Exhibit 99 Form 4 Joint Filer Information Name: EnCap Energy Capital Fund VIII Co-Investors, L.P. Address: 1100 LOUISIANA STREET, SUITE 4900 HOUSTON, TX 77002 Issuer & Ticket Symbol: Eclipse Resources Corporation [ECR] Date of Event Requiring Statement: 1/18/2018 Relationship of Reporting Person 10% Owner to Issuer: Signature: EnCap Energy Capital Fund VIII Co-Investors, L.P. By: EnCap Equity Fund VIII GP, L.P., its general partner By: EnCap Investments L.P., its general partner By: EnCap Investments GP, L.L.C, its general partner By: /s/ D. Martin Phillips, Managing Partner ---------------------------------------- Date: 1/22/2018 Name: EnCap Energy Capital Fund IX, L.P. Address: 1100 LOUISIANA STREET, SUITE 4900 HOUSTON, TX 77002 Issuer & Ticket Symbol: Eclipse Resources Corporation [ECR] Date of Event Requiring Statement: 1/18/2018 Relationship of Reporting Person 10% Owner to Issuer: Signature: EnCap Energy Capital Fund IX, L.P. By: EnCap Equity Fund IX GP, L.P., its general partner By: EnCap Investments L.P., its general partner By: EnCap Investments GP, L.L.C, its general partner By: /s/ D. Martin Phillips, Managing Partner ---------------------------------------- Date: 1/22/2018 Name: EnCap Partners GP, LLC Address: 1100 LOUISIANA STREET, SUITE 4900 HOUSTON, TX 77002 Issuer & Ticket Symbol: Eclipse Resources Corporation [ECR] Date of Event Requiring Statement: 1/18/2018 Relationship of Reporting Person 10% Owner to Issuer: Signature: By: /s/ D. Martin Phillips, Managing Partner ---------------------------------------- Date: 1/22/2018 Name: Robert L. Zorich Address: 1100 LOUISIANA STREET, SUITE 4900 HOUSTON, TX 77002 Issuer & Ticket Symbol: Eclipse Resources Corporation [ECR] Date of Event Requiring Statement: 1/18/2018 Relationship of Reporting Person Director to Issuer: Signature: /s/ Robert L. Zorich ---------------------- Date: 1/22/2018 Name: D. Martin Phillips Address: 1100 LOUISIANA STREET, SUITE 4900 HOUSTON, TX 77002 Issuer & Ticket Symbol: Eclipse Resources Corporation [ECR] Date of Event Requiring Statement: 1/18/2018 Relationship of Reporting Person Director to Issuer: Signature: /s/ D. Martin Phillips ----------------------- Date: 1/22/2018 Name: Douglas E. Swanson, Jr. Address: 1100 LOUISIANA STREET, SUITE 4900 HOUSTON, TX 77002 Issuer & Ticket Symbol: Eclipse Resources Corporation [ECR] Date of Event Requiring Statement: 1/18/2018 Relationship of Reporting Person Director to Issuer: Signature: /s/ Douglas E. Swanson, Jr. --------------------------- Date: 1/22/2018