The Effect Of Fault On Creep-damage And Seepage Characteristics In Salt Storage Cavern In Salt Formation

Storage caverns in salt rock are productive storage medium owning to its unique mechanical properties.Foreign experts and scholars have carried out various studies on the ideal state salt rock,and obtained numerous achievements after scientific researches,then storage caverns in rock salt could be applied to the practical engineering.However,the salt deposits in China are mainly generated by latchstring deposits,and the distribution of salt rock are formed as a multilevel structure,and the movement of the earth's crust formed faults with a certain angle inclination.Therefore,it is more complicated to store oil or natural gas in this kind of cavern in salt rock.In this paper,we analyzed the seepage characteristics of repository in salt rock with fault combining with the previous research results.In order to describe the flow of fluid in storage caverns more authentically,we adopt a creep-damage model in the calculation process,which makes it more realistic.We summarize and analyze the failure mechanism of bedded salt rock reservoir,and compare the numerical simulation of the seepage model with the rheological damage model.The pWIPP model and Userc_d rheological damage model are applied to the numerical simulation to study the seepage characteristics of salt reservoir,and then we got some valuable results.?1?The volumetric strain has a linear relationship with permeability of surrounding rock.when the volume strain of surrounding rock changes,the permeability of surrounding rock will be affected mainly because the increase of volume strain will directly lead to the expansion or connection of pores in salt rock,and this phenomenon in a fault and at its two sides is particularly prominent,so the volumetric strain in the surrounding rock of the fault reservoir has a great evolution in the fault zone.?2?After analyzing the results of the pWIPP model and the Userc_d rheological damage model,the plastic zone and the influence range of seepage considering damage is larger than that of the pWIPP model in the surrounding rock,which is mainly caused by the damage to the permeability and porosity of the surrounding rock.?3?The effect of damage on mudstone interlayer and fault is much larger than that of salt rock.In the late stage of reservoir operation,the damage of mudstone interlayer is much larger than that of salt rock.From the results of our study we can see that the smaller pressure in the reservoir,the seepage influence scope of mudstone interlayer and fault at has been through the whole calculation model,the seepage influence scope of mudstone interlayer decreases with increasing reservoir pressure.Up to now,the fault factor is considered in the brittle rock researches,and for the creep of salt rock many researchers are more likely to avoid this sort of problem.In this paper,we use the FLAC^3D modeling technology to solve this problem,and then get two innovative points.?1?In the numerical simulation of the rock mass containing a fault,the traditional modeling method is to build a plane with zero thickness.In this paper,we use the FISH language to establish the fault with a certain thickness,which is more accurate to describe the stress state of the fault.?2?We will consider the damage into the seepage characteristics of salt rock,realizing the dynamic change process of porosity and damage based on the relationship between damage and permeability.