轮台凝析气田水锥后注氮气吞吐实践与认识

塔里木盆地轮台凝析气田的底水沿高渗透带突进后,液相占据主要通道形成水封气,从而造成气井停喷。这种情况下.一般没有很好的治理手段,使用前期堵水、上提避水等治理措施也都基本无效。基于多年的探索研究,提出了"由堵改疏"的治理思路,即通过注氮气与地层剩余气沟通形成气体连续相,以达到恢复气井产能的目的。为此,开展了注氮气压锥机理、选井标准和注气参数优选设计等试验研究,注入膨胀性好、经济安全的氮气从水脊顶部薄弱处突破水锥屏障,使被液相占据的渗流通道重新开启,并与地层凝析气形成连续相,恢复自喷;根据压力变化将作用过程分为注入氮气压缩井底水脊、突破水锥屏障、稳定注气与地层凝析气形成连续相、焖井压锥降低水锁效应4个阶段。在S3-1井进行现场应用,日增油12.3 t,日增气2.8×10~4m~3,累计增油820 t,累计增气211×10~4m~3,增产效果显著。该工艺对类似凝析气井治理有一定指导意义,可以推广应用到其他凝析气田。

Practices in and understanding of nitrogen huff-and-puff after water coning in the Luntai Condensate Gas Field,Tarim Basin

After onrush of the bottom water along high-permeability zones in the Luntai Condensate Gas Field, Tarim Basin, with bottom water, liquid may occupy major channels to form water seal, which eventually leads to production losses in gas wells. No effective techniques have been available for such conditions and the previously adopted countermeasures like early water blockage, uplifting to avoid contacting with water, etc. were proven to be ineffective. Based on years of researches and exploration, the guidelines characterized by "dredging instead of blocking" were proposed. By means of nitrogen injection, communication can be established with residual gases in the reservoir formation to restore productivity of gas wells. Tests were conducted to determine nitrogen coning mechanisms, well selection and optimization of nitrogen flooding parameters. Through injection of nitrogen with favorable expansion capacities, economic and safety properties, water coning barriers can be destroyed in the weak back section. In this way, seepage channels occupied by fluids can be cleared up to regain the communication with condensate gas contained in reservoir formations. As a result, the productivity of relevant wells can be restored. With the changes in pressures taken into consideration, the process can be classified into four stages: injection of nitrogen to compress water crest, breakthrough of water coning barrier, communication with condensate gas in reservoir formation through stabilized gas injection, and well shut-off to further compress the water coning to release water lock. Field application in Well S3-1 showed a daily oil production increase of 12.3 t and a daily gas production increase of 2.8×10⁴ m³. With a total increased oil production of 820 t and total increased gas production of 211×10⁴ m³, significant productivity enhancements were observed. The newly developed technology may play an important role in EOR of condensate oil wells and may be applied in other condensate gas fields.