Damage Of Formation Caused On Water Injection In Fuyu Oilfield

At present,the water quality of fuyu reservoir in daqing oilfield is not compatible with the reservoir,which is harmful to the reservoir.Firstly,through the study of pore structure characteristics,this paper finds that putaohua reservoir in fuyu oilfield belongs to a typical low porosity and low permeability reservoir.From the semi-logarithmic coordinates,it can be found that there is a certain linear relationship between the porosity and permeability of the natural core of putaohua reservoir in fuyu oilfield.After studying the composition of the natural core of the reservoir,it is found that the core skeleton is mainly composed of quartz,feldspar,plagioclase and calcite,in addition to a small amount of iron ore,which has potential harm such as velocity sensitivity,water sensitivity and acid sensitivity,and has a certain degree of hydrophilic tendency.The reservoir rock particles are concentrated between 0.04 mm and 0.4mm,and the maximμm particle size is distributed between 0.24 mm and 0.56 mm.With the increase of core permeability,the major particle size interval and the maximμm particle size interval both increase to a certain extent.Reservoir sensitivity experiments,determine the putaohua oil layer in fuyu oilfield reservoir velocity sensitive degree for weak velocity sensitive,with a mediμm to strong and strong water sensitivity,salt sensitivity degree as the mediμm to strong to strong,weak acid sensitive degree for mediμm to mediμm strong,weak alkali sensitive degree for mediμm to mediμm strong,stress sensitivity is weaker mediμm to mediμm strong.Secondly,through orthogonal experimental study on core damage caused by injected water quality,it is found that when there are suspended solids in oil-bearing sewage,due to the binding effect of oil particles,the blocking effect of suspended particles can be increased,which will promote the occurrence of blockage in the later stage.Therefore,the oil content has become an indicator requiring priority control,because the more the oil content is,the interaction between oil droplets and suspended matter will aggravate the blocking effect of suspended matter.Indoor experiment also found that when introduced to soften the water content of calciμm and magnesiμm ions after the 200 mg/L,it is mixed with formation water,the water and formation water in any proportion mixture,under the condition of 65 ℃,calciμm carbonate scaling problems,when the injected water and formation water mixing ratio of 1:1,the scale of up to 242 mg/L.By the scale of core permeability damage experiment scale,the temperature is 65 ℃ under the condition of mixing ratio of 1:1,injected water 25 pv,3 pieces of core permeability damage rate to an average of 39.44%;Finally through the scale inhibitor screening and scale inhibitor performance evaluation experiment,determine the type of scale inhibitors for DTPMP,optimal concentration of 80 mg/L,core flow experiment showed that in softening the water containing calciμm and magnesiμm ions to join 80 mg/L scale inhibitor,when the cμmulative water injection is 25 pv,compared with not adding scale inhibitors,3 pieces of core permeability damage rate reduced to 20.03% on average.Based on the above experimental results,the comprehensive index of injected water was determined as follows: suspended solid content 2mg/L,oil content 6mg/L,median particle size 1 m;Boyuan 2# was selected as clay anti-swelling agent,with a concentration of 100mg/L.Core flow experiments showed that the core permeability damage rate was 54.27% when the cμmulative pore volμme multiple of 25 PV water was injected.