Light hydrocarbon content recovery method and device

Abstract

The present invention provides a method for recovering light hydrocarbon content, which comprises: taking a portion of the sample to be tested to measure the original free hydrocarbon content, and obtaining the original free hydrocarbon content of the sample to be tested; measuring the porosity and the free hydrocarbon content after rapid loss of the remaining sample to be tested, and obtaining the porosity parameter of the sample to be tested and the free hydrocarbon content after rapid loss; and fitting the recovery relationship based on the original free hydrocarbon content, the free hydrocarbon content after rapid loss, and the porosity parameter. The present invention establishes the relationship between the free hydrocarbon content after loss and the physical properties (porosity) of the sample and the original free hydrocarbon content by studying the light hydrocarbon loss process of a typical fresh core sample after placement, and based on the free hydrocarbon recovery correction relationship of the typical sample, it can realize the recovery and correction of the free hydrocarbon content of other core samples in the same region and the same layer.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas exploration and development, and in particular to a method and device for recovering light hydrocarbon content. Background Art

[0002] Free hydrocarbons are the most realistic movable oil components in the oil retained in mud shale. They are usually characterized by the pyrolysis S1 parameter (the hydrocarbon content released when the unit rock is heated to 300°C). They are mainly liquid light hydrocarbons and are very unstable and easy to volatilize and lose. Their content increases with the increase of thermal maturity of mud shale formations and varies with different types of organic matter. The free hydrocarbon components retained in mud shale will cause different degrees of loss during coring, room temperature placement, and especially during room temperature sample crushing. The higher the maturity of the mud shale, the greater the loss of hydrocarbons.

[0003] The current existing technologies are as follows:

[0004] 1) Zhu Rifang et al. processed and analyzed fresh samples under frozen and sealed conditions and compared the analysis and test data after 30 days of storage under normal conditions. They believed that when the evolution degree is in the mature evolution stage, the S1 light hydrocarbon loss rate is about 50% on average. In addition, they obtained the C14-component content by chromatographic analysis of crude oil produced in natural sections, and established a light hydrocarbon recovery method for the conventional sample chloroform asphalt "A". They believed that the light hydrocarbon loss when Ro is 0.9% is about 30%. However, for samples with different oil content and permeability, they did not point out the difference in light hydrocarbon loss rate and recovery method;

[0005] 2) Patent CN105223340 discloses a method for correcting chloroform asphalt "A" using group component data. The idea is similar to that of Zhu Rifang's literature, but there is a chromatographic effect in the migration process of crude oil, and the light hydrocarbon content in crude oil cannot fully represent the original light hydrocarbon content in the rock;

[0006] 3) Based on the method established by predecessors, Wang Juan used low-boiling point solvents to extract light hydrocarbons in a closed low-temperature manner to obtain the light hydrocarbon content of rock samples at different maturity stages, and established the light hydrocarbon recovery coefficient during the chloroform extraction process in the Dongying Sag. It is believed that the light hydrocarbon recovery coefficient is consistent with that obtained by the natural evolution profile method, but the light hydrocarbon loss during the sample placement process cannot be recovered and calculated by this method;

[0007] 4) Patent CN103543470 discloses a method of using hydrocarbon generation kinetics to simulate and calculate the ratio of light hydrocarbons (C6-13) to heavy hydrocarbons (C13+) of organic matter at different evolution stages. Based on the recovery of heavy hydrocarbons in S1, a light hydrocarbon correction method for residual hydrocarbons in the Damintun Depression was established. However, it is only applicable to closed systems where oil and gas migration has not occurred, and is not very applicable to common open shale oil systems with micro-migration of oil and gas.

