复杂构造区深层页岩气藏射孔参数优化及应用——以涪陵页岩气田白马区块为例

为了实现四川盆地涪陵页岩气田白马复杂构造区深层页岩气储量的有效动用,针对该区地质构造复杂、储层非均质性强、储层埋藏较深、压裂改造难度较大的实际情况,基于平面三维“井筒—多裂缝扩展”全耦合计算模型,考虑不同小层物性与应力的差异,模拟了不同穿行层位、压裂簇数、射孔数量等因素对多簇裂缝扩展差异的影响。研究结果表明：①降低簇间距、增加单段压裂簇数的多簇密切割有利于提高改造段内的主裂缝密度、缩短气体运移距离;②段内簇数并不是越多越好,在相同注入排量及压裂规模条件下,随着压裂簇数的增多,各簇缝长、缝高呈现出降低的趋势,同时多裂缝的非均匀扩展现象加重;③水平井穿行层位及各小层物性特征、应力状态也会影响到水力裂缝的扩展形态,会增强不同小层改造的非均匀性,进而造成最优簇数的不同;④减少单簇射孔数的限流压裂,有利于提高压裂段内改造均匀性、降低各簇进液量差异减小系数,但是较低的射孔孔数则会提高射孔孔眼摩阻、大幅度提高地面施工压力。现场实践结果表明,依据水平井穿行层位优化压裂工艺参数,同时配合限流射孔,压后气井增产效果明显。结论认为,该研究成果为实现白马区块深层页岩气资源的有效动用提供了理论指导与实践检验。

Optimization of application of perforation parameters of deep shale gas reservoirs in complex structural areas: a case study of the Baima Block of Fuling Shale Gas Field

Baima complex structure area in Fuling Shale Gas Field of the Sichuan Basin is characterized by complex geological structures, strong reservoir heterogeneity, great reservoir burial depth and difficult fracturing stimulation. And in order to realize the effective production of deep shale gas reserves in this area, this paper simulates the influences of different factors (e.g. trajectory position, number of fracturing clusters and number of perforations) on the propagation differences of multi-cluster fractures by considering the differences in physical properties and stress between different sublayers, based on the calculation model of plane three-dimensional fully coupled "wellbore-multifracture propagation". And the following research results were obtained. First, multi-cluster intensive cutting by reducing the cluster spacing and increasing the number of single-stage fracturing clusters is beneficial to increasing the density of main fractures and shortening the gas migration distance in the stimulated section. Second, increasing the number of clusters in one section does not mean better effects. Under the same injection rate and fracturing scale, the fracture length and fracture height of each cluster presents a decreasing trend and the non-uniform propagation of multiple fractures aggravates as the number of fracturing clusters increases. Third, the physical characteristics and stress state of horizontal-well trajectory position and each sublayer also influence the propagation morphology of hydraulic fractures and enhance the stimulation nonuniformity of different sublayers, which results in the differences in the optimal number of clusters. Fourth, the limited entry fracturing that reduces the number of single-cluster perforations is beneficial to improving the stimulation uniformity in the fracturing section and decreasing the reduction coefficient of fluid volume difference between different clusters, but a smaller number of perforations will increase the perforation friction and greatly improve the ground construction pressure. Field practice results show that the stimulation effect of the gas well after fracturing is remarkable by optimizing the fracturing process parameters according to the horizontal-well trajectory position, combined with the limited entry perforation. In conclusion, the research results provide theoretical guidance and practical experience for the effective production of deep shale gas resources in the Baima Block.