冷源外置式天然气水合物孔底冷冻绳索取样器关键机构的设计及实验研究

发布时间：2018-04-20 23:14

本文选题：冷源外置 + 天然气水合物　；参考：《吉林大学》2017年硕士论文

【摘要】：天然气水合物因其储量大、能量密度高、清洁和分布广泛等优点而被认为是最有希望接替传统能源的新能源。钻探取样是评价水合物储量和开采的前提,但天然气水合物常温常压下会分解,常规钻探取样技术无法满足水合物保真钻探取样的需求。保压取样技术利用球阀(翻板阀)密封岩心腔以及保温措施,在取样过程中维持水合物岩心的原始压力和温度,实现保真取样,目前常用的保压取样器包括PCB、PCS、FPC、PTCS等。冷冻取样技术是在分析了天然气水合物的温压特性和自保护效应的基础上,提出了在井下将水合物岩心冷冻至一个低温区间(240K-273K),从而抑制水合物分解,并增强水合物的自保护效应,实现保真取样。目前的提钻式孔底冷冻取样器存在提钻时间长、井下冷源储冷时间长以及操作时劳动强度大的问题,不利于水合物的保真取样。为解决这些技术问题,本论文提出冷源外置式孔底冷冻绳索取样器的设计思路,即采用绳索取心的方法,在钻进结束后,利用打捞器运送冷源至孔底并实施岩心冷冻,绳索取心方法可以实现快速提取岩心,冷源外置的方法可以解决冷源井下储冷时间长的问题。综合考虑了绳索取心方法和孔底冷冻方法,提出了取样器的结构设计要求。完成了冷源外置式绳索取心钻具的整体结构设计,绘制了整体结构图,并分析了取样器的工作原理。分析了六个常规机构,包括气动冷源注入机构、矛头机构、弹卡定位机构、悬挂机构、单动与缓冲机构和调节机构的结构组成和工作原理,并分析了关键机构,包括储冷机构、连接机构和岩心冷冻机构的重要性。首先,设计了连接机构,结构上可分为外置冷源模块部分和井下钻具部分,两部分分别设置在储冷机构的底部和冷冻机构的顶部;按功能可分为三个子机构:弹卡打捞子机构、密封阀子机构和支撑锁位子机构,分别完成套取井下钻具、连接处的密封和为连接过程提供支撑力及锁定连接状态。加工密封连接结构的样机,对各个子机构进行了验证试验,证明各机构均可实现预期功能;对连接机构整体进行验证性试验,证明连接机构可实现预期的功能;绘制了连接机构关键尺寸表,确定了指导连接机构设计的关键尺寸。建立试验台,测定了连接机构连接过程所需的拉力,分析确定了冷源外置取样器对卷扬机所提供拉力的要求为2880N。然后,设计了储冷机构及储冷方案,确定了以酒精为载冷剂,利用液氮与酒精混合,快速获得低温酒精的冷源制备方案,实验中发现该方法可制得温度低于冰点(-114℃)且具有良好流动性的低温酒精(-130℃);确定了以纳米气凝胶毡作为储冷腔保温层的储冷腔保温方案。完成了储冷机构的结构设计,分析了储冷机构的结构组成和工作原理,并加工样机、设计实验装置,对储冷机构进行了实验研究;在实验条件下,-130℃的低温酒精存储30min后,冷源温度降低为-95℃,绘制了储冷过程冷源温度变化曲线,确定了下一步岩心冷冻实验中冷源的初始温度为-95℃。最后,设计了岩心冷冻机构和冷冻方案,提出了冷冻机构的“两段式”结构布局,对比分析了两段式结构布局相较于传统三段式结构布局的优点在于漏热少、密封性好;提出了“底部注冷”的冷源注入方案,对比分析了底部注冷方案相较于传统的上部注冷方案的优点在于可实现冷源与岩心间的强制对流换热、确保岩心上下均匀制冷;结合岩心冷冻机构的特点,提出采用具有一定刚度的聚四氟乙烯作为冷冻腔保温材料。完成了冷冻机构的结构设计,分析了冷冻机构的结构组成和工作原理,并加工了样机、设计了实验装置,对岩心冷冻机构进行了实验研究,验证了“底部注冷”的冷源注入方案优于“顶部注冷”。以注入冷源的压力为变量,采取“底部注冷”的冷源注入方案进行了岩心冷冻实验,实验表明在0.30-0.40MPa之间存在以一临界压力,当注冷压力低于该值时,冷源在冷冻腔内流动状态为层流,而当注冷压力高于该值时,冷源在冷冻腔内流动状态为紊流:注冷压力在0.20MPa附近时可达到层流状态时最优的冷冻效果,其实验前期岩心降温速率为6.9℃/min,岩心最低温度可达-18.75℃,实验末岩心温度保持在-6±2.5℃内;当注冷压力为0.4MPa时,实验前期岩心降温速率可达15.75℃/min,岩心最低温度为-27℃,实验末岩心温度在0℃以下;分析认为,当注冷压力在0.3MPa到0.5MPa之间时,可达到紊流状态时最优的冷冻效果,即最优注冷压力在0.3-0.5MPa之间。
[Abstract]:Natural gas hydrate is considered as the most promising new energy for replacing traditional energy because of its large reserves, high energy density, wide cleanliness and wide distribution. Drilling sampling is the prerequisite for evaluating the reserves and mining of hydrate, but natural gas hydrate will be decomposed under normal temperature and pressure. Conventional drilling sampling technology can not meet the practice of hydrate drilling and drilling. The pressure and pressure sampling technology uses the ball valve (turn plate valve) to seal the core cavity and the insulation measures to maintain the original pressure and temperature of the hydrate core during the sampling process, and to realize the fidelity sampling. The current commonly used pressure sampler includes PCB, PCS, FPC, PTCS and so on. On the basis of the protective effect, it is proposed that the hydrate core is frozen into a low temperature range (240K-273K) in the downhole, so that the hydrate decomposition is suppressed, and the self protection effect of the hydrate is enhanced to realize the fidelity sampling. The current drilling type hole bottom freezing sampler has long drilling time, long cold storage time and labor intensity in operation. In order to solve these technical problems, in order to solve these technical problems, this paper puts forward the design idea of the cold rope sampling apparatus for cold source outside the hole bottom, that is, using the rope coring method, after the end of the drilling, the cold source is transported to the bottom of the hole and the core is frozen, and the rope coring method can be quickly extracted. The core and cold source external method can solve the problem of long cold storage time in the downhole of cold source. Considering the rope coring method and the hole bottom freezing method, the structure design requirements of the sampler are put forward. The overall structure design of the external coring coring tool for the cold source is completed, the whole structure drawing is drawn and the working principle of the sampler is analyzed. The structural composition and working principle of six conventional mechanisms, including pneumatic cold source injection mechanism, spearhead mechanism, projectile card positioning mechanism, suspension mechanism, single motion and buffer mechanism and adjusting mechanism, are analyzed. The importance of key mechanisms, including cold storage mechanism, connecting mechanism and Yan Xinleng freezing mechanism, is analyzed. First, the connecting mechanism is designed and the structure is designed. It can be divided into the external cold