[0008] 5) Patent CN109633778 discloses a method for establishing a light hydrocarbon recovery coefficient by comparing samples frozen under liquid nitrogen conditions with samples placed at room temperature. However, this method only recovers the amount of light hydrocarbons lost during the sample crushing process, but does not take into account the impact of the core placement time;

[0009] 6) JARVIE compared the S1 values ​​of samples after long-term storage and fresh samples from the wellbore core, and believed that the difference in free hydrocarbon content of samples after long-term storage can reach about 5 times. Chen et al. used the hydrogen index material balance method to calculate the light hydrocarbon loss ratio of type I kerogen at different evolutionary stages, and believed that after the source rock entered the oil generation window, before Ro reached 1.3%, the light hydrocarbon loss decreased with the increase of evolution degree, and after Ro reached 1.3%, the light hydrocarbon loss increased rapidly with the increase of evolution degree. Neither of them involved a specific recovery correction method;

[0010] Experimental studies have shown that the loss of light free hydrocarbons is a continuous process. With the different placement time of core samples, the free hydrocarbon content S1 measured in the laboratory varies greatly. The light hydrocarbon loss amount established based on the measured value after the sample is placed and the recovery result without considering the sample placement time cannot truly represent the original oil content information of the sample. The light hydrocarbon recovery correction needs to be based on fresh samples, but in the current low oil price environment, large-scale exploratory well deployment is very difficult. Therefore, the light hydrocarbon recovery correction method based on some fresh samples is an effective method.

[0011] Therefore, the present invention provides a method and device for recovering light hydrocarbon content. Summary of the invention

[0012] In order to solve the above problems, the present invention provides a method for recovering light hydrocarbon content, which comprises the following steps:

[0013] Taking a portion of the sample to be tested to measure the original free hydrocarbon content, to obtain the original free hydrocarbon content of the sample to be tested;

[0014] The remaining samples to be tested are measured for porosity and free hydrocarbon content after rapid loss to obtain porosity parameters and free hydrocarbon content after rapid loss of the samples to be tested;

[0015] A recovery relationship is obtained based on the original free hydrocarbon content, the free hydrocarbon content after rapid loss, and the porosity parameter fitting.

[0016] According to one embodiment of the present invention, the method further comprises:

[0017] For newly drilled cores, core samples with different lithology combinations and different oil abundances are selected as the samples to be tested;

[0018] The sample to be tested is frozen in liquid nitrogen and then sent to a laboratory for testing.

[0019] According to one embodiment of the present invention, the method further comprises:

[0020] Under the freezing state of liquid nitrogen, a portion of the sample to be tested is taken for closed crushing, and the crushed sample is subjected to rock pyrolysis analysis to obtain the original free hydrocarbon content of the sample to be tested.

[0021] According to one embodiment of the present invention, the method further comprises:

[0022] After the remaining samples to be tested return to normal temperature, the remaining samples to be tested are divided into two parts. The first part of the remaining samples to be tested is used for porosity determination, and the second part of the remaining samples to be tested is used for free hydrocarbon content determination after rapid dissipation.

[0023] According to one embodiment of the present invention, the method further comprises:

[0024] Under room temperature, the porosity of the remaining sample to be tested in the first part is measured by a helium method to obtain the porosity parameters of the sample to be tested.

[0025] According to one embodiment of the present invention, the method further comprises:

[0026] At each preset time interval, a portion of samples is taken from the second portion of samples to be tested and crushed in a closed state under liquid nitrogen freezing, and the crushed samples are subjected to pyrolysis analysis to obtain the current free hydrocarbon content. When the difference between the free hydrocarbon contents after two adjacent pyrolysis reactions is no greater than a preset threshold, the free hydrocarbon content after the last pyrolysis reaction is recorded as the free hydrocarbon content after the rapid loss.

[0027] According to one embodiment of the present invention, the method further comprises:

[0028] A scatter plot is drawn with the porosity parameter divided by the free hydrocarbon content after rapid dissipation as the horizontal axis and the original free hydrocarbon content divided by the free hydrocarbon content after rapid dissipation as the vertical axis;

[0029] Curve fitting is performed based on the scatter plot to obtain the recovery relationship.

