A method for classifying the degree of infiltration of carbonate buried hills

Abstract

The present invention discloses a method for classifying the leaching degree of carbonate buried hills, and relates to the technical field of oil and gas exploration and development. The method comprises the following steps: collecting element logging, logging interpretation and core analysis data of target wells; normalization processing of element logging data; constructing a leaching index calculation model for characterizing the leaching degree of carbonate rocks based on the element logging normalization data; and establishing a classification standard for the leaching degree of regional carbonate rocks. The present invention constructs a leaching index model that comprehensively reflects the leaching degree of calcium (Ca) and phosphorus (P) elements and the enrichment degree of aluminum (Al), iron (Fe), and silicon (Si) elements by using element logging data, thereby realizing the characterization of the leaching degree of carbonate rocks in the vertical direction during the logging stage.

Description

Technical Field

[0001] The invention belongs to the technical field of oil field exploration, and in particular relates to a method for dividing the degree of infiltration of carbonate buried hills. Background Art

[0002] Buried hill oil and gas reservoirs have become an important target for oilfield exploration. For carbonate formations, the development of reservoirs is controlled by factors such as sedimentary facies type, tectonic movement, deep dissolution and weathering and leaching. Among them, weathering and leaching is one of the main factors affecting the development of carbonate reservoirs. At present, the weathering and leaching degree of carbonate buried hills is mainly divided vertically by core, thin section, electrical characteristics and other data, but this method can only be realized after drilling using core, thin section and logging data, and it is difficult to divide the weathering and leaching degree of carbonate buried hills vertically during the logging stage.

[0003] As a soluble rock, carbonate rock is affected by the leaching effect of atmospheric precipitation, and the leaching of calcium (Ca) and phosphorus (P) elements is obvious, while aluminum (Al), iron (Fe), silicon (Si) and other elements are enriched. The degree of weathering and leaching has obvious differences in the vertical direction, showing different porosity and permeability characteristics, which determines its different oil and gas storage capacity. Therefore, strengthening the understanding of the degree of weathering and leaching of carbonate buried hills is of great practical significance for the exploration and development of oil fields. Element logging technology is a new technology that has emerged in recent years. It can measure the content of 17 types of elements such as calcium (Ca), phosphorus (P), aluminum (Al), iron (Fe), silicon (Si) in rock cuttings. By constructing a leaching index model that comprehensively reflects the leaching degree of calcium (Ca) and phosphorus (P) elements and the enrichment degree of aluminum (Al), iron (Fe), and silicon (Si), it provides a new technical means for the vertical division of the leaching degree of carbonate rocks. Summary of the invention

[0004] The purpose of the present invention is to establish a method for dividing the degree of infiltration of carbonate buried hills based on element logging data, thereby solving the problem that it is difficult to vertically divide the degree of weathering and infiltration of carbonate buried hills during logging.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for classifying the dripping degree of carbonate buried hills comprises the following steps:

[0007] 1) Collect element logging, logging interpretation and core analysis data of the target well;

[0008] 2) Normalization of element logging data;

[0009] 3) Based on the normalized element logging data, a calculation model for the infiltration index that characterizes the infiltration degree of carbonate rocks is constructed;

[0010] 4) Establish a standard for the classification of regional carbonate rock infiltration degree.

[0011] The element logging data specifically include: Ca element data, P element data, Al element data, Fe element data, and Si element data.

[0012] The element logging data normalization processing method is specifically as follows:

[0013] X m =(XX min ) / (X max -X min )

[0014] Where X m is the normalized value of the parameter, X is the actual measured value of the parameter, and X min is the minimum value of the parameter, X max is the maximum value of the parameter.

[0015] The dripping index model is specifically:

[0016] K=(X Si +X Al +X Fe ) / (X Ca +X P )

[0017] Where K is the dripping index, X Si is the normalized value of Si element, X Al is the normalized value of Al element, X Fe is the normalized value of Fe element, X Ca is the normalized value of Ca element, X P is the normalized value of the P element.

