南海神狐海域天然气水合物开采数值模拟

• Main Authors: 李刚, 李小森, 陈琦, 陈朝阳
• Format: Report
• Language: English
• Published: 2010
• Subjects: natural gas hydrate; depressurization; thermal stimulation; TOUGH plus HYDRATE; Shenhu; HEAT-FLOW; ACCRETIONARY PRISM; FLUID EXPULSION; MACKENZIE DELTA; MALLIK SITE; ENERGY; SEDIMENT; RESOURCE; CANADA; 天然气水合物; 降压开采; 注热开采; 南海神狐海域; Canada; Mackenzie Delta
• Online Access: http://ir.giec.ac.cn/handle/344007/31437

Considerable hydrate deposits are proved to exist by drilling in-situ in the Shenhu Area of South China Sea in China, and the survey and evaluation as a potential energy resource has been carried out. In May, 2007, gas hydrate samples have been collected in the Shenhu Area, which will become a strategical area of gas hydrate exploitation in China. TOUGH HYDRATE is employed to simulate the hydrate dissociation and water/gas production process with the single depressurization and the depressurized+thermal stimulation, based on the geological data of the SH2, SH3 and SH7 site in the Shenhu Area in South China Sea. The simulation results indicate that the hydrate dissociate at the area surrounding the production well, the boundary area of the bottom and top of the hydrate bearing layer (HBL). There is an inversion of the geothermal gradient at the interface between the overburden (OB) and the HBL because of hydrate dissociation-induced cooling in the HBL. Practically impermeable secondary hydrate barrier evolves around the wellbore, which sealed the hydrate body and prevented communication with the evolving upper dissociating interface at the end of the depressurization process. With the hot water injected from the top of the HBL, the secondary hydrate can be eliminated during the depressurization+thermal stimulation process. 实地钻探结果表明我国南海北部神狐海域存在大量天然气水合物,其作为未来我国潜在的可开发能源的调查和资源评价工作正在展开.利用国际上先进的多相多组分沉积物渗流模拟计算软件TOUGH＋HYDRATE,以2007年5月国土资源部广州地质调查局在南海北部神狐海域SH2,SH3和SH7站位的钻探、测井数据为基础,建立实际水合物藏分层地质模型,利用不同的开采井设计方式进行单井降压和降压＋注热开采模拟.结果表明,开采过程中水合物分解区域主要集中在开采井周边区域、水合物层与含水层界面处以及水合物层顶部靠近上盖层的区域.由于水合物分解吸热,水合物层的温度降低,使得热量从上盖层向水合物层传递,形成地温梯度的逆转,促进水合物层顶部逐渐产生分解界面.降压开采进行到后期开采井周围会形成渗透率很低的＂二次水合物＂,影响开采的进行,所以利用降压＋注热开采方法消除＂二次水合物＂,使开采过程顺利进行.