Evaluation of Fracturing Effects in Offshore Sandstone Reservoirs Based on Array Acoustic Logging Technology

In order to comply with the requirement to evaluate fracturing effects in offshore sandstone reservoirs, the application of P-wave tomography imaging technology and dipole scattering wave technology for fracturing effect evaluation of reservoirs were studied based on array acoustic logging data measured before and after fracturing. P-wave tomography imaging technology can rebuild the radial acoustic velocity profile of the formation near the borehole. By comparing the radial acoustic velocity changes of the formation near the borehole before and after fracturing, the reservoir fracturing height near the borehole can be evaluated, but the fracturing effect of the formation away from the borehole cannot. The dipole scattering wave technology uses the scattering wave energy to analyze the formation heterogeneity within tens of meters around the borehole. It can evaluate the spatial distribution of fractures away from the borehole. The combination of the above two technologies can accomplish the comprehensive evaluation of the fracturing effect of the formation near and away from the borehole. It has been applied in the fracturing Well X1 of the offshore sandstone reservoir. Compared with that before fracturing, the rock acoustic velocity was significantly reduced by the fractures created after fracturing near the borehole, and the fracturing height was about 13.80 m. Meanwhile, the difference area of scattered wave energy formed by fractures around the borehole showed that obvious fracturing volume stimulation was formed in the range of at least 14.00 m around the borehole, indicating that the fracturing effect was good. This method can not only identify the fracture heights of reservoir fracturing near and away from the borehole but also evaluate the radial length of the fractures to a specified extent.