水溶气对海上有水气藏开发指标的影响

Influence of water dissolved gas on development index in offshore water bearing reservoir

对于海上有水气藏,通常地层水中的水溶气含量不可忽视,尤其是高温高压气藏。通过研究降压开发过程中水溶气释放对气田开发指标的影响,结合气田地质油气藏特征、边底水分布、水体大小等情况,建立机理模型,根据数模软件计算,系统分析水溶气对海上有水气藏产量、采收率、水侵量、水气比、压降、天然气组分等开发指标的影响,并通过Y1气田实例分析对结论进行验证。研究结果表明:①考虑水溶气时地层水压缩系数变大,水侵量增加,水气比变大,从而采收率略有降低,并且天然气组分中的CO2含量逐渐上升;②对于水驱气藏水体倍数越小,采气速度越高,CO2上升量越大;③水溶气对水驱气田开发指标的影响不可忽略,尤其是对气藏水侵的影响。④该研究成果对于类似气藏的开发具有一定的参考作用。

To offsheore water bearing gas reservoir,the dissolved gas content in formation water of gas reservoir can not be ignored, especially in that with high temperature and high pressure.In order to study influence of water-dissolved gas release on development index in gas field during depressurization development,combining with geological and reservoir characteristics,edge/bottom water distribution and aquifer size,this paper analyzed influence of dissolved gas on development indexes like production,recovery,water influx,water gas ratio,pressure drop and gas component in high temperature and high pressure gas reservoir by numerical simulation. At last the results are testified by an example of Y1 gas field.Results show that when considering water-dissolved gas,formation water compression coefficient increases,water influx increases,water-gas ratio increases,recovery factor decreases slightly,and CO2 content in gas increases gradually.In water drive gas reservoir,the smaller the water aquifer size is,the higher the gas recovery rate is,the larger the CO2 rise is.Therefore,influence of water dissolved gas on development index of water drive gas field can not be ignored, especially on the water influx of gas reservoir.Research results are useful for similar gas reservoirs development.