Method of Calculating Clay Content Using Porosity Difference

Abstract

The present invention relates to the field of geological exploration and measurement, and is specifically a method for calculating clay content by using porosity difference, comprising the following steps: S1 collecting cores; S2 conducting porosity and X-diffraction whole-rock analysis on the cores respectively to determine the pores of the cores degree and clay content; S3 uses the comparison of core porosity and neutron and density curves to realize the depth homing of the core. The beneficial effects of the present invention are as follows: the present invention overcomes the problem that the accuracy of the clay mineral content calculation results is poor due to the difficulty in determining the clay neutron and density values ​​in the traditional clay content calculation method; at the same time, in the field oil field, neutron and density logging High popularity; therefore, the technical scheme of the present invention can be widely used in the calculation of the clay mineral content of the field reservoir. According to the analysis of the calculation results of the clay content of a large number of sandstone reservoirs in Xinjiang Oilfield, it is shown that the accuracy of the clay mineral content determined by the present invention is relatively high, and the relative error is less than 10%.

Description

technical field [0001] The invention relates to the field of geological exploration and measurement, in particular to a method for calculating clay content by using porosity difference. Background technique [0002] Technical solution of prior art one [0003] Calculation of clay content by neutron-density intersection method (Yong Shihe, Zhang Chaomo. Logging data processing and comprehensive interpretation. 2007) [0004] When having a freshwater sandstone scale neutron (Φ N ) and density porosity (Φ D ) value, the clay content of the rock can be determined using the neutron-density-porosity crossplot. The key to determining the clay content in this method is to clarify the three key points in the chart, which are skeleton points, clay points and water points. [0005] The skeleton minerals of glutenite are mainly quartz, followed by feldspar, and about 1% of heavy minerals. Feldspar is mainly orthoclase and microplagioclase with strong weathering resistance, and the ...

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Problems solved by technology

[0032] (1) The cost of natural gamma ray spectral logging is high and it is difficult to be widely used

[0033] (2) There are fine-grained sediments in the rocks, such as fine silt and stucco, whose particle size is comparable to that of clay minerals. These components will also adsorb a certain amount of radioactive minerals, making the final clay content larger

[0039] (2) When the shale content calculation is inaccurate, it will affect the accuracy of the clay content calculation

[0044] (1) Electrical imaging logging is expensive and difficult to be widely used

[0045] (2) The resistivity of fine-grained sediments such as fine silt and stucco is close to that of clay, and it is difficult to effectively distinguish them from clay, so the calculated clay content may be too large

[0046] Clay content is one of the basic characteristic parameters of reservoir rocks; the level of clay content can affect the development degree of the reservoir, the size of irreducible water saturation, fracturing process measures, etc.; the current method for calculating the content of clay minerals includes neutron-density Intersection method, combined neutron and density method, natural gamma ray spectrum logging calculation method, electrical imaging logging data calculation method; however, neutron-density intersection method, neutron and density combined Due to the influence of clay mineral types and content changes, it is difficult to determine the neutron and density values ​​of clay minerals, which affects the accuracy of the calculation results of the two methods. Its logging data is less, and its practicability is poor

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