A comparative analysis of offshore gas hydrates production test in Japan
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摘要:
截至目前,只有中国和日本实施了海域天然气水合物的试采,了解日本的海域水合物试采中遇到的问题及其对问题的分析情况,有助于中国下一步的水合物研究和开发工作。为了深入认识日本于2013年和2017年在日本海域南海海槽分别实施的两次试采,介绍了两次试采的部署实施情况及实际产气情况,梳理了日本对两次试采中出现的问题及其针对问题的分析研究成果,对比了两次试采中3口生产井的产气情况。发现日本两次试采都没有解决实际产气与预测结果存在差异的问题,认为加强对水合物储层特征和物理特性的认识是解决上述问题的关键;另外,水合物的生产是一个综合的过程,防砂、压降过程、排水等互相影响,在解决这些问题时应综合考虑,并应寻找稳产需要的各项生产参数的平衡点。
Abstract:At present, only China and Japan have implemented production test of offshore gas hydrates. The problems and lessons encountered in Japan shall be helpful to the hydrate research and development in China. The deployment, gas production, problem and research in Japanese two production tests completed in 2013 and 2017 in Nankai Trough were summarized, and the gas production of three production wells in two tests were compared. It was found that the two tests failed in solving the problem of the difference between actual and predicted gas production results, for which the characteristics and physical properties of hydrate reservoirs should have been the key issues. In addition, the production of hydrates is so complicated that sand control, decompression, drainage, etc., must be considered comprehensively, and balance between various production parameters required for stable production should be compromised.
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Key words:
- natural gas hydrate /
- offshore production test /
- Japan /
- Nankai Trough
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图 1 两次(2013和2017年)海域试采的井口位置和电阻率测井数据及相应的沉积单元[5]
Figure 1.
图 2 利用实测温度和密度剖面推导得出的AT1-P、AT1-P3和AT1-P2井的产气(红色)和产水(蓝色)情况[8]
Figure 2.
图 3 AT1-P、AT1-P3和AT1-P2井单位压降和单位生产层段条件下产水率的时间变化情况(a)以及AT1-P、AT1-P3和AT1-P2井单位压降和单位生产层段条件下产气率的时间变化情况(b)[8]
Figure 3.
图 4 2013年第1次海域试采中实际产气与预测结果对比[14]
Figure 4.
表 1 2013和2017年两次海域试采的部署实施情况对比[13]
Table 1. Comparison of deployment and implementation of 2013 and 2017 production tests[13]
第2次海域试采 第1次海域试采 作业平台 “地球号”深海钻探船 “地球号”深海钻探船 试采海域 第二渥美海丘,与第1次试采在位置和地质条件等方面接近 第二渥美海丘 井位部署 1口地质调查井,2口生产井,2口监测井 1口生产井,2口监测井,1口取芯井 生产试验系统 采用了重量更轻(约120 t)、更便于重新安装和切换作业、以及允许更大船偏距的修井立管系统,主要由立(套)管、紧急脱离装置(EDP)和防喷装置(WCP)等构成 使用了“地球号”的钻探设备以及防喷器,但该钻探设备的重量较大(超过300 t),断开、重新安装以及切换作业非常困难 气水分离 对气水分离系统作了重新设计,如使用内径较大的井(第1次试采为9.625″,第2次试采为13.375″)来降低流速,以及改进设备的放置等来提高气水分离效率 利用举升分离器使产出水和水合物分解产生的气体在井下分离,并分别通过2条流动管线举升至海面 防砂装置 采用了利用形状记忆聚合物(SMP)的膨胀封堵井壁与地层间环形空间的GeoFORM防砂系统。为了测试不同防砂装置的效果,将使用两种型号的GeoFORM防砂系统:一种是下入井底前就预先膨胀;另一种是在井底才膨胀 采用了裸眼砾石充填防砂措施,但砾石的移动破坏了筛网并进而造成了出砂 井中监测 监测井中进行温度和压力的实时监测;生产井中进行温度和压力的实时监测 监测井中仅进行了温度的实时监测;生产井中进行了温度的实时监测,并在几个点测量了压力 环境监测 海底溶解甲烷浓度变化的监测;海底地形变化的监测 海底溶解甲烷浓度变化的监测;海底地形变化的监测 其他监测 四分量地震勘探和时移地震勘探 四分量地震勘探和时移地震勘探 表 2 2013和2017年两次试采中3口生产井生产情况对比
Table 2. Comparison in production performance of the three production wells in 2013 and 2017 production trials
AT1-P井 AT1-P3井 AT1-P2井 压降幅度/MPa 9.2 7.85 约5.4 产气率/(m3/d) 20 000 3000~4000 10000 产水率/(m3/d) 200 70~90 300~500 单位压降单位层段下的产气率 高 低 高 出砂 严重 中 低 生产周期/d 6 12 ≥24 -
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