Research And Application Of Single - Step On - Line Acidification Technology For Water Injection Well

Acidizing of injection wells is an important technical method to remove formation damage,and decrease injection pressure or improve injection rate.Acidizing of removing formation damage has widely used in many injection development oil field of bohai bay.The current sandstone acidizing technology ensure the effectiveness of treatment by the use of preflush, treating fluid, over-flush fluid. However, the limited space of offshore platform makes the current technology is time-consuming and unable to implement on large scale. Aimed at realizing simple and rapid acidizing for offshore water injection well. Based on the above problems, we performed researches on a new and simple SSOA technology in this paper, the most distinguishing feature of this technology is to use a single kind of acid which has efficient ability of plugging and suppressing the secondary precipitation ability to replace the three-step conventional acidizing. It significantly simplifies the fluid injection process and pump the acid into water injection process. Online acidizing was performed as injection water was injected.The technology can ensure real-time monitor injection pressure and flow rate, simulate skin factor and analyze acidizing stimulation results, furthermore adjust the operate parameters,optimize injection volume,ensure optimal acidification effect,which can save substantial time of offshore oil field injection wells acidizing,space,cost and manpower and improve safety,the specific contents are as follows.1) The reservoir lithology and fluid characteristics of Shahejie formation in B oilfield are deeply analysed,the potential damage factors and sensitivity of this reservoir are evaluated as well.Finally,the acidizing object is clear.2) In order to know the damage range and degree of target reservoir as well as the damage mechanism of injection wells,the property of injected water are analyzed by Ion Chromatograph,Particle Size Analyzer and Energy Dispersive Spectrometer, and the blockage type and composition are analyzed by X-ray diffraction and SEM.3) Considering performance requirements of efficient blockage removal, slow reaction, low corrosion and damage, efficient secondary precipitation inhibition, and compatibility with injected water,two sets of single step acid systems are designed instead of three-stage conventional acid system, achieving the effect that "one" instead of "three".4) The construction parameters mainly including acid injection rate, acid injection strength are designed, and the acidizing real-time monitoring software is prepared, forming a set of online single step acidizing technology.5) More than80wells field test with100%success rate of the research result and the remarkable increase injection effects of two injection wells of Shahejie formation in B oilfield, proving the online single step acidizing technology is economic and efficient for injection wells in offshore oilfield.