Professional Evaluation of Enterprise Cybersecurity Architecture in Nigerian Oil and Gas Companies: A Case Study of NNPCL

Oil and gas companies operate critical national infrastructure whose cybersecurity compromise would have severe economic and safety consequences, making enterprise cybersecurity architecture evaluation a matter of strategic national importance in Nigeria. This study professionally evaluates the enterprise cybersecurity architecture of the Nigerian National Petroleum Company Limited, focusing on its operational technology and information technology security integration. A structured cybersecurity architecture assessment was conducted using the SABSA Enterprise Security Architecture Framework and the NIST Industrial Control System Security Guidelines, applied through document analysis of NNPCL available ICT governance publications, DSS security incident reports, and technical interviews with 20 cybersecurity professionals from NNPCL's ICT and operational technology security divisions. Architecture dimensions assessed include network segmentation between IT and OT systems, access control systems, threat detection and monitoring capability, security operations centre maturity, incident response processes, and supply chain security management. Qualitative and descriptive analysis were applied. Available critical infrastructure cybersecurity literature from Nigerian oil sector contexts identifies inadequate IT-OT network segmentation, third-party contractor access controls, and insufficient OT-specific intrusion detection as the primary vulnerability categories. The IEC 62443 Industrial Automation Cybersecurity Standard and NIST SP 800-82 provide the professional reference. Findings identify significant IT-OT convergence security gaps requiring immediate remediation. Recommendations address dedicated OT security monitoring, mandatory third-party access security vetting, and PIA-aligned cybersecurity investment mandates. Keywords: enterprise cybersecurity, NNPCL, oil and gas, OT security, critical infrastructure.