Bioclastic limestone reservoir diagenesis semi-quantitative evaluation method

Abstract

The present application provides a kind of bioclastical limestone reservoir diagenesis semi-quantitative evaluation method, comprising: step 1: carbonate reservoir diagenesis is divided according to preset standard;Step 2: obtain the carbonate reservoir image of target research area;Step 3: the carbonate reservoir image is labeled according to the preset standard;Step 4: the labeling result is counted, and the diagenesis of the carbonate reservoir in the target research area is semi-quantitatively evaluated according to the statistical result.The method provided by the present application can semi-quantitatively evaluate the diagenesis of carbonate reservoir, semi-quantitatively characterize the development degree of secondary pores and the content of different period cement, so as to help to determine the diagenetic difference of different development layer series, and finally provide guidance for oil and gas field development deployment.

Description

Technical Field

[0001] This invention relates to the field of geological technology, and in particular to a semi-quantitative evaluation method for diagenesis in bioclastic limestone reservoirs. Background Technology

[0002] Carbonate reservoirs are susceptible to diagenetic alteration. Varying degrees of dissolution and cementation lead to complex porosity and diverse pore types, exacerbating the heterogeneity of carbonate reservoirs. The intensity of diagenesis in carbonate reservoirs is typically assessed qualitatively using categorizations such as "strong," "weak," and "moderate." However, for diagenesis-controlled reservoirs, qualitative assessments are insufficient to meet the production needs of oil and gas fields, impacting the prediction of favorable development areas and the formulation of subsequent development strategies. Therefore, exploring a more accurate evaluation method to characterize the diagenetic intensity of carbonate reservoirs is crucial for oil and gas field development. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a semi-quantitative evaluation method for diagenesis in bioclastic limestone reservoirs.

[0004] A semi-quantitative evaluation method for diagenesis in bioclastic limestone reservoirs includes:

[0005] Step 1: Classify the diagenesis of carbonate reservoirs according to preset standards;

[0006] Step 2: Obtain images of carbonate reservoirs in the target study area;

[0007] Step 3: Annotate the carbonate reservoir image according to the preset standard;

[0008] Step 4: Statistically analyze the annotation results and conduct a semi-quantitative evaluation of the diagenesis of carbonate rocks in the target study area based on the statistical results.

[0009] Furthermore, in the semi-quantitative evaluation method for diagenesis of bioclastic limestone reservoirs as described above, the preset criteria are: pore type and cementation stage type.

[0010] Furthermore, in the semi-quantitative evaluation method for diagenesis of bioclastic limestone reservoirs as described above, the pore types include: mold pores, cavity pores, intragranular dissolution pores, composite pores, and dissolution pores / fissures.

[0011] Furthermore, in the semi-quantitative evaluation method for diagenesis of bioclastic limestone reservoirs as described above, the cementation stage types include: early cementation and late cementation.

[0012] Furthermore, in the semi-quantitative evaluation method for diagenesis of bioclastic limestone reservoirs as described above, the acid rock reservoir image includes at least four fields of view.

[0013] Furthermore, in the semi-quantitative evaluation method for diagenesis of bioclastic limestone reservoirs as described above, the step of statistically analyzing the labeled results and conducting a semi-quantitative evaluation of the carbonate rock diagenesis in the target study area based on the statistical results includes:

[0014] Determine the area occupied by each annotation type in the carbonate reservoir image;

[0015] Determine the proportion of the area occupied by each annotation type to the area of ​​the carbonate reservoir image;

[0016] The face rate and cementitious period for each type of labeling are determined based on the stated proportions.

[0017] A semi-quantitative evaluation of the diagenesis of carbonate rocks in the target study area was conducted based on the porosity and cementation stages.

[0018] The method provided by this invention can perform a semi-quantitative evaluation of diagenesis in carbonate reservoirs, and semi-quantitatively characterize the degree of secondary pore development and the cement content of different stages, thereby helping to clarify the diagenetic differences of different development strata and ultimately providing guidance for oil and gas field development deployment. Attached Figure Description

[0019] Figure 1 Flowchart of the semi-quantitative evaluation method for diagenesis in bioclastic limestone reservoirs provided by this invention;

[0020] Figure 2 Images of carbonate reservoirs with marked casting holes;

[0021] Figure 3 Images of carbonate reservoirs with marked cavity pores;

[0022] Figure 4 Image of a carbonate reservoir with fractures marked;

[0023] Figure 5 Image of a carbonate reservoir with labeled composite pores;

[0024] Figure 6 Image of a carbonate reservoir with intragranular dissolution pores;

[0025] Figure 7 Images of carbonate reservoirs marked with early cementation;

[0026] Figure 8 Cathodoluminescence images of the two-stage cemented material;

[0027] Figure 9 Image of a carbonate reservoir marked with late-stage cementation. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0029] Figure 1 The flowchart of the semi-quantitative evaluation method for diagenesis in bioclastic limestone reservoirs provided by this invention is as follows: Figure 1 As shown, the method includes:

[0030] Step 1: Classify the diagenesis of carbonate reservoirs according to preset standards.

