复杂地形条件下CO_(2)泄漏扩散规律研究

Study on the diffusion patterns of CO_(2)leakage under complex terrain conditions

随着“双碳”目标的提出,CO_(2)驱油技术在我国油田得到快速发展,应用前景巨大。然而,在油田复杂地形条件下CO_(2)泄漏风险更大,容易造成人员窒息。为有效控制CO_(2)驱油工艺过程中的CO_(2)泄漏扩散危害,需研究复杂地形条件下CO_(2)泄漏扩散规律。结合某油田CO_(2)驱油现场地形实际情况,开展了全尺寸CO_(2)泄漏扩散试验研究,分析了不同条件下的CO_(2)体积分数分布规律。结果表明:在不同泄漏情形下,CO_(2)时均体积分数由近及远均满足指数分布规律,阶梯地形条件下体积分数1%CO_(2)的影响范围约为65 m,比水泥平坦地形下远54.8%;此外,随泄漏时间延长,温度逐渐降低,整体呈现距离泄漏口越近,温度下降速率越快的特征,平均温度梯度约为0.39℃/m。因此,在阶梯形地形条件下应加密CO_(2)体积分数监测布点,在近场区域人员应佩戴防冻劳保用品。

With the introduction of the'double carbon'target,CO_(2)flooding technology has rapidly advanced in China’s oil fields,presenting significant application potential.However,the risk of CO_(2)leakage increases under the complex terrain conditions of these fields,posing a serious threat of asphyxiation to personnel.To effectively manage the hazards associated with CO_(2)leakage and diffusion during the CO_(2)flooding process,it is essential to investigate the patterns of CO_(2)leakage and diffusion in such challenging terrains.This study involved conducting a full-scale CO_(2)leakage and diffusion test,tailored to the specific circumstances of CO_(2)flooding in the oilfield.The analysis focused on the distribution of CO_(2)volume fractions under various conditions.The results indicated that upon ejection from the nozzle,the expanding airflow collides with the ground,transforming from a cylindrical jet into a fan-shaped jet with an edge angle of 40°.Under various leakage conditions,the time-averaged volume fraction of CO_(2)follows an exponential distribution law,decreasing from near to far.The pulsation volume fraction is higher in both the near and far field areas,while it is lower in the middle field area.In the far field,the CO_(2)cloud is fully heated,resulting in more intense thermal motion and greater fluctuations in volume fraction compared to the middle field.Under stepped terrain conditions,the influence range of a 1%CO_(2)volume fraction extends approximately 65 m.Due to the tendency for CO_(2)enrichment to occur behind the slope of stepped terrain,the influence range is approximately 54.8%greater than that observed on flat cement terrain.Additionally,as leakage time increases,the temperature gradually decreases,with the rate of temperature drop being faster the closer one is to the leakage port.The average temperature gradient is around 0.39℃/m.Consequently,when positioning CO_(2)volume fraction monitoring points,it is crucial to consider the stepped terrain conditions,ensuring a dense distribution at the bottom of the slope.In the event of CO_(2)leakage at the oil production site,in addition to utilizing positive pressure respiratory systems,personnel involved in the response should wear anti-freezing protective gear to prevent frostbite incidents.