Downhole methods and compositions used in such

A method to prepare a hydrocarbon-bearing formation for a stimulation operation, said method comprising the following steps:

• step a) providing a wellbore having a casing;
• step b) assessing at least a first location and a second location for perforation of said casing;
• step c) inserting a bottom hole assembly into said wellbore;
• said bottom hole assembly comprising a plug and a perforation tool and said bottom hole assembly being connected to a wireline;
• step d) injecting an acidic composition into said wellbore;
• wherein said acidic composition is in direct contact with said perforation tool, said wireline and said casing;
• step e) positioning and setting said plug in the wellbore at a position downhole but proximate to said first location;
• step f) positioning said perforation tool at said first location;
• step g) perforating said casing at said first location with the perforation tool thereby creating a first perforated area and a first cementitious debris;
• step h) causing said acidic composition to come into contact with said first perforated area and said first cementitious debris for a predetermined period of time to prepare the formation for said stimulation operation;
• step i) moving the perforation tool uphole to said second location;
• step j) perforating said casing at said second location with the perforation tool thereby creating a second perforated area and a second cementitious debris;
• step k) causing said acidic composition to come into contact with the second perforated area and said second cementitious debris for a predetermined period of time to prepare said formation for said stimulation operation;
• step l) removing the perforation tool from the wellbore;
• wherein said acid composition comprises a urea-HCl acid and a corrosion inhibitor package, said corrosion inhibitor package comprising at least two compounds selected from:
• Group B;
• Group C;
• Group D;
• Group E, where the at least two compounds are selected from different groups and wherein:
• Group B comprises compounds encompassed within the following general chemical description:
• acetylenic compound;
• unsaturated alcohol;
• acetylinic alcohol;
• alkoxylated acetylenic alcohol;
• alkoxy phenols;
• diacetylenic alcohols;
• C10-C16 ethoxylated alcohols;
• Group C comprises compounds encompassed within the following general chemical description:
• a group 15 metal including bismuth, antimony;
• antimony compounds;
• germanium compounds;
• Group D comprises compounds encompassed within the following general chemical description:
• sulfur-containing compounds;
• mercapto-compounds;
• organosulfur compounds reaction products of thiourea;
• thiodiglycol alkoxylates;
• Group E comprises compounds encompassed within the following general chemical description:
• nitrogen-containing surfactant;
• and non-ionic surfactant.