Method for calculating shale hydrocarbon discharge efficiency based on hydrocarbon potential method principle
Technical Field
The invention relates to the technical field of petroleum, in particular to a method for calculating shale hydrocarbon discharge efficiency based on a hydrocarbon potential method principle.
Background
Hydrocarbon source rock hydrocarbon discharge research is the weakest link in oil gas geochemistry research, and hydrocarbon discharge efficiency is a key parameter for accurately evaluating conventional oil gas and unconventional shale oil gas resources. In particular, in the case of shale, the higher the hydrocarbon discharge efficiency in the shale layer system, the less hydrocarbons remain in the shale, and therefore the magnitude of the hydrocarbon discharge efficiency in the shale layer system is necessarily linked to the magnitude of the amount of petroleum resources. Generally, hydrocarbon rejection efficiency may be defined as the ratio of the amount of hydrocarbons that have been produced and rejected to the original hydrocarbon production potential of the source rock. Based on this principle, the simplest and most common method for calculating shale hydrocarbon removal efficiency is material balance using pyrolysis parameters.
Rock pyrolysis refers to crushing Rock, heating the crushed Rock according to a program by using a Rock pyrolysis evaluator (Rock-Eval), and obtaining peaks at different temperatures in an analysis map. Wherein S1Refers to the hydrocarbon volatilized when the rock sample is heated to no more than 300 ℃, and is called the pyrolysis residual hydrocarbon amount (also called free hydrocarbon amount); s2The hydrocarbon amount generated by pyrolysis at the heating temperature of between 300 and 600 ℃ and the hydrocarbon amount generated by pyrolysis of cheese root is called residual hydrocarbon generation amount. The hydrocarbon source rock generates hydrocarbon potential index value (S) according to the principle of material conservation1+S2) the/TOC is theoretically kept constant all the time, and the hydrocarbon potential index will gradually decrease only when hydrocarbon discharge is started, wherein the corresponding condition is the hydrocarbon discharge threshold. The hydrocarbon source rock above the hydrocarbon expulsion threshold is in an immature stage, the hydrocarbon source rock has no hydrocarbon expulsion or hydrocarbon generation, and the pyrolysis hydrocarbon generation potential (S) is realized1+S2) Representing the original hydrocarbon-generating potential S0. When hydrocarbon discharge is started, hydrocarbons S which are generated in the hydrocarbon source rock but are not discharged are generated1Also, there is kerogen hydrocarbon-generating potential S that has not been hydrocarbon-generating2Thus the amount of discharged hydrocarbons is PE=S0-S1-S2. Thus the hydrocarbon removal efficiency P ═ PE/S0×100%=(S0-S1-S2)/S0×100%。
The above method is currently used for S0Is obtained by carrying out pyrolysis experiment on a large number of immature samples and selecting the largest S1+S2Value as originalInitial hydrocarbon potential value S0This value, although correlated with TOC and the degree of thermal evolution, is also affected by lithology and hydrocarbon conversion (different catalysis of different minerals). For example, mud shale deposited in a salt lake environment starts to generate and discharge hydrocarbons under the condition of low thermal evolution temperature. Thus directly using S1+S2The value represents that the original hydrocarbon generation potential is influenced by the sampling environment and the properties of the sample, and the original hydrocarbon generation potential of all samples is difficult to reflect, so that the calculated hydrocarbon discharging efficiency has larger error.
Disclosure of Invention
The invention aims to provide a method for calculating shale hydrocarbon-discharging efficiency based on a hydrocarbon-generating potential method principle, aiming at the problem that the existing hydrocarbon-discharging efficiency calculation method has large calculation errors.
The invention provides a method for calculating shale hydrocarbon-discharging efficiency based on a hydrocarbon-generating potential principle, and provides a unit original hydrocarbon-generating potential (S)0/TOC0) The value of (1) is not only related to the original hydrocarbon generation potential S0Related to the attribute TOC of the sample itself0Are directly related. And human errors caused by sampling can be effectively reduced by utilizing the ratio. Using the unit hydrocarbon potential of each sample ((S)1+S2) TOC)) is involved in the calculation of shale hydrocarbon removal efficiency, the results obtained are necessarily the most realistic. At this time, the formula for the hydrocarbon potential method to find the hydrocarbon discharging efficiency of the shale can be changed to: hydrocarbon discharge efficiency P ═ S0/TOC0-(S1+S2)/TOC]/(S0/TOC0)。
Wherein P represents the magnitude of hydrocarbon discharge efficiency; s0Refers to the maximum S obtained by carrying out pyrolysis experiments on a large number of immature samples1+S2A value; TOC0Means maximum S of immature sample1+S2The TOC value corresponding to the value; s1The target sample is subjected to pyrolysis to obtain hydrocarbon volatilized below 300 ℃; s2Refers to the amount of hydrocarbon generated by pyrolysis of a target sample at 300-600 ℃; TOC refers to the total organic carbon content obtained by pyrolysis of a target sample.
Based on the calculation thought, the shale hydrocarbon discharging efficiency calculation method comprises the following steps:
(1) taking a plurality of shale samples, crushing the shale samples, then carrying out heating pyrolysis on the shale samples by adopting a Rock pyrolysis instrument Rock-Eval to obtain an analysis map, and obtaining S of each sample from the analysis map1、S2And Tmax. S1The hydrocarbon volatilized when the heating temperature of the shale sample is not more than 300 ℃ is called as the pyrolysis residual hydrocarbon amount; s2The hydrocarbon amount generated by pyrolysis at the heating temperature of between 300 and 600 ℃ and the hydrocarbon amount generated by pyrolysis of cheese root is called residual hydrocarbon amount; tmax refers to the temperature corresponding to the maximum amount of kerogen pyrolysis hydrocarbon at a heating temperature of between 300 ℃ and 600 ℃. The number of shale samples is more than or equal to 20, and if the number of immature samples is less than or equal to 5, the number of shale samples needs to be further increased.
