Aging Properties Of Anhydrite Surrounding Rock And Long-term Stability Of Deep Anhydrite Crude Oil Storage Cavern

The anhydrite mine-out with good stability and tightness is a kind of available underground space resource and could be reused as underground crude oil storage space which could enrich the underground crude oil storage space with high safety,low investment and short construction period.And the reuse of anhydrite mine-out solves the recycling problem of underground anhydrite mine-out.However,in the field,there is no mature theoretical and engineering practice for reference,and there are still many scientific problems which must be solved.This paper chooses an anhydrite mine located in Anhui,North China as the engineering case,studies the stability and tightness of mine-out,and discusses the feasibility of anhydrite mine-out as underground crude oil storage space.The main research content and achievement could be listed as follows:(1)The physical test of anhydrite rock was carried out,and its mineral composition,mesostructured,pore characteristics and apparent density were analyzed.Based on the strength parameters of anhydrite rock,the parameters of Hoek-Brown and MohrCoulomb failure criteria were calculated.Combined with field investigation,the mechanical parameters of the anhydrite rock mass were obtained.(2)Based on the Brazilian disc splitting test,the tensile and compressive stressstrain curves of anhydrite rock were obtained,and the tensile mechanical properties of anhydrite rock are studied,including tensile Young's modulus and Poisson's ratio.Moreover,the elastoplastic constitutive model considering the difference of tensile and compressive properties of anhydrite rock is defined.Based on the element safety factor method(ESFM),this paper also quantitatively studys the stability of anhydrite mineout for construction period.(3)The uniaxial compression creep test of anhydrite rock was developed,and the particle swarm optimization algorithm(PSO)was introduced to calculate the parameters of the Burgers creep model of anhydrite rock.Moreover,the long-term deformation and loss of effective underground storage volume of mine-out under the natural conditions and crude oil storage conditions was studied.The long-term stability of mine-out as underground crude oil storage space was discussed.(4)The long-term interaction tests of anhydrite rock and water,crude oil with a certain pressure were finished.The internal pressure in test device was maintained at a level of 4~5MPa.And the physical and mechanical parameters variation of anhydrite rock samples,which were immersed in water and crude oil for 69 days,136 days,271 days,451 days and 549 days respectively,was tested.The mechanism of interaction between anhydrite rock and water,crude oil was revealed.And the influence of water and crude oil on the physical and mechanical properties of anhydrite rock and the effect of anhydrite rock on the quality of crude oil are evaluated.Moreover,the on-site drilling high pressure water injection tests,water storage and oil storage tests were carried out to evaluate the permeability of the anhydrite rock mass and the tightness of its mineout under the condition of long-term interaction between anhydrite and water,crude oil.(5)Based on above research work,including field investigation,laboratory test and numerical calculation,the feasibility of the anhydrite mine-out as an underground crude oil storage space is discussed,which also provides theoretical basis and technical supportf for the construction of underground anhydritre crude oil storage cavern.Furthermore,some challenges on the resue of anhydrite mini-out as underground crude oil space are also discussed.