Abstract
Well-leakage is a very difficult problem in the process of drilling at home and abroad. At present, it mainly relies on the cumulative effect of plugging slurry to implement plugging regardless of the number of times and costs. Commonly used plugging slurry and plugging technology are difficult to guarantee the success rate and scientific of plugging malignant leakage, which has an extremely bad impact on the development of the petroleum industry. In this study, With polyvinyl alcohol and acrylic acid as main agents, a plugging material of acrylic acid grafted polyvinyl alcohol was prepared, and the influence of the composition of the reaction system on the gel state of the system was studied. Through a series of singlefactor experiments, the best formula for preparing the plugging material was determined, polyvinyl alcohol and acrylic acid (specific gravity 1:3) + crosslinking agent (0.1wt%) + initiator (0.3wt%). The gel plugging agent using above formula to prepare has good gel strength and suitable gel time, and has a good application prospect in solving the problem of lost circulation.
Highlights
During drilling operations, when the pressure of the drilling fluid column exceeds the formation pressure and the fractured formation is encountered, the drilling fluid can enter the pores and fractures of the formation, leading to the occurrence of lost circulation accidents [13]
The reason was that when the dosage of polyvinyl alcohol in the reaction system was small, the contact probability between polyvinyl alcohol and the active radical produced by the initiator was small, which made the reaction slower and the gelation time of the reaction system longer
When the concentration of polyvinyl alcohol was higher than 12%, the gelation time of the gel system was no longer affected by the amount of polyvinyl alcohol
Summary
During drilling operations, when the pressure of the drilling fluid column exceeds the formation pressure and the fractured formation is encountered, the drilling fluid can enter the pores and fractures of the formation, leading to the occurrence of lost circulation accidents [13]. The advantages are obvious, with: (1) low density is beneficial to the protection of oil and gas reservoirs; (2) gelling time is controllable, and the controllable time range is large, which is convenient for it to accurately reach the missing layer for plugging; (3) plugging The leaking slurry has strong fluid loss performance, and the formation of filter cakes can help stabilize the well wall; (4) It can be used in various applications and can block micro-fractures and relatively large fractures; (5) The gel plugging agent has good compatibility with the formation [9,10,11] It will not affect the formation environment. A gel with a special three-dimensional network structure and high viscoelasticity is formed, and the number and types of intermolecular chemical bonds determine the shape and performance of the polymer spatial structure
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