Stratum volume density calculation method and system and stratum volume density calculation model

Abstract

The invention provides a formation volume density calculation method and system and a formation volume density calculation model.The formation volume density calculation method comprises the steps that a rock core sample is processed, and a dry rock core is obtained; measuring the dry rock core to obtain the volume density and porosity of the dry rock core and the density of fluid in pores; and substituting the obtained volume density, the porosity and the density of the fluid in the pores of the dry rock core into a preset stratum volume density calculation model to obtain the stratum rock volume density. According to the method, a stratum volume density calculation model is obtained through the volume density, the porosity and the density of the fluid in the pores of the dry rock core, so that if the stratum volume density needs to be obtained, experimental data obtained by the sample rock core is only required to be substituted into the stratum volume density calculation model without huge well logging work of engineering. A large amount of experimental data shows that the accuracy of the stratum volume density obtained by the method is high.

Description

Technical Field

[0001] The invention belongs to the technical field of petroleum exploration, and in particular relates to a formation volume density calculation method and system and a formation volume density calculation model. Background Art

[0002] Density logging is a logging method that studies rock properties and porosity by measuring the volume density of downhole rocks. In the 1950s, density logging was used in production. In the late 1960s, dual-source density logging close to the wellbore wall appeared. After the 1970s, lithology density logging was developed based on density logging. Summary of the invention

[0003] In order to enrich the methods for obtaining formation volume density, the present invention proposes a method for calculating formation volume density, in the hope that accurate formation volume density can be obtained without measuring the formation density through well logging.

[0004] The local layer volume density calculation method specifically includes the following steps:

[0005] Processing the core sample to obtain a dry core;

[0006] Obtaining the bulk density, porosity and density of the fluid in the pores of the dry core according to preset rules;

[0007] The obtained volume density, porosity, and density of the fluid in the pores of the dry core are substituted into a preset formation volume density calculation model to obtain the formation rock volume density. The preset formation volume density calculation model is:

[0008]

[0009] Among them, ρ b地层 is the bulk density of the formation rock, ρ b岩心 is the bulk density of the dry core, is the porosity of the dry core, ρ f is the density of the fluid in the pores.

[0010] Furthermore, the core sample is processed to obtain a dry core, comprising:

[0011] The core sample is made into a plunger shape and then placed in an oven for drying to obtain a dry core.

[0012] Further, the bulk density of the dry core is obtained, including:

[0013] The mass and volume of the dry core are obtained, and the bulk density of the dry core is calculated.

[0014] Further, obtaining the mass and volume of the dry core and calculating the volume density of the dry core includes:

[0015] Weigh the mass of the dry core;

[0016] Measure the length and diameter of the dry core and calculate the volume of the dry core;

[0017] The bulk density of the dry core is calculated using the mass and volume:

[0018] ρ b岩心 =m / v

[0019] Among them, ρ b岩心 is the bulk density of the dry core, m is the mass of the dry core, and v is the volume of the dry core.

[0020] Further, obtaining the porosity of the dried core includes:

[0021] The porosity of the dry core is measured using a porosity measuring instrument.

[0022] Further, the step of obtaining the density of the fluid in the pores of the dried core comprises:

[0023] The existing mud filtrate density is obtained as the density of the pore fluid in the dry core.

[0024] On the other hand, the present invention also discloses a formation volume density calculation system, comprising a core sample processing device, a parameter acquisition device, and a calculation device, wherein:

[0025] The core sample processing device is used to process the core sample to obtain a dry core;

[0026] The parameter acquisition device is used to obtain the volume density, porosity and density of the fluid in the pores of the dry core according to a preset rule;

[0027] The calculation device is used to substitute the obtained volume density, porosity, and density of the fluid in the pores of the dry core into a preset formation volume density calculation model to obtain the formation rock volume density. The preset formation volume density calculation model is:

[0028]

[0029] Among them, ρ b地层 is the bulk density of the formation rock, ρ b岩心 is the bulk density of the dry core, is the porosity of the dry core, ρ f is the density of the fluid in the pores.

