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沁水盆地南部郑庄区块岩石力学特征对压裂裂缝的影响及差异化开发对策

Influence of rock mechanics characteristics on fracturing fractures and differentiated development strategies in the Zhengzhuang block of the southern Qinshui Basin

  • 摘要: 煤储层岩石力学参数对天然裂缝的形成演化及人工裂缝的扩展规律具有重要控制作用,是影响煤储层压裂改造的关键因素。为明确郑庄区块岩石力学参数特征和压裂裂缝发育规律,实现煤储层高效改造和开发,利用阵列声波测井资料建立纵横波转换模型,基于岩石力学参数试验和测井计算建立动静态岩石力学参数转换模型,利用声波时差、密度等常规测井数据,计算得到郑庄区块岩石力学参数分布规律。在此基础上,利用FrSmart压裂模拟软件建立郑庄区块不同井区水平井的地质力学模型,开展压裂模拟探究岩石力学参数和压裂规模对压裂裂缝形态的影响,并针对不同井区提出差异化开发对策。研究结果表明:郑庄区块静态杨氏模量在0.28~1.45 GPa,平均为0.95 GPa,静态泊松比为0.31~0.34,平均为0.32,整体呈不均匀分布。随着煤储层杨氏模量的不断增大和泊松比的减小,压裂缝长和单缝宽均有逐渐减小的趋势。压裂缝长和单缝宽与压裂规模有正相关关系,增加压裂液量和砂量可以有效增加压裂缝长和单缝宽,提高裂缝体积。增大施工排量,压裂缝长、单缝宽、裂缝体积均大幅度增加。现场在郑庄区块北部开展大规模大排量压裂先导试验,裂缝监测结果显示:平均压裂缝长超400 m,缝宽在40 m以上,平均单段储层改造体积170×104 m3,改造效果较以往提升580%。在后续开发过程中,郑庄区块北部井区建议采用大规模大排量压裂,最佳井距为320 m;中北部井区建议采用中等压裂规模进行改造,最佳井距为300 m;西南部井区建议采用中等规模压裂,最佳井距为260 m。

     

    Abstract: The rock mechanical parameters of coal reservoirs play an important role in controlling the formation and evolution of natural fractures and the propagation of artificial fractures, and are the key factors affecting the fracturing transformation of coal reservoirs. In order to clarify the characteristics of rock mechanical parameters and the development law of fracturing fractures in Zhengzhuang block, and realize the efficient transformation and development of coal reservoirs, a longitudinal and transverse wave conversion model was established based on array acoustic logging data, a dynamic and static rock mechanical parameter conversion model was established based on rock mechanical parameter tests and logging calculations, and the distribution law of rock mechanical parameters in Zhengzhuang block was calculated by using conventional logging data such as acoustic time difference and density. On this basis, the FrSmart fracturing simulation software was used to establish the geomechanical models of horizontal wells in different well areas in the Zhengzhuang block, and the fracturing simulation was carried out to explore the influence of rock mechanical parameters and fracturing scale on the fracture morphology, and propose differentiated development strategies for different well areas. The results show that the static Young's modulus of Zhengzhuang block is between 0.28~1.45 GPa, the average value is 0.95 GPa, the static Poisson's ratio is 0.31~0.34, and the average value is 0.32, and the overall distribution is uneven. With the continuous increase of Young's modulus and the decrease of Poisson's ratio in coal reservoirs, the length of fracturing fractures decreases gradually, and the width of fracturing fractures gradually increases. There is a positive correlation between fracture length and fracture width and fracture scale, and increasing the amount of fracturing fluid and sand can effectively increase the fracture length and width and increase the fracture volume. With the increase of construction displacement, the length, width and volume of fractures were greatly increased. The pilot test of large-scale and large-displacement fracturing was carried out in the northern part of the Zhengzhuang block, and the fracture monitoring results showed that the average fracture length was more than 400m, the fracture width was more than 40 m, and the average volume of single reservoir reconstruction was 170×104 m3, and the transformation effect was increased by 580% compared with the past. In the subsequent development process, it is recommended to use large scale and high displacement fracturing in the northern well area of Zhengzhuang block, with an optimal well spacing of 320 m; It is recommended to use a moderate fracturing scale for the renovation of the central and northern well areas, with an optimal well spacing of 300 m; It is recommended to use medium scale fracturing in the southwestern well area, with an optimal well spacing of 260 m.

     

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