基于声波信号预测Kaiser应力点的水平地应力

声发射实验测试地应力方法需从地层原位取得的全尺寸岩样上钻取4个小尺寸岩芯,分别进行加载实验下的声发射测定。该方法将造成地层岩样损失,地应力评价成本较高。为此,根据岩石声学性质与力学特性具有较好的相关性特征,基于大量岩石试件的声波时差实验数据和加载条件下的声发射实验数据,构建声波时差与岩样Kaiser应力点的关系模型,并结合岩石声发射实验预测地应力计算模型,建立利用声波信号预测Kaiser应力点的地应力计算方法。而后,结合全尺寸岩芯的360°声波时差扫描数据,利用该方法进行致密油储层地应力预测分析,结果显示:建立的地应力计算方法预测结果相对于Anderson、Eaton、Newberry模型预测结果更接近压裂数据计算的地层应力值。说明该方法相对于传统的测井解释地应力方法更稳定,并且利用全尺寸岩芯360°声波时差扫描数据预测Kaiser应力点相对于声发射实验方法具有更好的经济性。

Study on the Calculated Method of Horizontal In-situ Stress Based on the Kaiser Stress Point Predicted by Acoustic Signal

The in-situ stress evaluation method by acoustic emission tests needs to carry out acoustic emission tests under the loading condition using four small-size cores drilled from a full-scale stratum rock sample. This method will result in the loss of strata rock samples and the high cost for the in-situ stress evaluation. In the present work, a series rock sores were carried out by acoustic emission tests and acoustic emission tests under the loading condition. According to the concept of the good correlation between acoustic properties and mechanical properties of rock, the relational function between acoustic interval transit time and Kaiser Stress Point of rock sample was obtained using the test results. Next, a new calculated method of horizontal in-situ stress based on the Kaiser stress point predicted by acoustic interval transit times using the relational function was developed based on the calculation model of the in-situ stress evaluation method by acoustic emission tests. Furthermore, using the 360° sonic scan data of the full-scale core, the horizontal in situ stress of a tight oil reservoir was evaluated by the new proposed method, as well as the results were compared with the values of in situ stress evaluated by hydraulic fracturing test data. The results show that the values of the horizontal in situ stress calculated by the proposed method have higher accuracy comparing with the results calculated by the models of Anderson, Eaton and Newberry. Therefore, this new proposed method to evaluate the horizontal in situ stress is not only more accurate comparing with the traditional logging interpretation method, but also have higher economy due to that there is no cost on the tests and rock cores loss.