[0030] Furthermore, the core sample processing device at least includes an oven, and the oven is used to process the core sample to obtain a dry core.

[0031] Furthermore, the parameter acquisition device at least includes a mass measurement device, a size measurement device, and a porosity measurement instrument, wherein:

[0032] The mass measuring device is used to obtain the mass of the dry core;

[0033] The size measuring device is used to obtain the length and diameter of the dry core;

[0034] The porosity measuring instrument is used to obtain the porosity of a dry core.

[0035] In a third aspect, the present invention further discloses a formation volume density calculation model, wherein the formation volume density calculation model is:

[0036]

[0037] Among them, ρ b地层 is the bulk density of the formation rock, ρ b岩心 is the bulk density of the dry core, is the porosity of the dry core, ρ f is the density of the fluid in the pores.

[0038] Based on the above technical solution, the beneficial effects of the present invention compared with the prior art are as follows:

[0039] The present invention discloses a method for calculating the volume density of a formation, which comprises processing a core sample to obtain a dry core; measuring the dry core to obtain the volume density, porosity and density of the fluid in the pores of the dry core; substituting the obtained volume density, porosity and density of the fluid in the pores of the dry core into a preset formation volume density calculation model to obtain the volume density of the formation rock. The applicant has found through a large number of experimental studies that the volume density of the formation is related to the volume density of the fluid in the bottom pores, the volume density of the rock skeleton, etc., and thus established a model for calculating the volume density of the formation by using the volume density, porosity and density of the fluid in the pores of the dry core. Therefore, if the volume density of the formation is to be obtained, it is not necessary to go through the extensive logging work, and it is only necessary to substitute the experimental data obtained from the sample core into the formation volume density calculation model. A large amount of experimental data shows that the formation volume density obtained by the present invention has high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0041] Figure 1 This is a schematic flow chart of a method for calculating formation volume density in Embodiment 1 of the present invention;

[0042] Figure 2 This is a schematic diagram of obtaining the formation volume density and the volume density measured by well logging of the formation rock density of the well in the first embodiment of the present invention using the core experimental data of a well;

[0043] Figure 3 This is a schematic diagram of the relationship between the formation volume density obtained from core experimental data of a certain well and the volume density value of the reservoir density logging of the well in the first embodiment of the present invention;

[0044] Figure 4 This is a schematic diagram of the structure of a formation volume density calculation system in Embodiment 2 of the present invention. DETAILED DESCRIPTION

[0045] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0046] Embodiment 1

[0047] Bulk density refers to the total density of rock per unit volume. When the rock has pores, the volume density includes the volume density of the fluid in the pores and the volume density of the rock skeleton. Therefore, the volume density of the rock measured by the density logging instrument is the volume density of the rock filled with fluid in the pores. The applicant found that the pores of the dried core do not contain fluid. The volume density of the core skeleton can be obtained by experimental measurement of the dry core. In addition, during the operation of the well site density logging, the fluid in the formation rock within its detection range is the mud filtrate, that is, the density of the fluid in the pores is the density of the mud filtrate, and the density of the fluid in the pores can be determined based on the density of the mud filtrate. In this way, the volume density of the formation rock can be calculated using the core data.

[0048] Based on the above findings, the applicant disclosed a method for calculating the volume density of a formation, such as Figure 1 As shown, the specific steps include:

[0049] S110, processing the core sample to obtain a dry core.

[0050] In order to facilitate the calculation of the volume of the core sample, the core sample is preferably made into a plunger shape and then placed in an oven for drying to obtain a dry core. Specifically, the temperature in the oven can be set to 105° C. and the drying time can be set to 24 hours.

[0051] S120, obtaining the volume density, porosity and density of the fluid in the pores of the dry core according to a preset rule.