[0018] The specific classification standard of carbonate rock infiltration degree in the region is: comparing and analyzing the infiltration index with the logging interpretation and core analysis data, and obtaining the classification standard of carbonate rock infiltration degree applicable to the work area by statistics.

[0019] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0020] (1) The present invention uses elemental data to characterize the infiltration degree of carbonate buried hills, which is an innovation in the application of logging data. At present, there is no method to directly characterize the control of atmospheric precipitation infiltration on carbonate reservoirs during the logging stage. The elemental logging data is used to realize the vertical characterization of the infiltration degree of carbonate buried hills.

[0021] (2) The present invention is real-time and based on element logging data, so that a dripping index curve that vertically reflects the dripping degree of carbonate buried hill can be obtained during the logging stage, thereby providing real-time guidance for the evaluation of the dripping degree of carbonate buried hill on site.

[0022] (3) The present invention is low-cost and does not require any additional cost for experimental analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Scatter plot of normalized values ​​of elements.

[0024] Figure 2 This is the result map of the classification of the infiltration degree of carbonate buried hills.

[0025] For ordinary technicians in this field, other relevant drawings can be obtained based on the above drawings without any creative work. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0027] Example 1

[0028] The method for classifying the dripping degree of carbonate buried hill of the present invention comprises the following steps:

[0029] 1) Collect element logging, logging interpretation and core analysis data of the target well. The element logging data include: calcium (Ca) element data, phosphorus (P) element data, aluminum (Al) element data, iron (Fe) element data, and silicon (Si) element data.

[0030] 2) Normalization of element logging data. The normalization method of element logging data is as follows: m =(XX min ) / (X max -X min ), where X m is the normalized value of the parameter, X is the actual measured value of the parameter, and X min is the minimum value of the parameter, X max is the maximum value of the parameter.

[0031] 3) Based on the normalized element logging data, a calculation model for the infiltration index that characterizes the infiltration degree of carbonate rocks is constructed. The infiltration index model is specifically: K = (X Si +X Al +X Fe ) / (X Ca +X P ), where X Si is the normalized value of silicon (Si), X Alis the normalized value of aluminum (Al), X Fe is the normalized value of iron (Fe), X Ca is the normalized value of calcium (Ca), X P is the normalized value of phosphorus (P).

[0032] 4) Establish the classification standard of regional carbonate rock infiltration degree. The classification standard of regional carbonate rock infiltration degree is as follows: compare and analyze the infiltration index with well logging, thin sections and cores, and obtain the classification standard of carbonate rock infiltration degree applicable to the work area.

[0033] The embodiment of the present invention takes the Paleozoic Ordovician carbonate buried hill strata of C3 well in Bohai C oilfield as an example. The Paleozoic Ordovician strata of the well are mainly limestone with a vertical thickness of 231 meters. The leaching index model of the well is calculated to characterize the leaching degree of calcium (Ca) and phosphorus (P) elements and the enrichment degree of aluminum (Al), iron (Fe), and silicon (Si) elements, thereby realizing the vertical division of the leaching degree of the carbonate buried hill.

[0034] See the following description for details:

[0035] 101: Collect element logging data of the target well;

[0036] Collect element logging data of Well C3, including Ca element data, P element data, Al element data, Fe element data and Si element data.

[0037] 102: Normalization of element logging data;

[0038] There are three wells, C1, C2 and C3, in Bohai C oilfield, which have encountered Paleozoic Ordovician carbonate buried hill strata. Taking silicon (Si) as an example, the maximum measured value of silicon (Si) in the logging data of the Paleozoic Ordovician section of the C work area is calculated. max and the minimum measured value X min , using the formula X Si =(XX min ) / (X max -X min ) to get the normalized value X of silicon (Si) element Si Similarly, the normalized values ​​of calcium (Ca), phosphorus (P), aluminum (Al), and iron (Fe) can be obtained.

[0039] like Figure 1 The scatter plot shown is the change of normalized values ​​of calcium (Ca), phosphorus (P), aluminum (Al), and iron (Fe) in the Paleozoic Ordovician carbonate buried hill strata of Well C3 in Bohai C Oilfield, indicating that under the action of atmospheric precipitation, the leaching intensity of Ca and P elements and the enrichment intensity of Si, Fe, and Al elements gradually weakened in the vertical direction.

