Inter-salt reservoir effectiveness identification method

Abstract

The invention provides an inter-salt reservoir effectiveness identification method. The inter-salt reservoir effectiveness identification method comprises the following steps: step 1) summarizing false reservoir identification marks; 2) matching the rock-electricity combination feature maps of the true and false reservoirs; 3) establishing a logging parameter intersection layout of the true and false reservoirs; 4) based on the logging parameter intersection layout, obtaining true and false reservoir logging parameter identification templates; (5) corresponding logging parameters of the well drilling target layer are plumped into the logging parameter identification template, and the effectiveness of the reservoir is identified according to the plumbing positions of all the parameters. According to the method, on the basis of a drilling model, rock core and slice summarization is utilized, a lithology identification standard of true and false reservoirs is established, an identification method of lithology characteristics and electrical characteristics of the inter-salt reservoirs is combined for the first time, a logging identification template is established, a key judgment basis is provided for evaluation of the effective reservoirs of the compact carbonate rocks under the salt, and therefore exploration and development efficiency is improved; the development cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of geology and well logging and mud logging services, and in particular relates to a method for identifying the effectiveness of inter-salt reservoirs. Background Art

[0002] In recent years, the exploration of subsalt strata has been continuously improved, and it has been found that inter-salt carbonate reservoirs in evaporite development strata or regional reservoirs are relatively developed. However, some salt-bearing karst pores are dissolved by drilling fluid during the drilling process, forming artificial karst pores, which are mistakenly interpreted as "reservoirs" in well logging interpretation, resulting in: (1) There are many salt-bearing strata, and such false reservoirs are often misinterpreted; (2) "false reservoirs" have no production capacity effect, and the processes of interpretation, perforation, and gas testing delay the exploration and development process, which is easy to cause waste of resources.

[0003] At present, most of the traditional technical means at home and abroad are aimed at the prediction and analysis of sub-salt reservoirs, while the evaluation and interpretation of effective reservoirs between gypsum-salt rocks have not been deeply studied, the relevant technology is not mature, and due to the strong heterogeneity of gypsum-salt rocks and dolomite, it is difficult to identify effective reservoirs "between salt and gypsum".

[0004] The invention patent application number is 202010390813.1, and the patent name is "A method for identifying the effectiveness of carbonate reservoirs based on the three-porosity model of rock". The rock "three-porosity" model is used as the theoretical volume model, and a conductive network in which matrix pores and connected fracture-vug pores are connected in parallel and matrix pores and non-connected fracture-vug pores are connected in series is adopted. The total porosity, matrix porosity, connected fracture-vug, and non-connected fracture-vug porosity of the carbonate rock are jointly calculated using compensated density (DEN), compensated neutron (CNL), acoustic time difference (AC), deep lateral resistivity (RLLD), and shallow lateral resistivity (RLLS). Finally, the total porosity, matrix porosity, connected fracture-vug porosity, and non-connected fracture-vug porosity are combined to calculate the formation cementation index m. According to the degree of reservoir superposition development, the ratio of the sum of the connected fracture-vug porosity and the non-connected fracture-vug porosity to the total porosity BZ and the cementation index m can quantitatively identify the reservoir effectiveness. However, since the pores between salts are artificial solution pores, the above method cannot be used to identify pseudo-reservoirs. Summary of the invention The purpose of the present invention is to provide a method for identifying the effectiveness of inter-salt reservoirs to overcome the above-mentioned technical problems existing in the prior art.

[0005] To this end, the technical solution provided by the present invention is as follows: A method for identifying the effectiveness of an inter-salt reservoir comprises the following steps: Step 1) Summarize the false reservoir identification signs; Step 2) Matching the rock-electric combination characteristic maps of the true and false reservoirs; Step 3) Establishing the intersection map of well logging parameters of true and false reservoirs; Step 4) Based on the logging parameter intersection map, two types of reservoir logging parameter identification templates, true and false, are obtained; Step 5) Project the corresponding logging parameters of the drilling target layer into the logging parameter identification template, and identify the effectiveness of the reservoir according to the location of each parameter projection. Step 1) is summarized based on the observation of cores and thin sections of the target layer in the coring wells in the study area, and the petrological evidence of pseudo-reservoirs in the inter-salt strata is identified.

[0006] Step 2) is to first identify the true and false reservoirs in the cores of the coring section of the study area according to the false reservoir identification marks in step 1), and then perform rock electrical depth correction to finally match the rock electrical combination characteristics of the true and false reservoirs.

