A method of assessing the effect of a production chemical on the stability of a water and oil emulsion, the emulsion comprising the production chemical, is provided. The method comprises: applying a potential difference across the emulsion at a detection site; measuring a current flowing through the emulsion due to the applied potential difference; and using this measured current to assess the effect of the production chemical. The step of using the measured current to assess the effect of the production chemical may comprise determining, based on the measured current, whether a critical potential of the emulsion has been reached or exceeded. The emulsion may be a crude oil emulsion. It may be a water-in-oil emulsion. The production chemical may be an emulsion breaker. Also provided is an apparatus for assessing the effect of a production chemical on a water and oil emulsion.

Drilling fluid compositions include an emulsifier having a generic structure A, structure B, or a combination thereof. Structure A includes an amide (e.g., amic acid group) and structure B includes a cyclic imide. The emulsifier of the emulsifier system is formed by reacting a fatty oil amine (e.g., oleyl amine), with a cyclic anhydride (e.g., succinic anhydride) in the absence of diluent or in a diluent that does not react with the starting materials. The reaction takes place via application of a stepwise increase in temperature. An emulsifier based on structure A is formed when the reaction temperature is maintained at 50 to 100° C. for 1 to 3 hours. A further increase in reaction temperature (e.g., up to 200° C.) can include water elimination which results predominately in the formation of a molecule represented by structure B.

Drilling fluid compositions include an emulsifier having a generic structure A, structure B, or a combination thereof. Structure A includes an amide (e.g., amic acid group) and structure B includes a cyclic imide. The emulsifier of the emulsifier system is formed by reacting a fatty oil amine (e.g., oleyl amine), with a cyclic anhydride (e.g., succinic anhydride) in the absence of diluent or in a diluent that does not react with the starting materials. The reaction takes place via application of a stepwise increase in temperature. An emulsifier based on structure A is formed when the reaction temperature is maintained at 50 to 100° C. for 1 to 3 hours. A further increase in reaction temperature (e.g., up to 200° C.) can include water elimination which results predominately in the formation of a molecule represented by structure B.

A wellbore fluid comprising an aqueous base fluid and a plurality of nanoparticles suspended in the aqueous base fluid. The nanoparticles are present in the wellbore fluid in an amount effective to have an effect of increasing the density by at least 0.2 lb/gal.

A wellbore fluid comprising an aqueous base fluid and a plurality of nanoparticles suspended in the aqueous base fluid. The nanoparticles are present in the wellbore fluid in an amount effective to have an effect of increasing the density by at least 0.2 lb/gal.

An invert emulsion fluid may include a oleaginous external phase, a nonoleaginous internal phase, wherein a ratio of the oleaginous external phase to nonoleaginous internal phase is less than 55:45, a emulsifier, a particulate weighting agent dispersed in the non-oleaginous internal phase, and a viscosifier stabilizing the dispersion of the particulate weighting agent in the non-oleaginous internal phase.

An invert emulsion fluid may include a oleaginous external phase, a nonoleaginous internal phase, wherein a ratio of the oleaginous external phase to nonoleaginous internal phase is less than 55:45, a emulsifier, a particulate weighting agent dispersed in the non-oleaginous internal phase, and a viscosifier stabilizing the dispersion of the particulate weighting agent in the non-oleaginous internal phase.

The organophilic clay comprises a smectite-type clay ion exchanged with quaternary ammonium ions, where at least 75 mol-% of said quaternary ammonium ions are bis-(2-hydroxypropyl)-dimethylammonium fatty acid esters and at least 90% of the fatty acid moieties of the bis-(2-hydroxypropyl)-dimethylammonium fatty acid esters have a structure RC(O) with group R being a linear alkyl or alkenyl group containing from 9 to 21 carbon atoms. The organophilic clay is useful for thickening oil based compositions, in particular drilling fluids for drilling oil or gas wells, comprising an oil phase.

The organophilic clay comprises a smectite-type clay ion exchanged with quaternary ammonium ions, where at least 75 mol-% of said quaternary ammonium ions are bis-(2-hydroxypropyl)-dimethylammonium fatty acid esters and at least 90% of the fatty acid moieties of the bis-(2-hydroxypropyl)-dimethylammonium fatty acid esters have a structure RC(O) with group R being a linear alkyl or alkenyl group containing from 9 to 21 carbon atoms. The organophilic clay is useful for thickening oil based compositions, in particular drilling fluids for drilling oil or gas wells, comprising an oil phase.

A drilling fluid composition comprising a continuous phase and a disperse phase, the continuous phase comprising fatty acid methyl esters derived from soy oil, and sunflower lecithin as an emulsifier. A method for increasing the electrical stability of a drilling fluid composition.