Numerical Simulation Study On Nitrogen-assisted Steam Transfer To SAGD In The W Block

With the decrease of conventional oil and gas resources in the world,the problem of how to effectively develop heavy oil reservoirs has attracted more and more attention from scholars.Steam huff and puff is an effective steam injection thermal oil recovery method,which can obtain a high oil recovery rate in the early stage of development.Due to the single well operation,the production risk is also smaller than that of steam flooding and hot water flooding.But after multiple rounds of throughput,the oil-vapor ratio also decreased,and the water content increased.Therefore,injection and production parameters need to be adjusted after multiple rounds of huff and puff,and nitrogen is used to assist steam huff and puff.In the later stage of development,steam huff and puff needs to be converted into a more advantageous SAGD technology to achieve the purpose of improving oil-vapor ratio and reducing water content.Block W belongs to the heavy oil reservoir.After multiple rounds of steam stimulation,the oil-steam ratio decreases,the water cut increases,and the development effect becomes poor.In response to the above problems,first of all,a three-dimensional geological model was established based on geological data,and then CMG numerical simulation software was used to establish a numerical model well to complete history matching.According to the numerical simulation results,the remaining oil distribution characteristics,classification,causes and main control factors of the block are ranked.By analyzing the production data of the block,the historical production dynamics of the block are analyzed to obtain the production decline rate and production decline value.The numerical simulation method and the orthogonal experiment method are used to optimize the injection-production parameters,the periodic nitrogen injection amount,the nitrogen injection method and the nitrogen injection interval.In the later stage of development,the steam huff and puff is converted into SAGD,and the type of auxiliary medium injected,the combination of vertical well and horizontal well,vertical distance,horizontal section length are selected by numerical simulation method and orthogonal experiment method,and the steam injection speed and steam are optimized.Dryness,production-injection ratio,injection concentration of hydrocarbon solvents,well simmering time,wellhead Sub-cool.Provide scientific basis for effective development of W block.