| With the rapid development of the world economy,people's demand for energy is also increasing.Oil and gas resources,as an important traditional energy source,have also become the focus of human attention.After years of exploitation,conventional oil and gas resources are hard to keep up with human needs.Fractured reservoir,as an unconventional reservoir,has a large number of oil and gas resources,and has become a research hotspot at domestic and abroad.At present,the identification of fractured reservoirs at home and abroad is mainly the combination of conventional logging and imaging logging.This method can identify fracture and calculate the length and width of fracture roughly.However,most of the fractured reservoirs exist in igneous or tight sandstone reservoirs,these reservoirs are very complex in lithology.There is uncertainty in the calculation of fractures by conventional logging data.Imaging logging has high cost and large amount of data processing,so it is difficult to use the whole well section.In addition,the result of imaging logging is limited to wellbore,and it is difficult to calculate the direction of fracture extension.So imaging logging is also limited.If the fracture is not parallel to the instrument axis,the propagation of longitudinal waves will be affected by fractures.Reflection and refraction will cause compressional wave attenuation,resulting in the first wave loss.The effect of the share wave on the fractures is more obvious than that of the compressional wave.When the fractures are not perpendicular to the axis of the instrument,the shear wave will split up,resulting in the fast share wave parallel to the fracture direction and the slow share wave perpendicular to the fracture direction.By analyzing the slowness difference and direction of fast and slow shear waves,we can calculate fracture azimuth and analyze anisotropy.In this paper,two methods of experimental measurement and algorithm development are used to study acoustic logging data of fractured reservoir.The study area is Wangfu fault depression.The identification of fractures and the calculation of fracture parameters: Fracture width,dip angle,strip number,azimuth angle and anisotropy.By this method can greatly improve the recognition rate of fractures,and have important reference and guiding significance for the quantitative evaluation of fractured reservoirs.A new method for evaluating fracture parameters based on dipole shear wave data was provided.In the aspect of experimental research,we used ultrasonic experiment to measure the propagation of sound waves with different fractures.First,rock samples were constructed with different widths,numbers and directions of fractures.According to the control variable method,different rock samples were measured,and the velocity and amplitude of acoustic wave were recorded.Secondly,the effects of different types of fractures on acoustic velocity and amplitude were analyzed.Finally,the rules were applied to the actual data and compared with the imaging logging,and the inversion results were tested.In terms of algorithm development,the artificial fish swarm algorithm was introduced into the calculation of fracture azimuth.Based on the inversion of shear wave anisotropy,an artificial fish swarm algorithm was established to solve the fracture azimuth.The algorithm of artificial fish swarm algorithm was applied to calculate the azimuth of fractures through MATLAB.The algorithm was applied to actual dipole shear wave data,and the azimuth of formation fractures was calculated by processing the data of XX well.Compared with the imaging logging,the azimuth error of the calculated result relative to the imaging logging was less than 5%.Finally,aiming at the geological structure and fault trend in Wangfu area,combined the experimental research with the algorithm,the fracture width,azimuth and anisotropy of the volcanic rock reservoir of the Huoshiling formation in the study area were calculated,and the application effect was good. |
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