CO2置换法开采水合物井网系统及注采参数分析

Influence of well pattern and injection-production parameters on gas hydrate recovery via CO2 injection and replacement method

为了探究井网系统及注采参数对水合物开发的影响,建立矿场尺度的非均质性水合物矿体三维模型,提出降压法辅助CO2置换法开采水合物的方法,并对井网形式、井距、CO2注气速度、生产井井底压力以及初始水合物饱和度等参数进行分析。结果表明:九点法井网相比于五点和七点法井网具有更大甲烷累积产气量和埋存率,并且大井距有利于增加甲烷累积产量,具有较好的埋存率和置换率;2.5 MPa井底压力的甲烷累积产气量和置换效率较高;CO2置换主要发生在井网的控制范围内,甲烷置换区域的储层温度上升5~10℃,CO2未波及区域储层温度下降3~5℃。

A combination of depressurization and CO2 injection to replace natural gas was proposed for the exploitation of natural gas hydrate reservoirs. In this study, a heterogeneous reservoir model was established for numerical simulation, and the effect of well pattern, well spacing, gas(CO2) injection rate, bottom hole pressure of production well and initial hydrate saturation on natural gas production were investigated. The simulation results show that a nine-spot well pattern has the maximum cumulative CH4 production and CO2 storage factor in comparison with five-spot and seven-spot well patterns, and a large well spacing is beneficial to increase gas production, in which high storage factor and replacement efficiency can be achieved. In addition, at 2.5 MPa of bottom hole pressure, optimum cumulative CH4 production and CO2 replacement efficiency can be obtained. CO2 replacement mainly occurs within the control range of the well pattern. The reservoir temperature in CH4 replacement area rises 5-10 ℃, and it can drop 3-5 ℃ in CO2 unswept areas.