This article is devoted to the development of an adapted methodology for calculating the discount rate for investment projects in the extractive sector, with a particular focus on projects involving lithium extraction from associated petroleum brines at gas condensate fields. Special attention is given to accounting for specific risks arising under conditions of significant macroeconomic instability and institutional uncertainty. The study substantiates that traditional models such as the Capital Asset Pricing Model (CAPM) do not adequately capture the impact of country-specific, industry-specific, and project-specific factors, leading to a distorted assessment of investment attractiveness. The main research method involves modifying the CAPM by introducing premiums for country and project-specific risks, supplemented by the use of expert-based factor analysis for quantitative risk assessment. The results demonstrate that incorporating additional adjustment coefficients enables the estimation of a discount rate at 22.68%, providing a more accurate reflection of the actual conditions under which the project is to be implemented. The practical value of this research lies in the applicability of the proposed methodology for substantiating managerial decision-making in volatile economic environments. The conclusion outlines directions for further research, including the assessment of project economic efficiency using integrated financial-economic models and the real options approach.