Quantifying wettability of organic-rich mudrocks is important for reliable formation evaluation, optimizing production, predicting water/hydrocarbon production, and selection of appropriate fracture fluids. Recent publications suggest that kerogen wettability can vary as a function of thermal maturity, ranging from water- to hydrocarbon-wet at low to high thermal maturities, respectively. However, clay minerals tend to preferentially be water-wet. It is therefore important to determine which of these constituents have a dominant contribution to overall wettability of the rock. To answer this question, we introduce methods to quantify the relative water-adsorption capacities of clay minerals, kerogen, and organic-rich mudrocks at different thermal-maturity levels. We started with isolating kerogen from organic-rich mudrock samples using chemical and physical separation methods and synthetically matured them to different thermal-maturity levels. We then prepared synthetic organic-rich mudrock samples by mixing known quantities of clay minerals, nonclay inorganic minerals, and kerogen. We then performed water-vapor adsorption measurements on pure clay minerals, pure kerogen samples, and synthetic organic-rich mudrock samples under controlled humidity conditions. Nuclear magnetic resonance (NMR) measurements were then used to quantify the volume of water adsorbed on clay minerals and organic-rich mudrock samples. We used the flotation test to qualitatively assess the wettability of the synthetic organic-rich mudrocks.

Water-vapor adsorption experiments showed that the volume of water adsorbed on the surface of nonheated kerogen samples at low thermal maturities is 5.31 mL/100 g, which decreases significantly to 0.09 mL/100 g when the kerogen sample is heat-treated to 450°C. The results can be attributed to strong attraction between the oxygen content in kerogen and water at low thermal maturities. We quantified the water-adsorption capacity of kerogen samples heat-treated at 450°C and found that volume of water adsorbed decreases with an increase in thermal maturity both in the presence and absence of bitumen. In the case of synthetic organic-rich mudrock samples, we found that the volume of water adsorbed in samples at higher thermal maturity decreases by 16% compared with organic-rich mudrocks at low thermal maturity at the same concentration of nonswelling clay minerals. Results from the flotation test showed that the oil-wettability of the synthetic organic-rich mudrock samples increases as its thermal maturity decreases, with a hydrogen index (HI) of 328 to 54 mg hydrocarbon/g organic carbon (mg-HC/g-OC). Results confirmed that kerogen and its geochemistry can have a significant influence on the overall wettability of organic-rich mudrocks even at low concentrations of 4 wt%. The outcomes of this paper can contribute to a better understanding of the parameters affecting wettability of organic-rich mudrocks and are promising for in-situ assessment of their wettability. This can potentially contribute to improved understanding of flow mechanisms in organic-rich mudrocks, which control hydrocarbon/water production.

量化富含有机物的泥岩的润湿性对于可靠的地层评估，优化产量，预测水/烃产量以及选择合适的压裂液至关重要。最近的出版物表明，干酪根的润湿性可以随热成熟度的变化而变化，在低至高热成熟度下分别为水润湿至烃润湿。然而，粘土矿物倾向于优先被水润湿。因此，重要的是确定这些成分中的哪些对岩石的总体润湿性起主要作用。为了回答这个问题，我们介绍了量化不同热成熟度水平下粘土矿物，干酪根和富含有机物的泥岩的相对吸水能力的方法。我们首先使用化学和物理分离方法从富含有机物的泥岩样品中分离出干酪根，然后将其合成成熟至不同的热成熟度水平。然后，我们通过混合已知数量的粘土矿物，非粘土无机矿物和干酪根来制备富含有机物的合成泥岩样品。然后，我们在受控的湿度条件下，对纯粘土矿物，纯干酪根样品和富含有机合成物的泥岩样品进行了水蒸气吸附测量。然后使用核磁共振（NMR）测量来量化吸附在粘土矿物和富含有机物的泥岩样品上的水量。我们使用浮选法定性地评估了富含有机有机物的合成泥岩的润湿性。

水蒸气吸附实验表明，在低热成熟度下未加热的干酪根样品表面吸附的水量为5.31 mL / 100 g，当将干酪根样品热处理至450°C时，水的含量显着降低至0.09 mL / 100 g C。该结果可归因于在低热成熟度下干酪根中的氧含量与水之间的强烈吸引力。我们对在450°C热处理的干酪根样品的吸水能力进行了量化，发现在存在和​​不存在沥青的情况下，随着热成熟度的增加，吸附的水量会减少。对于合成的富含有机物的泥岩样品，我们发现，在相同的非膨胀黏土矿物浓度下，在较高热成熟度下样品中吸附的水量与在较低热成熟度下富含有机物的泥岩相比降低了16％。浮选试验的结果表明，随着有机成熟度的降低，合成的富含有机物的泥岩样品的油润湿性增加，氢指数（HI）为328至54 mg烃/ g有机碳（mg-HC / g- OC）。结果证实，即使在4 wt％的低浓度下，干酪根及其地球化学也会对富含有机物的泥岩的总体润湿性产生重大影响。本文的成果可以有助于更好地理解影响富含有机物泥岩润湿性的参数，并有望就地评估其润湿性。