| According to the forecast analysis, the supply and demand gap of petroleum and natural gas will respectively come to200million tons and50billion cubic meters by2015in our country. China has become the world's second largest oil consumer, is currently the world's second largest oil importer. As soon as possible of underground oil and gas reserves, have great significance for the protection of oil and gas resources in the security and stability of supply to protect the national economy sustainable and stable development. Strategic reserves of oil related to the energy security of the country's natural gas safety gas supply is not only related to energy supply security, but also related to the daily lives of thousands of families. Strategic oil and gas reserves are imperative.Distribution and our salt deposits a layer thickness of thin (60to100m), the weak interlayer geological characteristics, the presence of dissection of rock salt deposits of oil and gas reservoir construction difficulty and complexity of some increase, while the mezzanine oil and gas storage the construction process and operation of stability has a great influence. Construction built chamber in the layered rock salt to the water-soluble oil and gas storage as the background, through experimental research, theoretical analysis, numerical simulation methods, the insoluble mezzanine mechanical properties under different temperature and concentration of salt solution soak role in-depth study on the basis of simulation sandwich initial fracture step, fluid similar simulation experiment and numerical simulation, through a series of experimental studies and simulation, process model to build the cavity and near the actual basically the same mezzanine and the analog solver.The main research contents and results are as follows:(1) Repeatedly add the uninstall under the plaster dry specimen strength under monotonic loading conditions of14.6MPa to12.3MPa, a decline of15.8%; peak intensity corresponding to the axial strain from0.39%to0.19%, a decline of up to51%. Repeatedly added to uninstall make the plaster strength and deformation were decreased, but the elastic modulus is essentially the same.(2) It is demonstrated that the strength of gypsum rock is weakened to different extents with brine temperature and concentration increasing and soaking time lasting. The strength softening coefficient can be as low as0.10after being soaked in hot and concentrated brine for60d. The elastic modulus of the gypsum rock is also linearly decreased with the temperature and concentration of brine increasing. The elastic modulus of gypsum rock is5.92GPa after being soaked in half saturated brine of40℃for60days, however it suddenly decreases to0.21GPa when being soaked in saturated brine of70℃for the same time. Similarly, the tensile strength also decreases from0.64—0.66MPa soaked in brine of40℃to0.27—0.47MPa of70℃. After being soaked in saturated brine of70℃for60d, a regressed equation for Mohr-Coulomb shear strength of the gypsum rock is obtained as τ=0.4+σ·tan38.9°. Two similar strength equations are also regressed as τ=1.24+σ·tan41.3°, τ=0.65+σ·tan39.3°when the soaked time is30d and80d respectively. It demonstrates that both the cohesion and inner friction coefficient of gypsum rock decrease with soaking time lasting.(3) In order to further accurately distinguish between gypsum rock under different conditions, failure modes and their differences, the reference to judge the basis for rock burst, the definition of a rock brittleness index-destruction of stiffness, similar to the uniaxial compression stress-strain curve peaks after the destruction of the segment slope. Calculated based on the measured results in dry,40°C half-saturation to70°C saturated solution of several conditions, the destruction of the gypsum rock stiffness for704.4.690.1,218.9.255.2,19.5GPa. The corresponding failure mode from brittle to brittle-ductile ductility transition.(4) In salt mining or reservoir construction process, due to a long soak in a certain temperature, salt solution, role, mezzanine volume expansion occurs, increase the quality weaken the strength of the multiple physical and chemical effects, mezzanine damage breaking down not on the cavityits column security threat. In the process of operation of the reservoir, mezzanine limited the scope of the physical structure changes in the stability of the surrounding geological conditions, not the oil and gas leak, you can ensure that the tight security of the oil and gas storage.(5) By the mechanical properties of different salt solutions soaked plaster sandwich and built chamber process, the establishment of the fracture mathematical model and a numerical calculation by FLAC3D software, which does not soak situation2.0m thick gypsum laminated fracture step is about2.6m, 70°C saturated salt solution soak step60d gypsum laminated fracture is reduced to0.5m.(6) Rock salt cavern-based experimental physical simulation results, the establishment of a fluid flow model for the numerical simulation model, numerical simulation results by analyzing the different pipeline location and mezzanine opening diameter of13models obtained hole diameter of0.5(actual10)m case, the pipes are located in the mezzanine of reverse circulation and piping are located in the mezzanine on the positive cycle of the parietal near the disturbance maximum; hole diameter of1.0(actual20) m the case, the pipes are located on the mezzanine of reverse circulationlaminated top and bottom surfaces and disturbance of the parietal near the peak; reverse circulation hole diameter of1.5(actual30) m, the pipes are located in the mezzanine laminated top and bottom surfaces and the parietal near the disturbance.(7) Containing gypsum laminated rock salt cavern construction process can be divided into four stages, first stage, from the body cavity surface interlayer distance of3-5m to the mezzanine to the initial fracture and secondary fracture, at this stage in order to avoid the sandwich fracture of the pipeline,will mention the pipeline to the mezzanine above the built chamber; sandwich the middle of the second stage of hole diameter from10m to15m, the central tube and intermediate tube are located under the mezzanine cycle is built chamber; sandwich the middle of the third stage of the hole diameter by15mincreased to25m, the central tube and the middle tube in the reverse circulation on the mezzanine was built cavity; sandwich the middle of the third stage of the hole diameter increased to25m above the central tube and intermediate tube are located in the mezzanine reverse circulation built chamber.(8) A salt mine geological data is consistent with field numerical simulation model of the analog mezzanine initial fracture and secondary fracture time and the shape of the cavity, the initial rupture time for the first12d, the fracture length is2.6m, sandwich the middle to openhole diameter of5.8m; the second break time for the first22d, breaking length2.5m mezzanine middle hole diameter of10.8m, thus avoiding the laminated fracture caused by the pipeline may squeeze and damage.
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