Use of oil and gas field chemicals

Details Use of oil and gas field chemicals Use of oil and gas field chemicals

1999-01-15

2001-05-01

Alexander, Lyle A. (Department: 1743)

Earth boring, well treating, and oil field chemistry

Well treating

Contains organic component

C507S247000, C166S295000, C166S307000, C166S305100

Reexamination Certificate

active

06225263

ABSTRACT:

This invention relates to oil and gas field chemicals and their use especially in increasing oil or gas recovery.
In use the rate of oil recovery from oil and gas fields often reduces with time.
The reduction is often associated with formation damage which can manifest itself as reduced permeability of the formation to oil or gas. In addition it is often desirable to inject water based fluids into a formation at a distance from a producing well to drive the oil into the well.
For stimulation of oil recovery by injection of chemicals into a producing well to overcome problems with formation damage e.g. water blocking, very dilute aqueous solutions of nonionic or anionic surfactants have been described, in particular alkoxylated alkyl sulphates and alkoxylated alkaryl sulphonates (see U.S. Pat. No. 5,092,405).
U.S. Pat. No. 3,902,557 describes a method of treating the formation surrounding a well by injection of a solvent including a C
4
to C
10
alkyl ether of a polyglycol ether containing a C
4
to C
10
alkyl ether of a polyglycol ether containing 10-22 carbon atoms per molecule. The solvent is said to improve the permeability of the formation adjacent to the well bore. C
4
to C
8
monoalkyl ethers of tri and tetra ethylene glycols are preferred in particular the hexyl ether while the butyl ether is also mentioned. The solvent may be diluted with an organic liquid such as alcohol, e.g. isopropanol.
Alkylglycol ethers have now been found that can give substantial improvements in recovery of oil or gas from underground formations, especially in overcoming problems of formation damage.
The present invention provides a method of recovering at least one of oil and gas from an underground formation comprising oil or gas, which comprises introducing into said formation at least one mono alkyl ether of polyethylene glycol in which the alkyl group has 3-5 carbons and the polyethylene glycol contains 3-6 ethylene oxy units (hereinafter called compound 1), and recovering oil and/or gas from said formation. The preferred monoalkyl ether is a mono butyl ether
The present invention also provides a method of increasing the recovery of at least one of oil and gas from an underground formation comprising it, which comprises introducing into said formation at least one compound 1, and recovering oil and/or gas from said formation.
The present invention also provides a method of recovering at least one of oil and gas from an underground formation comprising oil or gas wherein a formulation, comprising at least one mono alkyl ether of polyethylene glycol in which the alkyl group has 3-5 carbons and the polyethylene glycol contains 3-6 ethylene oxy units is introduced into said formation and oil and/or gas is recovered wherein the method is not a squeeze treatment in which at least one alkyltriglycol ether and at least one water miscible oil or gas field production chemical are introduced into the formation.
The compound is a monoalkyl ether of a polyethylene glycol, in which the alkyl group is a straight or branched chain alkyl group of 3-5 carbons, e.g. n or iso propyl, n, iso, sec., tert-butyl, n, iso, sec., tert-pentyl (amyl), especially n-butyl. There are 3-6 e.g. 4 or 5 ethylene oxy units in compounds 1, though 3 are most preferred. Examples of suitable compound 1 are the mono-n-butyl ether of triethylene glycol, also known as n butyl triglycol ether, and the mono-n butyl ethers of tetraethylene glycol and penta ethylene glycol. The compound 1 may be substantially pure or may be a mixture with at least one corresponding alkyl ether of another polyethylene glycol, especially with 3-6 ethylene oxy units, In particular the mixture may comprise at least 60% especially at least 80% e.g 60-99%, or 80-98% of the compound(s) 1 and up to 40% especially up to 20% e.g. 1-40% or 2-20% of these other glycol ethers. The mixture may also comprise the monoalkyl ethers of a mixture of the polyethylene glycols, said glycols with a molar average of 2.6-6.4 e.g. 2.9-4.5 or 4.0-5.8 ethylene oxy units. The glycol ethers, compounds 1 are usually weakly structuring amphiphiles. The mixture may also contain small amounts e.g. up to 10% each of C
