基于原位地应力测试及流变模型的深部泥页岩储层地应力状态研究

深部泥页岩储层地应力状态的准确确定是页岩气等非常规能源高效开发的关键。综合基于原位地应力测试获得水平最小主应力，建立基于流变模型的地应力剖面，应用成像测井技术确定水平最大主应力方向等，是准确确定泥页岩储层地应力的有效方法。将该研究思路应用于陕西汉中SZ1井，利用水压致裂原地应力测试方法获得储层水平最小主应力值范围为32~41 MPa；利用偶极声波测井数据获得岩石力学参数，结合地壳应变率和储层埋藏史，建立了SZ1井地应力剖面，结果表明牛蹄塘组1950~2025 m深度范围内水平主应力差介于10~15 MPa，水平最小主应力值范围为28~41 MPa，水平最大主应力值范围为47~49 MPa，预测得到的水平最小主应力值与实测结果具有较好的一致性。原地应力实测及流变模型预测结果揭示SZ1井地应力为正断型(S_v＞S_H＞S_h)或正断型与走滑型相结合的应力状态(S_v≈S_H＞S_h)。水平主应力差随伽玛值的升高而变小，表明地应力剖面与地层岩性具有较好的对应关系。基于成像测井揭示的钻孔诱导张裂隙分布特征，SZ1井水平最大主应力方向约为N74°W，与区域构造应力场方向基本一致。相关结论为准确认识SZ1井目标层地应力状态，以及后期水平井布设及压裂控制等提供了重要依据。 

Research on stress state in deep shale reservoirs based on in-situ stress measurement and rheological model

Accurately determining the stress state in deep shale reservoirs is the key to the efficient development of shale gas and other unconventional energy sources. An effective method to increase the evaluation and calculation accuracy of in-situ stress parameters in a deep shale reservoir is to combine different methods to obtain different stress information, such as obtaining the minimum horizontal principal stress based on the in-situ stress measurement, predicting the magnitudes of horizontal stress difference and the horizontal principal stresses by establishing the stress profile based on the rheological model, and estimating the direction of the maximum horizontal principal stress by the wellbore failure imaging logging. We applied this research idea to Well SZ1 in Hanzhong, Shaanxi Province. The minimum horizontal principal stress obtained by hydraulic fracturing ranged from 32 to 41 MPa; Then, the variation laws of rock rheological parameters with the depth were determined by the rock mechanical parameters obtained from cross-dipole acoustic logging data. And combined with the burial history of the reservoir and the strain rate of the crust, the stress profile of Well SZ1 was established. The results show that the magnitude of horizontal stress difference in the depth range of 1950~2025 m in the Niutitang Formation is between 10~15 MPa, and ranges of the minimum and maximum principal stresses are 28~41 MPa and 47~49 MPa, respectively. The predicted horizontal minimum principal stress values are in good agreement with the measured results. Based on the in situ stress measurement and predicted stress profiles, Well SZ1 is characterized by normal faulting (S_v > S_H > S_h)or a combination of normal and strike-slip faulting regimes (S_v≈S_H > S_h).The horizontal stress difference decreases with the increase of the gamma value, indicating that the stress profile has a good corresponding relationship with the formation lithology. Based on the distribution characteristics of borehole-induced tensile fractures recorded by imaging logging, the direction of the maximum horizontal principal stress in Well SZ1 is ~N74°W, which is consistent with the direction of the regional tectonic stress field. This study provides an important basis for accurately understanding the in-situ stress state of the target layer of Well SZ1, as well as the later horizontal well layout and fracturing control.