Calcium carbonate coated tracers for assessing acid stimulation operations in a hydrocarbon well
Methods for assessing the effectiveness of an acid stimulation operation in a hydrocarbon well. The methods use encapsulated tracer particles comprising a tracer material that is coated with a calcium carbonate shell. Different encapsulated tracer particles are placed into different portions of a well. A subsequent acid stimulation operation dissolves the calcium carbonate shell and releases the tracer material. The different tracer materials indicate the effectiveness of the acid stimulation operation in different portions of the well.
1 . A method of assessing an acid stimulation of a hydrocarbon well, the method comprising:
pumping a first fracturing slurry comprising first encapsulated tracer particles into a first annular pack of a first fracturing stage in the hydrocarbon well, wherein the first encapsulated tracer particles comprise a first tracer coated with calcium carbonate;
pumping a second fracturing slurry comprising second encapsulated tracer particles into a second annular pack of a second fracturing stage in the hydrocarbon well, wherein the second encapsulated tracer particles comprise a second tracer coated with calcium carbonate;
at a subsequent time after pumping the first fracturing slurry and the second fracturing slurry, pumping an acid solution into the hydrocarbon well; and
measuring an amount of the first tracer and the second tracer in a produced fluid from the hydrocarbon well;
wherein the pumping an acid solution into the hydrocarbon well comprises an acid treatment for remedial stimulation of the hydrocarbon well when productivity of the hydrocarbon well has declined.
2 . The method of claim 1 , wherein the acid solution dissolves the calcium carbonate coating the first encapsulated tracer particles and the calcium carbonate coating the second encapsulated tracer particles.
3 . The method of claim 1 , wherein the first annular pack accesses a first zone of the hydrocarbon well and the second annular pack accesses a second zone of the hydrocarbon well.
4 . The method of claim 1 , wherein the first encapsulated tracer particles and the second encapsulated tracer particles have an average diameter greater than zero and less than 3 mm.
5 . The method of claim 4 , wherein the first fracturing slurry and the second fracturing slurry further comprise proppant particles having an average diameter greater than zero and less than 3 mm.
6 . The method of claim 1 , wherein the first encapsulated tracer particles and the second encapsulated tracer particles have an average diameter greater than zero and less than 1 mm.
7 . The method of claim 6 , wherein the first fracturing slurry and the second fracturing slurry further comprise proppant particles having an average diameter greater than zero and less than 1 mm.
8 . The method of claim 1 , wherein:
a concentration of the first encapsulated tracer particles as a percentage by weight of total solids in the first slurry is greater than 0% and less than 10%; and
a concentration of the second encapsulated tracer particles as a percentage by weight of total solids in the second slurry is greater than 0% and less than 10%.
9 . The method of claim 1 wherein the first annular pack is placed around a first sand control screen and the second annular pack is placed around a second sand control screen.