Research on acid stimulation of Extra-low permeability reservoir in Weibei Oilfield

Chang36 block in Weibei oilfield is typical extra-low permeability reservoir with poor fluid supply in oil layer,which needs acidification.Based on the above characteristics,YS acid formula is developed.Its dissolution ability is93.1%and its anti-swelling ability is 65.2%.The mechanism which was analyzed by SEM and XRD,proves that the YS acid formula is proper for applications,Which acidizes cements in karst reservoir(including calcite,dolomite and clay minerals),and maintain good skeleton structure.Currently,the acid application to Chang 27-3 well leads to an average increase of 0.6t/d and achieves good result.