Method of inhibiting or controlling release of well treatment agent
A microemulsion delivery system containing a well treatment agent in a water-in-oil microemulsion may be used for well remediation as well as in other treatment operations including stimulation, acidizing, and drilling. In addition, the water-in-oil microemulsion delivery system may be used to clean surface equipment and downhole equipment.
1. A method of inhibiting or controlling release of a well treatment agent in a well, a subterranean formation, a flow conduit or a vessel by introducing into the well, subterranean formation, flow conduit or vessel the well treatment agent in a water-in-oil microemulsion, wherein (a) the water-in-oil microemulsion provides for continuous release of the well treatment agent over a sustained period of time of at least six months; (b) the oil phase of the water-in-oil microemulsion is a solvent-surfactant blend; and (c) the amount of surfactant in the blend is from about 35 to about 80% by volume.
2. The method of claim 1 , wherein the water-in-oil microemulsion is introduced into a gas well, oil well or geothermal well.
3. The method of claim 1 , wherein the microemulsion has an oil phase comprising a solvent selected from the group consisting of unsaturated aliphatic cyclic hydrocarbons, a surfactant having an HLB value between from about 8 to about 18, and a C 1 -C 20 alcohol or glycol.
4. The method of claim 3 , wherein the surfactant is selected from the group consisting of polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, linear alcohol alkoxylates, alkyl ether sulfates, dodecylbenzene sulfonic acid (DDBSA), linear nonyl-phenols, dioxane, ethylene oxide, ethoxylated castor oils and mixtures thereof.
5. The method of claim 3 , wherein the water-in-oil microemulsion further contains an alcohol, a glycol or a mixture thereof.
6. The method of claim 5 , wherein the alcohol or glycol is selected from the group consisting of isopropanol, t-butanol, n-butanol, n-pentanol, n-hexanol, 2-ethyl-hexanol, ethylene glycol, polyethylene glycol, propylene glycol, triethylene glycol and mixtures thereof.
7. The method of claim 1 , wherein the microemulsion has an oil phase comprising a solvent of either a terpene or an alkyl, cyclic or aryl acid ester of a short chain alcohol or a mixture thereof.
8. The method of claim 7 , wherein the terpene is a monoterpene, a diterpene or a mixture thereof.
9. The method of claim 6 , wherein the monoterpene is d-limonene.
10. The method of claim 7 , wherein the solvent is an alkyl, cyclic or aryl acid ester or a mixture thereof.
11. The method of claim 1 , wherein the well treatment agent is at least one member selected from the group consisting of scale inhibitors, salt inhibitors, paraffin inhibitors, demulsifying agents, gas hydrate inhibitors, pH adjustment agents, corrosion inhibitors, asphaltene inhibitors, crosslinking agents, crosslinking delaying agents, oxygen scavengers, biocides, breakers, buffers, acids and esters.
12. The method of claim 1 , wherein the well treatment agent has a particle size between from about 0.001 to about 100 microns.
13. The method of claim 1 , wherein the microemulsion has an oil phase selected from the group consisting of diesel, kerosene, crude oil, condensate, synthetic oils, an ester, linear-α-olefins, poly-α-olefins, paraffins, linear alkyl benzenes, esters, acetals and mixtures thereof.
14. The method of claim 1 , wherein the amount of well treatment agent in the water-in-oil microemulsion is between from about 2 to about 20 weight percent.
15. The method of claim 1 , wherein a well treatment fluid contains the water-in-oil microemulsion and further wherein the amount of water-in-oil microemulsion in the well treatment fluid is between from about 15 ppm to about 100,000 ppm.
16. The method of claim 1 , wherein the water-in-oil microemulsion is introduced into the well or formation with a treatment fluid selected from the group consisting of stimulation fluids, drilling fluids, drill-in fluids, completion fluids and fluid loss control pills.
17. The method of claim 16 , wherein the treatment fluid is injected directly into the well through a delivery tube and removes fines, asphaltenes, paraffins or water blocks or a combination thereof formed during treatment of the well.
18. The method of claim 1 , wherein the water-in-oil microemulsion provides for continuous release of the well treatment agent introduced into the well up to three years.