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设计试验方法流程对塔中地区深层致密砂岩储层岩样进行不同围压条件下声学测试,提出基于声学数据反演定量研究致密砂岩储层微裂隙应力敏感性的评价方法。通过Biot相洽理论和DEM理论组合模型分别对岩石裂隙密度?和孔隙纵横比?进行反演,探讨了不同围压条件下岩石?、?的变化规律,并对微裂隙应力敏感性进行评价。结果表明:?随围压的增加而降低,?随围压的增加而增加,这主要是由于微裂隙的闭合引起的;根据不同围压条件下?值降低幅度可以确定发生闭合的裂隙或依然保持张开的裂隙所占的百分比;在较高围压条件下依然具有较大?值的样品应力敏感性较弱,反之,应力敏感性较强;定义试验中岩石内部孔裂隙性质发生急剧变化的点为转折点,发现该点对应的?值相差不大,该值可视为该致密砂岩储层的裂隙共性特征,并可作为裂隙相对发育程度的对比指标;分别探讨了?值(围压65 MPa)及所定义转折压力与岩石孔隙度间的相关性,结果表明,两者正相关性均非常好,对于该地区深层低渗致密砂岩储层而言,存在低应力敏感性的有利类型裂隙受岩石物理性质影响程度最大。
The design and test method is applied to the acoustic tests under different confining pressures of the deep tight sandstone reservoirs in the Tazhong area. The method for quantitatively studying the stress sensitivity of the tight fractured sandstone reservoirs based on the acoustic data inversion is proposed. The rock fracture density and pore aspect ratio were inversely reconstructed by the Biot theory and the DEM theory. The variation law of rock mass and rock mass under different confining pressure was discussed, and the stress sensitivity of the micro-fracture was evaluated. The results show that:? Decreases with the increase of confining pressure and increases with the increase of confining pressure, which is mainly caused by the closure of microcracks; and according to the decrease of? The percentage of open fractures remains the same; the samples with larger values at higher confining pressure are less sensitive to stress and vice versa, and the stress sensitivity is stronger; the nature of fracture fissures within the defined rock undergoes drastic changes The results show that the corresponding values of this point have little difference, which can be regarded as the common features of the fractures in the tight sandstone reservoirs and can be used as a contrast indicator of the relative development degree of fractures. The values of confining pressure 65 MPa) and the correlation between turning pressure and rock porosity. The results show that the positive correlation between the two is very good. For the deep low permeability tight sandstone reservoirs in this area, there is a favorable type of low stress sensitivity Fissures are most affected by the physical properties of rocks.