Stratum organic carbon content calculation method and system

Abstract

The invention discloses a stratum organic carbon content calculation method and system. The method can comprise the steps that the relation between stratum lithology and electrical property is determined, and two pieces of lithology sensitive logging information are selected; normalization processing is conducted on the lithology sensitive logging information, and then lithology correction factors are calculated; superposition coefficients corresponding to different stratums are calculated, and correction deltaLogR is calculated according to the superposition coefficients and lithology correction factors; an organic carbon content calculation model isestablished according to the corrected deltaLogR; and the organic carbon content of the stratum is calculated according to the organic carbon content calculation model. According to the method, the lithology correction factor is established to correct the deltaLogR, the organic carbon content in the stratum is calculated, the calculation result is high in accuracy degree, high in operability and wide in application range, and reliable technical support is provided for comprehensive evaluation of the hydrocarbon source rock of the stratum.

Description

technical field [0001] The invention relates to the technical field of petroleum geophysical exploration, and more specifically, to a method and system for calculating the organic carbon content of formations. Background technique [0002] At present, the methods for calculating organic carbon content at home and abroad mainly include core measurement method, mathematical statistical analysis method and △LogR method, etc. The application of these methods in the field of calculating organic carbon content has been done a lot of research by predecessors. For example, the core measurement method is currently the most accurate method for measuring the organic carbon content of the formation, but it is difficult to continuously measure the organic carbon content of the formation vertically, and it cannot be applied in wells without coring. At the same time, the method is expensive and cannot be widely used. The △LogR method is within a certain range, the acoustic transit time dif...

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Problems solved by technology

For example, the core measurement method is currently the most accurate method for measuring the organic carbon content of the formation, but it is difficult to continuously measure the organic carbon content of the formation vertically, and it cannot be applied in wells without coring. At the same time, the method is expensive and cannot be widely used. The △LogR method is within a certain range, the acoustic transit time difference and the resistivity change in a certain proportion with the porosity, and the difference between the responses between the two is mainly the response of organic carbon, and the organic carbon content can be calculated accordingly, but this The premise of the method is that the source rock formations, including lithology, depositional environment, organic matter maturity and other geological backgrounds, are basically the same. Therefore, this method has obvious limitations in the evaluation of organic carbon content in complex lithology, tight lithology and other formations; The variable coefficient optimization is carried out on the basis of the traditional △LogR method. It is considered that when the superposition coefficient adopts a fixed value, the calculation model does not consider the change of the coefficient under different geological backgrounds. After using the variable coefficient, the selection of the coefficient is the coefficient transformation under different geological backgrounds. The selection of the coefficient is to select the coefficient with the smallest relative error in different formations to make the calculation result more accurate. However, this method only considers the influence of different geological backgrounds on the superposition coefficient, and does not consider the influence of geological background changes on other parameters. Moreover, the corresponding coefficients are selected in the minimum value of the relative error of the calculation results. Because there are many parameters that affect the calculation results, only the relative error is simply considered, and the influence of the selection of other parameters on the calculation results is not considered. The rationality of the selection of coefficients is questionable.

Optimizing on the basis of the traditional △LogR method, it is considered that the use range of the superposition coefficient in the △LogR technique is not applicable in the domestic research area, and the one-to-one mapping principle is used to map the acoustic time difference and resistivity parameters in the research area to △LogR applicable In the scope of the traditional △LogR method, the applicability of the traditional △LogR method is improved, and natural gamma is used for correction to increase the anti-interference ability of the model and make the calculation results more accurate. However, this method maps the formation information of the study area to the original calculation model Within the scope of application, the original logging information reflecting the formation changes, which cannot truly reflect the formation conditions

[0003] In the prior art, a method and device for determining the organic carbon content of source rocks based on well logging multi-parameters are disclosed, using natural gamma ray, acoustic time difference, resistivity, compensated neutron, natural gamma ray, The relationship between logging data such as density and organic carbon content is established, and more logging parameters are used to reflect the organic carbon content of the reservoir in the study area relatively well. However, this method has obvious regional characteristics. Due to the complexity of model parameters in different Different calculation models need to be re-established in different areas and formations; the correlation between some logging curves selected in this method and the organic carbon content of cores is low, which is not conducive to the accurate calculation of organic carbon content; in addition, this method does not consider complex lithology The impact of the important factor of medium lithology change on the logging response characteristics, so the organic carbon content in complex formations cannot be accurately calculated, and the applicability is low

[0004] The current calculation methods of organic carbon content mainly have the following problems: (1) For complex lithologic formations, various lithologic minerals have different compositions and contents, and the logging response characteristics are very different, which affects the calculation of organic carbon content using well logging data. (2) The existing technology is only based on the evaluation of organic carbon content in reservoirs with stable depositional environment and small lithology changes. For example, the commonly used mathematical analysis and modeling of core organic carbon content and logging data cannot effectively calculate rock organic carbon content in complex reservoirs

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