Study On Formation Damage Caused By Injected Water In QZ Oilfield

In the world,more and more experts are committed to the research of oilfield development technology,among which the most effective and most widely used oilfield development technology is water injection technology.The direct influence factor of oilfield development effect is the quality of water injection.When using inferior water to develop oil field,the end face of oil layer percolation is more likely to be blocked,which has a serious impact on injection pressure and water absorption capacity of injection well,resulting in heterogeneous reservoir,which ultimately leads to oil well output and oil layer energy can not reach the expectation.Therefore,in the process of oilfield development by water injection,it is necessary to study whether and how the formation structure is affected by the water quality of injection water.QZ oilfield is low hole-a low porosity,ultra-low permeability reservoir,the related technical personnel use QZ water flooding development oilfield,due to injection water containing excessive amounts of suspended solids and oil content,and suspended particle size is beyond the scope allowed seriously,need more water injection pressure,resulting in the extremely fast production decline,and less water injection problem,It is difficult to reduce the blockage of seepage end face of oil layer by means of negative pressure,which makes the production of oil well decrease seriously.In view of the situation of the oilfield,this paper formulated different suspended matter particle size,suspended matter content and different oil content of the injection water solution for core flow experiment,and studied the damage law,damage range and damage mechanism of different suspended matter particle size,suspended matter content and oil content on the core of the injection water.The evaluation experiment on the effect of rock sour plugging was carried out,and the corresponding protection measures were formulated.Through the above experiments,the main conclusions of this paper are as follows:(1)The suspended matter content in injected water is 112.6mg/L,the suspended matter particle size is 10.48?m,and the oil content is 87.35mg/L,which are not up to the standard according to the water quality analysis industry standard.(2)With the increase of water injection,the larger the particle size,suspended matter content and oil content of the injected water,the greater the injection pressure,and the greater the damage rate and degree of the core.In general,the damage of the injected water to the core is mainly concentrated in the area from 0 to 2/5 of the injection well,followed by the area from 2/5 to 4/5.With the increase of suspended matter content and oil content,the damage range increases.(3)Mercury injection parameters before and after core damage by injection water with particle size of 0.77?m and 1.16?m were compared.It was found that the damage was mainly caused by the blockage of large suspended matter particles in the large pores within 0-2/5from the injection well.In the area from 2/5 to 4/5 of the injection well,the damage is mainly caused by the deposition of tiny particles in the injected water in small pores.The damage in the area 4/5 to 5/5 from the injection well is caused by the deposition of a small number of microscopic particles in the large pores.(4)The injected water contains C,O,Fe,Na,Mg,Sr,Al,Si,Cl,Ca and other elements with a large proportion of calcium carbonate;After acidizing with hydrochloric acid and soil acid,the permeability of the core is recovered better,and the acidizing effect is better after adding surfactant into oil-bearing injected water.On the basis of theory and with experiments as the main research means,this paper clarified the damage degree,damage range and damage mechanism of injected water to the formation and analyzed the plugging effect after damage,providing theoretical basis for the development of oilfield water injection in the future.