渤海L油田注水井欠注原因及对策分析

渤海L油田部分注水井投注后表现出注入压力快速升高、注入困难的情况，注水量无法满足油藏配注量。为此对L油田注水井欠注原因进行分析，通过岩心驱替实验评价储层岩石敏感性、钻完井液损害以及注入水对储层伤害，采用静态配伍性实验评价注入水与地层水之间的配伍性。结果显示储层具有强速敏损害，而部分注水井在投注初期注入量即远远超过了速敏损害临界注入量，造成了不可逆的微粒运移伤害。钻完井顺序工作液对岩心渗透率损害率可达35.5%～48.2%，单一注入水对岩心渗透率损害率达31%～35.2%，钻井液固相侵入和注水水质长期超标造成的储层损害是L油田注水井普遍注入能力较差的关键原因。建议L油田新井返排后投注或在投注初期进行酸化减弱钻井液损害，初期注入量应控制在速敏临界流量之下，逐级提高注入量避免发生微粒运移伤害，同时加强注入水悬浮物含量、含油量以及硫酸盐还原菌等关键指标的控制。

Analysis of Under-injection in Injection Wells and the Countermeasures of Bohai Sea L Oilfield

Some water injection wells of Bohai Sea L Oilfield show that injection pressure increases rapidly and injection is difficult, and the amount of water injection can not meet the reservoir injection allocation. Therefore, the under-injection causes of injection wells in L Oilfield are analyzed. The reservoir rock sensitivity, drilling and completion fluids damage and injection water damage to reservoir are evaluated by core displacement experiments. The compatibility between injection water and formation water is evaluated by static compatibility test. The results show that the reservoir has strong velocity sensitivity damage and the water injection rate of some wells at initial stage is far more than critical injection rate of velocity sensitivity damage, resulting in irreversible particle migration damage. The core permeability damage rate of drilling and completion sequence operating fluids is between 35.5% to 48.2%, and that of single injection water is between 31% and 35.2%. The reservoir damage caused by solids invasion in drilling fluids and injection water quality exceeding the standard for a long time is the key reason for the generally poor injection capacity of injection wells in L Oilfield. It is suggested that new wells begin injecting after flowback or acidification should be carried out at initial stage to reduce the damage of drilling fluids. The initial injection rate should be controlled below the critical injection rate of velocity sensitivity, and the injection rate should be increased step by step to avoid the damage of particle migration. Meanwhile the control of key indexes such as suspended solids content, oil content and sulfate reducing bacteria in injection water should be strengthened.