3-5
alkyl monoalkyl ethers of polyethylene glycols with 7-20 e.g. 7-10 ethylene oxy units, especially with a total of up to 40% or 30% of these ethers.
Compound(s) 1 may be used alone or may be used in admixture with other glycol ethers still such as mono alkyl ethers of mono and di ethylene glycol, in which the alkyl group which may be straight or branched has 1-8 carbons e.g. methyl, ethyl, propyl, butyl, hexyl or octyl. Examples are Ethylene glycol mono ethyl ether, Ethylene glycol mono-n-propyl ether, Ethylene glycol monoiso-propyl ether, Ethylene glycol mono-n-butyl ether, Ethylene glycol mono-isobutyl ether, Ethylene glycol mono-2-butyl ether, Ethylene glycol mono-tert-butyl ether, Diethylene glycol mono-n-propyl ether, Diethylene glycol mono-iso-propyl ether, Diethylene glycol mono-n-butyl ether, Diethylene glycol mono-isobutyl ether, Diethylene glycol mono-2-butyl ether, Diethylene glycol mono-tert-butyl ether, Diethylene glycol mono-n-pentyl ether, Diethylene glycol mono-2-methylbutyl ether, Diethylene glycol mono-3-methylbutyl ether, Diethylene glycol mono-2-pentyl ether, Diethylene glycol mono-3-pentyl ether, Diethylene glycol mono-tert-pentyl ether. Mono-methyl or mono ethyl ethers of triethylene glycol may also be used. The amounts of compound(s) 1 in these mixtures may be at least 60% especially at least 70% e.g. 60-98% or 70-98%, and the amount of the other glycol ether may be up to 40% e.g. up to 20% such as 1-40% or 2-30% by weight of the total mixture. In the present invention it is possible to use co-product streams from glycol ether manufacturing processes which contain a high proportion of glycol ethers, especially alkyl triglycol ethers such as e.g. n-butyltriglycol ether. Such a co-product stream may comprise a majority of n-butyltriglycol ether with smaller amounts of other alkyl triglycol ethers. One such co-product stream comprises 70-80o% e.g. about 75% w/w of n-butyltriglycol ether, 1-5% e.g. about 2.5% w/w of butyldiglycol ether, 15-25% e.g about 19% of butyl tetraglycol ether and 1-5% about 2% of butyl pentaglycol ether. A mixture of about 75% w/w n-butyl triglycol ether, about 2.5% w/w of butyl diglycol ether, about 19% butyl tetraglycol ether and about 2% of butyl pentaglycol ether, hereinafter called Mixture 2 is preferred.
The compound 1 may have an hydrophilic lipophitic balance (HLB) value of 12-17 preferably 14-16.5, especially 14.5-16. The compound 1 is preferably a compound capable when mixed with distilled water and octane in at least one proportion of forming 3 liquid phases at a temperature, which is at least one value in the range 20-200° C., e.g. especially 50-150° C. or 100-130° C. Relative weight proportions of the compound 1, distilled water and octane giving these 3 phases can be 10-50:60-20:50. The compound 1 may also have a cloud point in admixture with distilled water/or especially with water containing up to salt saturation e.g. up to 40 g/l sodium chloride, of 0-250° C., especially 50-150° C., in particular below the reservoir temperature, but may be miscible with the distilled water or formation water at up to 130° C.
The compound 1 may be injected into the formation undiluted, but may also be mixed with water in an aqueous formulation containing at least 1%, particularly 6% and especially at least 15% by weight of compound 1; the formulation may contain 1-99% e.g. 1-60%, particularly 6-50% and especially 15-50% and preferably 25-45% of compound 1. The aqueous medium with the compound 1 may be fresh, tap, river, sea, produced or formation water, with a total salinity of 0-250 g/l e.g. 5-50g/l such as 1045 g/l (especially with a high barium content such as 50-3000 ppm Ba) and pH of 0.5-10 e.g. 3-8 such as 4-6. The formulation may contain a weight amount of compound 1 greater than (preferably at least 5 or 10% greater than) the concentration of compound 1 in the lowest “aqueous” phase of the 3 phase mixture of compound

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