Method for treatment of underground reservoirs

#This application is the U.S. national phase of International Application No. PCT/GB2008/002297 filed 3 Jul. 2008, which designated the U.S. and claims priority to UK Application No. GB 002297, filed 3 Jul. 2008, the entire contents of each of which are hereby incorporated by reference.

#The present invention relates to the production of oil, gas or water from wells drilled into underground reservoirs. It is also applicable to injection wells.

#During drilling, completion, workover and production operations there are numerous situations where the production or injection rate of an oil, gas or water well following these operations is limited or impaired due to the presence of formation damage. Types of damage include, but are not limited to, the presence of invert emulsion filter cakes, filter cakes from use of water-based muds, fluids filtrates or residues (including from hydraulic fracturing fluids, and gravel packing fluids) particulate materials such as fluid loss control agents and weighting agents, rock fines, biofilms, scales, emulsions, “water blocks” and hydrocarbon accumulations, including but not being limited to asphaltenes, waxes and paraffins.

#In order to confirm the presence of micelles in the micellar dispersions of the present invention, a number of exemplary dispersions were made up in filtered artificial sea water (Sigma sea salts Sigma Aldrich product number S-9883) using 10% v/v ORCA 1 or ORCA 2 (proprietary blends of surfactants commercially available from Cleansorb Limited) in combination with 10% v/v ORCA A, ORCA B or ORCA C (proprietary blends of carboxylic acid esters commercially available from Cleansorb Limited). Particle size analysis of the dispersions was carried out at 25° C. using a Malvern Zetasizer Nano ZS by laser light scattering.

#The average particle (micelle) size of the dispersions is shown in Table 1.

#TABLE 1 Average particle size and polydispersity index in examples of micellar dispersions Composition Z average Polydispersity Sample (in artificial sea water) Particle size (nm) index A 10% v/v ORCA 2 plus 9.89 0.231 10% v/v ORCA A B 10% v/v ORCA 2 plus 11.49 0.241 10% v/v ORCA B C 10% v/v ORCA 2 plus 8.70 0.266 10% v/v ORCA C D 10% v/v ORCA 1 plus 10.12 0.265 10% v/v ORCA A E 10% v/v ORCA 1 plus 12.14 0.335 10% v/v ORCA B F 10% v/v ORCA 1 plus 23.87 0.214 10% v/v ORCA C