[0031] Specifically, the preset criteria are: pore type and cementation stage type. The pore types include: mold pores, cavity pores, intragranular dissolution pores, composite pores, and dissolution pores / cracks. The cementation stage types include: early-stage cementation and late-stage cementation. Based on geological data such as thin sections and fluid inclusions of the study area, pore types and cementation at different stages were identified under a microscope. Pore types include: mold pores, cavity pores, intragranular dissolution pores, composite pores, and dissolution pores / cracks; cementation stage types include early-stage filling and late-stage filling. The identifying characteristic of mold pores is complete erosion of the particles and a clear pore outline. The identifying characteristic of cavity pores is a biologically regular cavity, generally similar in shape and closely arranged together. The identifying characteristic of intragranular dissolution pores is incomplete erosion of the particle interior. The identifying characteristic of composite pores is erosion of the matrix between particles, generally triangular or forked in shape. Microscopic identification of dissolution pores / cracks is characterized by pores with a diameter greater than 2 mm. In early cemented materials, fluid inclusions are mainly composed of a single liquid phase, with relatively dim cathodic emission, and appear under the microscope as uniformly thick ring edges or pore linings. In late cemented materials, fluid inclusions are characterized by the widespread development of multiple phases of gas-liquid two-phase inclusions (homogenization temperature distribution range from 60 to 120 °C), with stronger cathodic emission, and are characterized under the microscope as coarse crystals.

[0032] Step 2: Obtain images of carbonate reservoirs in the target study area.

[0033] Step 3: Label the carbonate reservoir image according to the preset standard.

[0034] Specifically, each rock thin section was photographed and stitched together using multiple fields of view (at least four fields of view, i.e., one field of view selected from each of the four quadrants: top, bottom, left, and right). Different pore types and cementation stages were identified in the thin section photographs. Using graphic design software (such as CorelDRAW), different colors were used to mark the pore types and cementation stages, such as... Figures 2-9 As shown, different markings are used to label the specific types of pores and the specific stages of cementation.

[0035] Step 4: Statistically analyze the annotation results and conduct a semi-quantitative evaluation of the diagenesis of carbonate rocks in the target study area based on the statistical results.

[0036] Specifically, the labeled thin section images are imported into image analysis software, which automatically identifies and calculates the proportion of each color area in the image, i.e., the proportion of each statistical object. Based on these proportion statistics, a histogram of pore type and diameter distribution is compiled. By clarifying the proportion of pore types and cementation at different stages, a precise semi-quantitative evaluation of diagenesis in carbonate reservoirs can be achieved.

[0037] By analyzing the data, the proportion of each type of pore and cement was determined, and the final porosity and cementation stages were obtained, providing a basis for semi-quantitative evaluation of diagenesis in carbonate reservoirs.

[0038] Pore ​​type Face rate (%) Pore ​​percentage Number of pores mold hole 1.04 63 62 Biological cavity pores 0.26 37 37 Total porosity 1.3 100 99

[0039] The method provided by this invention enables a semi-quantitative evaluation of complex carbonate rock diagenesis, offering greater precision than traditional manual qualitative identification and making it more suitable for evaluating highly heterogeneous reservoirs. This system has already been applied in the Al-Ahdab and Halfaya oil fields in Iraq, in the Middle East.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for semi-quantitative evaluation of diagenesis of bioclastic limestone reservoirs, characterized in that, The method comprises the following steps: Step 1: dividing the carbonatite reservoir diagenesis according to preset standards; Step 2: obtaining a carbonatite reservoir image of a target research area; Step 3: labeling the carbonatite reservoir image according to the preset standards; Step 4: counting the labeling results, and semi-quantitatively evaluating the carbonatite diagenesis of the target research area according to the counting results; The preset standards are: pore types and cementation period types; The carbonatite reservoir image comprises at least four visual fields; The counting of the labeling results and the semi-quantitative evaluation of the carbonatite diagenesis of the target research area according to the counting results comprise: determining the area occupied by each labeling type in the carbonatite reservoir image; determining the proportion of the area occupied by each labeling type in the area of the carbonatite reservoir image; determining the face pore rate and the cementation period of each labeling type according to the proportion; semi-quantitatively evaluating the carbonatite diagenesis of the target research area according to the face pore rate and the cementation period.

2. The method for bioclastic limestone reservoir diagenetic semi-quantitative evaluation according to claim 1, characterized in that, The pore types comprise: mold pores, body cavity pores, intragranular dissolved pores, composite pores and dissolved pores / dissolved fissures.

3. The method for bioclastic limestone reservoir diagenetic semi-quantitative evaluation according to claim 1, characterized in that, The cementation period types comprise: early cementation filling and late cementation filling.

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