The Mechanism Study And Effect Evaluation Of Increasing Injection On Ultra-Low Permeability Reservoir In Dongsheng Oilfield

With the deepening of oilfield development and constantly improve the technology,low permeability and ultra-low permeability reservoirs has become an important growth point of recoverable reserves.Water injection is widely used in low permeability reservoirs development,but because of its special geological conditions,the present problems of water injection development are high water injection pressure and injection difficulty.The injection technology of the low permeability reservoirs could be conducted by acidification and fracturing treatment,radial drilling treatment,and surfactant injection treatment.But all kinds of augmented injection technology effect of prediction,evaluation of effect and applicable scope of the study are lack both in domestic and abroad.In this paper,taking Niuzhuang,Gaoqing blocks of Dongsheng ultra-low permeability blocks as the research object,collecting and analyzing the reservoir geological characteristics,injection water quality data,sensitivity experiments data and water injection production data,oilfield water injection status and existing problems is evaluated,and the influence factors of formation damage is analyzed,the mechanism of acidification and fracturing and radial drilling is researched,by considering technical specifications,the effect of injection treatment of evaluation index is selected,and the evaluation method and hierarchical method is determined;the augmented injection effect prediction model is established,the adaptability of each technological study of field application provides guidance for the process,by evaluating and analyzing the water injection measures of 35 Wells in Dongsheng company from 2007²015of ultra-low permeability,Finally through the indoor experiment,according to the characteristics of the Niuzhuang block screened for augmented injection of activated water system and augmented injection acid system.Research results show that the reason of insufficient water injection wells in ultra-low permeability blocks is that a poor reservoir property,reservoir rock oil wet,cause a large water injection resistance,injection water quality is not up to standard,suspended solid concentration levels caused the hole plugging,saprophytic bacteria,iron bacteria number excessive damage caused the bacteria damage,high reservoir temperature,plugging removal process of acidification effect reduced.The smaller the pore throat is,the lower the formation permeability is,for Wells after fracturing augmented injection effect,the more obvious the wells augmented injection effect is,need according to actual condition of each well optimize fracture length and width,so as to achieve more economic effect of augmented injectionFor Niuzhuang block injection Wells radial drilling optimization way of holes for:four holes with screw,adjacent hole Angle 90°,100¹30m long,2⁶cm aperture,radial drilling Wells in oil sheet can obtain larger augmented injection multiples,for oil sheet,under the condition of little interference between the perforation,on horizontal direction as far as possible to increase the number of perforation can obtain better water augmented injection effect,for thicker oil pay,under the condition of little interference between the perforation,on vertical direction as far as possible to increase the number of perforation can achieve better water augmented injection effect.Optimizing the water activity of augmented injection formula:Niuzhuang injection water+60 mg/L(Wtxwood chemical antiscale agent+1%clay stabilizer?Shengli chemical engineering?DH+0.1%corrosion inhibitors-2?Dehua group?+0.1%step-down augmented injection surfactant?Dehua group?.Optimizing the step-down augmented injection of acid system as follows:12%hydrochloric acid+3%citric acid+12%fluoboric acid?H₃BF₄?+0.5%clay stabilizer?Shengli chemical engineering?+1%ferric ion stabilizer?Dongsheng industrial and trading?+1.5%and heat-resistant acidification corrosion inhibitor?Dehua group?.The results of the study can improve Dongsheng block water injection conditions,provide guidance to low permeability reservoir water flooding condition.