基于流变模型的地应力剖面预测——以贵州黔北地区安页1井为例

地应力是非常规油气勘探开发中"甜点"评价、水平井部署和压裂设计的重要基础参数。目前国内外主要将基于弹性模型的常规储层地应力评价技术应用于泥页岩储层,未考虑流变特性对泥页岩储层地应力分布规律的影响,导致泥页岩储层地应力评价结果误差较大。为了提高地应力参数评价计算的准确性,提出了一种基于流变模型的地应力评价新方法(以下简称新方法),利用偶极声波测井数据获取的岩石力学参数,参考相关试验结果确定岩石流变参数随深度变化的规律,结合盆地埋藏史和地壳应变率,建立了贵州黔北地区安页1井地应力剖面。新方法评价得到的地应力值与小型压裂实测和应力多边形法确定的地应力值的对比分析结果表明:新方法预测的安页1井地应力剖面与实测结果吻合较好,并且其地应力评价结果与伽马测井结果也具有较好的对应关系,即随着黏土矿物或有机质含量的升高,水平主应力差变小。结论认为,采用新方法得到的地应力评价结果更加符合于真实的地应力分布规律。

In-situ stress profile prediction based on the rheological model: A case study of Well AY-1 in the Qianbei area of Guizhou Province

In-situ stress is a key parameter in the sweet-spot assessment, horizontal well arrangement and fracturing design in the exploration and development of unconventional oil and gas reservoirs. At present, the elastic model based on in-situ stress evaluation technology which is used for conventional reservoirs is applied to shale reservoirs at home and abroad while the effects of rheological behaviors on the distribution laws of in-situ stress in shale reservoirs are not taken into consideration, which brings a larger error to the evaluation result of in-situ stress of shale reservoirs. In this paper, a new in-situ stress evaluation method base on the rheological model was put forward to increase the evaluation and calculation accuracy of in-situ stress parameters. Then, the variation laws of rock rheological parameters with the depth were determined by using the rock mechanical parameters obtained from cross-dipole acoustic logging data, referring to the related experimental results. And combined with the burial history of the basin and the strain rate of the crust, the in-situ stress profile of Well AY-1 in the Qianbei area of Guizhou Province was established. Finally, the in-situ stress evaluated by the new method was compared with the one measured in the mini frac and the one determined by the stress polygon method. And it is indicated that the in-situ stress profile of Well AY-1 predicted by the new method is consistent with the test result and its in-situ evaluation result presents a good corresponding relationship with the result of Gamma logging. As the content of clay mineral or organic matter increases, the horizontal principal stress difference decreases, indicating that the in-situ stress evaluation result by the new method is in better accordance with the distribution law of true in-situ stress.