**5. Conclusions**

In this paper, the optimal allocation of limited NG resources to different sectors of consumption (including household business, industry, petrochemical industries, power plants, injection to oil fields, and export) in Iran during 2018–2025 is studied. The multiobjective linear planning model has been used for modeling. Lexicography method is employed and the objective functions of the goal programming model are solved according to their assigned priority, in order to minimize the deviation from the specified goal. Energy security strategies differ in each country and region. Energy-importing countries often

consider energy security as the security of energy supply, while energy-exporting countries prefer to refer to it as security of energy demand. It should be noted that energy security is crucial for decision-makers in terms of supply, moreover, it is highly influential on energy pricing as well political power. Two main objective functions are considered in this study: (1) maximizing energy security index (minimizing energy security cost), and (2) minimizing the relative weight of different consumption sectors from negative to a goal by using GP multi-objective decision-making technique. Therefore, the objective function and systematic constraints of multi-objective GP decision-making techniques are presented based on the relative weight of the various sectors and also on the basis of information extracted from the gas industry prospectus and energy and hydrocarbon balance sheets. The goal share of different natural gas sectors (based on the gas industry outlook in Iran), the base consumption of the various sectors (based on energy and hydrocarbon balances in Iran), and the volume of basic natural gas, the allocable and predicted limit per year are given in the tables. The results of this study are used for optimal allocation of natural gas to different consumption sectors as well as for future planning. Household business, power plants, petrochemical industries, industry, export, and injection to oil fields are the highest consuming sectors in 2025, respectively. Also based on cost minimization function, power plants, petrochemical industries, and industries in general are the more consuming sectors, respectively.

The results show that if Iran's gas production plans are successful and the level of gas production achieves the levels announced in the development plans, it needs to target a great level of gas exports to maximize social welfare. In other words, the gas exports should not be one of the priorities of Iran's policy when the production level is faced with constraint (which is confirmed by other studies over the past decade), and domestic consumptions and, in particular, injection into oil fields has higher security. But if policies of increasing production are successful and the level of Iran's production is increased with a level that is predicted in the sixth development plan, the mass exportation of gas will lead to increased social welfare. This shows the need for extensive planning investments in this area. One of the most important policy implications is the increasing transmission capacities of Iran. It is also worth mentioning that one of the reasons for the high level of energy consumption in the final sectors is the lack of attention to correct the pattern of consumption. Of course, in this regard the large subsidies received by the energy sector, especially the gas sector, is an important reason for it. Also, for the natural gas demand model, official prices of natural gas have been used, which also include subsidies, and should be considered in the analysis of the results. Therefore, although the increased volume of natural gas needs special attention in the next three decades and the necessary infrastructure for the extraction of gas resources in the area of final gas consumption must be developed, at the same time crucial strategies should be used that lead to improving consumption patterns.

**Author Contributions:** Conceptualization, I.M.-K. and S.G.; methodology, S.G. and I.M-K.; software, I.G.S.; validation, I.M.-K. and V.D., formal analysis, I.M.-K.; investigation, I.M.-K. and S.G.; resources, V.D.; writing—original draft preparation, S.G. and I.G.S.; writing—review and editing, I.G.S.; visualization, S.G. and V.D.; supervision, I.M.-K. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data of this study is available from the authors upon request.

**Conflicts of Interest:** The authors declare no conflict of interest.
