The objectives of the thesis are to propose the concept of subsea production system with seabed storage tank, perform the Reliability, Availability, and Maintainability (RAM) analysis for seabed storage tank using Fault Tree Analysis (FTA), and assess the production availability for the subsea production system with seabed storage tank. The proposed concept is expected to optimize production from oil fields in the deep sea, helping to improve the production and transportation of hydrocarbon resources from deep sea fields and may dramatically reduce the floater size by removing the floater from the crude storage function and may widen the operational envelope of the production and transfer of the well fluid to shuttle tankers. The reliability assessment of the seabed storage tank performs a four-step procedure. A four-step procedure is to define the system boundary, collect the reliability data, construct a fault tree and estimate the reliability. The failure and repair data are obtained from the component of the lowest level of the seabed storage tank because the seabed storage tank is a new system unknown reliability data. The maintainability analysis is estimated in accordance with MIL-HDBK 472 Procedure V. The production availability is analyzed using the commercial code MAROS, which is based on Monte-Carlo simulation methods. The failure rates and active repair times of the equipment for the proposed new subsea systems are collected from generic reliability data sources. Production availability and system criticality of subsea production system with seabed storage tank was performed. The overall oil production availability of 30 years is predicted to be approximately 98.55%. In terms of system criticality, the major contributor of oil production losses is the seabed storage tank, which is associated with approximately 0.5% of the production losses and contributing with approximately 35.6% of the total losses.