压裂井高效返排技术在川西地区的先导性试验

川西地区的气藏具有低渗、致密、压力低的特点，常规压裂后返排时间长，返排率通常较低，这势必要求加快排液速度，以降低对储层的伤害。然而，压裂井加快排液速度和控制支撑剂回流返吐是相互矛盾的，排液速度太快就可能超过临界出砂流速，导致支撑剂回流；排液速度太低又会导致排液时间增加和返排率下降。通过多年的探索和研究，发展了一套高效返排新技术--液氮助排＋纤维防砂＋优化放喷，在川西率先进行了4口井先导性试验，施工成功率100％，24 ｈ内返排率均在65％以上，并且返排中未见出砂现象，增产效果显著。该技术的研究和应用，为同类气藏的高效开发提供了很好的思路，值得进一步推广和应用。

PILOT TESTS ON FRACTURING WELLS FLOWBACK TECHNOLOGY IN HIGH EFFICIENCY IN WEST SICHUAN BASIN

With characteristics of low permeability, tightness and low pressure, the gas reservoirs in the western Sichuan basin after conventional fracture would have a long time for flowback and a relatively low flowback ratio, which demands to speed up the flowback speed so as to decrease the damage to fracture. However, promoting liquid drainage velocity and controlling the backflow of proppant are mutually contradictory in fracturing wells. High drainage velocity may exceed critical sand producing velocity and cause proppant backflow, while low drainage velocity may cause flowing time increasing and returning efficiency reducing. Through exploration and research for many years, a new technology for flowback in a high efficiency (by combining liquid nitrogen cleanup, fiber sand control and optimizing bean up together) is developed. Pilot tests are made in 4 wells in the western Sichuan basin with success ratio of 100%, returning efficiency rate of 65% in 24 hours and no sand producing phenomenon appeared in the process of flowback, which help obtain a remarkable stimulation effect. The study and application of this technology offer an excellent clue for developing the same type of gas reservoirs efficiently, deserving further extension and application.