页岩气压裂返排液回用处理技术研究与应用

鄂尔多斯盆地页岩气压裂返排液具有总铁含量高(30~50 mg/L)、黏度高(2.8~3.2 mPa·s)、悬浮物含量高(大于300 mg/L)和细菌含量高(大于10~4个/mL,)的"四高"特点,直接外排会造成严重的环境污染和水资源浪费。为此,有针对性地开展了"隔油除砂—氧化—絮凝沉降—膜过滤"的"四步法"处理工艺的技术应用研究。该工艺在强化絮凝沉降效果的基础上,采用一步法膜过滤技术,既提高了水质处理效果,又缩减了处理工艺流程。同时,通过对处理工艺参数的优化,研发出了一套模块化橇装式压裂返排液回用处理装置。现场应用的效果表明:处理后的水质连续稳定达标,既可满足平均空气渗透率小于等于10 mD地层的回注要求,也可用于配制胍胶和滑溜水压裂液。该研究成果较好地解决了页岩气压裂返排液的"四高"问题,为国内外页岩气及其他非常规油气废水治理和回用提供了技术支撑。

Researchand application of recycling treatment technology for shale gas fracturing flowback fluid:A case study

The shale gas fracturing flowback fluid of the Ordos Basin is characterized by the so-called "four highs": high total iron contents (30-50 mg/L), high viscosity (2.8-3.2 mPa·s), high suspended matter contents (＞ 300 mg/L) and high bacterial contents（＞10⁴ germs/mL）; Undoubtedly, direct discharge would result in severe environmental pollution and water resource waste. Therefore, a four-step treatment technology consisting of oil removal and desanding -- oxidation -- flocculating settling -- membrane filtration was developed. On the basis of strengthening the flocculating settling effect, a one-step membrane filtration method was adopted to not only improve the water treatment effect, but reduce the treatment procedures. Meanwhile, based on the optimization of the treatment parameters, a set of modularized skid-mounted fracturing flowback fluid recycling treatment units was developed. Field application shows that the treated water is up to the standards continuously and stably, not only meeting the reinjection requirements of formation with the average air permeability of less than or equal to 10 mD, but also suitable for preparing guar gum and slick water fracturing fluid. These study results have satisfactorily solved the disposal of shale gas fracturing flowback fluid with the "four highs" issue, and provide technical support for the recycling treatment of waste water generated in fracturing of shale gas and other unconventional oil and gas reservoirs in the world.