Evaluation and application of chelating agents for blockage removal in Caofeidian 12-1 Offshore Sandstone Reservoir in China
DOI:
https://doi.org/10.62813/see.2024.01.07Keywords:
Offshore, Acidizing, ChelationAbstract
Acidizing is a common measure used to stimulate sandstone reservoirs; however, drawbacks are associated with conventional acidizing formulas and flowback usually causes adverse impact on subsequent production processes. To optimize the acidizing treatment for formation blockage removal in low-production wells in the Caofeidian (CFD) 12-1 Offshore Sandstone Reservoir and alleviate the impact of acidizing flowback fluid on production processes, a chelating agent system for damage removal was developed and evaluated by laboratory tests of rock dissolution, chelation, demulsification, wax and asphaltene dissolution, and core flood. Laboratory evaluation tests indicate that the dissolution ratio of clay minerals by the chelating system is 23%-72% of the mud acid system, which is a moderate dissolution capacity and can effectively protect loose sandstone reservoirs. The chelating system shows strong chelation ability with high-valence metal cations, and the conductivity of post-reaction residual fluid is only 1/50 to 1/60 of that after conventional acidization. The demulsification ratio of the post-reaction residual fluid exceeds 98%, and the dissolution rates for wax and asphaltene are 0.0249g/min and 0.029g/min, respectively. After injecting chelating agents for blockage removal, the sandstone reservoir core permeability increased by 1.67 times. This chelating system was successfully applied in the CFD 12-1 E10H well and achieved a cumulative oil increase of 9,561m3 after operations, with flowback fluid entering the production process directly and no negative impact on the process. Both laboratory and field application results demonstrate that the chelating system has moderate dissolution performance, strong chelation ability with high-valence metal cations, and minimal impact of flowback fluid on the production stream process, which could be utilized for stimulation in similar reservoirs.
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Copyright (c) 2024 Xinming Rong, Chunlin Wang, Xun Du, Zhibin Kui, Jiazhen Zheng, Xinrui Zhao
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