Productivity Study For The Fractured Horizontal Well In Thin Inter-bedded Low Permeability Reservoir

The proportion of thin inter-bedded low permeability reservoir is increasing in new reserves,and it has become an important part of China's petroleum industry.Due to the characteristics of poor physical properties and dispersed effective reservoir in thin inter-bedded low permeability reservoirs,fractured horizontal well is developed at home and abroad.It's very important to accurately calculate the productivity of fractured horizontal well in thin inter-bedded low permeability reservoir to realize the effective and economy development of oilfield and formulate the reasonable development plan of reservoir.Based on the literatures on the research of production capacity of fractured horizontal well,the paper systematically studied the basic theory and calculation method of the steady-state and unsteady-state productivity of fractured horizontal well in thin inter-bedded low permeability reservoirs.What's more,it also separately studies the production capacity of the five-point well pattern,the anti-seven-point well pattern and the anti-nine-point well pattern where straight wells are deployed for water flooding and fractured horizontal wells are developed for extracting oil.The paper has made the following research results:(1)The steady-state productivity model of fractured horizontal well in thin inter-bedded low permeability reservoir is established,which has considered the effect of starting pressure gradient,stress sensitivity,segregation influence,fracture interference and horizontal wellbore pressure drop.The model can be solved by MATLAB programming to study the influence of different factors on the steady-state productivity,and the order of influence of each factor on the production capacity is determined;(2)Based on excitation zone boundary movement law and steady-state productivity model,the unsteady-state productivity model of fractured horizontal well in thin inter-bedded low permeability reservoirs is established by using steady state successive substitution method.This model is also solved by MATLAB programming to analyze the unsteady productivity characteristics of fractured horizontal wells.The impact of various elements on the unsteady production capacity is also studied.The orthogonal optimization method is used to optimize many factors simultaneously and obtain the influence order and the optimal value of factors;(3)The equivalent well diameter calculation method of fractured horizontal well is obtained by comparing the production calculating formula of vertical well and fractured horizontal well.Based on the equivalent well diameter and well pattern seepage theory,the production capacity and water breakthrough time of the five-point well pattern,the anti-seven-point well pattern and the anti-nine-point well pattern can be researched respectively in thin inter-bedded low permeability reservoirs where straight wells are for water flooding and fractured horizontal wells are for oil.