[0052] Specifically, the mass m (g) of the dry plug-shaped core can be weighed using a balance, and the length and diameter of the plug-shaped core can be measured using a vernier caliper to calculate the volume v (cm 3 ), using the dry state plunger core mass and apparent volume, calculate the bulk density of the core skeleton:

[0053] ρ b岩心 =mv

[0054] Among them, ρ b岩心 is the bulk density of the dry core, m is the mass of the dry core, and v is the volume of the dry core.

[0055] In practical applications, the precision of the balance is 0.001g, the precision of the vernier caliper is 0.02mm, and the mass, length, and diameter of the plunger core are measured three times, with a relative error of no more than 5%, and the average of the three times is the measurement result. The volume density of the core skeleton is calculated using the mass and apparent volume of the plunger core in the dry state measured.

[0056] It is also necessary to use a porosity measuring instrument to measure the porosity of the dry core according to the gas Boyle's law. (v / v). In practical applications, the porosity of each core is measured three times using a porosity measuring instrument, and the relative error does not exceed 5%, and the average of the three times is the measurement result.

[0057] In addition, it is necessary to consult the mud performance data of the well site operation to obtain the mud filtrate density as the density of the pore fluid in the dry core ρ f .

[0058] S130, substituting the obtained volume density, porosity, and density of the fluid in the pores of the dry core into a preset formation volume density calculation model to obtain the formation rock volume density, wherein the preset formation volume density calculation model is:

[0059]

[0060] Among them, ρ b地层 is the bulk density of the formation rock, ρ b岩心 is the bulk density of the dry core, is the porosity of the dry core, ρ fis the density of the fluid in the pores.

[0061] For ease of understanding, combined Figure 2 , the derivation process of the formation volume density calculation model is further explained.

[0062] According to theoretical knowledge:

[0063]

[0064] In the formula, ρ b地层 is the bulk density of formation rock, M is the mass of formation rock, and V is the volume of formation rock.

[0065] The applicant analyzed the composition of the formation rock and found that the mass of the formation rock includes the sum of the mass of the rock skeleton and the mass of the pore fluid, namely:

[0066] M=M 岩石骨架 +M 孔隙流体

[0067] The mass of the rock skeleton is the mass of the core in a dry state, the mass of the pore fluid is the mass of the fluid in the rock, and the mass of the fluid in the rock is the product of the rock porosity and the density of the fluid in the rock pores. Based on the above analysis, the following relationship expression can be derived:

[0068]

[0069] In the formula, ρ b地层 is the volume density of the formation rock, M is the mass of the formation rock, V is the volume of the formation rock, and M 岩石骨架 is the rock skeleton mass, ρ b岩石 =M 岩石骨架 / V, is the volume density of rock, M 孔隙流体 is the mass of fluid in the rock, is the rock porosity ρ f is the density of the fluid in the rock pores. b岩石 It can be determined in the laboratory by core experiments and is equivalent to ρ b岩心 , It can be determined by core porosity experiments in the laboratory, so the above model is simplified to a model for calculating the formation volume density from the core:

[0070] ρ b岩心 and It can be obtained by plunger core experiment. During the operation of well site density logging, the fluid in the formation rock within the detection range is mud filtrate. Therefore, ρ is determined according to the density of mud filtrate. f Once the calculation methods for each parameter are determined, the model can be used to determine the volume density of the formation rock.

[0071] The inventors conducted a large number of experiments to verify the effect of this embodiment. Table 1 shows the volume density of the formation obtained by using the core experimental data of a well and the volume density value of the reservoir density logging of the well. Figure 3 The figure is a schematic diagram of the relationship between the formation volume density obtained from the core experimental data of a well in the embodiment of the present invention and the volume density value of the reservoir density logging of the well. Through the analysis of the cross plot, it can be seen that the results calculated by this method are consistent with the change law of the density logging results, and have a high consistency. There are certain differences in the specific data, which is mainly caused by the influence of the irregularity of the wellbore and the mud on the density logging. It can be seen that this method can accurately calculate the volume density of the formation rock, and can be used as an effective method to judge the accuracy of density logging.

