A Method For S-wave Velocity Estimation Based On Rock Physics Analysis

S-wave velocity is the input of pre-stack inversion and the precision of the reservoir and gas-water identification depend on S-wave velocity inversion. For the numerical simulation of wave equation, S-wave velocity is also very important.However,for most of the work areas are often lack of S-wave velocity data. So it increases the difficulty of numerical simulation and reservoir inversion. For estimate the high precision S-wave velocity,this paper starts the research with the theories of S-wave velocity,improves and conclusion the methods and study the topic from the methods of empirical and rock physics models. First, this paper does some research about experience formula. Because experience formula must base on water saturation rocks, we introduce the Gassmann fluid replacement and P-wave modulus to improve the precision of inversion. Then this paper discuss the conventional rock physics models with “rock matrix equivalent parameter model” 、 “pore fluid equivalent parameter model”、 “Fissure medium equivalent parameter model”、 “porous media equivalent parameter model” and compare the difference between the same type models. Besides, this paper does the forward modeling about sandstone reservoir and the carbonate reservoir and makes the template of the two kinds of lithology. Based on the forward model and the difference between sandstone reservoir and the carbonate reservoir, author propose new rock physics models to estimate S-wave velocity of the two kinds of lithology. The last, this paper uses the log data of SLG gas field and AMH gas field to prove the correctness of the methods. The calculation results show that the method proposed by this paper improve the accuracy of S-wave velocity estimation, The actual data show that the inversion and measured P-wave velocity is complete coincidence, the trend of inversion and measured shear velocity curve is consistency, amplitude considerable, relative error is small, high precision.The key results of this paper are as follows:(1)The author propose an improved modulus inversion method and it solves the value issues of the matrix minerals modulus in S-wave inversion effectively.(2)In view of the feature of sandstone reservoir, and combination with improved modulus inversion method with Xu-White model to propose a new workflow to estimate S-wave velocity of low porosity sandstone reservoir.(3)In view of the carbonate reservoir, the pore structure is more complex. This paper adopt the inversion of pore structure to estimate the optimization pore aspect ratio then propose a new workflow to estimate S-wave velocity of carbonate reservoir. The methods of this paper are the extension and complement of conventional method and have practical application prospect to other blocks.