[0007] Step 3) The specific process is as follows: extract key logging parameters of well locations, summarize the logging data of true and false reservoirs, and establish a logging parameter cross-plot.

[0008] The specific process of step 4) is as follows: Based on the logging parameter cross-plot, four sets of logging parameter identification templates for true and false inter-salt reservoirs, namely AC-DEN, RLLD-RLLS, RLLS-DEN and RLLD-DEN, are obtained.

[0009] The specific process of step 5) is as follows: according to the logging parameter identification template obtained in step 4), the four logging parameters of AC, DEN, RLLD and RLLS of the drilling target layer are exported, and then the corresponding logging parameters are projected into the logging parameter identification template. Finally, the true and false reservoirs are judged according to the positions of the projected points of each parameter to identify the effectiveness of the reservoir.

[0010] After step 5) the true or false identification of the reservoir, the effectiveness of the reservoir is verified and tested through the lithological characteristics of the coring section.

[0011] In step 1), the identification marks of false reservoirs include two aspects: (1) core scale: many dissolved pores are seen on the surface, while fresh sections are dense and pore-free; (2) thin section scale: in alcohol-ground sections, pores can be seen filled with rock salt, while in water-ground sections, there is no filling in the pores.

[0012] The beneficial effects of the present invention are: Starting from the drilling model, the present invention uses core and thin section summaries to establish petrological identification standards for true and false reservoirs and logging identification templates, providing key discrimination basis for the evaluation of effective reservoirs of subsalt tight carbonate rocks, thereby improving exploration and development efficiency and reducing development costs.

[0013] The present invention combines the identification methods of the lithological characteristics and electrical characteristics of the "inter-salt" reservoir for the first time, creatively and effectively identifying the authenticity of the "inter-salt" reservoir in the study area, and enhancing the accurate understanding of the "inter-salt" reservoir.

[0014] The present invention can pre-identify true and false reservoirs in "inter-salt" based on the well logging identification template of the study area, exclude such false reservoirs, provide a basis for the next step of risk exploration deployment, and avoid unnecessary waste of resources in advance. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic diagram of the pseudo reservoir formation of the present invention; Figure 2 The lithological characteristic photos of the pseudo-reservoir core slices of the present invention are as follows; Figure 3 This is the rock-electric combination characteristic diagram of the true reservoir of the target layer section of the embodiment of the present invention; Figure 4 It is a pseudo reservoir rock-electric combination characteristic diagram of the target layer section of the embodiment of the present invention; Figure 5 AC-DEN intersection recognition template for true and false reservoir logging of target layer segments in the embodiment of the present invention; Figure 6 It is a RLLD-RLLS intersection recognition template for true and false reservoir logging of the target layer segment in the embodiment of the present invention; Figure 7 The target layer segment of the embodiment of the present invention has two types of reservoir logging, true and false, RLLS-DEN intersection recognition templates; Figure 8 The embodiment of the present invention provides a true and false two types of reservoir logging RLLD-DEN intersection recognition template for the target layer segment; Fig. 9 A new well reservoir validity identification and verification chart according to an embodiment of the present invention; Fig.10 A flow chart of a method for identifying the effectiveness of an "inter-salt" reservoir rock electrical system provided in an implementation case of the present invention. DETAILED DESCRIPTION

[0016] The following describes the implementation of the present invention through specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0017] The exemplary embodiments of the present invention are now described with reference to the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to disclose the present invention in detail and completely and to fully convey the scope of the present invention to those skilled in the art. The terms used in the exemplary embodiments shown in the accompanying drawings are not intended to limit the present invention.

[0018] Unless otherwise specified, the terms (including technical terms) used herein have the commonly understood meanings to those skilled in the art. In addition, it is understood that the terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings.

[0019] Example 1 This embodiment provides a method for identifying the effectiveness of an inter-salt reservoir, comprising the following steps: Step 1) Summarize the false reservoir identification signs; Step 2) Matching the rock-electric combination characteristic maps of the true and false reservoirs; Step 3) Establishing the intersection map of well logging parameters of true and false reservoirs; Step 4) Based on the logging parameter intersection map, two types of reservoir logging parameter identification templates, true and false, are obtained; Step 5) Project the corresponding logging parameters of the drilling target layer into the logging parameter identification template, and identify the effectiveness of the reservoir according to the location of each parameter projection. The present invention combines the identification methods of the lithological characteristics and electrical characteristics of the "inter-salt" reservoir for the first time, creatively and effectively identifying the authenticity of the "inter-salt" reservoir in the study area, and enhancing the accurate understanding of the "inter-salt" reservoir.

