ABSTRACT Stress-sensitive permeability imposes a significant impact on production performance in a tight formation; however, the widely used models assume the constant permeability or same stress-sensitive level for different systems, resulting in incorrect prediction of production rate and reservoir properties. In this work, theoretical models have been formulated, validated, and used to characterize the transient rate behaviour of a horizontal well with multistage fractures at constant wellbore pressure in tight formations by taking the different stress-sensitive effects in matrix and fracture subsystems into account. More specifically, a matrix-fracture fluid flow model with considering stress-sensitive effect was developed, during which the resulting nonlinear governing equation caused by stress-sensitive matrix permeability was weakened and linearized by using the Pedrosa's transform formulation and perturbation technique, respectively. Then, a slab source function was developed to obtain the solution for such a linearized problem in the Laplace domain. Meanwhile, a semi-analytical method is applied to solve the matrix-fracture flow models by discretizing each hydraulic fracture into small segments. Furthermore, the Blasingame type curves are generated to examine the stress-sensitive effects. In particular, stress-sensitivity in matrix and hydraulic fracture subsystems can be respectively analyzed. It is found that stress-sensitive permeability in either the matrix subsystem or the fracture subsystem has its negative influence on production rate. Such an influence is increased as the permeability modulus in matrix and fractures is increased. The matrix permeability modulus mainly decreases the production rate in the intermediate and late flow period, while its effect on the early time production rate is relatively small compared with other flow periods. Stress-sensitivity in fractures mainly affects the early time production rate and imposes a negligible impact on production rate during the intermediate and late period. The production rate is increased with an increase in the initial fracture conductivity. The dominant flow which contributes to the majority of the total production gradually shifts from the near-wellbore fracture segments to the near-tip fracture segments for the intermediate and high conductive fracture cases, while, for the low conductive fractures, the near-wellbore fluid flow is dominant for the entire period. Due to the inherent constraints in a tight formation, rate transient analysis is found to be more physically representative for accurately describing performance of a horizontal well with multistage fractures compared to the traditional pressure transient testing.

中文翻译：

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考虑应力敏感效应的致密地层多级裂缝水平井瞬态速率特性半解析模拟

摘要 应力敏感渗透率对致密地层的生产性能有显着影响；然而，广泛使用的模型假设不同系统的渗透率恒定或应力敏感水平相同，从而导致对产量和储层特性的预测不正确。在这项工作中，通过考虑基质和裂缝子系统中不同的应力敏感效应，理论模型已被制定、验证并用于表征在致密地层中在恒定井筒压力下具有多级裂缝的水平井的瞬态速率行为。更具体地说，开发了考虑应力敏感效应的基质-裂缝流体流动模型，在此期间，由应力敏感矩阵渗透率引起的非线性控制方程分别通过使用 Pedrosa 变换公式和微扰技术弱化和线性化。然后，开发了一个平板源函数以获得拉普拉斯域中这种线性化问题的解。同时，通过将每个水力裂缝离散成小段，应用半解析方法来求解基质-裂缝流动模型。此外，生成 Blasingame 类型曲线以检查应力敏感效应。特别是，可以分别分析基质和水力压裂子系统中的应力敏感性。结果表明，无论是基质子系统还是裂缝子系统中的应力敏感渗透率都对生产率有负面影响。这种影响随着基质和裂缝中渗透率模量的增加而增加。基质渗透率模量主要降低中后期流动期的产量，而对早期产量的影响与其他流动期相比较小。裂缝中的应力敏感性主要影响早期生产率，对中后期生产率的影响可以忽略不计。生产速度随着初始裂缝导流能力的增加而增加。对于中高导裂缝情况，占总产量大部分的主导流逐渐从近井眼裂缝段转移到近端裂缝段，而对于低导裂缝，近井筒流体流动在整个时期占主导地位。由于致密地层的固有限制，与传统的压力瞬态测试相比，速率瞬态分析在准确描述具有多级裂缝的水平井的性能方面更具物理代表性。