基于止裂韧性修正的超临界CO2管道止裂模型建立与拓展

Development and extension of a crack arrest model for supercritical CO2 pipelines based on crack arrest toughness correction

  • 摘要:
    目的 碳捕集、利用与封存(CCUS)技术的规模化发展,必然推动超临界CO2管道输送技术的研发与工程应用,由于原始的止裂模型无法预测超临界CO2管道的止裂韧性,并且相关的止裂应力修正公式表明,不同修正方法计算结果均存在差异,且与CO2管道设计相关标准中预测结果相差较大,使得超临界CO2管道止裂控制体系仍未建立,成为限制CCUS技术广泛应用的难题,因此迫切需要建立更经济有效,适用于工程的超临界CO2管道止裂评估模型。
    方法 针对该问题,本文借助目前国内外公开的CO2管道全尺寸爆破试验数据,涵盖不同管径、壁厚、钢级及试验工况,基于动态断裂力学的止裂判据,依据CO2管道设计相关标准,采用止裂韧性参数修正法对现有阻力—驱动力曲线进行修正,对比了不同修正系数的止裂评估效果,拟合现有数据得到最佳修正系数k,同时采用饱和压力ps代替裂尖压力pc的方法,建立了超临界CO2管道止裂评估模型。
    结果 研究结果表明,不同模型的止裂评估结果对CO2管道不完全适用,止裂应力公式用于CO2管道时误差较大,管道的止裂能力可能会被明显高估;采用拟合得到的止裂韧性参数修正系数k=3.09时,样本范围内稳定性较高,止裂评估效果最好,建立的修正模型解决了传统止裂预测模型非保守的问题,拓展了止裂评估图的评估范围;为延长油田CCUS二期工程L22管道设计提供了止裂评估方案,通过调节壁厚提高材料的止裂韧性和设置外部止裂器的止裂控制措施建议。
    结论 本研究建立的止裂评估模型具有较高的准确度与工程适用性,为了适应CCUS规模化应用带来的管材和管径等参数范围的变化,建议后续结合已有的全尺寸爆破试验数据,采用有限元双向流固耦合模拟技术进一步开展止裂研究。

     

    Abstract:
    Objective The large-scale deployment of Carbon Capture, Utilization, and Storage (CCUS) technology necessitates the advancement and engineering application of supercritical CO2 pipeline transport. However, conventional crack arrest models fail to accurately predict the crack arrest toughness of these pipelines. Furthermore, existing stress correction formulas yield highly inconsistent results that deviate significantly from current CO2 pipeline design standards. Consequently, the lack of an established crack arrest control system presents a major barrier to widespread CCUS adoption, highlighting an urgent need for a more cost-effective, engineering-applicable crack arrest evaluation model.
    Methods To address the above issue, full-scale burst test data of CO2 pipelines publicly available worldwide were adopted in this study, covering different pipe diameters, wall thicknesses, steel grades, and test conditions. Existing resistance-driving force curves were modified via the crack arrest toughness parameter correction method, based on the crack arrest criteria of dynamic fracture mechanics and relevant CO2 pipeline design standards. The crack arrest evaluation performances of different correction coefficients were compared, and the optimal correction coefficient k was obtained by fitting the measured data. Meanwhile, a novel crack arrest evaluation model for supercritical CO2 pipelines was established by replacing the crack tip pressure pc with the saturation pressure ps.
    Results The research results indicated that existing crack arrest evaluation models were not fully applicable to CO2 pipelines, as traditional crack arrest stress formulas led to large calculation errors and a remarkable overestimation of pipeline crack arrest capacity. When the fitted correction coefficient of the crack arrest toughness parameter (k) was set to 3.09, the proposed model demonstrated high stability and optimal crack arrest evaluation performance within the sample range. This modified model eliminated the non-conservative defects of traditional prediction models and broadened the application scope of crack arrest evaluation diagrams. Additionally, a crack arrest evaluation scheme was formulated for the design of Pipeline L22 in the Phase II CCUS Project of Yanchang Oilfield. Corresponding crack arrest control recommendations were put forward, including increasing wall thickness to enhance material crack arrest toughness and installing external crack arresters.
    Conclusion The crack arrest evaluation model developed in this study demonstrates high accuracy and engineering applicability. To accommodate variations in pipeline material and diameter resulting from large-scale CCUS deployment, future research should utilize finite element simulation technology with two-way fluid-structure interaction in conjunction with existing full-scale burst test data.

     

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