玛湖致密砾岩裂缝干扰规律

Fracture Interference Law of Mahu Tight Conglomerate

玛湖致密砾岩油藏是目前重要的陆上原油上产的主要组成部分,系统的油藏工程评价显示,其裂缝的扩展规律与页岩为代表的非常规储层具有典型的差异,“绕砾成缝”是其重要的控制机理,裂缝的干扰特征也有显著的差异。基于考虑“基质本构、固液耦合、任意方向破裂表征”的离散元计算模型,研究了砾岩油藏裂缝扩展过程中的干扰规律。研究表明,应力差较小情况下,裂缝受到砾石吸引作用大于应力差作用,加之裂缝间的相互作用,使得裂缝逐渐向两侧发育,裂缝受到砾石阻碍作用,导致相互贯通,裂缝向两侧发育消耗能量,导致裂缝较短,在应力差较大的情况下,应力差作用大于裂缝受到砾石吸引作用,裂缝沿着最大主应力方向发育,裂缝集中发育,主裂缝较长。应力和砾石共同作用下的裂缝和干扰机理的研究为后期不同应力差条件下的合理改造和开发对策提供重要的支撑。

Mahu tight conglomerate reservoir is an important component of onshore crude oil production at present. Systematic reservoir engineering evaluation shows that the fracture propagation law of Mahu tight conglomerate reservoir is different from that of unconventional reservoir represented by shale. The “fracture around gravel” is an important control mechanism, and the interference characteristics of fracture are also significantly different. Based on the discrete element model of “matrix constitutive, solid-liquid coupling and fracture characterization in any direction”, the interference law of fracture propagation in conglomerate reservoir was studied. The results show that, when the stress difference is small, the attraction of the crack to the gravel is greater than that of the stress difference. In addition, the interaction between the cracks makes the cracks gradually develop to both sides, and the cracks are hindered by the gravel, resulting in mutual penetration. The development of the cracks to both sides consumes energy, resulting in shorter cracks. When the stress difference is large, the effect of the stress difference is greater than that of the crack to the gravel under the action of attraction, the fractures develop along the direction of the maximum principal stress, the fractures are concentrated, and the main fractures are long. The research on the mechanism of cracks and interference under the joint action of stress and gravel provides important support for the reasonable transformation and development countermeasures under different stress difference conditions in the later stage.