启动压力对南海北部水合物藏开发动态的影响  

The impact of threshold pressure gradient on the production dynamics of gas hydrate reservoirs in the northern South China Sea

作　　者：余路 李贤 崔国栋 邢东辉 陆红锋[1] 王烨嘉 YU Lu;LI Xian;CUI Guodong;XING Donghui;LU Hongfeng;WANG Yejia(National Engineering Research Center of Gas Hydrate Exploration and Development,Guangzhou Marine Geological Survey,Guangzhou 510075,China;School of Engineering,China University of Geosciences(Wuhan),Wuhan 430074,China;Guangdong Center of Marine Development Planning Research,Guangzhou 510220,China)

机构地区：[1]广州海洋地质调查局天然气水合物勘查开发国家工程研究中心,广东广州510075 [2]中国地质大学(武汉)工程学院,湖北武汉430074 [3]广东省海洋发展规划研究中心,广东广州510220

出　　处：《地学前缘》2025年第2期178-194,共17页Earth Science Frontiers

基　　金：广东省海洋经济发展(海洋六大产业)专项资金项目(粤自然资合[2022]46号);广东省基础与应用基础研究项目(2022A1515011902);广州市科技计划项目(202206050002);广州市基础研究计划与应用基础研究项目(202201011463)。

摘　　要：南海北部神狐海域水合物资源丰富,具有工业性开发远景。勘查和试采结果均表明,该区域水合物系统多为Ⅰ型水合物藏,水合物层下伏游离气层,泥质含量高,储层渗流存在启动压力梯度,极大地影响水合物系统生产动态。本文针对南海泥质粉砂储层中水合物开发实际渗流过程,建立考虑启动压力梯度的渗流数学模型,在TOUGH+HYDRATE模拟器基础上自主开发了启动压力梯度耦合求解功能,以神狐海域SHSC-4井站位水合物藏为目标,利用室内实验所得目标储层启动压力值,开展了垂直井及水平井降压开采数值模拟,探究了南海神狐海域泥质粉砂水合物藏启动压力梯度对产能及开采过程中储层压力、温度、各相饱和度分布演化规律的影响。结果表明,启动压力梯度的存在抑制储层中的压降扩散,远井处水合物无法分解。生产中出现“低产水量,高气水比”现象,水平井开采后期几乎无水产出。启动压力的存在可避免水合物分解前缘出现二次水合物,消除二次水合物棱镜体对气相的圈闭。尽管抑制远井水合物分解,但10年模拟结果显示启动压力梯度的存在可以促进Ⅰ型水合物藏的产能,尤其在直井开采下,产能可提高近40%,这是由于液相产出的减少及储层高压力梯度增强了生产井前期对三相混合层和游离气层中气相抽汲能力。The South China Sea holds abundant gas hydrate resources with significant potential for industrial development,as demonstrated by successful natural gas hydrate pilot tests in the Shenhu area.Most gas hydrate-bearing sediments in the South China Sea are classified as ClassⅠgas hydrate deposits,underlain by a two-phase zone containing mobile gas.These reservoirs are characterized by unconsolidated argillaceous siltstones and a threshold pressure gradient(TPG),which significantly impacts gas production.A mathematical model incorporating TPG was developed to simulate multiphase flow in typical subsea sediments,and a TPG module was integrated into the TOUGH+HYDRATE simulator in this study.The Well SHSC4,located in the Shenhu test field,was selected to evaluate the effects of TPG on gas production.Simulation results reveal that TPG restricts pressure propagation,preventing hydrate dissociation near the reservoir boundaries.A phenomenon of low water output and a high gas-to-water ratio was observed during gas production.The water production from the horizontal well nearly ceased in the later stages.The TPG plays a critical role in preventing the formation of secondary gas hydrate shells in the free dissociation zone and eliminating gas traps.A review of 10 years of production data indicates that TPG can enhance gas production from ClassⅠgas hydrate deposits while TPG limits the recoverable reserves of gas hydrate.Notably,gas production increased by nearly 40%,attributed to TPG's ability to improve free gas drainage in vertical wells.These findings highlight the dual role of TPG in both restricting and promoting gas production,offering valuable insights for optimizing gas hydrate exploitation in the South China Sea.

关 键 词：天然气水合物 启动压力梯度 数值模拟 Ⅰ型水合物藏 中国南海 

分 类 号：TE332[石油与天然气工程—油气田开发工程] TE331[天文地球—海洋科学] P744.4