate with pour point according to standard ASTM D 97 below −5° C., improving the lubricity of water-based muds, comprising at least one compound selected from the group consisting of: the diglycerol mono- and diesters, the acids and the ester derivatives of monocarboxylic fatty acids comprising from 16 to 22 carbon atoms per chain, the acids and the ester derivatives of resin acids, the monoesters of polyol comprising more than 4 hydroxylated groups and of carboxylic fatty acids comprising from 6 to 12 carbon atoms, saturated and unsaturated by at least one unsaturation, and the mono- and polyalkoxylated esters of saturated and unsaturated dicarboxylic acids comprising from 6 to 12 carbon atoms. The use of this concentrate in a water-based mud and the water-based mud containing said concentrate that can be used for drilling.

Methods and compositions comprising an emulsion or a microemulsion for use treating an oil and/or gas well are provided. In some embodiments, the emulsion or the microemulsion comprises an aqueous phase, a solvent, a surfactant comprising alkyl polyglycoside, an alcohol, and, optionally, one or more additives.

Drilling fluid compositions include invert emulsion fluids having an oleaginous phase, an aqueous phase, and an emulsifier composition that includes an ethoxylated alcohol compound and a polyaminated fatty acid compound. The ethoxylated alcohol compound has the formula R.sup.1—(OCH.sub.2CH.sub.2).sub.n—OH, where R.sup.1 is a hydrocarbyl group having from 8 to 22 carbon atoms and n is from 1 to 8. The ethoxylated alcohol compound has a Hydrophilic-Lipophilic Balance (HLB) of less than or equal to 6. The polyaminated fatty acid compound has the formula R.sup.2—CO—NH—CH.sub.2—CH.sub.2—N(COR.sup.2)—CH.sub.2—CH.sub.2—NH—CO—R.sup.3, where R.sup.2 is a hydrocarbyl group having from 1 to 20 carbon atoms and R.sup.3 is a hydrocarbyl group having from 1 to 10 carbon atoms or an alkylene carboxylate group having formula —R.sup.4—COOH, where R.sup.4 is a saturated or unsaturated hydrocarbylene having from 1 to 10 carbon atoms. Methods of drilling wells include operating a drill in a wellbore in the presence of drilling fluid compositions.

Drilling fluid compositions include invert emulsion fluids having an oleaginous phase, an aqueous phase, and an emulsifier composition that includes an ethoxylated alcohol compound and a polyaminated fatty acid compound. The ethoxylated alcohol compound has the formula R.sup.1—(OCH.sub.2CH.sub.2).sub.n—OH, where R.sup.1 is a hydrocarbyl group having from 8 to 22 carbon atoms and n is from 1 to 8. The ethoxylated alcohol compound has a Hydrophilic-Lipophilic Balance (HLB) of less than or equal to 6. The polyaminated fatty acid compound has the formula R.sup.2—CO—NH—CH.sub.2—CH.sub.2—N(COR.sup.2)—CH.sub.2—CH.sub.2—NH—CO—R.sup.3, where R.sup.2 is a hydrocarbyl group having from 1 to 20 carbon atoms and R.sup.3 is a hydrocarbyl group having from 1 to 10 carbon atoms or an alkylene carboxylate group having formula —R.sup.4—COOH, where R.sup.4 is a saturated or unsaturated hydrocarbylene having from 1 to 10 carbon atoms. Methods of drilling wells include operating a drill in a wellbore in the presence of drilling fluid compositions.

The present invention refers to a composition for water-based foamed fluid with high thermal stability for drilling depressed areas in oil and gas wells, comprising: i) a base fluid or drilling water consisting of fresh water; ii) a stabilizing agent; ii) a viscosifying agent; iv) a filtering reducing agent; v) a clay inhibiting agent; vi) an alkalizing agent and acid gas sequestering agent; vii) a thermal stabilizing agent; and viii) a foaming agent. Also, the present invention refers to a system that uses said composition for fluid and water-based foamed fluid with high thermal stability, the method of preparing the composition for fluid, the method of preparing the fluid and application of the composition and fluid in a water-based foamed fluid system with high thermal stability for drilling depressed or low-pressure areas in oil and gas wells.

Methods and compositions for modified well fluids. One method including combining an amount of a synthetic functionalized additive with an intermediate well fluid composition to form a synthetic functionalized additive-containing well fluid composition; the synthetic functionalized additive comprising a synthetic layered magnesium silicate that is covalently bonded to a functional group, and the intermediate well fluid composition comprising a water-based continuous phase with solid particles, wherein the synthetic functionalized additive increases suspension stability of the solid particles versus a well fluid composition comprising the solid particles without the synthetic functionalized additive.

Techniques for drilling wellbores are described. The techniques include a) introducing a drilling fluid composition into a borehole defined by a formation; b) introducing a thinner composition including at least one tannin and at least one metal salt into the borehole; and c) contacting the thinner composition and the drilling fluid composition in the borehole, wherein the at least one tannin and at least one metal salt are not complexed ex situ. The at least one metal salt includes at least one copper salt, at least one zinc salt, or both at least one copper salt and at least one zinc salt.

In one embodiment, a retarded acid system comprises an aqueous acid and a retarding surfactant. The aqueous acid may comprise from 5 wt. % to 25 wt. % of a strong acid, that is, an acid having a K.sub.a greater than or equal to 0.01. The aqueous acid may further comprise from 75 wt. % to 95 wt. % water. The retarding surfactant may have the general chemical formula R—(OC.sub.2H.sub.4).sub.X—OH where R is a hydrocarbon having from 11 to 15 carbon atoms and x is an integer from 6 to 10. The retarding surfactant may have a hydrophilic-lipophilic balance from 8 to 16.

In one embodiment, a retarded acid system comprises an aqueous acid and a retarding surfactant. The aqueous acid may comprise from 5 wt. % to 25 wt. % of a strong acid, that is, an acid having a K.sub.a greater than or equal to 0.01. The aqueous acid may further comprise from 75 wt. % to 95 wt. % water. The retarding surfactant may have the general chemical formula R—(OC.sub.2H.sub.4).sub.X—OH where R is a hydrocarbon having from 11 to 15 carbon atoms and x is an integer from 6 to 10. The retarding surfactant may have a hydrophilic-lipophilic balance from 8 to 16.