Apparatus and method for behind casing washout

1. A casing washout perforating gun assembly for use in a wellbore, the casing washout perforating gun assembly comprising:

a carrier gun body;

an uphole plurality of charges supported within the carrier gun body, the uphole plurality of charges having an uphole size or uphole explosive design to perforate uphole openings having uphole opening areas within a wellbore casing; and

a downhole plurality of charges supported within the carrier gun body, the downhole plurality of charges having a different downhole size or different downhole explosive design to perforate downhole openings having downhole opening areas within the wellbore casing, the downhole opening areas at least 20 percent less than the uphole opening areas.

2. The casing washout perforating gun assembly as recited in claim 1 , wherein the downhole plurality of charges and uphole plurality of charges each include:

a case exterior, the case exterior including an outer surface, and an inner surface forming a cavity;

a liner located within the cavity; and

explosive material located within a gap between the inner surface of the case exterior and the liner.

3. The casing washout perforating gun assembly as recited in claim 2 , wherein a diameter (d 1 ) of the case exterior for the downhole plurality of charges is at least 20 percent smaller than a diameter (d 2 ) of the case exterior for the uphole plurality of charges.

4. The casing washout perforating gun assembly as recited in claim 3 , wherein the diameter (d 1 ) of the case exterior for the downhole plurality of charges is at least 50 percent smaller than the diameter (d 2 ) of the case exterior for the uphole plurality of charges.

5. The casing washout perforating gun assembly as recited in claim 1 , wherein the downhole plurality of charges are linearly aligned within the carrier gun body.

6. The casing washout perforating gun assembly as recited in claim 1 , wherein the downhole plurality of charges are helically aligned within the carrier gun body.

7. The casing washout perforating gun assembly as recited in claim 1 , wherein the downhole plurality of charges are left-hand helically aligned within the carrier gun body.

8. The casing washout perforating gun assembly as recited in claim 7 , wherein the uphole plurality of charges are right-hand helically aligned within the carrier gun body.

9. The casing washout perforating gun assembly as recited in claim 1 , wherein the downhole plurality of charges are positioned within the carrier gun body to create angled perforations in the wellbore casing.

10. The casing washout perforating gun assembly as recited in claim 9 , wherein the downhole plurality of charges are positioned within the carrier gun body to create uphole angled perforations in the wellbore casing.

11. The casing washout perforating gun assembly as recited in claim 10 , wherein the uphole plurality of charges are positioned within the carrier gun body to create downhole angled perforations in the wellbore casing.

12. A method for washing and plugging a wellbore, comprising:

deploying a casing washout perforating gun assembly into a longitudinal section of a wellbore casing located within a wellbore, the casing washout perforating gun assembly including:

a carrier gun body;

a downhole plurality of charges supported within the carrier gun body; and

an uphole plurality of charges supported within the carrier gun body;

perforating a plurality of smaller downhole openings within the longitudinal section of the wellbore casing using the downhole plurality of charges, and a plurality of larger uphole openings within the wellbore casing using the uphole plurality of charges, the plurality of smaller downhole openings having downhole opening areas at least 20 percent less than uphole opening areas of the plurality of larger uphole openings;

deploying a washing tool into the wellbore casing proximate the plurality of smaller downhole openings and plurality of larger uphole openings;

pumping washing fluid through the washing tool radially outward into an annulus between the wellbore casing and the wellbore through the plurality of smaller downhole openings and retrieving excess washing fluid and debris from the annulus radially inward through the plurality of larger uphole openings, thereby cleaning the annulus; and

pumping a fluidized plugging material through a work string into the wellbore casing proximate the longitudinal section, and thereby into the cleaned annulus, using one or more of the plurality of smaller downhole openings and plurality of larger uphole openings, to plug the wellbore casing and the cleaned annulus along at least a portion of the longitudinal section of the wellbore.

13. The method as recited in claim 12 , wherein a diameter (d s ) of the plurality of smaller downhole openings is at least 50 percent smaller than a diameter (d 1 ) of the plurality of larger uphole openings.

14. The method as recited in claim 12 , wherein the plurality of smaller downhole openings are linearly aligned in the wellbore casing.

15. The method as recited in claim 12 , wherein the plurality of smaller downhole openings are helically aligned in the wellbore casing.

16. The method as recited in claim 15 , wherein the plurality of smaller downhole openings are left-hand helically aligned in the wellbore casing, and the plurality of larger uphole openings are right-hand helically aligned in the wellbore casing.

17. The method as recited in claim 12 , wherein the plurality of smaller downhole openings are angled relative to a longitudinal face of the wellbore casing.

18. The method as recited in claim 17 , wherein the plurality of smaller downhole openings are angled uphole relative to a longitudinal face of the wellbore casing.

19. The method as recited in claim 18 , wherein the plurality of larger uphole openings are angled downhole relative to a longitudinal face of the wellbore casing.