Offshore Gas Field Development Strategy and Flow Assurance Prediction and Optimization in Harsh Environment

Abstract

AbstractAn offshore gas field located in a cold area; with an average temperature of 13 Celsius degree and −1.2 Celsius degree under sea level. The reservoir is located 200 meters under the sea floor, where the sea floor is 850-1100 meter depth and 120 Km away from shore. The objective is to develop an offshore production system for the gas field and maintain the necessary production, taking into account flow assurance, economics, and environmental effect.The required design includes reservoir pressure forecasting, completion design, drilling strategy, and production flowline network modeling. The first step was forecasting the reservoir pressure by trial and error equation, then completion design to calculate the possible production increment from every well and calculate the cumulative produced volume to predict the changes in the fluid composition. The drilling strategy and completion design were carried out under the following assumptions: wells are having same completion design, production rate, and static reservoir pressure. The production network simulated with the designed completions using a steady-state multiphase flow simulator, with the sub-sea template and manifold strategy.For the flowline network, polyurethane coat was used for each pipe to reduce the heat transfer from the sea water to the flowing fluids. The back-pressure equation was used to develop the IPR model and flash separation to predict the gas composition changes assuming the reservoir is an isothermal system. The base year started with eight wells, to achieve the required production per year, 70 MMSCM per day. Erosional velocity ratio kept under 1 for the designed 16 years. Pipelines coating was required to prevent flowline damage and deal the forming hydrates. A total of 30 wells to be drilled to cover the production needed for each year.An offshore gas field study is explained in details with the simulation design procedure and pre-planning strategy for harsh cold environment flow assurance concerns and production difficulties. In addition to helpful estimation equations.