The Mechanism And Application Of CO₂ Puff And Huff In The Horizontal Well Of Tight Oil Multi Stage Fracturing

The H oilfield,a super low permeability fractured sandstone reservoir,achieved a certain effect after development in recent years.Especially since 2010,oil production has a growth by using the multistage fracturing horizontal wells.But with the development of the C reservoir,problems including oil production declining rapidly,reservoir energy reducing quickly and low recovery exposed gradually.We need expanding research on the way of CO₂ huff and puff to increase oil production because that the water injection development of the block is not ideal in the H oilfield pilot test.This paper is based on the existing indoor test,makes fitting calculation of the phase state changes of crude oil before and after the injection of CO₂ by PVTi software,and gives the component simulation PVT parameters.A typical numerical simulation model for the specific geological features of C reservoir is established by combining the production dynamic data of horizontal well failure in oil field,the influence factors of the development of CO₂ huff and puff including the conditions of immiscible and near miscible phase and mixed phase conditions,the time of depletion turn to CO₂ huff and puff,Optimal cycle injection volume and the best injection speed,the best soak time and its influence factors are analyzed,the effect of CO₂ huff and puff in vertical wells,horizontal wells and horizontal wells are compared,and the effect of CO₂ huff and puff effect under different water saturation are also compared.Then optimizing the HH37 wells CO₂ huff and puff test wells group,establishing the test well group numerical simulation model,matching the well production dynamic history,and optimizing the test well group injection production parameters including the huff and puff time,cyclic injection rate,the injection rate,soaking time.From the predicted production index of test wells group,the oil production,the average oil production per well and oil recovery will increase 40284 t,4476t and 2.60% respectively in 5 cycle.This paper defined the influence factors of CO₂ huff and puff in tight reservoir with the fractured horizontal well,proposed the technology development policy,and provided technical support for long-term development of H oilfield reserves,it also has important significance for the development of low permeability sandstone reservoirs.