[0020] Example 2 Based on Example 1, this example provides a method for identifying the effectiveness of inter-salt reservoirs. Step 1) is based on observations of cores and thin sections of target layers in coring wells in the study area, and is summarized after identifying petrological evidence of pseudo-reservoirs in inter-salt strata.

[0021] like Figure 1 As shown in Figure 2, some salt-bearing karst pores were dissolved by drilling fluid during the drilling process, forming artificial karst pores, which were mistakenly interpreted as "reservoirs" in well logging interpretation. Figure 2 Shown is a photograph of the lithological characteristics of a pseudo-reservoir core thin section.

[0022] Starting from the drilling model, the present invention uses core and thin section summaries to establish petrological identification standards for true and false reservoirs and logging identification templates, providing key discrimination basis for the evaluation of effective reservoirs of subsalt tight carbonate rocks, thereby improving exploration and development efficiency and reducing development costs.

[0023] Example 3 Based on Example 1, this example provides a method for identifying the effectiveness of inter-salt reservoirs. Step 2) is to first identify the true and false reservoirs of the cores of the coring section in the study area according to the false reservoir identification mark in step 1), and then perform rock electrical depth correction to finally match the rock electrical combination characteristics of the true and false reservoirs. Figure 3 and Figure 4 shown.

[0024] Step 3) The specific process is as follows: extract key logging parameters of well locations, summarize the logging data of true and false reservoirs, and establish a logging parameter cross-plot.

[0025] The specific process of step 4) is as follows: Based on the logging parameter cross-plot, four sets of logging parameter identification templates for true and false inter-salt reservoirs, namely AC-DEN, RLLD-RLLS, RLLS-DEN and RLLD-DEN, are obtained.

[0026] The present invention can pre-identify true and false reservoirs in "inter-salt" based on the well logging identification template of the study area, exclude such false reservoirs, provide a basis for the next step of risk exploration deployment, and avoid unnecessary waste of resources in advance.

[0027] Example 4 On the basis of Example 1, this example provides a method for identifying the effectiveness of inter-salt reservoirs. The specific process of step 5) is as follows: according to the logging parameter identification template obtained in step 4), the four logging parameters of AC, DEN, RLLD, and RLLS of the drilling target layer are exported, and then the corresponding logging parameters are projected into the logging parameter identification template. Finally, the true and false reservoirs are judged according to the positions of the projections of each parameter to identify the effectiveness of the reservoir.

[0028] When the four logging parameters are in the corresponding positions of the true and false reservoirs, the true and false can be clearly judged. Among them, AC is the acoustic time difference, DEN is the formation density, RLLD is the deep lateral logging, and RLLS is the shallow lateral logging.

[0029] Example 5 In order to further illustrate the effect of the present invention in detail, this embodiment takes the Majiagou group as an example to introduce the present invention.

[0030] like Fig.10 As shown, the following steps are included: S1: Summarize the lithology identification characteristics of "inter-salt" pseudo-reservoir Based on the identification of reservoir properties of a large number of inter-salt strata, such as Figure 2 As shown in the figure, it is believed that the pseudo-reservoir of the inter-salt strata has the following characteristics: 1) At the core scale, many dissolution pores are seen on the surface, while the fresh section is dense and pore-free; 2) At the thin section scale, the alcohol-ground slices show that the pores are filled with rock salt, while the water-ground slices have almost no fillings in the pores.

[0031] S2: Combine lithology and logging characteristics to match the rock electrical characteristics of true and false reservoirs Using the drilling core data of the salt-bearing strata and regions in the study area, the rock electrical characteristics of the true and false reservoirs are matched ( Figure 3 , Figure 4As shown in the figure), extract the respective key logging parameters to prepare for the next step of establishing a logging recognition template.

[0032] S3: Establishing the cross-plot of logging parameters for the “inter-salt” reservoir in the study area By extracting the key logging parameters of the exploration wells in the study area, we compiled and built a database of true and false reservoirs, and established an "inter-salt" logging parameter intersection map.