[0040] 103: Constructing a calculation model of the infiltration index to characterize the infiltration degree of carbonate rocks based on the normalized element logging data;

[0041] Based on the normalized data of element logging, the calculation equation of dripping index is established:

[0042] K=(X Si +X Al +X Fe ) / (X Ca +X P ) (1)

[0043] Where X Si is the normalized value of silicon (Si), X Al is the normalized value of aluminum (Al), X Fe is the normalized value of iron (Fe), X Ca is the normalized value of calcium (Ca), X P is the normalized value of phosphorus (P).

[0044] 104: Establish a standard for the classification of regional carbonate rock infiltration degree.

[0045] The calculation result of the infiltration index can be obtained according to formula 1. The result is compared with the well logging interpretation and core data to obtain the carbonate infiltration degree classification standard as shown in Table 1. Table 1 shows the infiltration degree classification standard of the Paleozoic Ordovician carbonate buried hill strata in Bohai C Oilfield. The range of variation varies in different regions.

[0046] Table 1 Classification criteria for carbonate buried hill oozing degree

[0047]

[0048] The above calculation process is used to calculate the evaluation parameters of the infiltration index of the new well, and then the infiltration degree of the carbonate buried hill is divided vertically using the work area standards to finally complete the evaluation.

[0049] In order to ensure the accuracy of the classification of the infiltration degree of the Paleozoic Ordovician carbonate buried hill in Bohai C Oilfield, it is also necessary to conduct a reliability test on the classification results. The embodiment of the present invention uses the net-to-gross ratio to evaluate the accuracy of the classification of the infiltration degree of the carbonate buried hill, as described below:

[0050] The net-to-gross ratio is the ratio of the vertical thickness of the reservoir interpreted by logging to the vertical thickness of the well section. The closer the value is to 100%, the more developed the formation encountered by drilling is, and the stronger the infiltration effect on the formation is. In the example of the present invention: the net-to-gross ratio of the strong infiltration zone is 100%, the net-to-gross ratio of the medium infiltration zone is 40.97%, and the net-to-gross ratio of the weak infiltration zone is 2.29%. Figure 2The results show that the classification results of formation infiltration degree are consistent with the actual logging results, and the infiltration index constructed based on element logging data can be used to divide the infiltration degree of carbonate buried hills vertically.

[0051] The present invention is further described above with the aid of specific embodiments. However, it should be understood that the specifics herein should not be construed as limiting the essence and scope of the present invention. Various modifications made to the above embodiments by ordinary technicians in the field after reading this specification are all within the scope of protection of the present invention.

Claims

1. A method for classifying the degree of infiltration of carbonate buried hills, characterized in that: It consists of the following steps: Step 1: Collect element logging, logging interpretation and core analysis data of the target well; The element logging data specifically include: Ca element data, P element data, Al element data, Fe element data, and Si element data; Step 2: Normalization processing of element logging data; the normalization processing method of element logging data is specifically as follows: X m =(X-X min ) / (X max -X min ) Where X m is the normalized value of the parameter, X is the actual measured value of the parameter, and X min is the minimum value of the parameter, X max is the maximum value of the parameter; Step 3: construct a calculation model for the infiltration index that characterizes the infiltration degree of carbonate rocks based on the element logging normalized data; the infiltration index model is specifically: K=(X Si +X Al +X Fe ) / (X Ca +X P ) Where K is the dripping index, X Si is the normalized value of Si element, X Al is the normalized value of Al element, X Fe is the normalized value of Fe element, X Ca is the normalized value of Ca element, X P is the normalized value of the P element; Step 4: Establish a standard for the classification of regional carbonate rock infiltration degree; the specific standard for the classification of regional carbonate rock infiltration degree is: compare and analyze the infiltration index with the logging interpretation and core analysis data, and statistically obtain the classification standard for the carbonate rock infiltration degree applicable to the work area.

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