Core stress sensitivity measuring method

Abstract

The invention discloses a core stress sensitivity measuring method based on nuclear magnetic resonance. Core stress sensitivity is measured on the basis of conventional displacement experiments and nuclear magnetic resonance testing methods. The method includes the steps that core pretreatment is conducted; a core is subjected to pressurized saturation to simulate formation water; the core is placed in a non-magnetic core clamp to be fixed to an NMR coil; confining pressure is set to test the nuclear magnetic resonance T2 relaxation spectrum of the core; stress values are set for repeated testing at intervals; the highest static stress values are sequentially reduced from 20 MPa to 2.5 MPa, each stress value is kept for a certain period of time to test the T2 spectrum, and the current conventional permeability and NMR permeability are obtained through computation; a core conventional stress sensitivity curve is drawn. By means of the method, people can understand the core stress sensitivity change rule from the micro perspective, characteristics such as pore size distribution, porosity changes and NMR permeability in the experiment process are provided, and change rules of microfracture compact matrix limestone pore size distribution, porosity and permeability in stress sensitivity testing can be effectively detected.

Description

technical field [0001] The invention relates to a rock core stress measurement technology, in particular to a method for measuring rock core stress sensitivity based on nuclear magnetic resonance (NMR), which can be applied in the petroleum industry. Background technique [0002] The NMR signal mainly comes from the interaction between the hydrogen nuclei and the magnetic field. Limestone cores in a mineral water-saturated state contain a large number of H-1 nuclei. At this time, when the Lamor frequency is used to excite the cores in a magnetic field, a strong NMR signal can be observed. Relaxation is an extremely important physical quantity in hydrogen nuclear magnetic resonance. It characterizes the process of the magnetization vector from deviating from the equilibrium state to returning to the equilibrium state when it is excited by a radio frequency field to generate nuclear magnetic resonance. [0003] The H-1 nuclei in pores of different sizes have different contact...

AI Technical Summary

Problems solved by technology

Conventional testing methods and methods are difficult to obtain important reservoir rock seepage physical property parameters such as pore size distribution characteristics and movable fluid distribution in tight limestone reservoirs, and there is a lack of effective theoretical methods to deepen the understanding of multi-parameter coupling of pores, throats, and fractures. Reservoir petrophysical property changes and fluid distribution changes caused by the action

Therefore, it is extremely difficult to understand the flow characteristics and fluid distribution laws of tight limestone ultra-low permeability reservoirs through existing technologies

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