[0033] S4: Template for identifying logging parameters of “inter-salt” reservoirs in the summary area Based on the petrological identification and rock electrical characteristics matching of more than 200 sets of "inter-salt" true and false reservoirs in the middle and lower combinations of Majiagou Formation, the AC-DEN, RLLD-RLLS, RLLS-DEN and RLLD-DEN logging recognition templates are summarized as follows: Figure 5 , Figure 6 , Figure 7 and Figure 8 The two have a high degree of distinction, which is specifically manifested in the electrical characteristics of the pseudo-reservoir: low density, high resistivity, and large lateral difference between deep and shallow.

[0034] S5: Identification of true and false reservoirs in newly drilled “salt inter-layers” Taking the newly drilled Yuyang 1 well as the research object, according to the logging identification template, the AC, DEN, RLLD, RLLS and other logging data of the 3350-3360m section of the newly drilled Yuyang 1 well were projected. The projected area is located in the pseudo-reservoir and is identified as a "pseudo-reservoir".

[0035] S6: Verification of the effectiveness of “inter-salt” reservoirs The S5 discrimination results were verified and tested based on the lithological characteristics of the 3350-3360m coring section of the recently drilled well, Yuyang 1 Well. Fig. 9 As shown in the figure, the macroscopic lithology of the coring section is generally characterized by salt-bearing micrite dolomite with full filling of rock salt and poor porosity and permeability, which is consistent with the S5 identification result and is a pseudo-reservoir, which can be applied to guide the next step of oil and gas exploration deployment.

[0036] The above examples are merely illustrative of the present invention and do not constitute a limitation on the protection scope of the present invention. All designs that are the same or similar to the present invention fall within the protection scope of the present invention.

Claims

1. A method for identifying the effectiveness of inter-salt reservoirs, characterized in that: The following steps are involved: Step 1) Summarize the false reservoir identification signs; Step 2) Matching the rock-electric combination characteristic maps of the true and false reservoirs; Step 3) Establishing the intersection map of well logging parameters of true and false reservoirs; Step 4) Based on the logging parameter intersection map, two types of reservoir logging parameter identification templates, true and false, are obtained; Step 5) Project the corresponding logging parameters of the drilling target layer into the logging parameter identification template, and identify the effectiveness of the reservoir according to the location of each parameter projection.

2. The method for identifying the effectiveness of inter-salt reservoirs according to claim 1, characterized in that: Step 1) is summarized based on the observation of cores and thin sections of the target layer in the coring wells in the study area, and the petrological evidence of pseudo-reservoirs in the inter-salt strata is identified.

3. The method for identifying the effectiveness of inter-salt reservoirs according to claim 1, characterized in that: Step 2) is to first identify the true and false reservoirs in the cores of the coring section of the study area according to the false reservoir identification marks in step 1), and then perform rock electrical depth correction to finally match the rock electrical combination characteristics of the true and false reservoirs.

4. The method for identifying the effectiveness of inter-salt reservoirs according to claim 1, characterized in that: Step 3) The specific process is as follows: extract key logging parameters of well locations, summarize the logging data of true and false reservoirs, and establish a logging parameter cross-plot.

5. The method for identifying the effectiveness of inter-salt reservoirs according to claim 1, characterized in that: The specific process of step 4) is as follows: Based on the logging parameter cross-plot, four sets of logging parameter identification templates for true and false inter-salt reservoirs, namely AC-DEN, RLLD-RLLS, RLLS-DEN and RLLD-DEN, are obtained.

6. The method for identifying the effectiveness of inter-salt reservoirs according to claim 5, characterized in that: The specific process of step 5) is as follows: according to the logging parameter identification template obtained in step 4), the four logging parameters of AC, DEN, RLLD and RLLS of the drilling target layer are exported, and then the corresponding logging parameters are projected into the logging parameter identification template. Finally, the true and false reservoirs are judged according to the positions of the projected points of each parameter to identify the effectiveness of the reservoir.

7. The method for identifying the effectiveness of inter-salt reservoirs according to claim 1, characterized in that: After step 5) the true or false identification of the reservoir, the effectiveness of the reservoir is verified and tested through the lithological characteristics of the coring section.

8. The method for identifying the effectiveness of inter-salt reservoirs according to claim 1, characterized in that: In step 1), the identification marks of false reservoirs include two aspects: (1) core scale: many dissolved pores are seen on the surface, while fresh sections are dense and pore-free; (2) thin section scale: in alcohol-ground sections, pores can be seen filled with rock salt, while in water-ground sections, there is no filling in the pores.

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