source module part and the downhole drilling tool section. The two parts are set at the bottom of the cold storage mechanism and the top of the freezing mechanism respectively. According to the function, it can be divided into three subunits: the projectile card fishing sub mechanism, the sealing valve sub mechanism and the supporting lock position mechanism, respectively, to complete the drilling tools under the well, the seal at the connection and the connection process. The supporting force and locking connection state. The prototype of the machined seal connection structure was tested to prove that each mechanism could realize the expected function, and the connecting mechanism was tested to prove that the connecting mechanism could realize the expected function; the key dimension table of connecting mechanism was drawn and the guiding connection mechanism was established. A test bench was set up to determine the tension required for the connection process of the connecting mechanism. The requirement for the pulling force provided by the external sampler of the cold source was determined to be 2880N., then the cooling mechanism and the cooling scheme were designed, and the alcohol as the refrigerant was determined, and the liquid nitrogen and alcohol were mixed to quickly obtain the cold alcohol cold. In the source preparation scheme, it is found in the experiment that the method can produce low temperature alcohol (-114 C) with low temperature and good fluidity (-130 C). The thermal insulation scheme of the cold storage cavity with nano aerogel felt as the insulation layer of the cold storage cavity is determined. The structure design of the cooling mechanism is completed, the structure and working principle of the cooling mechanism are analyzed, and the structure of the cooling mechanism is analyzed. In the experimental condition, the cold source temperature of -130 C is reduced to -95 C, and the cold source temperature change curve of the cold storage process is drawn. The initial temperature of the cold source in the next step of the core freezing experiment is -95 C. Finally, the core cooling machine is designed. The "two section" structure layout of the freezing mechanism is put forward, and the advantages of the two section structure layout compared with the traditional three section structure layout are less heat leakage and better sealing, and the cold source injection scheme of "bottom injection" is put forward. The comparison and analysis of the bottom injection cooling scheme is compared to the traditional top cooling scheme. The advantage of it is to realize the forced convection heat transfer between the cold source and the core, to ensure the uniform cooling on the core, and to combine the characteristics of the core cryopreservation mechanism, to adopt a polytetrafluoroethylene as the thermal insulation material with a certain stiffness. The prototype is processed, the experimental device is designed, and the experimental research on the core freezing mechanism is carried out. It is proved that the cold source injection scheme of "bottom injection" is superior to the "top injection cooling". The cold source injection scheme of "bottom injection" is used to freeze the rock core freezing experiment with the injection of cold source. The experiment shows that the cryopreservation is stored between 0.30-0.40MPa. At a critical pressure, when the cooling pressure is lower than that of this value, the flow state of the cooling source is laminar in the cryopreservation chamber. When the cooling pressure is higher than that, the flow state of the cold source in the cryopreservation cavity is turbulent. The optimal freezing effect is reached when the cooling pressure reaches the laminar state near 0.20MPa, and the cooling rate of the core is 6.9 /min at the early stage of the experiment. The lowest core temperature of the core is up to -18.75 C, and the core temperature at the end of the experiment is kept at -6 2.5 C. When the injection cooling pressure is 0.4MPa, the cooling rate of core is up to 15.75 /min, the lowest core temperature is -27 C, and the core temperature is below 0 C at the end of the experiment. It is concluded that when the cooling pressure is between 0.3MPa and 0.5MPa, the temperature can reach the turbulent state. The best freezing effect is that the best injection pressure is between 0.3-0.5MPa.

【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】：P618.13;P634

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