| Energy, especially oil, gas, coal and other non-renewable resources, plays an important role in the promotion of world economic development and raising the level of human life, these resources are facing the crisis of depletion because of the unlimited exploitation, therefore, the necessary energy reserves are of strategic importance for this problem.Yantai Wanhua underground water-sealing storage caverns lie in Yantai, Shandong Province, which has the largest storage capacity of LPG reserves being build recently and is the first one with the capacity up to100×104m3in our country. This paper which has the underground water-sealing storage in rock caverns project of Yantai Wanhua as the basis, gets the hydraulic conductivity in the study area and calculates the permeability tensor, then obtains the principal values and principal directions of the hydraulic conductivity which can depict the anisotropy characteristics of the permeability in fractured rock mass on the basis of the geological, hydrogeological investigation and site hydrogeological test. According to the geostatistics theory, it analyzes the spatial variability of hydraulic conductivity, and uses the sequential indicator simulation to study the space distribution of the permeability in fractured rock mass, which can provide a reliable basis and theoretical support for the subsequent design of the water curtain, the evaluation of water seal effect and inflow, water inrush point block and so on.The early Yanshanian biotite adamellite is the major lithology in the study area, as Low permeability fractured rock mass media is the ideal location for the underground water-sealing storage. The research of spatial structure and basic hydraulic parameters can provide critical hydrogeological data for the following analysis of fracture flow simulation and water seal effect evaluation. Different quantity of anisotropic tectonic stress occurring has had so significant impact on the rock mass so that it shows the characteristics of heterogeneity, randomness, diversity and complexity. All of these characteristics make the research of rock mass strcture more complex. However, it was found that geometry elements of the fracture in rock mass are regulared statistically and be controled by regional tectonic movement, so that the identification of tectonic movement in study areas is basis for fracture network simulation and fracture flow model establishing. It is significant for studying the space attributing of the permeability in fractured rock mass by researching the developing characteristics of fractures fully.The hydraulic conductivity of the fractured rock mass media is an important parameter to reflect the permeability, the heterogeneity of the fractured rock mass media determines the anisotropy of the hydraulic conductivity, so that the anisotropy, spatial variability and the sequential indicator simulation of the permeable field which are used to reveal the the space distribution characteristics of the permeability is based on the obtaining of the hydraulic conductivity.The permeability tensor can reflect the anisotropy of the permeability in fractured rock mass, this paper calculates the permeability tensor of the fractured rock mass in the study area by means of the fracture measurement based on the VBA program according to the surface fractures measurements and the interpretation of fractures in borehole imaging, and then obtains the principal values and principal permeability directions of the permeability.The hydraulic conductivity changes when its spatial location changes, with significant spatial variability. This paper regards the hydraulic conductivity as a regionalized variable which the spatial variability analysis is based on, and then uses the sequential indicator simulation to reveal the the space distribution characteristics of the permeability in the study area, which can provide a reliable basis for the construction of caverns.According to the above theories and analysis, this paper performed the following research tasks:(1)Based on the existing information and the geological survey this paper finds that the early Yanshanian biotite adamellite is the major lithology of the fractured rock mass and the tectonic is undeveloped but some secondary faults are developed surrounding the study area, which affect and control the boundary of cavern. The fracture zone, joint fissure zone and regional distributing joints in the venue have a larger impact on the construction of caverns engineering in which the fracture is developed. The fracture geometry characteristics, derived from field investigation and borehole imaging technique, shows the majority of fractures occur due to tectonic and have a steep dip. There are five groups superior joints in the venue(dip direction∠dip):68°∠84°,115°∠81°248°∠86°、297°∠73°、324°∠19°.(2)In order to obtain the hydraulic conductivity of different aquifer media the paper uses water lifting, water interjecting, water pressing, and water pumping hydrogeological test. The results indicate that the hydraulic conductivity magnitude of quaternary aquifer varies from10-2to 10-1m/d, otherwise in fissured bedrock aquifers the magnitude ranges from10-5to10-3m/d.The permeability of the latter is most less than the former. Rock mass permeability meets the guideline of relevant codes for underground water-sealed storage cavern construct. This paper makes statistics on the fractures corresponds to the length of water pressure test segments by the borehole imaging, and introduces the advantage hydraulic conductivity and calculates the principal values and principal directions of the permeability tensor to reflect the anisotropy characteristics of the permeability in fractured rock mass.(3) Regarding the hydraulic conductivity as a regionalized variable and following the intrinsic hypothesis, this paper obtains3thresholds (-3.99....) in the cumulative frequency curve using geostatistics technique, then does the spatial variability analysis on three principal permeability directions which are calculated by means of the fissure measurement. The results indicate the variogram model approximates to the spherical model. This paper takes the maximum principal permeability directions K1and the minimum principal permeability directions K3as the major theme to establish the variogram nested structure model based on the above analysis finally.(4)Selecting266hydraulic conductivities as the original simulation data, this paper does the sequential indicator simulation by WinGslib, and divides the simulation results into three parts to reveal the distribution and variation of hydraulic conductivity field in fractured rock mass medias which are located in the water curtain system and cavern, then combines with the results of engineering geological drilling and geophysical survey to make the comparative analysis.The results indicate that the sequential indicator simulation can reflect the spatial distribution of hydraulic conductivity field in the study area generally. Finally this paper analyzes the whole and partial spatial distribution characteristics of the permeability in in fractured rock mass media by the sequential indicator simulation combined with existing achievements. The sequential indicator simulation utilizes the existing data fully to restore the spatial correlation and volatility of the hydraulic conductivity, which reflects the heterogeneity of the fractured rock mass media. It is a rather good mathematical tool to describe the spatial distributing characteristics of the hydraulic conductivity field in the study area. |
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