Research On Uniform Plugging Removal System For All Sections Of Oil-Water Wells In Offshore M Oilfields

The main horizons for the development of the offshore M oilfield are the Guantao Formation and the Minghuazhen Formation.The Minghuazhen Formation is a meandering river deposit,and the Guantao Formation is a braided river deposit.M oilfield is a medium-high porosity and permeability loose sandstone reservoir with large vertical thickness,strong heterogeneity,extremely uneven injection-production profile,screen completion and gravelpacking completion methods,due to the long-term failure of water injection quality and crude oil the high content of asphaltenes,early workover operations of oil and water wells,profile control and water shutoff,etc.have caused serious damage to oil and water wells,and rapid decline in water injection capacity and liquid production capacity.After multiple rounds of acidification and plugging removal,the plugging-removing effect has continuously deteriorated and the plugging-removing validity period has been continuously shortened.Therefore,in view of the problems in the M oilfield,a more in-depth study was carried out,combined with reservoir characteristics and completion methods,analyzed the damage mechanism,and proposed targeted solutions.The specific research content is as follows:(1)Re-understand the target reservoir and clarify the potential damage factors: the main damage factors of the reservoir are water sensitivity,velocity sensitivity,crude oil emulsification,etc.The order of other damage factors is foreign solid invasion,stress sensitivity,cold damage,inorganic Scale and so on.(2)Analyze the damage mechanism and clarify the composition of the blockage: oil well damage is mainly composed of sludge formed by particle migration and crude oil.Water sensitivity damage caused by workover fluid loss and polymer plugging agent damage are also part of the damage.The cause of oil well damage,after the new well is put into production,the emulsification damage cannot be ignored.The main damage types of water injection wells are oil-containing and suspended matter.Among them,the suspended matter is mainly organic matter.The organic matter is mainly linear hydrocarbons,colloidal asphaltenes and trace demulsifier components,followed by corrosion scale products and calcium scale.(3)Put forward the idea of plugging removal and develop a composite plug-removing fluid system: According to the different components of the plugging material,combined with the characteristics of the reservoir,it is proposed to "remove the organic matter first,and then solve the inorganic matter;Unblocking and activating each production zone" the idea of unblocking.For the removal of organic substances,it is recommended to use BLJ-YS organic plugging remover;for the removal of inorganic substances in oil wells,it is recommended to use fluoroboric acid and polyhydrogen acid systems.The acid concentration and corresponding additives are optimized,and the various indicators of the system meet the industry standard requirements.The recommended formula is: pre-fluid(8%HCl+additives(1%BLJ1-3+1%BLJ1-7+1%BLJ-18+1%BLJ5-5+1%BLJ1-1))+ body acid(polyhydrogen Acid system(6%HCl+3%BLJ601+5%BLJ701+additives)or fluoroboric acid system(8%HCl+10%HBF4+additives))+ post-position liquid(10% BLJ-19+1%BLJ1-7+1%BLJ-18+1%BLJ5-5+1%BLJ1-1);For the removal of inorganic substances in water injection wells,it is recommended to use the ZXA single-step acid system,the acid concentration and corresponding additives are optimized,and the various indicators of the system meet the industry standard requirements,The recommended formula is: 6%ZXA-2+6%BLJ701+1%BLJ-18+1%BLJ5-5+1%BLJ1-1+5%BLJ-19.In order to uniformly remove the plugging and activate each production zone,the VES-DA diverting agent is optimized,which can meet the diversion and diversion of the plugging solution in gravel packing and screen completion,and achieve uniform plugging removal for the entire well section.