海洋天然气水合物试开采数值模拟及方案优化

发布时间：2018-03-16 17:41

本文选题：海洋水合物　切入点：试开采验证　出处：《吉林大学》2017年硕士论文　论文类型：学位论文

【摘要】：天然气水合物是一种开采潜力巨大的清洁能源。降压法及降压注热联合开采方法,可以改变水合物相平衡条件使水合物不稳定分解,是开采水合物最有效和最常用的方法。已有研究多是直接利用模拟软件进行不同方案下水合物优化开采研究,缺少场地开采和模拟计算的对比验证。本文首先结合日本Nankai海槽场地资料和实际开采条件,包括开采场地水合物饱和度、渗透率、孔隙度和实际温压条件以及开采试验的开采压力等,利用TOUGH+hydrate模拟软件,获得开采周期内开采井的产气速率和产水速率等。然后将模拟计算结果与实测开采数据进行对比验证。对比结果发现,在模型能够较为精确地刻画水合物储层的渗透率及水合物饱和度非均质分布时,获得的模拟产气速率结果与实际试开采数据拟合较好,说明TOUGH+hydrate模拟软件可以正确地刻画水合物的开采过程,可被用于研究天然气水合物开采评价工作中。在验证数值模拟软件的可靠性后,本文选取我国主要的天然气水合物赋存区域——南海北部陆坡神狐海域作为本次天然气水合物优化开采的研究区。根据2007年广州海洋地质调查局对南海神狐海域进行钻探的资料分析,利用在SH2钻孔得到的地质资料,模拟评价单一水平井和双水平井降压及降压注热联合开采水合物的产气能力。通过分析不同降压幅度和注热幅度对水合物开采速率的影响发现,单一水平井降压注热联合开采(500W/m注热功率)比单独降压开采总体产气提升20%,具体在初期可以大幅度提高产气,但后期提升作用不明显,这可能是因为随着开采,井周围水合物含量减少的原因。双水平井采用上井降压下井注热开采方式时,其产气速率始终低于双水平井均降压时的产气速率。两种布井方式下产气速率变化趋势相似,均是在开采初期迅速降低,在生产后期趋于平稳缓慢降低。在开采初期,井底压力越低,水合物分解的驱动力越大,产气速率越高,相应的产气速率降低幅度也越大,开采后期各方案生产速率的差距减小甚至趋于相同。在2.7MPa的井底开采压力下,开采五年时双水平井的累积产气量是单一水平井累积产气量的2.3倍,累积产水量是单一水平井累积产气量的1.9倍。
[Abstract]:Natural gas hydrate is a kind of clean energy with great potential for exploitation. Depressurization and depressurization combined with heat injection can change the phase equilibrium conditions of hydrate and make the hydrate unsteady decompose. It is the most effective and most commonly used method to exploit hydrate. Most of the studies have been done directly by using simulation software to study the optimal exploitation of hydrate under different schemes. This paper first combines the site data of the Nankai trough in Japan and the actual mining conditions, including hydrate saturation, permeability of the mining site. The porosity, the actual temperature and pressure conditions and the mining pressure of the mining test are simulated by TOUGH hydrate software. The gas production rate and water production rate of the well are obtained during the production cycle. Then, the simulated calculation results are compared with the actual mining data, and the comparison results show that, When the model can accurately describe the permeability of hydrate reservoir and the heterogeneous distribution of hydrate saturation, the simulated gas production rate obtained fits well with the actual test production data. It shows that TOUGH hydrate simulation software can accurately describe the process of hydrate exploitation, and can be used to study the evaluation of natural gas hydrate exploitation. In this paper, the main gas hydrate occurrence area in China, Shenhu sea area on the northern slope of the South China Sea, is selected as the research area for the optimal exploitation of natural gas hydrate. According to the Guangzhou Marine Geological Survey in 2007, the Shenhu sea area of the South China Sea was entered into. Analysis of the data of drilling, Based on the geological data obtained from drilling in SH2, this paper simulates and evaluates the gas production ability of single horizontal well and double horizontal well in combination with depressurization and injection heat injection. By analyzing the influence of different pressure reduction and heat injection amplitude on hydrate extraction rate, it is found that, A single horizontal well with reduced pressure and heat injection combined production (500 W / m heat injection power) can increase the total gas production by 20% compared with the single down pressure production. In the initial stage, the gas production can be greatly increased, but the later stage of the lifting effect is not obvious. This may be due to the fact that with the development, The reason for the decrease of hydrate content around the well is that the gas production rate of double horizontal wells is always lower than that of dual horizontal wells when the injection heat production method is adopted in the upper well and down well, and the variation trend of the gas production rate is similar under the two kinds of well distribution modes. In the early stage of exploitation, the lower the bottom hole pressure, the greater the driving force of hydrate decomposition, the higher the gas production rate, and the greater the decrease of the corresponding gas production rate. The difference of production rate between different schemes is decreasing or even being the same in the later stage of mining. Under the pressure of 2.7 MPA, the cumulative gas production of the double horizontal well is 2.3 times that of the single horizontal well during the five years of exploitation, and the cumulative gas production of the double horizontal well is 2.3 times of that of the single horizontal well. Cumulative water production is 1.9 times that of a single horizontal well.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TE53

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