Evaluation of the Effectiveness of Workovers for Low Amplitude and Strong Edge Water Reservoirs in South America

A low amplitude sandstone reservoir in South America was put into production in 1978, and currently has a comprehensive water cut of 93.7%. In response to the challenges of dispersed remaining oil in the main oil fields and difficult workovers to tap potential, this article evaluates the effectiveness of workovers for edge-bottom water reservoirs by oil fields and classification based on statistical analysis of dynamic production over the years. The dynamic changes in workovers and their main control factors are analyzed, and the oil increase effects of different types of workovers on different oil fields and layers at different development stages are clarified. The potential of workovers is analyzed by layer series and workover type. Research has shown that the workovers are mainly concentrated in A and C oilfields, with the main workovers being squeezing, changing zone, sidetracking, restart, double tubing, and swabbing. The total workovers are 366 wells. The workload of changing zone and swabbing workovers accounts for the largest proportion, with 125 and 116 wells respectively, accounting for 34% and 32% of the total workload; The second is squeezing and restart, both accounting for 13%. The workover increased oil by 12 MMB, accounting for 3.3% of the total production of the block, with an average single well workover increasing oil by 32 Mbbl. Re-perforation, as well as changing zone, have the highest increase in oil production, with 3.9MMB and 3.5 MMB respectively, accounting for 1.1% and 1.0% of the total production of the block. The main potential workovers for the main old oil fields include drilling and sidetracking; The potential for workovers to develop multiple layers of oil layers is mainly the potential for changing zone of undeveloped oil layers. Based on the evaluation of the effectiveness of the workovers, it is forecasted that the future potential of the workovers will be approximately 9.4 Mbbl. This article has certain reference significance for workovers to tap the potential of ultra-high water cut sandstone reservoirs.