Research And Application Of LMR Seismic Inversion Methods In Shale Gas Reservoir

In the study of shale gas reservoirs,it’s very important to using the geophysical data of shale to learn the gas content and fracturing difficulty. The geophysical parameters λp、up can define the rock’s incompressibility and rock’s stiffness respectively. Under normal circumstances, in reservoirs, λp shows a low value and μp shows a high value. If elastic parameters, namely λp and μp, in shale gas reservoirs can have a good application, it will be very advantageous to study the shale gas reservoirs’gas content and fracturing ability. A good way to obtain the elastic parameters is to using the geophysical data, especially the inversion of seismic data. By the LMR inversion in shale, you can have access to these more sensitive elastic parameters. On basis of analysis and summary, a more reliable evaluation of the reservoir preparation is obtained by looking for ways to research into the shale gas reservoirs’gas content and fracturing difficulty. This paper explores several methods of LMR inversion and the geological meaning of Lame parameters for shale gas reservoirs. Finally, we summarize and have a practical application in the work area. The main achievements are as follows.1 In the study of the world’s typical shale gas reservoirs, they has a certain commonality and difference in the log response characteristics and seismic response characteristics. Under the impact of shale gas and lithology, in general, the λp shows a low value,μp shows a high value. Impedance inversion, prestack density, prestack compressional wave velocity, prestack shear wave velocity and Poisson ratio all generally show low values. By calculating, the λp shows a low value, μp shows a high value, as well as Young’s modulus. The shale gas reservoir has the anisotropy.2 By logging data interpretation in the work area, in the Segment One, μp has the highest value,λP has the lowest value, Mu shows high value, Ld shows low value, K and E have relative high values, Vp/Vs and PR also show low values. Vp/Vs is more sensitive to gas, showing low value. When the shale gas reservoir owns gas, the DEN becmes lower. The Segment One is the best and it has the most gas content, so the DEN is the lowest,μp shows highest value,λp shows lowest value. So, it also proves the Segment One is the best in gas content. It is easily crushed, belonging to high-quality shale.3 In the work area, density has the highest degree of differentiation among the elastic parameters. Under normal circumstances,λp shows a low value, μp shows a high value.λP will show a low value. In the Segment One,λP has the lowest value, μP has the highest value. Thus, λp and μp have a certain degree of physical relationships with the gas content, stiffness, resistance to fracture and lithology.4 By comparing several different LMR inversion methods, through model compution and analyzing inversion section, we can optimize the LMR inversion method of shale gas reservoirs. We get the further in-depth understanding of the inversion results from four aspects, namely comparison of different calculation methods with other related auxiliary elastic parameters, even well section, layer slice. The cumulative error of shale LMR inversion is not great. For shale gas reservoirs, both λp and μp have the ability to identify the gas in the shale. Ap is more sensitive. When there is gas in shale, λp exhibits a low value. The more the gas, the lower the value. The μp exhibits high value. The μp is associated with the rock rigidity, resistance to fracture, crushing difficulty and compressive or tensile resistance. The higher the value, the greater difficulty of fracturing. Through analysis, taking λp and μp inversion as a reference, the Segment One of the study area is the best shale significantly.