Dense sandstone oil-gas storage layer crack recognition method

Abstract

The invention relates to a dense sandstone oil-gas storage layer crack recognition method. The recognition method comprises the steps that firstly, the comprehensive expression form of the relation among the reservoir base block depth induction conductivity, porosity and the mud content is established; secondly, the mud content, the porosity and the depth induction conductivity corresponding to various depth sampling points of a single-well to-be-recognized well section sandstone reservoir section are obtained, a data fitting method is adopted in the same sandstone reservoir section for determining undetermined parameters in the comprehensive expression form, and the base block depth induction conductivity corresponding to various depth sampling points in the sandstone reservoir section isdetermined; and thirdly, comparison is conducted on the well logging response feature value of a depth induction conductivity curve corresponding to various depth sampling points in the same sandstone reservoir section and the base block depth induction conductivity, and when the depth induction conductivity of one section is larger than the base block depth induction conductivity, the section isjudged as a crack development section. By means of the recognition method, the crack development layer section of the dense sandstone oil-gas storage layer can be accurately and reliably recognized.

Description

technical field [0001] The invention relates to a method for identifying reservoir fractures in tight sandstone oil and gas reservoirs, and belongs to the field of well logging technology for identifying reservoir fractures by using well logging data. Background technique [0002] Tight sandstone reservoirs are generally characterized by low porosity and low permeability, and fractures often play an important role in tight sandstone oil and gas reservoirs. Fractures can significantly improve the seepage capacity of reservoirs and promote the development of this type of oil and gas reservoirs with industrial value. scale, the current methods for identifying reservoir fractures mainly include drilling and coring, imaging logging, conventional logging, etc. Drilling and coring can directly observe the development of fractures, but due to factors such as cost, ordinary wells do not Coring, and stress release will also lead to the appearance of non-formation fractures in the core...

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Problems solved by technology

[0002] Tight sandstone reservoirs are generally characterized by low porosity and low permeability, and fractures often play an important role in tight sandstone oil and gas reservoirs. Fractures can significantly improve the seepage capacity of reservoirs and promote the development of this type of oil and gas reservoirs with industrial value. scale, the current methods for identifying reservoir fractures mainly include drilling and coring, imaging logging, conventional logging, etc. Drilling and coring can directly observe the development of fractures, but due to factors such as cost, ordinary wells do not Coring, and stress release will also lead to the appearance of non-formation fractures in the core; imaging logging is an important technical means to identify reservoir fractures in modern logging technology, but it is also limited by the cost of logging, there are only a few in a research area Only key wells will be measured; most of the wells in the study area have conventional logging data, but using conventional logging data to identify fractures in tight sandstone oil and gas layers has always been a difficult problem in logging evaluation technology

[0003] The existing method of conventional logging data to identify reservoir fractures in oil and gas reservoirs is realized by calibrating conventional logging data with limited drilling coring data and imaging logging data. There are mainly four methods for using conventional logging data to identify tight sandstone oil and gas. The method of hiding reservoir fractures: the first method is the double lateral resistivity difference method. When there are no fractures and no radial resistivity changes in the formation, the deep and shallow lateral resistivities should be coincident, and horizontal fractures can strengthen the lateral resistivity. The focusing effect of well logging reduces the measured resistance, and the focusing effect of horizontal fractures on the deep lateral resistivity is stronger than that of the shallow lateral resistivity, so that the deep lateral resistivity value is smaller than the shallow lateral resistivity, that is, Negative difference, the effective conductive section of the high-angle fracture remains unchanged in the radial direction, while the conductive section of the pore gradually increases in the radial direction, so within the shallow laterolog detection range, the ratio of the effective conductive section of the fracture to the pore It is much larger than the deep lateral log, so that the deep lateral resistivity value is greater than the shallow lateral resistivity value, which is a positive difference. It is often impossible to qualitatively identify effective fractures by using th...

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