Preliminary Study On Influencing Factors Of Ignition Time Of In Situ Combustion

Ignition is a key process in the process of In-situ Combustion,and the determination of ignition time is very important for ignition.Aiming at the problem of poor ignition effect in the firing process of heavy oil in D66 block of LH oilfield,this paper firstly determines the prediction methods of ignition time under different ignition modes through literature research and theoretical analysis,and then studies the effects of reservoir physical properties,air injection parameters and gas injection modes on ignition time by combining field data with theoretical analysis.The results show that because of the serious reservoir heterogeneity and the great difference of KH values among the small layers in this block,the general gas injection during ignition process can not precisely control the gas absorption of each layer in the reservoir according to the actual situation of the reservoir,and can not effectively regulate the interlayer contradiction of the reservoir.It is easy to cause gas channeling along a single layer,resulting in excessive gas absorption in a single layer.Other layers have little or no gas absorption,and the difference of ventilation intensity among layers is large,and the ignition time is different.After successful ignition,the fire line is preferentially advanced to the reservoir with good physical properties,which results in the ineffective use of reservoir and unsatisfactory effect of fire drive.In stratified gas injection,the gas injection volume of each layer in the reservoir can be adjusted appropriately according to the actual situation of the reservoir,so as to effectively adjust the gas absorption profile of the reservoir,avoid excessive single layer gas absorption,shorten the gap of ventilation intensity between layers,and reduce the difference of ignition time.Layered gas injection is also conducive to the control of the front of the fire drive after successful ignition,which makes the reservoir more productive and the production well more productive.Therefore,stratified gas injection should be given priority in the selection of gas injection mode in order to achieve good ignition effect in the firing process of D66 block.