Abstract：In-situ stress is critical to well instability in silt formations during drilling. Based on the analysis of in-situ stress measurement methods such as hydraulic fracturing method，Kaiser effect method，differential strain analysis(DSA) method and multi-pole logging method，it is difficult to acquire in-situ stress of complex silt formations through any method mentioned above. The best way is the combination of the advantages of these methods. Two methods to determine the in-situ stress are presented in this paper. The in-situ stress ratio can be measured by DSA method if there are drilling cores in the fracturing test，while the in-situ stress difference can be measured by multi-pole logging method if there is no drilling core in the fracturing test. Combined the acquired in-situ stress relative value with the fracture pressure mode for fracturing test，the horizontal in-situ stress can be determined. These two combined methods，in which one is the combination of formation fracturing test with DSA method and the other is the combination of formation fracturing test with multi-pole logging method，are feasible in field application.