[0072] In this embodiment, the applicant has found through a large number of experimental studies that the volume density of the formation is related to the volume density of the fluid in the bottom pores, the volume density of the rock skeleton, etc. Therefore, based on the core porosity experiment, a model of the core volume density and the volume density of the formation rock is established, so that the volume density of the formation rock is directly calculated using the core data. The parameters in the model are all from the experimental results, and the data quality is reliable and accurate. Well logging instruments, including density well logging instruments, are often affected by multiple factors such as the regularity of the wellbore and the mud properties. Compared with the experimental results, the influencing factors will increase and the accuracy will decrease. Therefore, if the volume density of the formation is to be obtained, it is not necessary to go through the extensive well logging work, but to use the method provided in the embodiment of the present invention.

[0073] Table 1

[0074]

[0075]

[0076]

[0077]

[0078] Embodiment 2

[0079] The present invention also discloses a formation volume density calculation system, such as Figure 4 As shown, it includes a core sample processing device 10, a parameter acquisition device 20, and a calculation device 30, wherein:

[0080] The core sample processing device 10 is used to process the core sample to obtain a dry core.

[0081] The core sample processing device at least includes an oven, which is used to process the core sample to obtain a dry core. In order to facilitate the calculation of the volume of the core sample, the core sample is preferably made into a plunger shape and then placed in an oven for drying to obtain a dry core. Specifically, the temperature in the oven can be set to 105°C and the drying time can be set to 24 hours.

[0082] The parameter acquisition device 20 is used to obtain the volume density, porosity and density of the fluid in the pores of the dry core according to a preset rule.

[0083] The parameter acquisition device 20 at least includes a mass measuring device, a size measuring device, and a porosity measuring instrument. The mass measuring device is used to obtain the mass of the dry core; the size measuring device is used to obtain the length and diameter of the dry core; and the porosity measuring instrument is used to obtain the porosity of the dry core.

[0084] Specifically, the mass m (g) of the dry plug-shaped core can be weighed using a balance, and the length and diameter of the plug-shaped core can be measured using a vernier caliper. The volume v (cm 3 ), using the dry state plunger core mass and apparent volume, calculate the bulk density of the core skeleton:

[0085] ρ b岩心 =m / v

[0086] Among them, ρ b岩心 is the bulk density of the dry core, m is the mass of the dry core, and v is the volume of the dry core.

[0087] In practical applications, the precision of the balance is 0.001g, the precision of the vernier caliper is 0.02mm, and the mass, length, and diameter of the plunger core are measured three times, with a relative error of no more than 5%, and the average of the three times is the measurement result. The volume density of the core skeleton is calculated using the mass and apparent volume of the plunger core in the dry state measured.

[0088] It is also necessary to use a porosity measuring instrument to measure the porosity of the dry core according to the gas Boyle's law. (v / v).

[0089] In practical applications, the porosity of each core is measured three times using a porosity measuring instrument, with a relative error of no more than 5%, and the average of the three times is taken as the measurement result.

[0090] In addition, the applicant found that during the operation of the well site density logging, the fluid in the formation rock within the detection range is the mud filtrate, that is, the density of the fluid in the pore is the density of the mud filtrate, and the density of the fluid in the pore can be determined based on the density of the mud filtrate. In this step, it is necessary to obtain the mud performance data of the well site operation, and obtain the mud filtrate density as the density of the fluid in the pore of the dry core ρf .

[0091] The calculation device 30 is used to substitute the obtained volume density, porosity, and density of the fluid in the pores of the dry core into a preset formation volume density calculation model to obtain the formation rock volume density. The preset formation volume density calculation model is:

[0092]

[0093] Among them, ρ b地层 is the bulk density of the formation rock, ρ b岩心 is the bulk density of the dry core, is the porosity of the dry core, ρ f is the density of the fluid in the pores.

