Research On The Technology Of Plugging Removal In Nanniwan Oilfield

Study area A of Nanniwan oilfield belongs to ultra-low permeability oilfield.In the process of oilfield exploitation,due to the long-term water injection,the permeability of water injection well decreases and the water absorption capacity of oil layer decreases due to the formation plugging,resulting in the phenomenon that the water injection pressure increases and the water injection quantity fails to meet the standard,resulting in the failure of timely supplement of formation energy and the decline of oil well production.In this paper,the Chang 4 + 5 reservoir in this area is studied systematically.The pore types in this area are mainly secondary dissolution pores and primary intergranular pores.The reservoir is characterized by medium to strong acid sensitivity,medium to weak velocity sensitivity,weak water sensitivity and weak pressure sensitivity.Combined with the current situation of water injection development in the study area,the plugging types of water injection wells in Chang 4+ 5 formation are systematically analyzed.The main cause of formation plugging is scaling caused by the injection water quality not up to the standard,and the secondary cause is formation plugging caused by medium weak speed sensitivity.The effective period of the technology is generally short.In view of this problem,combined with the reservoir characteristics of the study area,the multi hydrogen acid plug removal system is optimized.The evaluation is carried out from the aspects of the selection of additives,the performance of multi hydrogen acid,the performance of multi hydrogen acid plugging remover and the multi hydrogen acid solution to the formation.The results show that the multi hydrogen acid system has good plugging removal effect.In the field test,N199-1well and N281 well are selected for the test.The results show that the multi hydrogen acid plugging remover has good plugging removal effect for the target well,which provides a reference for plugging removal and injection increase of water injection wells in this area.