Understanding the behavior and composition of fracturing flowback water (FFW) can provide insight into in situ water–rock interactions, assessment of the success of the fracturing operations. FFW was collected from three wells (Z202-H1, Z203, and Z205) for up to 108 days after fracturing in the same area of western Chongqing, China. The samples were analyzed for the concentrations of various ions (Na⁺, K⁺, Ca²⁺, Mg²⁺, Ba²⁺, Sr²⁺, Cl⁻, SO₄²⁻, Br⁻, HCO₃⁻, etc.) and for the stable isotope composition (δD and δ¹⁸O) of water. With increasing flowback time, the ionic concentration and total salinity increased (e.g., from 315 mg/L to 37117 mg/L after 38 days for well Z203), stable isotopic ratios became heavier (e.g., δD values changed from −23.59‰ to −14.32‰, δ¹⁸O values changed from −3.91‰ to −1.92‰). The total salinity of the FFW is shown to be the result of mixing of the highly saline formation water and the low-salinity fracturing water. FFW from Z205 had higher concentrations of Li⁺ and NO₃⁻, heavier stable isotope compositions, larger Na⁺/Cl⁻ ratio, smaller (Cl⁻-Na⁺)/Mg²⁺ ratio, and larger SO₄²⁻ × 100/Cl⁻ ratio compared to the other two wells. All these phenomena revealed that Z205 is more likely to contact with active aquifers which is not conducive to natural gas preservation, because Z205 is close to (less 300 m from) a grade II fault. The RITS and RSIH with flowback time in Z203 were higher than Z202-H1, which shows that FFW from Z203 contained a greater fraction of formation water released from pores or fractures due to complex the network fractures formed by fracturing. Therefore, the fracturing operations of Z203 is better than Z202-H1. This result can reveal the reason for the production difference of adjacent wells, which is difficult to explain by similar total SRV.

了解压裂返排水（FFW）的行为和组成，可以深入了解原位水-岩相互作用，评估压裂作业的成功。在重庆西部同一地区压裂后，从三口井（Z202-H1，Z203和Z205）采集了FFW，长达108天。分析样品的各种离子的浓度（钠⁺，K ⁺，钙²⁺，镁²⁺，钡²⁺，锶²⁺，氯^-，SO ₄ ^2-，溴^-，HCO ₃ ^-等）和稳定的同位素组成（δD和δ¹⁸ O）的水。随着回流时间增加，Z203井的离子浓度和总盐度增加（例如，在38天后从315 mg / L增加到37117 mg / L），稳定的同位素比变大（例如，δD值从−23.59‰变为− 14.32‰，δ ^18个从-3.91变为O值‰至-1.92‰）。FFW的总盐度显示为高盐度地层水和低盐度压裂水混合的结果。FFW从Z205具有较高浓度的Li ⁺和NO ₃ ^- ，更重的稳定同位素组合物中，较大的Na ⁺ /氯^-比，更小的（CL ^- -Na ⁺）/镁²⁺比率，和较大的SO ₄^2-  ×100 /氯^-比相比于其他两个井。所有这些现象都表明，Z205更可能与活跃的含水层接触，这不利于天然气的保存，因为Z205接近II级断层（距该层不到300 m）。Z203中具有回流时间的RITS和RSIH高于Z202-H1，这表明Z203中的FFW含有较大比例的从孔隙或裂缝释放的地层水，这是由于压裂形成的复杂网络裂缝所致。因此，Z203的压裂操作优于Z202-H1。这一结果可以揭示相邻井产量差异的原因，这很难用相似的总SRV来解释。