Evaluation method of shale organic matter porosity

Abstract

The invention relates to an evaluation method of shale organic matter porosity. The method is characterized by the following steps: 1) organic carbon content and total pore volume or total porosity of shale samples under homologous organic matter type and same organic matter thermal evolution degree in an area to be measured are measured; 2) relation between the organic carbon content and total pore volume or total porosity is established; 3) a plane-coordinate system with the organic carbon content being the horizontal axis and with the total pore volume or total porosity being the vertical axis is established; 4) data of the organic carbon content and total pore volume or total porosity of the shale samples are introduced into the plane-coordinate system, a straight line is fitted out, and slope and vertical intercept of the straight line are calculated; and 5) organic matter pore volume or organic matter porosity of the shale samples in the area to be measured is calculated, and organic matter porosity of shale is further evaluated so as to finish reservoir capacity evaluation of shale reservoir stratum of the area to be measured. The method of the invention is easy to operate, and is practical and low-cost.

Description

technical field [0001] The invention relates to a method for evaluating the porosity of organic matter in mud shale, belonging to the field of geological exploration. Background technique [0002] Shale gas is a natural gas resource that can be exploited in muddy shale formations. Shale gas is a typical unconventional natural gas, which is produced in low porosity and permeability reservoir rock series dominated by organic-rich shale. There are significant differences in the controlling factors for the enrichment and accumulation of shale gas and conventional gas. Shale gas accumulation mainly includes self-generation and self-storage, early accumulation time, no obvious traps, low porosity and low permeability of reservoirs, and various gas occurrence states and shale gas reservoirs are easier to preserve. The researchers found that the organic matter in shale will produce a large number of pores during the thermal evolution process. These pores are important storage spac...

AI Technical Summary

Problems solved by technology

Because the organic matter is difficult to be extracted relatively completely, and the method for directly quantitatively measuring the organic matter pore volume and porosity of mud shale is not yet mature, it is impossible to obtain the organic matter pore volume and porosity of mud shale more accurately.

There are three main methods for evaluating the porosity of organic matter in mud shale: the first is the method of argon ion polishing combined with scanning electron microscopy, which semi-quantitatively analyzes the size and porosity of organic matter in mud shale through human observation. The main disadvantage is human influence. The second method is to calculate the porosity of mud shale by computerized tomography technology, and obtain the volume of organic matter and organic pore volume by tomography to calculate the organic matter porosity and organic matter porosity of mud shale. This method can theoretically accurately measure the organic matter porosity of shale, but the tomographic scanning technology is still immature, it is difficult to identify organic pores and inorganic pores, and the cost of tomographic scanning testing is high. The third is to use scanning electron microscopy or field emission electron gun scanning electron microscopy technology, and use the area counting method to obtain the surface porosity of the total organic pores, and then calculate the organic matter porosity and shale organic matter porosity. When using this method, the computer cannot accurately identify Organic pores and inorganic pores, but the counting of the area of ​​organic pores is greatly affected by human factors, and the calculation is inaccurate and time-consuming.

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