Research On Digital Core Construction And Pore Structure Characterization Of Rock From Tight Oil Reservoir

With the increase in the exploration and development of unconventional oil and gas resources,tight oil is widely concerned as one of the unconventional oil and gas resource types.The pore structure of tight oil reservoir rock is complex,and the pore scale is dominated by nanometer scale.Therefore,it is difficult to study the micro-pore structure of tight oil reservoirs by using conventional experimental techniques such as pressure mercury analysis.The digital core technology is a new reservoir rock pore structure characterization method,which can realize the precise characterization of micropore structure by constructing the digital core of the tight oil reservoir rock.This paper mainly carried out the research on the digital core construction and the analysis of the characteristics of microscopic pore structure of tight oil reservoir rock.Firstly,the method of constructing the digital core of dense rock based on CT scan and MCMC is studied.Based on the maximum ball algorithm and percolation theory,the pore infiltration parameters and micropore structure parameters of the digital core are calculated,and the corresponding results are compared with the results of pore permeability measurement and mercury injection.Then,the method of constructing three-phase digital cores based on multi-threshold algorithm for dense rock was studied.The multi-scale digital cores were constructed based on the three-phase digital core combined with the superposition algorithm.From the pore permeability parameters and microscopic pore structure parameters,The digital core features constructed by the two methods are compared and analyzed.Finally,based on the multi-scale digital core,the microstructure characteristics of the tight oil reservoir rock are characterized and analyzed.The main conclusions of this paper are:(1)Based on multi-threshold algorithm and superposition algorithm,a set of new methods for constructing digital core of tight oil reservoirs is esTab lished,which can reflect the multiscale pore structure of tight oil reservoir rocks.(2)Based on the multi-threshold algorithm,a digital core reflecting the tight oil reservoir rock was constructed.The comparison was made with experimental data from pore throat radius distribution,porosity,permeability and average pore and throat radius,which verified the rationality of the method.(3)Based on the esTab lished digital core of tight oil reservoir rocks,the pore structure of tight oil reservoir rocks was characterized and analyzed.It was found that the tight oil reservoir rocks are dominated by nano-and micro-pore spaces,and the small pores has an absolute advantage in quantity and volume,but its connectivity is poor,so it is the main storage space for oil reservoirs.The macropores are the main flow spaces for oil reservoirs which has a small number and volume.(4)By studying multi-threshold algorithms and applying them to digital cores,a method for constructing multi-scale digital cores of tight oil reservoir rocks was created,which can accurately reflect and characterize the pore structure of tight oil reservoirs at multiple scales.The defects of the traditional digital core construction method on the scale are made up.The results of the dissertation can analyze the pore structure of tight oil reservoirs more conveniently and quickly,providing a reference for the effective exploration of oil reservoirs in tight oil reservoirs.