[0094] The specific working principle of the formation volume density calculation system of this embodiment can be referred to in Example 1, and will not be repeated here. After a large number of experimental studies, the applicant found that the formation volume density is related to the volume density of the fluid in the bottom pores, the volume density of the rock skeleton, etc., so a formation volume density calculation model was established by the volume density, porosity, and density of the fluid in the pores of the dry core. Therefore, if the formation volume density is to be obtained, it is not necessary to go through the huge logging work, and it is only necessary to substitute the experimental data obtained from the sample core into the formation volume density calculation model. A large amount of experimental data shows that the formation volume density obtained by the present invention has high accuracy.

[0095] Embodiment 3

[0096] The embodiment of the present invention further discloses a formation volume density calculation model, which is:

[0097]

[0098] Among them, ρ b地层 is the bulk density of the formation rock, ρ b岩心 is the bulk density of the dry core, is the porosity of the dry core, ρ f is the density of the fluid in the pores.

[0099] For ease of understanding, the derivation process of the formation volume density calculation model is further explained below.

[0100] According to theoretical knowledge:

[0101]

[0102] In the formula, ρ b地层 is the bulk density of formation rock, M is the mass of formation rock, and V is the volume of formation rock.

[0103] The applicant analyzed the composition of the formation rock and found that the mass of the formation rock includes the sum of the mass of the rock skeleton and the mass of the pore fluid, namely:

[0104] M=M 岩石骨架 +M 孔隙流体

[0105] The mass of the rock skeleton is the mass of the core in a dry state, the mass of the pore fluid is the mass of the fluid in the rock, and the mass of the fluid in the rock is the product of the rock porosity and the density of the fluid in the rock pores. Based on the above derivation, the following relationship expression can be obtained:

[0106]

[0107] In the formula, ρ b地层 is the volume density of the formation rock, M is the mass of the formation rock, V is the volume of the formation rock, and M 岩石骨架 is the rock skeleton mass, ρ b岩石 =M 岩石骨架 / V, is the volume density of rock, M 孔隙流体 is the mass of fluid in the rock, is the rock porosity ρ f is the density of the fluid in the rock pores. b岩石 It can be determined in the laboratory by core experiments and is equivalent to ρ b岩心 , It can be determined by core porosity experiments in the laboratory, so the above model is simplified to a model for calculating the formation volume density from the core:

[0108] It is understandable that the core sampling data of the main target layer of oil and gas exploration wells and evaluation wells are rich, and the formation volume density can be calculated using the core experimental data to achieve the purpose of obtaining a higher precision formation rock volume density using the core data. In practical applications, the inventor can consider using various methods to obtain the parameters in the formation volume density calculation model, and the embodiments of the present invention are not limited to this.

[0109] In this embodiment, the applicant has found through a large number of experimental studies that the volume density of the formation is related to the volume density of the fluid in the bottom pores, the volume density of the rock skeleton, etc. Therefore, based on the core porosity experiment, a model of the core volume density and the volume density of the formation rock is established, so that the volume density of the formation rock is directly calculated using the core data. The parameters in the model are all from the experimental results, and the data quality is reliable and accurate. Well logging instruments, including density well logging instruments, are often affected by multiple factors such as the regularity of the wellbore and the mud properties. Compared with the experimental results, the influencing factors will increase and the accuracy will decrease. Therefore, if the volume density of the formation is to be obtained, it is not necessary to go through the extensive well logging work, but to use the method provided in the embodiment of the present invention.

[0110] In the above detailed description, various features are grouped together in a single embodiment to simplify the disclosure. This method of disclosure should not be interpreted as reflecting an intention that the embodiments of the claimed subject matter require more features than are clearly stated in each claim. On the contrary, as reflected in the appended claims, the invention is in a state of having less than all the features of the disclosed individual embodiments. Therefore, the appended claims are hereby expressly incorporated into the detailed description, with each claim standing on its own as a separate preferred embodiment of the invention.

