四川盆地深煤储层体积压裂实践与认识——以NT1H井为例

Practice and insights into volumetric fracturing in deep coal reservoirs of the Sichuan Basin: A case study of the NT1H well

  • 摘要: 四川盆地的深煤储层勘探、开发仍处于初期阶段,尚未建立与其适配的体积压裂技术体系。为此,系统对比了龙潭组19号煤、大吉区块深8号煤及川南龙马溪组页岩的地质与工程差异,基于三维离散元法建立了模拟裂缝扩展与输砂的一体化压裂数值模型,以优化施工参数。研究结果表明:①龙潭组煤岩结构好、品质优,且生烃潜力巨大,呈区域稳定分布态势,但其纵向上呈薄互层分布,中间夹矸主要为泥页岩。②龙潭组煤岩与大吉区块深8号煤岩基础静态参数接近,但纵向连续厚度更小;相较于龙马溪组页岩,其孔渗条件更好、杨氏模量更低、泊松比更高、割理与微裂隙等更发育,因而整体改造难度更大。③针对龙潭组的深煤储层特征,初步形成了具有特色的体积压裂理念。实践结果表明:采用该体积压裂技术,NT1H井实现了最高日产气量10.6×104 m3,稳定日产达8.0×104 m3。该成果对四川盆地深煤岩的压裂改造具有指导意义,并为同类区块改造提供了重要参考。

     

    Abstract: Exploration and development of deep coal seams in the Sichuan Basin remain in their early stages, with no suitable volumetric fracturing technology system yet established. To address this problem, this work compares the geological and engineering characteristics of the Longtan Formation Coal 19, the Daji Block Deep Coal 8, and the Longmaxi Formation shale in southern Sichuan. Based on the 3D discrete element method, an integrated numerical fracturing model simulating fracture propagation and proppant transport was developed to optimize operational parameters. The study reveals: ① The Longtan Formation exhibits well-structured coal seams with high quality and substantial hydrocarbon potential, distributed regionally in a stable pattern. However, it displays thin interbedded distribution vertically, with intercalated gangue primarily consisting of mudstone and shale. ② The Longtan Formation coal rock exhibits static parameters similar to those of the Daji Block Deep coal 8, but with thinner continuous vertical thickness. Compared to the Longmaxi Formation shale, it possesses better porosity and permeability conditions, lower Young's modulus, higher Poisson's ratio, and more developed joints and microfractures, making overall stimulation more challenging. ③ Based on the reservoir characteristics of the deep Longtan Formation coalbeds, a distinctive volumetric fracturing concept was initially developed. Field results demonstrate that this volumetric fracturing technology enabled the NT1H well to achieve a peak daily gas production of 10.6×104 m3 and a stable daily output of 8.0×104 m3. These findings provide valuable guidance for fracturing operations in deep coal seams within the Sichuan Basin and serve as an important reference for similar block stimulation projects.

     

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