海上底水锥进气井注氮气复产工艺探索

Exploration of Nitrogen Injection Production Resuming Technology for Offshore Bottom Water Coning Gas Wells

底水锥进会使气井产量快速递减和采出程度大幅下降,尤其在海上高采气速度下底水锥进影响更显著。为了能够使此类井成功复产,开展了注氮气压水锥研究和现场试验。通过数值模拟研究,确定了水锥面的物理形态,并据此优化氮气的注入量和焖井时间。A3井实施两轮次累计注入38×10^(4) m^(3)氮气。现场试验表明:通过高压注入氮气可以有效突破水锥面对气相的封堵,建立气相与井筒的通道。两轮次分别返排出10%~15%的氮气后,天然气的含量即可达100%,说明只需要较少的注入量即可突破水锥面;但底水能量强,现场处理能力有限,频繁更换生产制度导致大量产水,累计自喷15×10^(4) m^(3)天然气后停喷。在后期的治理中需要控制油嘴,防止井底流压波动加剧产水,影响复产效果。本次注氮气压水锥工艺探索对同类底水气藏的复产有一定的借鉴和指导意义。

Bottom water coning results in rapid decrease of gas well production and significant decline in recovery.Especially at high offshore gas production speed,the impact of bottom water coning is more severe.In order to resume production for these wells,studies of nitrogen injection for water coning control and field tests were carried out.Through numerical simulation,the physical shape of the water cone was determined,and the nitrogen injection volume and shut-in time were optimized accordingly.Two cycles of injection of 38×10^(4) m^(3) nitrogen in total were performed at Well A3.The field test shows that the nitrogen injection under high pressure can effectively break through the sealing of water cone and establish a channel between the gas phase and the wellbore.After 10%-15%of nitrogen flowed back,the content of natural gas reached 100%,indicating that only a small amount of injection is needed to break through the water cone.However,due to the strong energy of the bottom water,limited capability of field treatment and the frequent changes of production system,a large amount of water was produced,and 15×10^(4) m^(3) of natural gas was produced through natural flow until the flow stopped.The nozzle needs to be controlled in the later stage of treatment to prevent the fluctuation of flow pressure at the bottom of the well from increasing water production and affecting production recovery.This study provides reference and guidance for optimizing the production recovery of similar gas reservoirs with bottom water.