S team injection includes the concept of thermal EOR where when heated, thevisurfaceosity of the oil will decrease so that the oil will flow more easily, so thepurpose of steam injection is to reduce the visurfaceosity of the oil. The mainprinciple of Steam Injection is that steam is injected into the formation withaprocess continuous so that special wells are needed to function as injection wells.Y field has a reservoir type suitable for steam injection because it has high reservoirrock permeability, large oil porosity and saturation, high visurfaceosity, and lowto medium reservoir pressure. This research analyzes the determination of steambreakthrough in reservoir X Field Y with the formulation of the problem, namelywhat are the parameters that influence the calculation of the steam injection rate,how the steam injection phases are, how much heat is needed to the steambreakthrough phase, can the Neuman method affect evaluation of the steambreakthrough that will be determined in the field, and how long it takes for thesteam to be injected into the reservoir to experience a breakthrough in the field.The purpose of this research is to determine how much heat it needs to breakthrough the steam phase and to find out how long it will take until the reservoirexperiences steam breakthrough phase. The method that will be used in thisresearch is themethod Neuman and the required data, namely the area based onthe study area, the pressure and temperature data injected according to the steamgenerator capacity in the study area, and the characteristics of the reservoir in thestudy area. The results of research on Reservoir X Field Y obtained how long ittakes steam to reach the production well and themethod Neuman can find out whenthe steam breakthrough or time to develop the steam chest, how much steam is needed to experience thephase steam breakthrough and the Neuman method. canalso be used as a zone monitor or aarea mature so that it can find out whether areservoir needs steam or not ( Steam management). The conclusion obtained fromthis study is the length of time required for steam to be injected into the reservoirto experience a breakthrough in the field in Scenario 1 for 257.8 days, Scenario 2for 255.7 days, Scenario 3 for 254.1 days, Scenario. 4 for 1,151.6 days, Scenario 5for 1,142.4 days, Scenario 6 for 1,135.2 days, Scenario 7 for 2,916.6 days, Scenario8 for 2,893.2 days and Scenario 9 for 2,875.0 days. The best scenario in Field Y isScenario 3 because the smallest well spacing means that the estimated amount ofunsweep oilwill be less and also the amount of steam injection pressure highestandtemperature will provide displacement efficiency the best.pada Lapangan Y adalah Skenario 3 karena well spacing paling kecil yang berartiestimasi jumlah minyak yang belum tersapu (unsweep oil) akan lebih sedikit danjuga besaran steam injection pressure dan temperatur paling tinggi akanmemberikan displacement efficiency yang terbaik