Based on Iran's sixth development plan, the country's oil and gas industry requires an investment of about $200bn in the next five years to increase production. The Iranian government, to attract and motivate international oil company investment in their oil and gas fields, has presented a new type of risk service contract: the Iranian Petroleum Contract (IPC). This paper summarizes the features of the IPC and presents mathematical models of its fiscal regime for the benefit and guidance of both the National Iranian Oil Company (NIOC) and the contractors. Next, adopting bargaining game theory provides a mathematical model for reaching a win-win situation between the NIOC and the contractor. Finally, a numerical example is given and a sensitivity analysis performed to illustrate the implementation of the proposed models. The contractor and the NIOC may use these models when preparing their proposal and in the course of actual negotiations to calculate their internal rate of return, remuneration fee, and net present value for developing the fields at different conditions of their bargaining power, and derive a logical bargain to protect their best possible interests.