【作者】 姜海洋；

【导师】 孙金声； 李彦龙；

【作者基本信息】 中国石油大学(华东) ， 石油与天然气工程（专业学位）， 2023， 硕士

【摘要】 天然气水合物储藏量大、热值高及清洁低碳,是潜在的接替能源。降压法开采水合物是目前水合物开采最为有效的方法,并在多次试采活动中得到证实。但是降压法存在后期产能不足、开采速率低的缺点,实现水合物商业化开采的目标仍然不足。因此,需采取有效的增产措施提高开采产能。水力割缝改造具有改善渗流能力、增大压力传递效率的特征,已在试采中得到应用。出砂是制约水合物安全长期开发的瓶颈问题,在水合物试采中普遍发生。因此,厘清水力割缝条件下降压开采过程中的水合物储层出砂行为及破坏形态演化对于阐明出砂机制、明确防砂控砂措施以及实现水合物商业化具有重要意义。本论文利用水合物微观相态与储层模拟系统,研究了水力割缝条件下水合物分解前和降压分解过程中的微观破坏形态及演化过程,揭示了不同储层条件(水合物饱和度、割缝参数)和工程条件(驱替模式、降压速率)下的影响规律,并且对出砂特征和压力特征进行了分析,探讨了可能的出砂原因。研究结果表明,在水合物分解前,破坏形态演化依次为集合体侵入、间歇性蠕动以及冲蚀沟,受到水合物饱和度和驱替模式的影响而有所区别,形成机制在井周地层及割缝周围地层也有所不同。而在降压分解过程中微观破坏形态分别为垮塌、集体蠕动以及蚯蚓洞,演化规律受到水合物饱和度以及割缝参数的影响,对井周地层及割缝周围地层的破坏形态演化机制进行了分析,并对其形态演化进行了刻画。结合出砂特征分析和显微观测,认为割缝砾石层在地层出砂过程中起到了防砂挡砂的作用,并对出砂量及其中值粒径造成较大的影响,致使在不同储层条件和工程条件下的出砂规律较为复杂。降压开采水合物,储层容易受到焦耳-汤姆逊效应促使水合物自保护效应产生,导致井眼出现水合物二次生成,甚至出现高饱和度储层降压分解致使进出口两端堵塞的现象。更多还原

【Abstract】 Natural gas hydrate is a potential alternative energy source with large reserves,high calorific value and clean low carbon.The depressurization method is the most effective method for hydrate mining,and has been confirmed in many trial mining activities.Therefore,effective measures should be taken to increase production capacity.Hydraulic slotting transformation has the characteristics of improving seepage capacity and increasing pressure transfer efficiency,and has been applied in trial production.Sand production is a bottleneck problem restricting the long-term development of hydrate safety,which is common in hydrate trial production.Therefore,it is of great significance to clarify the sand production behavior and morphological failure evolution of hydrate reservoirs in the process of descending pressure mining under hydraulic slotting conditions to clarify the sand production mechanism,clarify sand control measures and realize the commercialization of hydrate.In this thesis,the microscopic failure modes and evolution processes before and during hydrate decomposition under hydraulic slotting conditions were studied by using hydrate microscopic phase state and reservoir simulation system.The effects of different reservoir conditions(hydrate saturation,slotting parameters)and engineering conditions(displacement mode,depressurization rate)are revealed.The characteristics of sand production and pressure characteristics are analyzed,and the possible causes of sand production are discussed.The results show that the evolution of failure morphology before hydrate decomposition is collective intrusion,intermittent creeping and erosion ditch.The failure morphology is different due to the influence of hydrate saturation and displacement mode.And the formation mechanism is also different in the formation around the well and the formation around the slit.In the process of decompression and decomposition,the sand forms are local collapse,collective creeping and wormhole.The evolution lawis affected by hydrate saturation and slotting parameters.The microscopic failure morphology evolution mechanism of the formation around the well and the formation around the slotting is analyzed,and the morphological evolution is described.Combined with the analysis of sand production characteristics and microscopic observation,it is considered that the slotted gravel layer plays a role of sand control in the process of sand production.It has a great influence on the sand production and its median particle size.Therefore,the sand production law under different reservoir factors and engineering factors is more complicated.When hydrate is produced by depressurization,the reservoir is easily affected by the Joule-Thomson effect to promote the self-protection effect of hydrate,which leads to the secondary formation of hydrate in the wellbore.Even the phenomenon of blockage at both ends of the inlet and outlet caused by the decomposition of the high saturation reservoir.更多还原