Research And Application Of Forward And Inverse Analysis Of The Influence Of Borehole In-situ Stress On The Full-wave Sonic Logging

Measures such as acidification and fracturing are the important means to increase oil and gas production in low-porosity and low-permeability heterogeneous reservoirs.However,such measures can easily lead to problems such as fractures,invasion and abnormal stress in the reservoir,which will directly change the lithology of the reservoir and the original stress state of the formation,and affect the evaluation of the reservoir.This thesis uses MPAL logging tool to explore and evaluate uniform or non-uniform reservoirs.It provides a theoretical basis for the logging interpretation of multipole sonic logging in complex formations.The following are the main research contents and results:The first part studies the influence of intrusion and low sonic zoning on monopole sonic logging.Under fast and slow formations,the influence of the radial depth and contrast of invasion and low-sound velocity annulus on the response characteristics of array waveforms and elastic wave velocity is studied.The results show that: under the influence of invasion,the head wave velocity of the fast and slow formations decreases with the increase of the radial depth of the invasion.As the invasion degree increases,the impact on the head wave velocity becomes more significant.The first wave arrival time of the array waveform lags behind.Stoneley The amplitude of the propagating pseudo Rayleigh wave attenuates and the arrival time is delayed;under the influence of the low sound velocity annulus,the head wave velocity of the fast and slow formations both decrease as the radial depth of the low sound velocity annulus increases.The second part studies the response characteristics of formation fractures,temperature and sound source frequency changes to monopole sonic logging.The influence models of fracture,temperature and sound source change are constructed respectively to study the fracture depth and development direction,the elastic wave sound velocity change law and the array waveform response characteristics under different wellbore temperature environments and different monopole sound source frequencies.The results show that in fractured formations,the longitudinal wave velocity decreases as the fracture depth increases,and does not change with the direction of fracture development;the shear wave velocity first increases and then decreases as the fracture depth increases.The impact of the fracture is more significant;the Stoneley wave velocity decreases as the fracture depth increases,and it first increases and then decreases with the development direction of the fracture;the low temperature area under the fast and slow formations has little effect on the sound velocity,and the temperature The speed of sound is distorted when the temperature is greater than 40?;the longitudinal wave speed increases with the increase of the sound source frequency,the transverse wave speed decreases with the increase of the sound source frequency,and the Stoneley wave speed decreases with the increase of the frequency.The larger the sound source frequency,the array The resolution of each elastic wave mode of sound wave is higher.The third part is the study of the influence of abnormal stress beside the well on dipole sonic logging.Based on the COMSOL numerical simulation software,the forward response numerical simulation of dipole sonic logging is carried out under this anisotropic formation condition.The results show that: in different stress direction change models,the change of stress direction angle has obvious influence on the waveform amplitude and energy of the same direction component and cross component in the array waveform;The wave amplitude of the directional component has a significant influence and changes in a gradual manner.The fourth part is the inversion and application of formation anisotropy parameters based on the dipole acoustic logging response information database.Establish a response information database based on forward data,formulate a mathematical model and inversion process suitable for the inversion of this thesis,and propose a new method for calculating the degree of anisotropy of the formation;actual logging data is used to verify the inversion process.The results show that the accurate inversion of the formation anisotropy parameters by this inversion method verifies the correctness of the forward modeling;the energy anisotropy inversion method can reflect the reservoir anisotropy more accurately than the traditional array anisotropy inversion method Heterogeneity strength: This method plays a role in reservoir oil and gas prediction and evaluation in the inversion of actual oilfield sonic logging data.