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目前,研究并搞清构造裂缝的形成时间、位置、产状、规模及分布密度对于低渗透、超低渗透砂岩储层的勘探开发至关重要,但具有很大难度。基于应变能理论建立一套综合地质力学模型以定量预测裂缝参数及分布,如裂缝线密度和体密度等。首先,在岩石力学实验的基础上将脆性储层中由构造应力引起的总能量划分为裂缝表面能、摩擦耗能和残余应变能3种类型,其中前两者即为与裂缝产生相关的能量,并以此为桥梁推导建立应力—应变和裂缝参数之间的关系模型。其次基于地震解释结果建立复杂构造区含断层的古地质模型、岩石力学实验、测井解释,通过动静校正的方法获得砂岩、泥岩的强度参数,从而建立地质力学模型。最终,进行古应力场数值模拟计算裂缝参数三维展布特征,并以实际井点数据进行验证。结果表明地质力学模型法不同于一般的几何分析方法,具有较高的可靠性和适用性,能够预测不同构造运动阶段的裂缝参数分布,并能够进行三维空间显示;裂缝的充填程度不仅影响着裂缝开度,也在很大程度上影响着低渗透砂岩储层的渗流特征,这对于进一步实现现今裂缝开度的定量预测以及储层数值模拟具有重要意义。
At present, it is very difficult to study and understand the formation time, location, occurrence, scale and distribution density of structural fractures for exploration and development of low permeability and ultra-low permeability sandstone reservoirs. Based on the theory of strain energy, an integrated geomechanical model was established to quantitatively predict fracture parameters and distribution, such as crack linear density and bulk density. First of all, on the basis of rock mechanics experiments, the total energy caused by tectonic stress in brittle reservoirs is divided into three types: crack surface energy, friction energy and residual strain energy, of which the first two are the energy related to fracture generation , And use this as a bridge to deduce the relationship model between stress-strain and fracture parameters. Secondly, based on the seismic interpretation results, the paleo-geological models of fault-containing structures in complex tectonic zones were established, and the rock mechanics experiments and log interpretation were carried out to obtain the strength parameters of sandstone and mudstone through the method of dynamic and static correction so as to establish the geomechanical model. Finally, the numerical simulation of paleocastal stress field is used to calculate the 3D distribution of fracture parameters and validated by actual well point data. The results show that the geomechanical model method is different from the general geometric analysis method and has high reliability and applicability. It can predict the distribution of fracture parameters in different tectonic movement stages and display in three-dimensional space. The degree of fracture filling not only affects the fracture The opening degree also affects the seepage characteristics of low permeability sandstone reservoirs to a great extent, which is of great significance for the further realization of the quantitative prediction of the present fracture opening and the numerical simulation of reservoir.