# US 2025/0146388 A1 · Tandem subs for perforating gun systems > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2025/0146388 A1 - Document ID: US20250146388A1 - Status: Published application - Kind: A1 - Application number: 18/940,488 - Filed: 2024-11-07 - Published: 2025-05-08 - Earliest claimed: 2023-11-07 - Assignees: G&H Diversified Manufacturing LP - Applicants: G&H Diversified Manufacturing LP - Inventors: James Edward Kash; Ryan Ward; Benjamin Vascal Knight - Web page: https://patentgrep.com/patent/US20250146388A1 ## CPC - E21B 43/116: Gun or shaped-charge perforators - E21B 43/1185: Ignition systems - E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS ## Abstract A method for forming a tandem sub for a perforating gun system includes forming a tubular housing including a longitudinal first end, a longitudinal second end opposite the first end, a central passage defined by an inner surface that forms a seal bore defining a minimum inner diameter of the central passage and an annular receptacle, wherein the housing is connectable to an outer housing of a perforating gun, and installing a pass-thru assembly including an electrically conductive signal bar and a surrounding electrical insulator in the central passage of the housing whereby a radial gap is formed between an outer surface of the insulator of the pass-thru assembly at a longitudinal end of the pass-thru assembly and a portion of the inner surface of the housing defining the receptacle. ## Claims ### Claim 1 A tandem sub for a perforating gun system, comprising: a tubular housing comprising a longitudinal first end, a longitudinal second end opposite the first end, a central passage defined by an inner surface that forms a seal bore defining a minimum inner diameter of the central passage and an annular receptacle, wherein the housing is connectable to an outer housing of a perforating gun; and an electrical pass-thru assembly configured to electrically connect to the perforating gun and comprising a longitudinal first end, a longitudinal second end opposite the first end, an electrically conductive signal bar, and an electrical insulator surrounding a periphery of the signal bar; wherein the signal bar has a longitudinal first end defining a first electrical contact of the tandem sub and configured to establish an electrical connection with a first electrical component separate from and external the tandem sub, and a longitudinal second end opposite the first end and defining a second electrical contact of the tandem sub that is longitudinally opposite and electrically connected to the first electrical contact and configured to establish an electrical connection with a second electrical component separate from and external the tandem sub, wherein the signal bar is rigid along the entire longitudinal length thereof extending from the first end to the second end; wherein the insulator has an outer surface sealingly contacting the seal bore of the housing when the pass-thru assembly is installed in the housing; wherein one of the first end and the second end of the pass-thru assembly longitudinally overlaps the receptacle of the housing when the pass-thru assembly is installed in the housing whereby a radial gap is formed between the outer surface of the insulator and a portion of the inner surface of the housing defining the receptacle. ### Claim 2 (depends on 1) The tandem sub of claim 1, wherein the radial gap is equal to or greater than 0.040 inches. ### Claim 3 (depends on 1) The tandem sub of claim 1, wherein the radial gap is equal to or greater than 0.050 inches. ### Claim 4 (depends on 1) The tandem sub of claim 1, wherein the radial gap is equal to or greater than 0.060 inches. ### Claim 5 (depends on 1) The tandem sub of claim 1, wherein a ratio of the radial gap to an outer diameter of the pass-thru assembly is between 5% and 25%. ### Claim 6 (depends on 1) The tandem sub of claim 1, wherein a ratio of the radial gap to an outer diameter of the pass-thru assembly is between 6% and 18%. ### Claim 7 (depends on 1) The tandem sub of claim 1, wherein a ratio of the radial gap to an outer diameter of the pass-thru assembly is between 7.5% and 12%. ### Claim 8 (depends on 1) The tandem sub of claim 1, wherein the receptacle of the housing is located directly adjacent to the seal bore. ### Claim 9 (depends on 1) The tandem sub of claim 1, wherein a radius of the receptacle is at least 20% greater than a radius of the seal bore. ### Claim 10 (depends on 1) The tandem sub of claim 1, wherein a radius of the receptacle is at least 40% greater than a radius of the seal bore. ### Claim 11 (depends on 1) The tandem sub of claim 1, wherein a radius of the receptacle is at least 50% greater than a radius of the seal bore. ### Claim 12 (depends on 1) The tandem sub of claim 1, wherein a radius of the receptacle is at least 100% greater than a radius of the seal bore. ### Claim 13 (depends on 1) The tandem sub of claim 1, wherein the first end of the pass-thru assembly corresponds to an uphole end of the pass-thru assembly when the pass-thru assembly is installed in the housing. ### Claim 14 (depends on 1) The tandem sub of claim 1, wherein the pass-thru assembly comprises one or more annular seal assemblies positioned along the outer surface of the insulator for sealing against the seal bore of the housing when the pass-thru assembly is installed in the outer housing. ### Claim 15 (depends on 1) The tandem sub of claim 1, wherein the signal bar is positioned in the central passage of the housing. ### Claim 16 (depends on 15) The tandem sub of claim 15, wherein the central passage of the housing comprises a longitudinal first end, a longitudinal second end opposite the first end, and wherein the pass-thru assembly creates a pressure seal between the first end and the second end of the central passage. ### Claim 17 (depends on 1) The tandem sub of claim 1, wherein the insulator of the pass-thru assembly comprises a molded insulator sealably adhered to an outer surface of the signal