【作者】 杨圣文；

【导师】 樊栓狮；

【作者基本信息】 华南理工大学 ， 能源环境材料及技术， 2013， 博士

【摘要】 世界能源消费量巨大，导致传统石化能源供给紧张。同时由于传统石化能源储量只够未来几十年的使用，急需寻找新的替代能源。天然气水合物在自然界储量巨大，其中的碳含量是传统石化能源总含碳量的数倍，有潜力成为未来的主要能源。因此水合物的工业化开采非常迫切，急需寻找天然气水合物工业化开采的方法。本文将自然界天然气水合物藏分为4类，Ⅰ类水合物在现有技术条件下容易开采，Ⅳ水合物饱和度低不值得开采，Ⅱ类、Ⅲ类水合物开采存在较大争议。Ⅱ类水合物为水合物长期开采后的形态，未来水合物开采必须面对此类水合物开采问题，中国南海神狐海域水合物为Ⅲ类。本文针对Ⅱ类、Ⅲ类水合物藏，采用不同开采策略进行开采模拟。采用HydrateResSim对水合物进行开采模拟。为了验证数值模拟与实际水合物分解情况的吻合度，首先用过量水在实验室条件下，多孔介质中合成Ⅱ类水合物，然后1MPa定压分解，对比实验室水合物分解情况与数值模拟结果的一致性。在此基础上，进行Ⅱ类水合物藏开采模拟。Ⅱ类水合物藏上层为水合物，下层为水，其渗透性良好，采用竖直井开采。同时考虑单一减压法难于独立有效开采，所以采用加热辅助开采。采用加热热流密度为1200W/m，加热长度共20m，总共加热功率24000W；井内压力根据工程实践设置为0.2P0，0.5P0，0.8P0，因此Ⅱ类水合物藏开采策略为竖直井加热减压开采。0.2P0开采条件下开采情况最为理想，开采500天水合物分解气体释放平均速率为1.5m/s，井内气体收集平均速率约0.25m/s，水合物分解释放气体总体积6.5×10~7m~3，气体收集总体积1.0×10~7m~3，水收集总质量1.1×10~9kg，水气体积比约为6，采收比约0.15，加热分解水合物贡献为8.5%，开采过程能效比为5.1。从开采前期500天情况看，Ⅱ类水合物工业开采困难。但从开采发展趋势看，气水体积比及气体收集速率呈上升趋势，表明Ⅱ类水合物开采后期情况将得到改善。Ⅲ类水合物藏存在上下非渗透层，而且为单层水合物，其渗透率低，制约水合物开采。采用水平井能有效克服这类水合物藏渗透率低的约束，因此采用水平井加热减压联合开采Ⅲ类水合物。井内温度压力开采条件参考油气工程实践设置为0.2P0&42℃，0.5P0&42℃，0.8P0&42℃。Ⅲ类水合物藏3D开采模拟时0.2P0&42℃开采条件下开采情况最好，模拟开采450天，气体释放速率达到4-5m~3/s，累积释放气体1.6×10~8m~3（约为每天350,000m~3），达到工业开采要求。Ⅲ类水合物藏2D开采模拟显示，0.2P0&42℃开采条件下，开采8500天水合物全部分解，累积分解气体6.8×10~5m~3，累积收集气体3.5×10~5m~3，累积收集水质量1.1×10~6kg，气体采收比约0.5，气水体积比持续上升，最高达304。加热分解了5.28%的水合物，其余水合物由减压推动力分解。水合物藏中开采得到的天然气按高热值计算，Ⅲ类水合物开采过程能效比达到188。更多还原

【Abstract】 The energy consumed around the world is very huge, which leads the shortage of energysupply. At the same time, the traditional fossil fuel in reservoirs can only satisfy the demandof the whole world for several decades. Finding a new replacement energy resource is veryurgent. Natural gas hydrate is a new energy resource, and the carbon in hydrate reservoirs istwo times of that in traditional fossil fuel. This indicated that the hydrates can be the potentialenergy resource in the future.The natural gas production from hydrate reservoirs method and strategies were the mostimportant issues in hydrate dissociation. Class1hydrates were easy to be recovered, andClass4was unworthy of attention for their low saturation. The natural gas productionfeasibility from Class2and Class3was controversial. Class2hydrate reservoirs is the statefor long term of other kind of hydrate reservoirs. People have deal with this kind of hydrate.Shenhu hydrate reservoirs in South China Sea was Class3. The feasibility of this two kinds ofhydrate reservoirs will be studied in this paper.HydrateResSim code was used to simulate the production of natural gas from reservoirs. Inorder to check the consistent and reliability of the code to hydrate reservoirs dissociation, thelab level experiment was conducted. The formation and dissociation of hydrates in porousmedia were conducted. The experiment show that the hydrates of55g were synthesized in2000s and dissociated in1200s, and the gas in the cell was about15L in total. The data inthe hydrate formation and dissociation were consistent with the numerical simulation result.Based on this, a numerical simulation that Class2hydrate was dissociated in vertical well indepressurization and thermal co-stimulation method for their good permeability wasdeveloped. The perforations and heating injection were taken in hydrate and mobile fluidinterface layers. Heating flux was1200W/m in20m length wellhole. And the pressure of thewell was set in0.2P0,0.5P0,0.8P0three levels. Simulation result shows that the productiondata under condition of0.2P0was the most favorable. The gas release rate was1.5m/s within500days production. Gas collection rate in the well was0.25m/s in average. Cumulativewater was1.1×10~9kg. Gas to water volume ratio was about6and gas collection to release ratewas0.15in average. Base on the production data of Class2hydrate reservoirs, heatingcontribution to hydrate dissociation and EER were calculated. Thermal dissociated8.5%ofthe hydrates, and the EER were about5.1. From the data above, it was indicated that Class2hydrate production in industry level was negative. However, the gas to water volume ratio andthe gas collecting rate were increasing, which indicated that the Class2hydrate production situation would be better for the later production stage.For Class3hydrate reservoirs, the horizontal well, depressurization and thermalco-stimulation method would be used for their low permeability. The production parametersof well pressure and temperature were set in0.2P0&42℃,0.5P0&42℃0.8P0&42℃threelevel according to oil production engineering. Simulation results of Class3hydrate reservoirswere very exciting. From3D simulation, gas release rate was4-5m~3/s in average in450daysand the cumulative gas was1.6×10~8m~3，approximately350,000m~3/d. this gas release rate cansatify the gas commercial production requirement.2D simulation of Class3hydratesdissociation showed that under production condition of0.2P0&42℃，all the hydrates weredissociated. The cumulative gas was6.8×10~5m~3and3.5×10~5m~3were collected. Whichindicated that gas collected to released rate was about0.5. The cumulative water in the wellwas1.1×10~6kg，and gas to water volume ratio were increasing, at the end, reaching to304.Based on the simulation data of Class3hydrate dissociation, the heating contribution tohydrate dissociation and EER were calculated. The results show that heating contribution tohydrate dissociation was5.28%, and EER were188. Equation Section (Next)Equation Section (Next)更多还原