天然气水合物水平井降压开采多相渗流—传热—力学耦合数值模拟:方法和南海场地应用  

Coupled thermal-hydrodynamic-mechanical numerical simulation of natural gas hydrate horizontal well depressurization production:Method and application in South China Sea

作　　者：赵小龙 王增林[2] 赵益忠[1] 左家强[1] 李鹏[1] 梁伟[1] 王冰[1] 陈雪[1] 雷宏武[3] 金光荣 ZHAO Xiaolong;WANG Zenglin;ZHAO Yizhong;ZUO Jiaqiang;LI Peng;LIANG Wei;WANG Bing;CHEN Xue;LEI Hongwu;JIN Guangrong(Research Institute of Petroleum Engineering,Sinopec Shengli Oilfield Company,Dongying,Shandong 257000,China;Sinopec Shengli Oilfield Company,Dongying,Shandong 257000,China;State Key Laboratory of Geomechanics and Geotechnical Engineering//Institute of Rock and Soil Mechanics,Chinese Academy of Sciences,Wuhan,Hubei 430071,China;Guangzhou Institute of Energy Conversion,Chinese Academy of Sciences,Guangzhou,Guangdong 510640,China)

机构地区：[1]中国石化胜利油田分公司石油工程技术研究院 [2]中国石化胜利油田分公司 [3]岩土力学与工程国家重点实验室·中国科学院武汉岩土力学研究所 [4]中国科学院广州能源研究所

出　　处：《天然气工业》2022年第3期138-149,共12页Natural Gas Industry

基　　金：国家自然科学基金青年科学基金项目“南海低渗泥质粉砂水合物储层的非达西渗流特征及其对产能的影响研究”(编号:42102302);中国石化科技部油气开发基础前瞻研究项目“天然气水合物钻完井关键技术与取心装备研制”(编号:P20040-3);中国石化胜利油田博士后研究项目“天然气水合物藏出砂动态预测及技术政策界限”(编号:YKB2107)。

摘　　要：为安全高效开采天然气水合物,研究开采过程中水合物储层的稳定性至关重要,THM耦合数值模拟能清晰认识水平井开采水合物过程中的力学响应规律,但由于模型常被简化为垂直于生产井的剖面来进行模拟,对真实地层变形空间的演化特征刻画不足。为此,基于水合物开采程序TOUGH+HYDRATE,引入对FLAC力学程序的交互接口,构建了适用于水平井大规模开采的多相渗流—传热—力学(THM)耦合模拟程序,并基于我国第二次水合物试采场地资料,在以水平井试采实际产气量约束THM耦合模型的基础上,研究了水平井中长期开发条件下的气水产出与地层变形规律。研究结果表明:(1)在7 MPa生产压力、300 m井长条件下,水平井开采1年的产气量可达1190×10^(4)m^(3),压降在游离气层中的影响范围较大,产气来源于游离气层和水合物层,水合物分解范围不大;(2)预测试采60天时的海底沉降约为0.16 m,开采1年后可达0.52 m。结论认为:(1)水平井开采水合物会引起较大范围的海底沉降,海底面呈线性持续下沉,空间上的沉降呈椭圆形分布;(2)水平井及其上方的变形(垂向位移)最大,是最易发生地层破坏的位置;(3)建议后期结合海底地形、峡谷展布、矿体空间厚度不均等特征,研究中长期开采下的海底变形和滑坡风险。In order to produce natural gas hydrate safely and efficiently,it is quite crucial to research the stability of hydrate reservoir in the process of its exploitation.The coupled thermal-hydrodynamic-mechanical(THM)numerical simulation can clearly present the mechanical response laws in the process of hydrate exploitation by horizontal well,but the model is often simplified as a profile vertical to the production well,so the evolution characteristics of real formation deformation space cannot be described sufficiently.To this end,this paper develops a coupled THM simulator applicable to the large-scale hydrate exploitation by horizontal well by introducing interactive interface to the FLAC mechanics program based on the hydrate exploitation program TOUGH+HYDRATE.Then,based on the field data of second hydrate production test in South China Sea,the gas and water production and formation deformation laws under the middle-and long-term development conditions of horizontal wells are studied by taking the actual gas production of horizontal well during the production test as the constraint of coupled THM model.And the following research results are obtained.First,when the production pressure is 7 MPa and the horizontal well length is 300m,the gas production of horizontal well can reach 1190×10^(4)m^(3),the pressure drop has a larger influence range in the free gas layer,the produced gas mainly comes from the free gas layer and the hydrate layer and the hydrate dissociation range is not large.Second,it is predicted that the seafloor settlement is about 0.16 m after 60 days’production test and 0.52 m after one year’s production.In conclusion,hydrate exploitation by horizontal well can cause a large range of seafloor settlement.The seafloor surface settles linearly and continuously and the spatial settlement distribute is in the shape of ellipse.What’s more,the greatest deformation(vertical displacement)occurs at the horizontal well and above it,where formation damage happens the easiest.It is recommended to study se

关 键 词：天然气水合物 南海神狐海域 渗流—传热—力学多场耦合 降压开采 数值模拟 水平井 地层稳定性 第二次试采 

分 类 号：TE5[石油与天然气工程—油气田开发工程]