Subsurface uncertainties in reservoir characterization remains a challenge in decision making in the development phase of hydrocarbon maturation process due to geological complexity and limitations in reservoir data to provide sufficient understanding of the subsurface. This study focuses on identifying, managing, narrowing these uncertainties and generating reservoir realizations and optimum development concept consistent with available data. Hence, the objective of this study is to generate a technically feasible & economically viable development plan for X1, X2W and X2E reservoirs in KOCA field. The methodology deployed on this study is a multi-disciplinary integrated approach in a parallel setting with early focus on uncertainty identification, quantification, management and iterations amongst the team. Sensitivity analysis was used to evaluate the respective impact of the identified uncertainties on in-place and recoverable volumes and realizations were constrained by the most impacting uncertain parameters to generate a low case, base case and high case valid realizations of the subsurface. Development concepts were selected to optimize recovery using the base case realization with preliminary economic evaluations used to determine concepts economic viability. The result of this study identifies Structure, Net-to-Gross, and Permeability as the top three uncertainties with most impact on volumes. Deterministic low, base and high case GIIP volumes computed are 354Bscf, 681Bscf and 1.1Tscf, while recoveries were 261Bscf, 546Bscf and 913Bscf respectively. Deterministic low, base and high case STOIIP volumes computed are 0.4MMSTB, 1.5MMSTB and 3.4MMSTB, while recoveries were 0.1MMSTB, 0.2MMSTB, and 0.02MMSTB respectively. Optimum subsurface development concept is two vertical gas well, no horizontal well is needed to develop the thin (12ft) oil rim and finally quick look project economics revealed that the project would be economically viable even for the Low-Case outcome: NPV (10%) is $150M and VIR (10%) is 3.92.