FLOW PROFILE ANALYSIS OF SUBSEA PIPELINE TO MAINTAIN PRODUCTION IN THE OFFSHORE OIL AND GAS FIELD

• Main Author: Herawati Napitupulu, Mangisi
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/46333
• Institution: Institut Teknologi Bandung

In the oil industry, multiphase flow is a phenomenon that often occurs. Flow regimes are important to explain multiphase flows, where flow regimes vary depending on the speed of individual components in the multiphase flow. slug flow, as one of flow regime, can cause significant pressure fluctuations that will have an impact on the durability of the facilities structure (pipelines, separators, etc.). Offshore pipeline-riser installations face major challenges with multiphase flow. One type of severe slug is induced by a vertical well and riser which causes the pressure to rise to create a pressure and insulated rate. Severe slug flow has various impacts, namely: fluid overflow and high pressure in the separator, overload on the gas compressor, fatigue, increased corrosion and decreased production. PT XYZ has production facilities in the South offshore field consisting of the remote platform and Production Platform which produces ± 55,000 BLPD gross liquid, ± 93.67% water cut, net oil ± 9,266 BOPD and total gas ± 37.4 MMCFD. Platform V, STS-A, STS-B and Platform P are the scope of the flow analysis. Platform V has eleven (11) active wells, STS-A has three (3) active wells and STS-B also has three (3) active wells. Each of these platforms has a subsea pipeline that leads to the same gross separator on the production platform. The V-P pipeline has a diameter of 12 inches and length 900-meters, the STS-A-P pipeline has a diameter of 12 inches with length 3900-meters and the pipeline STS-B-P has a diameter of 8 inches with length 3600-meters, and the gross separator has gas capacity of 20 MMSCFD and a liquid of 20,000 BPD with a operating pressure of 109 psig. Flow profiles analysis of the three subsea pipelines needs to be done to understand the impact of mass source increase due to additional of development well. By using the analysis result, will provide the flow phenomena, and also inform the capacity capabilities of existing gross separator to accommodate netwotk total surge volum. This flow analysis is using OLGA flow assurance simulator and PVTSim software. Result of OLGA simulation using the FA-slugtracking model shows that under current operating conditions, in the internode networks of V, STS-A and STS-B, the slug flow regime occurs in the subsea pipeline V, which impacts the flow regime in the STS-A pipeline and STS-B. Flow pressure oscillates throughout the internode network. In the current operating conditions, gross separator at production platform can still accommodate the surge volume of fluid occured, but if there will be addition of source mass from the new of wells, the slug flow regime occurs in all pipes, the inlet pressure of each pipe oscillates and the existing gross separator cannot accommodate the entire fluid surge volume from the three pipes due to the gross separator capacity to accommodate surge volume is only 5.5 m3. The alternatives in reducing and/or eliminating slugs are to use topside choking for internode networks V, STS-A and STS-B prior entering gross separator and also to study options for making new gross separator on platform V to handle all fluids from V platform wells. Topside choking platforms cannot significantly eliminate slug for the internode network but the new gross separator on platform V is proven to be able to remove slug from the platform V fluid flow where both streams from the STS-A and STS B platforms continue to flow to the gross separator in the production platform. If in the near future there will be new wells, PT. XYZ needs to conduct a thorough assessment of all existing surface facilities to ensure its ability and capacity to be able to process additional fluid from new wells.