Abstract: Petroleum additive formulations include a petroleum additive dissolved in a carrier fluid including at least one compound of the formula (I): (R2)p-Ph-(CH2)m—COO—(AO)n—R1 where; R1 is C1 to C10 alkyl; AO is alkyleneoxy; n is 0 or from 1 to 100; m is 0, 1 or 2; and Ph is a phenyl group, which may be substituted with groups (R2)p; where each R2 is independently C1 to C4 alkyl or alkoxy; and p is 0, 1 or 2. Further, crude petroleum or petroleum refinery streams can be treated by adding a petroleum additive dissolved in a carrier fluid of the formula (I) to the product stream. Desirably the carrier fluid is or includes iso-propyl benzoate and/or 2-ethyl hexyl benzoate.

Abstract: Drilling, completing or workover of a well, particularly an oil and/or gas well, is carried out using a fluid which includes a continuous phase including an ester of the formula (I): (R2)p-Ph-(CH2)m—COO-(AO)n-R1 where R1, AO, n, m, Ph, R2 and p have defined meanings and particularly where the esters are alkyl or alkenyl benzoate esters. These esters are beneficial by having a range of viscosities, especially extending to low viscosities, and attractive toxicological and environmental profiles for use in drilling, completion and/or workover of wells.

Abstract: Stimulation, particularly fracturing or acidising, of hydrocarbon wells having bores leading to hydrocarbon bearing uses a fluid including a continuous phase of or including a compound of the formula (1): (R2)p—Ph—(CH2)m—COO—(AO)n—R1 where R1, AO, n, m, Ph, R2 and p having defined meanings and particularly where the esters are alkyl or alkenyl benzoate esters. These esters are beneficial by having a range of viscosities, especially extending to low viscosities, and attractive toxicological and environmental profiles for use in well stimulation.

Abstract: Drilling, completing or workover of a well, particularly an oil and/or gas well, is carried out using a fluid which includes a continuous phase including an ester of the formula (I): (R2)p-Ph-(CH2)m—COO-(AO)n—R1 where R1, AO, n, m, Ph, R2 and p have defined meanings and particularly where the esters are alkyl or alkenyl benzoate esters. These esters are beneficial by having a range of viscosities, especially extending to low viscosities, and attractive toxicological and environmental profiles for use in drilling, completion and/or workover of wells.

Abstract: The deposition of asphaltenes and/or petroleum waxes can be inhibited and/or asphaltenes and/or petroleum waxes can be removed from a well, pipe or vessel by contacting the asphaltene and/or petroleum wax or the well pipe or vessel adjacent a location where deposition of asphaltene and/or petroleum wax is expected, with a solvent including at least one compound of the formula (I): R1—(AO)n—OOC—(CH2)m—Ph—(R2)p where R1 is a C1 to C20 hydrocarbyl group; AO is an alkyleneoxy group and may vary along the (poly)alkyleneoxy chain; n is 1 or from 1 to 100; m is 0, 1 or 2; and Ph is a phenyl group, which may be substituted with groups (R2)p where each R2 is independently a C1 to C4 alkyl or alkoxy group; and p is 0, 1 or 2, and subsequently removing the solvent with softened, dissolved or dipersed asphaltenes and/or petroleum waxes from the well, pipe or vessel.

Abstract: Stimulation, particularly fracturing or acidising, of hydrocarbon wells having bores leading to hydrocarbon bearing uses a fluid including a continuous phase of or including a compound of the formula (I): (R2)p—Ph—(CH2)m—COO—(AO)n—R1 where R1, AO, n, m, Ph, R2 and p have defined meanings and particularly where the esters are alkyl or alkenyl benzoate esters. These esters are beneficial by having a range of viscosities, especially extending to low viscosities. and attractive toxicological and environmental profiles for use in well stimulation.

Abstract: Petroleum additive formulations include a petroleum additive dissolved in a carrier fluid including at least one compound of the formula (I): (R2)p—Ph—(CH2)m—COO—(AO)n—R1 where; R1 is C1 to C10 alkyl; AO is alkyleneoxy; n is 0 or from 1 to 100; m is 0, 1 or 2; and Ph is a phenyl group, which may be substituted with groups (R2)p; where each R2 is independently C1 to C4 alkyl or alkoxy; and p is 0, 1 or 2. Further, crude petroleum or petroleum refinery streams can be treated by adding a petroleum additive dissolved in a carrier fluid of the formula (I) to the product stream. Desirably the carrier fluid is or includes iso-propyl benzoate and/or 2-ethyl hexyl benzoate.

Abstract: A thickener and surfactant for a driving fluid used in enhanced oil recovery comprises a salt of a sulphated polyoxyethylene alcohol in which at least 40 wt % of the alcohol portion of the sulphated polyoxyethylene alcohol is a C.sub.8 to C.sub.20 primary alcohol having a C.sub.1 to C.sub.3 alkyl substituent in the 2-position of an otherwise linear chain. The balance of the alcohol portion may be made up of a linear primary alcohol of same carbon number as the 2-alkyl branched alcohol.