Method for constructing pseudo capillary pressure curves by using NMR (nuclear magnetic resonance) logging

Abstract

The invention discloses a method for constructing pseudo capillary pressure curves by using NMR (nuclear magnetic resonance) logging. The method comprises the steps as follows: according to NMR logging data measured actually and limited capillary pressure data, seven different relaxation time is set; NMR T2 spectra are divided into eight parts; the percentage content of porosity components of the eight parts is calculated; a transformation model between the mercury-injection saturability and the percentage content of the NMR porosity components under different mercury-injection pressures is built; according to the transformation model, the mercury-injection saturability under different mercury-injection pressures is calculated; according to the calculated mercury-injection saturability and the mercury-injection pressure corresponding to the mercury-injection saturability, the pseudo capillary pressure curves are constructed; and according to the pseudo capillary pressure curves, pore throat radius distribution is obtained, evaluation parameters of a pore structure of a reservoir stratum are calculated, and the purpose of constructing the pseudo capillary pressure curves by using NMR logging data accurately and carrying out continuous quantitative evaluation on the pore structure of the reservoir stratum is achieved.

Description

technical field [0001] The invention belongs to the field of reservoir evaluation, in particular to a method for constructing a pseudo-capillary pressure curve using nuclear magnetic resonance logging. Background technique [0002] As the country's demand for energy continues to increase, a large number of conventional reservoirs have been developed, and their production is decreasing day by day. Increasing the exploration and development of low-porosity, low-permeability-tight reservoirs has become an important way for the country to solve the shortage of oil and gas supply and ensure energy security. Low-porosity and low-permeability-tight reservoirs often have the characteristics of tight reservoirs, low resistivity contrast, complex pore structure, and strong heterogeneity, which lead to poor application of conventional reservoir evaluation methods and a large number of potential reservoirs. reservoirs are misjudged as water layers or non-reservoirs, and it is difficult...

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Problems solved by technology

However, in actual reservoir evaluation, these two intermediate parameters are difficult to obtain accurately, especially in tight reservoirs and complex lithology gas-bearing reservoirs, the porosity and permeability parameters are more difficult to obtain effectively, giving Using the above method to construct the pseudo-capillary pressure curve increases the difficulty

At the same time, the permeability parameter cannot be obtained from NMR T 2 The direct acquisition of the spectrum requires the use of special calculation methods. The introduction of these calculation processes will inevitably lead to human errors, and these errors will eventually be transmitted to the establishment of the pseudo-capillary pressure curve model, resulting in the use of existing methods. Pseudo-capillary pressure curves have large errors, which cannot achieve the purpose of accurately and quantitatively evaluating reservoir pore structure using nuclear magnetic resonance logging data

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