The revenue of Nigeria Government comes majorly from oil and gas operations that are carried out through international and indigenous oil companies. This revenue is generated through fiscal instruments which are designated as taxes, royalty, profit oil, rentals. Crypto levies like Niger Delta Development Agency levy and education tax etc, also apply. The federal government has always sort out ways to derive more from the oil and gas activities since its inception. This they have pursued through legislative reforms, amongst which are the Deep Offshore and Inland Basin Production Sharing Contract (amended) act 2019, and the most current one which is the Petroleum Industry Act (PIA, 2021). The 2021 PIA has a significant difference from previous fiscal legislative acts as the Petroleum Profit Tax (PPT) has been splitted into Corporate Income Tax (CIT) and Nigeria Hydrocarbon Tax (NHT). In this research work we applied the deterministic spreadsheet to a Nigeria deep water asset to access the impact of the Production Sharing Contract (amended) act 2019 and Petroleum Industry Act 2021 regimes. The uncertainties and risks associated with the venture were analyzed with the results from the deterministic model by a simulation tool @Risk, a Monte Carlo simulation tool. The 2021 PIA gave a Net Present Value (NPV) of 595.18 MM$ which is positive and above opportunity cost of capital, Internal Rate of Return (IRR) of 23.7%, a Profitability Index (PI) of 1.34, the Host Government take of 88.1%, and Contractor take of 11.9%. The investment under the fiscal regime of 2021 PIA gave positive values of profitability indicators which gave higher profits than that of the Production Sharing Contract (amended) act 2019 that generated government take of 82.2%.