(2) Will Tmax<The 435 ℃ sample was defined as an immature sample, and all immature samples were statistically analyzed for S1+S2Value, select the maximum S1+S2Value, defined as S0。
(3) Measuring the maximum S in the step (2) by using a carbon-sulfur analyzer1+S2Value-corresponding Total Organic Carbon (TOC) of shale sample0The content of (a). The specific determination method comprises the following steps: firstly, treating a shale sample with hydrochloric acid to remove inorganic carbon, then sending the shale sample into a carbon-sulfur analyzer, controlling combustion by using a computer, and measuring the content of carbon dioxide by using an infrared detector to obtain the content of total organic carbon.
(4) Determining the total organic carbon TOC content of a certain target shale sample according to the testing method in the step (3); s of the shale sample1、S2And substituting the TOC value into the following formula to calculate the hydrocarbon discharge efficiency P of the shale sample:
compared with the prior art, the invention has the advantages that:
the method for calculating the hydrocarbon discharging efficiency of the invention provides a unit original hydrocarbon generation potential (S)0/TOC0) The value is directly related to the TOCRelated to this value not only the original hydrocarbon-forming potential S0Related to the properties of the sample itself (TOC)0) The direct correlation can effectively reduce the human error caused by sampling by utilizing the ratio, and the obtained result is more real and credible. The method avoids the error of the single sample attribute on the shale hydrocarbon discharging efficiency calculation, and the real conditions of all samples can be considered in the calculation process, so that the method is a reliable method for calculating the shale hydrocarbon discharging efficiency in the future. For shale layer series, the higher the hydrocarbon removal efficiency, the less hydrocarbons remaining inside the shale, and the more hydrocarbons in the adjacent rock types of the shale. Therefore, the hydrocarbon discharge efficiency is related to the amount of petroleum resources, and can be used for guiding the exploration and development of petroleum.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.
Drawings
FIG. 1 is a graph of the calculated efficiency of the novel process of the present invention.
Fig. 2 is a graph of the hydrocarbon discharge efficiency calculated by the prior art method.
Detailed Description
The preferred embodiments of the present invention will be described in conjunction with the accompanying drawings, and it will be understood that they are described herein for the purpose of illustration and explanation and not limitation.
The method for calculating the shale hydrocarbon discharging efficiency based on the hydrocarbon potential method principle comprises the following specific operation steps:
(1) the shale sample is heated by a Rock-Eval (Rock-Eval), and peaks at different temperatures can be obtained in an analysis map. Wherein S1Refers to the hydrocarbon volatilized when the rock sample is heated to no more than 300 ℃, and is called the pyrolysis residual hydrocarbon amount (also called free hydrocarbon amount); s2The hydrocarbon amount generated by pyrolysis at the heating temperature of between 300 and 600 ℃ and the hydrocarbon amount generated by pyrolysis of cheese root is called residual hydrocarbon amount; tmax refers to the temperature corresponding to the maximum amount of kerogen pyrolysis hydrocarbons when heated between 300 ℃ and 600 ℃.
By aligning a large number ofCarrying out pyrolysis experiment on the crushed shale samples to obtain S of each sample1、S2And Tmax, Tmax obtained by pyrolysis<The 435 ℃ sample was defined as the immature sample. S of immature sample1+S2Counting the values to select the maximum S1+S2It is defined as S0。
(2) And (4) measuring the content of the total organic carbon of the crushed shale sample by using a carbon-sulfur analyzer. The operation steps are as follows: the sample is treated with hydrochloric acid to remove inorganic carbon, then the sample is sent to an instrument, the combustion is controlled by a computer, the content of carbon dioxide is measured by an infrared detector, and the content of organic carbon is printed out according to the program. Measurement of maximum S in immature samples according to this method1+S2Total organic carbon TOC of corresponding samples0。
(3) Removal of TOC0Determining the total organic carbon TOC of a shale sample needing to calculate the hydrocarbon discharge efficiency besides the corresponding shale sample, and determining the S of the shale sample1、S2And substituting the TOC value into the following formula to calculate the hydrocarbon discharge efficiency P of the shale sample:
a plot of the hydrocarbon removal efficiency of a sample of shale in an area calculated according to the method of the present invention is shown in fig. 1. Additionally, a graph of the calculated hydrocarbon removal efficiency for the same shale sample using the prior art method is shown in fig. 2. The existing old method is as follows: calculating the hydrocarbon discharging efficiency by a material balance method of pyrolysis parameters, and using a formula P ═ PE/S0×100%=(S0-S1-S2)/S0X 100% calculating the hydrocarbon expulsion efficiency P.
It can be seen that Tmax in fig. 2 is at 450 ℃ (at mature stage), the hydrocarbon discharging efficiency is as high as 90%, mutation occurs, and the hydrocarbon discharging efficiency is basically unchanged and approaches to 100% with the increase of evolution degree, obviously, the phenomenon is not consistent with the normal evolution rule. The normal rule is that as maturity increases, the value of hydrocarbon removal efficiency increases. However, in fig. 1, the variation trend more conforms to the normal evolution law, the hydrocarbon discharge efficiency is close to 90% when Tmax is 465 ℃, and the hydrocarbon discharge efficiency gradually increases along with the increase of the evolution degree, so that the method more conforms to the actual geological condition.
Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.