The oil and gas industry and risks are very related to each other. There are several risks known in this industry, from economic risks, political risks, environmental and safety risks, up to geological risks itself. Because oil and gas are a non-renewable source of energy, the more mature an oil and gas field is, the risks for the company to develop a project investment may be lower and higher at the same time. Entering its declining phase, PT MNO who is trusted to operate an ex-termination oil and gas field in East Kalimantan which has been producing for almost 50 years, is required to find a way to survive until end of contract in 2037 by developing the remaining hydrocarbon resources which become more and more marginal. The project development is proposed as a bundling to allow flexibility during execution phase in selecting the well candidates based on recent data acquired from previous wells drilled, hence reducing the risks. Field Development Package (FDP) 2.3 is prepared as part of PT MNO long term plan and commitment after receiving incentive from Government of Indonesia in 2021. According to the Company Guideline, a risk register is mandatory to be developed since beginning of project which covers risks identification, risks analysis, and risks evaluation. The project team is also responsible to define risks treatment to manage the risks borne by the project. This is in line with the requirement for Good Corporate Governance, where risk management is introduced since beginning of the project life-cycle. This study covers the risk assessment on the basis of selected project scope which has been validated technically. The risk assessment will determine the major risks in FDP 2.3 considering available historical data of oil price, drilling cost realization, and facility cost realization. These risks need to be monitored to ensure the FDP 2.3 will create value for the shareholder as per plan or avoid loss at the minimum. The most important risks concluded in this study is oil price lower than economic assumption, production target not achieved, and no fix gas sales contract to absorb production. The company may focus in these risks for the risk management of future project development.