| N23-A section is located at western Niuzhuang oilfield in the Dongying Depression of Bohai Gulf Basin.With two faults crossing,the distribution of stress is quite complicated.The uncertainty of the distribution of stress field affects location planning in the section,design of development well pattern and enhanced recovery results of the low permeability section.Therefore,the directions and magnitudes of stress field of N23-A section is being studied through a detailed analysis.The single well stress is calculated the research on structural stress field,in door petrophysical core analysis,geomechanical analysis,well logging interpretation and hydraulic fracture analysis.After all wells' stress data have been studied,three wells are selected as the limit condition,then geological structural model and finite element simulation model are built,the optimal simulation boundary condition is calculated.Through stress field limited element simulation,the maximum horizontal stress in this section is determined to be between 66.1-96.05 MPa,the minimum horizontal stress is between 51.7-70.8 MPa.The maximum horizontal stress direction consists of three main areas:northeast 125-135° of the inner area between N23-A section's two faults,northeast 110-115°of the western area of northeastern secondary fault,northeast 75° to northeast 90° of maximum horizontal stress direction of well N25-40 and N25-60 with certain deviation.Regional stress is concentrated within 100 meters near the fault,the stress field changes greatly.From the results of stress field study,N23-A section maximum horizontal direction is determined to be NE 90-120°.Based upon the rule that the major flow direction after hydraulic fracture is in a accordance with maximum horizontal stress direction,It is suggested that the injection-production pattern be arranged according to the direction of maximum principal stress in each region. |
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