Flowback/Produced fluid samples were collected from several wells from two Utica/Point Pleasant (UPP) sites (UPPW and UPPS) in Ohio, and one Marcellus (Marcellus Shale Energy and Environment Laboratory (MSEEL)) site in West Virginia over a period of approximately two years.

Although these formations have different ages, depositional environments, diagenetic histories, and geochemical and mineralogical compositions (i.e. the UPP is significantly more carbonate rich than the Marcellus which is more siliceous), analysis of trends in fluid species over time shows that, overall, the TDS and major solubilized elements (Na, Ca, Cl) in the UPP and Marcellus brines are remarkably similar. Total dissolved solutes (TDS) in these brines ranged from approximately 40 to 250 g/L salt, and in general, concentrations increased with time elapsed since natural gas well completion and stimulation. The behavior of Na, Br, and Cl suggests that the produced water signatures from these formations are largely derived from the native formational brines which display evidence of originating from evaporated seawater. There is a strong correlation between Cl and Br, indicating that both species behave conservatively, and the similarity among each of these brines suggests no appreciable contribution of salt from halite dissolution because Br is excluded from the halite structure. Cl/Br ratios in the brines range from ~80 to 120 (mg/L/mg/L). Other elements, such as K, which readily reacts between fluids and ion exchange sites on clays, generally exhibit conservative behavior for an individual site, but show significant variations among each of the different well pads.

The concentrations of Sr and Ba vary dramatically among well sites, and increase with respect to Cl⁻ over time, suggesting increasing solubilization, presumably from desorption from clay minerals or dissolution of carbonates or sulfates from the source formation(s). The UPPW well site has very low Ba due to high-sulfate input fluid, which resulted in precipitation of barite/celestite in the brines. In contrast the UPPS well site had elevated Sr (~ 3500 mg/L), presumably due to the use of Sr-rich recycled brine used in hydraulic fracturing. The Marcellus site had the highest Ba concentrations (up to 10 g/l) and highest Ba/Sr ratios in the fluids, due to the high concentration of barium in the Marcellus target (~ 1000 ppm, as compared to ~200 ppm in the UPP). These observations suggest that solutes in the FP fluids are derived from native brines, water-rock interactions that have occurred over geologic time scales, as well as some contribution from contemporaneous reactions in the subsurface. The results also show that the composition of the injected fluid can influence flowback fluid chemistry and possibly production efficiency.

在一段时间内，从俄亥俄州两个Utica / Point Pleasant（UPP）站点（UPPW和UPPS）和西弗吉尼亚州一个Marcellus（Marcellus页岩能源与环境实验室（MSEEL））站点的几口井中收集了返排液/生产液样本。大约两年。

尽管这些地层具有不同的年龄，沉积环境，成岩史，地球化学和矿物组成（即UPP比Marcellus的碳酸盐含量高得多，而Marcellus的硅质含量更高。）对流体种类随时间变化趋势的分析表明，总体而言，UPP和Marcellus盐水中的TDS和主要可溶元素（Na，Ca，Cl）显着类似。这些盐水中的总溶解溶质（TDS）范围约为40至250 g / L盐，通常，自天然气井完井和增产以来，浓度随时间的流逝而增加。Na，Br和Cl的行为表明，这些地层的采出水特征主要来自天然的地层盐水，这些盐水显示出源自蒸发海水的证据。Cl和Br之间有很强的相关性，表明这两个物种的行为都较为保守，这些卤水之间的相似性表明，由于Br从卤石结构中排除，盐从卤石溶解中没有明显贡献。盐水中的Cl / Br比范围为〜80至120（mg / L / mg / L）。其他元素（例如K）容易在流体和粘土上的离子交换位点之间发生反应，通常对单个位点表现出保守的行为，但在每个不同的孔垫之间显示出显着的变化。

Sr，Ba中的浓度以及站点之间相差很大，并且相对于氯增加^-随着时间的流逝，这表明增加的增溶作用，大概是由于粘土矿物的解吸或源层中碳酸盐或硫酸盐的溶解所致。由于高硫酸盐输入流体，UPPW井场的Ba极低，导致盐水中的重晶石/天青石沉淀。相反，UPPS井场的Sr（〜3500 mg / L）升高，大概是由于在水力压裂中使用了富含Sr的循环盐水。由于Marcellus目标中钡的浓度很高（〜1000 ppm，而Marcellus标靶中的〜200 ppm），因此在流体中，Marcellus部位的Ba浓度最高（最高10 g / l），Ba / Sr比最高。 UPP）。这些观察结果表明，FP流体中的溶质来自天然盐水，在地质时间范围内发生的水-岩相互作用，以及地下同时发生的一些反应。结果还表明，注入流体的成分会影响回流流体的化学性质，并可能影响生产效率。