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ABSTRACT: Underground gas storage is characterized by large gas injection and withdrawal cycles, making the wellbore bear repeated loading and unloading. Subjecting cement sheath to these conditions can cause damage, thus compromising its ability to provide complete zonal isolation. Wellbore annulus plugging with high-strength resin technology was studied to evaluate its effectiveness in controlling unwanted fluid migration through triaxial mechanical properties test, corrosion inhibiting ability test, and anti-gas channeling performance evaluation. The experimental results showed that the curing time was extended by 1.9 hrs by doubling the amount of diluent. At the same time, doubling the amount of the curing agent increased the compressive strength by 5.3 MPa. Under the triaxial test conditions, the four resin materials exhibited high compressive strength, low elastic modulus, and low Poisson’s ratio. Injection of corrosive CO2 at 0.5 MPa, reduced the compressive strength of the four resins within the range of 4.9% ~24.3%. A 100g of epoxy resin mixed with 10 g of diluent and 20 g of the curing agent significantly reduced the curing time. In addition, this mixture increased the maximum differential stress, and elastic modulus to 100.5 MPa and 3.325 GPa, respectively, after 1.6 h. The gas test anti-channeling pressure of the 5 cm sample was as high as 19.1 MPa. The test samples maintained long-term stability under continuous high pressure and tightness under the action of the alternating load of a significant pressure difference. This study uses high-strength plugging gel technology to provide a technical guide for wellbore remedial redress and plugging in underground gas storage.
1. INTRODUCTION The formation is effectively sealed with cement to prevent cross-flow under differential pressure and ensure smooth oil and gas production (Jordan et al., 2015; De et al., 2017; Hatambeigi et al., 2020; Valov et al., 2022). Cement has the disadvantages of high brittleness, poor corrosion resistance, and insufficient durability. Under the action of alternating load, micro-cracks and micro-annulus can easily be generated on the wellbore system. In addition, the presence of an acidic medium such as CO2 can cause the cement barrier to corrode, further compromising its ability to prevent unwanted fluid migration.
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