[0030] According to one embodiment of the present invention, the restoration relationship is expressed by the following formula:

[0031]

[0032] Among them, S1 o represents the original free hydrocarbon content, S1 T represents the free hydrocarbon content after the rapid dissipation, a and b represent coefficients, and Φ represents the porosity parameter.

[0033] According to one embodiment of the present invention, the method further comprises:

[0034] Obtaining the free hydrocarbon content and porosity parameters of the core sample in the same layer as the area where the sample to be tested is located after rapid dissipation;

[0035] In combination with the recovery relationship, the original free hydrocarbon content of the core sample in the same layer as the area where the sample to be tested is located is calculated.

[0036] According to another aspect of the present invention, there is also provided a light hydrocarbon content recovery device, which recovers the original free hydrocarbon content by using the light hydrocarbon content recovery method as described in any one of the above items, and the device comprises:

[0037] An original free hydrocarbon content module, which is used to take a portion of the sample to be tested to measure the original free hydrocarbon content, and obtain the original free hydrocarbon content of the sample to be tested;

[0038] A fast-dissipating free hydrocarbon content module, which is used to measure the porosity of the remaining sample to be tested and the free hydrocarbon content after fast dissipation, and obtain the porosity parameters of the sample to be tested and the free hydrocarbon content after fast dissipation;

[0039] A recovery relation module is used to obtain a recovery relation based on the original free hydrocarbon content, the free hydrocarbon content after rapid loss and the porosity parameter fitting.

[0040] The light hydrocarbon content recovery method and device provided by the present invention establishes the relationship between the free hydrocarbon content after the loss and the physical properties (porosity) of the sample and the original free hydrocarbon content by studying the light hydrocarbon loss process of a typical fresh core sample after placement, and based on the free hydrocarbon recovery correction relationship of the typical sample, the free hydrocarbon content of other core samples in the same area and the same layer can be restored and corrected.

[0041] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0043] Figure 1 A flow chart of a method for recovering light hydrocarbon content according to an embodiment of the present invention is shown;

[0044] Figure 2 A fitting curve diagram of key parameters of a typical core of the third section of a well A in Qianjiang Sag according to an embodiment of the present invention is shown;

[0045] Figure 3 A curve diagram showing the original free hydrocarbon content recovery value and the current free hydrocarbon content value of the core of the third section of a certain well B in Qianjiang Sag according to an embodiment of the present invention;

[0046] Figure 4 A comparative curve diagram showing the results of recovering the original free hydrocarbon content of the core of the third section of a well B in Qianjiang Sag using different methods according to one embodiment of the present invention; and

[0047] Figure 5 A structural block diagram of a light hydrocarbon content recovery device according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0048] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0049] Figure 1 A flow chart of a method for recovering light hydrocarbon content according to an embodiment of the present invention is shown.

[0050] like Figure 1 In step S101, a portion of the sample to be tested is taken to measure the original free hydrocarbon content to obtain the original free hydrocarbon content of the sample to be tested.

[0051] Specifically, a portion of the sample to be tested is taken for closed crushing in a liquid nitrogen freezing state, and the crushed sample is subjected to rock pyrolysis analysis to obtain the original free hydrocarbon content of the sample to be tested.

[0052] In one embodiment, 5-10 grams of the sample to be tested is selected and crushed in a closed state under liquid nitrogen freezing. The crushed sample is promptly subjected to rock pyrolysis analysis to obtain the original free hydrocarbon content of the sample.

[0053] In one embodiment, the samples to be tested can be obtained by the following steps: first, for newly drilled cores, core samples with different lithology combinations and different oil abundances are selected as the samples to be tested. Then, the samples to be tested are frozen in liquid nitrogen and then sent to a laboratory for testing.

[0054] like Figure 1 In step S102, the porosity and the free hydrocarbon content after rapid loss of the remaining samples to be tested are measured to obtain the porosity parameters and the free hydrocarbon content after rapid loss of the samples to be tested.