[0111] The above description includes examples of one or more embodiments. Of course, it is not possible to describe all possible combinations of components or methods for the purpose of describing the above embodiments, but it should be recognized by those skilled in the art that the various embodiments may be further combined and arranged. Therefore, the embodiments described herein are intended to cover all such changes, modifications and variations that fall within the scope of protection of the appended claims. In addition, with respect to the term "comprising" used in the specification or claims, the word is encompassed in a manner similar to the term "including", as explained by "including," used as a transitional word in the claims. In addition, any term "or" used in the specification of the claims is intended to mean "non-exclusive or".

Claims

1. A method for calculating formation volume density, characterized in that: include: Processing the core sample to obtain a dry core; Obtaining the bulk density, porosity and density of the fluid in the pores of the dry core according to preset rules; The obtained volume density, porosity, and density of the fluid in the pores of the dry core are substituted into a preset formation volume density calculation model to obtain the formation rock volume density. The preset formation volume density calculation model is: Among them, ρ b地层 is the bulk density of the formation rock, ρ b岩心 is the bulk density of the dry core, is the porosity of the dry core, ρ f is the density of the fluid in the pores.

2. The method for calculating formation volume density according to claim 1, characterized in that: The method of processing the core sample to obtain a dry core comprises: The core sample is made into a plunger shape and then placed in an oven for drying to obtain a dry core.

3. The method for calculating formation volume density according to claim 1, characterized in that: The step of obtaining the volume density of the dry core according to a preset rule includes: The mass and volume of the dry core are obtained, and the bulk density of the dry core is calculated.

4. The method for calculating formation volume density according to claim 3, characterized in that: The method of obtaining the mass and volume of the dry core according to the preset rules includes: Weigh the mass of the dry core; Measure the length and diameter of the dry core and calculate the volume of the dry core; The bulk density of the dry core is calculated using the mass and volume: ρ b岩心 =mv Among them, ρ b岩心 is the bulk density of the dry core, m is the mass of the dry core, and v is the volume of the dry core.

5. The method for calculating formation volume density according to claim 1, characterized in that: The step of obtaining the porosity of the dry core according to a preset rule includes: The porosity of the dry core is measured using a porosity measuring instrument.

6. The method for calculating formation volume density according to claim 1, characterized in that: The step of obtaining the density of the fluid in the pores of the dry core according to a preset rule includes: The existing mud filtrate density is obtained as the density of the pore fluid in the dry core.

7. A formation volume density calculation system, characterized in that: It includes a core sample processing device, a parameter acquisition device, and a calculation device, wherein: The core sample processing device is used to process the core sample to obtain a dry core; The parameter acquisition device is used to obtain the volume density, porosity and density of the fluid in the pores of the dry core according to a preset rule; The calculation device is used to substitute the obtained volume density, porosity, and density of the fluid in the pores of the dry core into a preset formation volume density calculation model to obtain the formation rock volume density. The preset formation volume density calculation model is: Among them, ρ b地层 is the bulk density of the formation rock, ρ b岩心 is the bulk density of the dry core, is the porosity of the dry core, ρ f is the density of the fluid in the pores.

8. The formation volume density calculation system according to claim 7, characterized in that: The core sample processing device at least comprises an oven, and the oven is used to process the core sample to obtain a dry core.

9. The formation volume density calculation system according to claim 7, characterized in that: The parameter acquisition device at least includes a mass measurement device, a size measurement device, and a porosity measurement instrument, wherein: The mass measuring device is used to obtain the mass of the dry core; The size measuring device is used to obtain the length and diameter of the dry core; The porosity measuring instrument is used to obtain the porosity of a dry core.

10. A formation volume density calculation model, characterized in that: The formation volume density calculation model is: Among them, ρ b地层 is the bulk density of the formation rock, ρ b岩心 is the bulk density of the dry core, is the porosity of the dry core, ρ f is the density of the fluid in the pores.

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