高温裂缝性油藏超深井堵水现场试验成败因素分析

Water shut-off in deep producers in high temperature fractured reservoirs

准噶尔盆地腹部的石西油田是裂缝性油藏,具有高温、高压、高矿化度和超深井底水锥进的特点。分析5 次油井堵水的现场试验结果,分别采用两性离子聚合物凝胶堵剂或石灰水泥类无机堵剂均难以满足降水增油的需求,分别采用无机硅胶堵剂聚合物凝胶封口剂体系或植物纤维性预交联体膨颗粒堵剂聚合物凝胶封口剂体系虽可封堵油井,但造成油水产量均下降。所以需调整堵剂体系,改善施工工艺,以确保堵剂选择性进入水层形成封堵,而不对油层产生伤害。采用三段塞(暂堵剂改性栲胶堵剂水泥封口剂)进行石西油田超深井的堵水达到了降水增油的目的,但需调整封堵半径,才可获得更佳的堵水效果。现场试验证明:如果明确油藏和油井情况,采用具一定选择性封堵水层能力的堵剂和注入工艺,可大幅度提高封堵高温油藏超深油井出水的成功率。

Shixi Oilfield locates in the middle of Junggar Basin, with the characteristics of high temperature, high formation pressure, high salinity and water cone in ultra deep producers. Five oilfield tests of water shut-off showed that treatments to use an amphoteric ion polymer gel or an inorganic system of lime-cement as plugging agents could neither decrease water cut nor increase oil production. Producers could be shut-off with inorganic silica gel-polymer gel seal, or with pre-crosslinking swellable granules made from plant fiber-polymer gel seal, which resulted in output decrease of both oil and water. In order to ensure that plugging agents selectively enter water bearing formation to form barrier without pay zone damage, it was required to adjust plugging agent system and improve injection process. A three slug technique, in which a temporary plugging agent, a main slug (surfited larch tannin extract) and the sealing cement were injected separately, was used successfully in a water shut-off pilot test in the faulted reservoir in Shixi Oilfield. Although the test brought out the purpose of decreasing water cut and increasing oil output, the better result would have been produced with a higher plugged radius. It was demonstrated that: success ratio of water shut-off in ultra deep producers in high temperature reservoirs could be boosted greatly if the reservoir and producer condition was clear, and plugging agent systems which could selectively seal the water bearing formation and an improved injection technique were used.