[0055] Specifically, after the remaining samples to be tested return to room temperature, the remaining samples to be tested are divided into two parts, the first part of the remaining samples to be tested is used for porosity determination, and the second part of the remaining samples to be tested is used for free hydrocarbon content determination after rapid dissipation.

[0056] Furthermore, at room temperature, the porosity of the remaining samples to be tested in the first part is measured by a helium method to obtain the porosity parameters of the samples to be tested.

[0057] Furthermore, at each preset time interval, a portion of samples is taken from the second portion of samples to be tested and crushed in a closed state under liquid nitrogen freezing, and the crushed samples are subjected to pyrolysis analysis to obtain the current free hydrocarbon content; when the difference between the free hydrocarbon contents after two adjacent pyrolysis steps is no greater than a preset threshold, the free hydrocarbon content after the last pyrolysis is recorded as the free hydrocarbon content after the rapid loss.

[0058] In one embodiment, at intervals of one month, a portion of the samples are taken from the second portion of the samples to be tested at room temperature, and the samples are frozen, sealed, crushed, and then pyrolyzed to obtain the current free hydrocarbon content. The free hydrocarbon content is compared with the free hydrocarbon content result of the last pyrolysis. If the difference between the two test results is no more than 10%, it is determined that the rapid loss process is completed, and the free hydrocarbon content after the last pyrolysis is recorded, i.e., S1 T value.

[0059] like Figure 1 In step S103, a recovery relationship is obtained by fitting based on the original free hydrocarbon content, the free hydrocarbon content after rapid loss, and the porosity parameter.

[0060] Specifically, step S103 includes the following steps:

[0061] S1031. Draw a scatter plot with the porosity parameter divided by the free hydrocarbon content after rapid dissipation as the horizontal axis and the original free hydrocarbon content divided by the free hydrocarbon content after rapid dissipation as the vertical axis.

[0062] S1032. Perform curve fitting based on the scatter plot to obtain a recovery relationship.

[0063] Specifically, the recovery relationship is expressed by the following formula:

[0064]

[0065] Among them, S1 o Indicates the original free hydrocarbon content, S1 T It represents the free hydrocarbon content after rapid dissipation, a and b represent coefficients, and Ф represents the porosity parameter.

[0066] Specifically, during the fitting process, the values ​​of coefficient a and coefficient b are determined to obtain a recovery relationship.

[0067] In one embodiment, the method further comprises:

[0068] S104, obtaining the free hydrocarbon content and porosity parameters of the core sample in the same layer as the area where the sample to be tested is located after rapid dissipation.

[0069] S105. Based on the recovery relationship, the original free hydrocarbon content of the core sample in the same layer as the area where the sample to be tested is located is calculated.

[0070] In summary, in view of the shortcomings of the existing methods, the present invention studies the light hydrocarbon loss process of typical fresh core samples after placement, and establishes the relationship between the free hydrocarbon content after loss and the physical properties (porosity) of the sample and the original free hydrocarbon content. In addition, based on the free hydrocarbon recovery correction relationship of the typical sample, the free hydrocarbon content of other core samples in the same region and the same layer can be restored and corrected.

[0071] In one embodiment, a 10-meter core of the third section of Well A in Qianjiang Depression in Jianghan Basin is taken as an example, in which mainly developed lithologies such as laminated / layered argillaceous dolomite, dolomitic mudstone, argillaceous limestone, and glauberite mudstone.

[0072] According to the on-site core observation, 10 typical samples were selected as the modeling data source, and closed frozen crushed samples and porosity test experiments were carried out to obtain the original free hydrocarbon content S1 o , S1 after rapid dissipation T The values ​​and corresponding porosity Ф values ​​are shown in Table 1 and the fitting results are shown in Figure 2 .

