Heat exchanger networks (HENs) play a key role in energy recovery in refineries, gas-processing plants and integrated petrochemical complexes since they decide how much process heat is reused internally before outside heating and cooling utilities have to be bought. This review looks at the developments published between 2020 and 2025 and uses them to formulate an optimisation programme specific to oil and gas facilities that are operating in accordance with Vision 2030. The evidence shows that the most effective retrofit approaches no longer regard pinch targets, network topology, exchanger design, fouling, pressure drop, maintenance and operability as independent issues; on the contrary, recent research has progressively combined thermodynamic targeting with mathematical programming, detailed thermal-hydraulic models, asset-life planning, real-time performance monitoring and the selection of retrofit measures within budgetary limitations. Refinery case studies show that significant reductions in utility and operating costs can be obtained through both low-disruption measures and more extensive reconfiguration of the network, although the outcomes depend heavily on the existing topology, the stream temperatures, the current state of fouling and the execution constraints. For Saudi facilities, the best approach therefore is not a single, universal HEN design but rather a step-by-step decision framework: first diagnose the actual losses in heat recovery, set realistic targets, rank the various retrofit options according to their energy and carbon value, take into account the hydraulic and fouling penalties, and then maintain the savings by means of digital monitoring and coordinated maintenance. The review suggests an implementation framework for Vision 2030 that connects HEN optimisation to fuel displacement, carbon-intensity reduction, reliability and capital discipline. It also points out gaps in dynamic optimisation, the treatment of uncertainty, site-wide integration, carbon-aware objective functions and validation based on data from Saudi plants. The main manuscript contains 4,400 words (from the Abstract to the Conclusion; excluding the title, headings, keywords, tables, figure captions and references).