Method for determining gas production rate of organic matrix in biochemical gas production stage

Abstract

The invention provides a method for determining a gas production rate of an organic matrix in a biochemical gas production stage, and belongs to the technical field of oil and gas resource evaluation. The method comprises the following specific steps: collecting four characterization parameters of a source rock in the biochemical gas production stage of one area, namely residual hydrocarbon amount of chloroform bitumen "A", vitrinite reflectance Ro reflecting the thermal evolution degree of the source rock, organic carbon content TOC and burial depth h; establishing a graph of relation of "A" / TOC and Ro or h according to the characterization parameters of the source rock; determining the exhaust threshold of a biogenic gas according to the graph, wherein the value at the threshold is "A"<0> / TOC<0>; calculating the restoration index of the hydrocarbon generation rate of the source rock according to "A" / TOC and "A"<0> / TOC<0> under different Ro or h conditions, and calculating the total hydrocarbon generation rate of the source rock under a variety of maturity conditions through the index and the "A"<0> / TOC<0>; calculating the gas production rate of the biogenic gas of the source rock according to the difference value of the total hydrocarbon generation rate and the residual hydrocarbon rate. By adopting the method, the problems of the original methods of calculating gas production rate, such as simulation experiment and the like are solved, and important technical support is provided for biogenic gas resource evaluation.

Description

Technical field [0001] The invention relates to the technical field of oil and gas resource evaluation, in particular to the calculation of the amount of biogas resources generated by the source rock in the biochemical gas generation stage during the low maturity period, using the chloroform bitumen "A" value in the source rock characterization parameters , Total organic carbon content TOC value, buried depth h value and Ro value, etc., based on the principle that the total hydrocarbon generation of source rocks is equal to the sum of the discharged hydrocarbons and the residual hydrocarbons to determine the biogas production of organic parent material in the biochemical gas generation stage A method of predominance. Background technique [0002] TISSOT proposes that among the four stages of source rock hydrocarbon generation, the biochemical gas generation stage is the initial stage of oil and gas generation. This stage is characterized by shallow stratum burial, generally no mo...

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Problems solved by technology

Although it is said that using experimental means to simulate the process of biogas generation in nature, and finally using the data of biogas simulation experiments to obtain the gas production rate, this method still has the following three shortcomings: (1) The simulation experiment cannot give The amount of biogas generated at different burial depths on the profile, but the biogas generated at different burial depths has different contribution values ​​to accumulation

(2) The simulation results of the same sample at different times and by different scholars are very different, indicating that the gas production is related to the experimental conditions (bacteria, fermentation conditions, culture medium), that is, the reliability of the data cannot be guaranteed

(3) The experimental conditions in the laboratory are very different from the actual geological conditions, and the contribution value of the biogas produced in the simulation experiment from geological organic matter cannot be guaranteed, and the objectivity of the results is not strong

Generally speaking, the disadvantages of this method of determining gas production rate are: due to the particularity of geological conditions, the simulated gas production rate of experimental samples under experimental conditions cannot objectively represent the gas production rate under actual conditions

[0012] At the same time, some theoretical calculation methods used by the predecessors have solved the objectivity of the simulation experiment to obtain the gas production rate to a certain extent, but these methods based on the material balance have their own great defects; among them The element balance method and the carbon isotope balance method only use the balance of individual elements such as C and H to represent the transformation balance of the entire organic matter, which is very one-sided; among them, the chemical kinetic method and other methods also use experimental data more or less The objectivity of the calculation results is affected; among them, the hydrocarbon generation potential method, the S 1 , S 2 Such data must be obtained through a large number of pyrolysis experiments, and it is difficult to obtain data. At the same time, this method is generally only applied to the calculation of hydrocarbon production rate in the stage of thermal degradation oil and gas generation or pyrolysis condensate gas generation stage. The calculation of the biogas production rate in the chemical gas generation stage is still an unknown field, and the S 2 The components in the uncertainty are very large, which will affect the obtained results

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