天然气水合物降压开采半解析两相产能模型

天然气水合物(NGH)被认为是最具潜力的新能源之一,目前开采产能低成为制约其高效开发的关键技术难题.本文综合考虑NGH相变、储层孔渗物性变化、气水两相渗流等复杂开采机理,建立NGH降压开采气水两相产能半解析模型,计算分析NGH降压开采动态和产能影响因素,并提出提高产能措施方向.研究结果表明,NGH降压开采前期,分解前缘移动速度较大,分解区域不断扩大,产气、产水升高;随着NGH的分解,NGH饱和度逐渐降低,产气降低,产水也随之下降;井底压力、NGH分解速率常数、渗透率等因素对产气速率影响较大,井底压力越小、储层渗透率及NGH分解速率常数越大,产气速率峰值越大;为提高NGH降压开采产能可采用向储层注热、注催化剂或水平井、水力压裂等技术措施.

The semi-analytical two-phase productivity model of natural gas hydrate by depressurization

Natural gas hydrate(NGH)is considered as one of the most potential new energy.How to improve the capacity of NGH has become a key technical problem restricting the efficient development of NGH.In this paper,a gas-water two phase semi-analytical model of NGH depressurization production is established by considering the NGH phase transition,the permeability change during NGH decomposition.The production performance and the influencing factors of production capacity were analyzed,and the measures of improving production capacity were suggested in the paper.The result shows,in the early stage of NGH depressurization,the decomposition front moves faster,the decomposition area expands continuously,so the gas production rate and water production rate of production wells increase.With the decomposition of NGH,the saturation of NGH decreases gradually,the gas production rate of production wells decreases,and the water production rate also decreases and finally stabilizes at a small value.The bottom hole pressure,NGH decomposition rate constant,permeability have great influence on gas production rate.The smaller the bottom hole pressure and the greater the reservoir permeability and the NGH decomposition rate constant,the greater the peak gas production rate.In order to improve the capacity of NGH production wells,such measures as injecting heat into reservoir,injecting catalyst or horizontal well technology and hydraulic fracturing technology can be adopted.