[0073] Table 1 Test values ​​of key parameters of typical cores from the third section of Well A in Qianjiang Sag

[0074]

[0075]

[0076] Depend on Figure 2 The fitting results show that the a value is 1.2514 and the b value is 0.2157. After sorting, they are brought into the recovery equation to establish the following recovery equation:

[0077] S1 o =S1 T ×1.2514×e^(0.2157*(Ф / S1 T ))

[0078] Afterwards, the core samples of other wells in the same layer in the area were restored and calculated. The above formula was used to correct the original free hydrocarbons of 38 core samples of the third section of the Qianjiang Sag in the Jianghan Basin. These 35 samples were placed in the core library for a long time without taking any measures. The restoration results are shown in Table 2.

[0079] Table 2 Recovery results of free hydrocarbon S1 in the core of the third section of Well B in Qianjiang Sag

[0080]

[0081]

[0082] Recovery value and current measured S1 T Value comparison( Figure 3 ) shows that the recovered free hydrocarbon content (original free hydrocarbon content S1 o ) is generally different from the light hydrocarbon loss under different physical conditions, but there is a correlation overall, which also shows that maturity controls the fluidity and loss of hydrocarbon fluids. Ultimately, maturity controls the proportion of light hydrocarbons, which is the basis of light hydrocarbon volatilization loss.

[0083] Comparison of the two methods currently used in the industry to recover the samples from Well B ( Figure 4 ), the present invention is comparable to the two methods in the prior art, but the results are not consistent. Affected by the porosity and permeability conditions of the rock samples themselves, the calculation results of the present invention reflect the heterogeneity of the samples, and the results are more reasonable and objective.

[0084] Figure 5 The light hydrocarbon content recovery device 500 according to one embodiment of the present invention is shown as a structural block diagram. The original free hydrocarbon content is recovered by the light hydrocarbon content recovery method as described in any one of the above items. The light hydrocarbon content recovery device 500 comprises: an original free hydrocarbon content module 501, a fast-dissipated free hydrocarbon content module 502 and a recovery relation module 503.

[0085] The original free hydrocarbon content module 501 is used to take a portion of the sample to be tested to measure the original free hydrocarbon content, so as to obtain the original free hydrocarbon content of the sample to be tested.

[0086] The fast-dissipating free hydrocarbon content module 502 is used to measure the porosity of the remaining samples to be tested and the free hydrocarbon content after fast dissipation, and obtain the porosity parameters of the samples to be tested and the free hydrocarbon content after fast dissipation.

[0087] The recovery relation module 503 is used to obtain the recovery relation based on the original free hydrocarbon content, the free hydrocarbon content after rapid loss and the porosity parameter fitting.

[0088] In summary, the light hydrocarbon content recovery method and device provided by the present invention establishes the relationship between the free hydrocarbon content after loss and the physical properties (porosity) of the sample and the original free hydrocarbon content by studying the light hydrocarbon loss process of a typical fresh core sample after placement, and based on the free hydrocarbon recovery correction relationship of the typical sample, it is possible to realize the recovery and correction of the free hydrocarbon content of other core samples in the same area and the same layer.

[0089] It should be understood that the embodiments disclosed in the present invention are not limited to the specific structures, processing steps or materials disclosed herein, but should be extended to equivalent substitutions of these features understood by ordinary technicians in the relevant field. It should also be understood that the terms used herein are only used for the purpose of describing specific embodiments and are not meant to be limiting.

[0090] The "one embodiment" or "embodiment" mentioned in the specification means that the specific features, structures or characteristics described in conjunction with the embodiment are included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment" or "embodiment" appearing in various places throughout the specification do not necessarily refer to the same embodiment.

[0091] Although the embodiments disclosed in the present invention are as above, the contents described are only embodiments adopted for facilitating the understanding of the present invention and are not intended to limit the present invention. Any technician in the technical field to which the present invention belongs can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in the present invention, but the patent protection scope of the present invention shall still be subject to the scope defined in the attached claims.