bar. ### Claim 18 (depends on 1) The tandem sub of claim 1, wherein the insulator extends continuously across the entire longitudinal length of the signal bar. ### Claim 19 A method for forming a tandem sub for a perforating gun system, comprising: (a) forming a tubular housing comprising a longitudinal first end, a longitudinal second end opposite the first end, a central passage defined by an inner surface that forms a seal bore defining a minimum inner diameter of the central passage and an annular receptacle, wherein the housing is connectable to an outer housing of a perforating gun; and (b) installing a pass-thru assembly comprising an electrically conductive signal bar and a surrounding electrical insulator in the central passage of the housing whereby a radial gap is formed between an outer surface of the insulator of the pass-thru assembly at a longitudinal end of the pass-thru assembly and a portion of the inner surface of the housing defining the receptacle. ### Claim 20 (depends on 19) The method of claim 19, wherein a magnitude of the radial gap is selected based on one or more parameters of an electrical circuit formable using the signal bar of the pass-thru assembly. ### Claim 21 (depends on 19) The method of claim 19, further comprising: (c) positioning one or more annular seal assemblies along the outer surface of the insulator of the pass-thru assembly whereby the one or more seal assemblies seal against a portion of the inner surface of the housing defining the seal bore when the pass-thru assembly is installed in the central passage of the housing. ### Claim 22 (depends on 19) The method of claim 19, wherein (b) comprises longitudinally sliding the pass-thru assembly into and through the central passage of the housing whereby the end of the pass-thru assembly longitudinally overlaps the receptacle of the housing. ### Claim 23 (depends on 19) The method of claim 19, wherein the radial gap is equal to or greater than 0.040 inches. ### Claim 24 (depends on 19) The method of claim 19, wherein the radial gap is equal to or greater than 0.050 inches. ### Claim 25 (depends on 19) The method of claim 19, wherein the radial gap is equal to or greater than 0.060 inches. ### Claim 26 (depends on 19) The method of claim 19, wherein a ratio of the radial gap to an outer diameter of the pass-thru assembly is between 5% and 25%. ### Claim 27 (depends on 19) The method of claim 19, wherein a ratio of the radial gap to an outer diameter of the pass-thru assembly is between 6% and 18%. ### Claim 28 (depends on 19) The method of claim 19, wherein a ratio of the radial gap to an outer diameter of the pass-thru assembly is between 7.5% and 12%. ### Claim 29 (depends on 19) The method of claim 19, wherein a radius of the receptacle is at least 20% greater than a radius of the seal bore. ### Claim 30 (depends on 19) The method of claim 19, wherein a radius of the receptacle is at least 40% greater than a radius of the seal bore. ### Claim 31 (depends on 19) The method of claim 19, wherein a radius of the receptacle is at least 50% greater than a radius of the seal bore. ### Claim 32 (depends on 19) The method of claim 19, wherein a radius of the receptacle is at least 100% greater than a radius of the seal bore. ### Claim 33 A method for operating a perforating gun system, comprising: (a) connecting a tandem sub of the perforating gun system to a perforating gun of the perforating gun system, the tandem sub comprising a tubular housing having a central passage and a pass-thru assembly comprising an electrically conductive signal bar and a surrounding electrical insulator, the pass-thru assembly installed in the central passage of the housing whereby a radial gap is formed between an outer surface of the insulator of the pass-thru assembly at a longitudinal end of the pass-thru assembly and a portion of an inner surface of the housing defining a receptacle; (b) conveying a tool string comprising the tandem sub and the perforating gun connected therewith into a wellbore; (c) establishing an electrical signal path extending through the signal bar of the pass-thru assembly of the tandem sub; and (d) establishing an electrical ground path extending through the housing of the tandem sub and spaced from the signal path by the radial gap. ### Claim 34 (depends on 33) The method of claim 33, wherein the radial gap is equal to or greater than 0.040 inches. ### Claim 35 (depends on 33) The method of claim 33, wherein the radial gap is equal to or greater than 0.050 inches. ### Claim 36 (depends on 33) The method of claim 33, wherein the radial gap is equal to or greater than 0.060 inches. ### Claim 37 (depends on 33) The method of claim 33, wherein a ratio of the radial gap to an outer diameter of the pass-thru assembly is between 5% and 25%. ### Claim 38 (depends on 33) The method of claim 33, wherein a ratio of the radial gap to an outer diameter of the pass-thru assembly is between 6% and 18%. ### Claim 39 (depends on 33) The method of claim 33, wherein a ratio of the radial gap to an outer diameter of the pass-thru assembly is between 7.5% and 12%. ### Claim 40 (depends on 33) The method of claim 33, wherein a radius of the receptacle is at least 20% greater than a radius of a seal bore formed by the central passage and defining a minimum inner diameter of the central passage. ### Claim 41 (depends on 33) The method of claim 33, wherein a radius of the receptacle is at least 40% greater than a radius of a seal bore formed by the central passage and defining a minimum inner diameter of the central passage. ### Claim 42 (depends on 33) The method of claim 33, wherein a radius of the receptacle is at least 50% greater than a radius of a seal bore formed by the central passage and defining a minimum inner diameter of the central passage. ### Claim 43 (depends on 33) The method of claim 33, wherein a radius of the receptacle is at least 100% greater than a radius of a seal bore formed by the central passage and defining a minimum inner diameter of the central passage.