Claims

1. A method for recovering light hydrocarbon content, characterized in that: The method comprises the following steps: Taking a portion of the sample to be tested to measure the original free hydrocarbon content, to obtain the original free hydrocarbon content of the sample to be tested; The remaining samples to be tested are measured for porosity and free hydrocarbon content after rapid loss to obtain porosity parameters and free hydrocarbon content after rapid loss of the samples to be tested; A recovery relationship is obtained by fitting based on the original free hydrocarbon content, the free hydrocarbon content after rapid loss, and the porosity parameter; The recovery relationship is expressed by the following formula: Among them, S1 o represents the original free hydrocarbon content, S1 T represents the free hydrocarbon content after the rapid dissipation, a and b represent coefficients, and Φ represents the porosity parameter.

2. The method for recovering light hydrocarbon content according to claim 1, characterized in that: The method further comprises: For newly drilled cores, core samples with different lithology combinations and different oil abundances are selected as the samples to be tested; The sample to be tested is frozen in liquid nitrogen and then sent to a laboratory for testing.

3. The method for recovering light hydrocarbon content according to claim 1, characterized in that: The method further comprises: Under the freezing state of liquid nitrogen, a portion of the sample to be tested is taken for closed crushing, and the crushed sample is subjected to rock pyrolysis analysis to obtain the original free hydrocarbon content of the sample to be tested.

4. The method for recovering light hydrocarbon content according to claim 1, characterized in that: The method further comprises: After the remaining samples to be tested return to normal temperature, the remaining samples to be tested are divided into two parts. The first part of the remaining samples to be tested is used for porosity determination, and the second part of the remaining samples to be tested is used for free hydrocarbon content determination after rapid dissipation.

5. The method for recovering light hydrocarbon content according to claim 4, characterized in that: The method further comprises: Under room temperature, the porosity of the remaining sample to be tested in the first part is measured by a helium method to obtain the porosity parameters of the sample to be tested.

6. The method for recovering light hydrocarbon content according to claim 4, characterized in that: The method further comprises: At each preset time interval, a portion of the samples from the remaining samples to be tested in the second part are taken for closed crushing in a liquid nitrogen freezing state, and the crushed samples are subjected to pyrolysis analysis to obtain the current free hydrocarbon content. When the difference between the free hydrocarbon contents after two adjacent pyrolysis reactions is no greater than a preset threshold, the free hydrocarbon content after the last pyrolysis reaction is recorded as the free hydrocarbon content after the rapid loss.

7. The method for recovering light hydrocarbon content according to claim 1, characterized in that: The method further comprises: A scatter plot is drawn with the porosity parameter divided by the free hydrocarbon content after rapid dissipation as the horizontal axis and the original free hydrocarbon content divided by the free hydrocarbon content after rapid dissipation as the vertical axis; Curve fitting is performed based on the scatter plot to obtain the recovery relationship.

8. The method for recovering light hydrocarbon content according to claim 1, characterized in that: The method further comprises: Obtaining the free hydrocarbon content and porosity parameters of the core sample in the same layer as the area where the sample to be tested is located after rapid dissipation; In combination with the recovery relationship, the original free hydrocarbon content of the core sample in the same layer as the area where the sample to be tested is located is calculated.

9. A light hydrocarbon content recovery device, characterized in that: The original free hydrocarbon content is recovered by the light hydrocarbon content recovery method according to any one of claims 1 to 8, wherein the device comprises: An original free hydrocarbon content module, which is used to take a portion of the sample to be tested to measure the original free hydrocarbon content, and obtain the original free hydrocarbon content of the sample to be tested; A fast-dissipating free hydrocarbon content module, which is used to measure the porosity of the remaining sample to be tested and the free hydrocarbon content after fast dissipation, and obtain the porosity parameters of the sample to be tested and the free hydrocarbon content after fast dissipation; A recovery relation module is used to obtain a recovery relation based on the original free hydrocarbon content, the free hydrocarbon content after rapid loss and the porosity parameter fitting.

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