Method of judging formation fluid properties using gas logging curve morphology function

Abstract

The present invention discloses a method for discriminating formation fluid properties by using a morphological function of a gas logging curve, and relates to the technical field of geological evaluation while drilling. In this scheme, gas logging data is functionalized with respect to well depth, and a main trend calculation formula of the function is established through standardization processing, trend analysis, and extreme value transformation, and a trend slope ratio is calculated. The difference in trend slope ratios of gas logging curves corresponding to sandstone reservoirs containing different fluids is used to establish a discrimination standard and form a discrimination method, which is then used to discriminate formation fluid properties of sandstone reservoirs in new wells while drilling. This method effectively solves the problem of difficulty in discriminating fluid properties while drilling in low-pressure, high-bound water, and thin-layer sandstone reservoirs in the Sulige area. The conformity rate of formation fluid property discrimination while drilling using this method reaches 89.3%, which significantly exceeds the conformity rate of existing discrimination methods such as the plate method, and the discrimination results are more reliable.

Description

Technical Field

[0001] The present invention relates to the technical field of geological evaluation while drilling, and in particular to a method for discriminating formation fluid properties using a gas logging curve morphology function. Background Art

[0002] At present, the identification of formation fluid properties while drilling is mainly based on the changing characteristics of logging parameters such as temperature, conductivity, chloride ions, and the comprehensive response of gas logging display parameters and curve morphology, or by using fluid identification technology based on these parameters. It is widely used and has good results.

[0003] However, for the He 8 and Shan 1 sandstone reservoirs, the primary target layers in the Sulige area, the low pressure, high bound water content, and thin layers result in minimal or no change in temperature, conductivity, and chloride ion parameters during drilling through the aquifer. The parameter response rate is less than 10%, making it ineffective for while-drilling identification of formation fluid properties. Furthermore, due to the lack of a clear gas-water boundary in sandstone reservoirs and the low pressure and thin layers, the gas logging curve exhibits rapid rises and falls, rather than the characteristic rapid decline followed by a slower decrease characteristic of aquifers.

[0004] Since the formation fluid property response characteristics of these commonly used logging parameters such as temperature, conductivity, chloride ions, and gas logging displays are not obvious, the existing methods based on subtle changes in temperature and conductivity, methods based on the morphological changes of gas logging curves, and methods based on gas logging display values ​​are all unsatisfactory. The discrimination compliance rate is generally around 70%, which is significantly low.

[0005] Therefore, it is urgent to develop new methods with regional applicability to overcome the difficulties in while-drilling evaluation of formation fluid properties in low-pressure, high-bound water, and thin-layer sandstone reservoirs. Summary of the Invention

[0006] The present invention aims to provide a method for discriminating formation fluid properties using a gas logging curve morphology function. This method converts gas logging data into a function of well depth. Through standardization, trend analysis, and extreme value transformation, a formula for calculating the function's main trend is established, and the trend slope ratio is calculated. By utilizing the differences in the trend slope ratios of gas logging curves corresponding to sandstone reservoirs containing different fluids, a discrimination standard is established, resulting in a reliable method for determining formation fluid properties.

[0007] The present invention is achieved through the following technical solutions:

[0008] A method for discriminating formation fluid properties using a gas logging curve morphology function comprises the following steps:

[0009] a. Collect the logging data and oil test information of the wells that have been tested in the study area, and select the test sections based on the test results;

[0010] b. Extract the gas testing data of the corresponding gas testing display section according to the screened oil testing section;

[0011] c. Standardize the drilling time and displacement of the total hydrocarbons in the extracted gas logging data;

[0012] d. Taking a single set of sandstone reservoirs as a benchmark, the data before the normalized total hydrocarbon peak is taken as the gas logging ascending section, and the data after the total hydrocarbon peak is taken as the gas logging descending section. The gas logging ascending section and gas logging descending section data are respectively fitted with a cubic function to the well depth to obtain the gas logging ascending function and gas logging descending function;

[0013] e. Based on the trend of the cubic function slope, select the value with a depth coverage rate exceeding 50% as the main trend of the function;

[0014] f. Calculate the trend slope ratio based on the main trend values ​​of the gas logging ascending function and the gas logging descending function of each sandstone reservoir;

[0015] g. Integrate the trend slope ratios of each sandstone reservoir and establish a discrimination standard based on the corresponding oil testing conclusions to form a discrimination method.

[0016] Furthermore, in step a, oil testing sections in which multiple sets of sandstone reservoirs were tested simultaneously and the oil testing conclusions were that a single fluid was present, and oil testing sections in which only one set of sandstone reservoirs was tested, are screened out from the tested oil wells to match the formation fluid properties corresponding to the sandstone reservoirs in the oil testing sections.

[0017] Furthermore, in step b, the gas logging data of the gas logging display section is extracted as a whole from the screened oil testing section, taking a single set of sandstone reservoirs as a benchmark.

[0018] Furthermore, in step c, the total hydrocarbons in the extracted gas logging data are subjected to standardization processing of drilling time and displacement;

[0019] The formula for normalizing drilling time and displacement of the total hydrocarbons in the extracted gas logging data is formula (I):

[0020] TG 标准 = TG × V / V 标准 × t / t 标准 Formula (I),

[0021] in, TG 标准 is the standard total hydrocarbon; V is the displacement; V 标准 For standard displacement; t For drilling time; t 标准is the standard drilling time. The selection of standard displacement and standard drilling time is determined by the average value of the sandstone section in the study area.

[0022] Furthermore, in step c, the standard displacement is 20-30 L / s, and the standard drilling time is 5-10 min / m.

[0023] Furthermore, in step d, the aforementioned single set of sandstone reservoirs is used as a benchmark, the total hydrocarbon base value at the beginning of the gas logging display is used as the starting point, the total hydrocarbon recovery value at the end of the gas logging display is used as the ending point, and the total hydrocarbon peak value after normalization is used as the boundary. The normalized total hydrocarbon curve is divided into a gas logging rising section and a gas logging falling section. The data of the gas logging rising section and the gas logging falling section are respectively fitted with a cubic function to the well depth, and the gas logging rising function and the gas logging falling function are obtained as the relationship (II)

[0024] TG 标准 =a × H 3 + b × H 2 c × H + d Formula (II),

[0025] in, H For the well depth, a 、 b 、 c 、 d are the fitting formula coefficients.

[0026] Furthermore, in step d, if the same set of sandstone reservoirs contains two gas logging displays, the two displays are merged to extract the gas logging ascending segment data of the first gas logging display and the gas logging descending segment data of the second gas logging display; if the gas logging display segment is thick and the peak duration is long, the gas logging ascending segment data is extracted to the first near-peak point, and the total hydrocarbon value at the near-peak point exceeds 85% of the total hydrocarbon value at the peak point, and the gas logging descending segment data is extracted starting from the last near-peak point.

[0027] Furthermore, in step e, based on the cubic function obtained by fitting, the function slope is obtained as equation (III),

[0028] k=3a × H 2 +2b × H+ c (III), in, k is the slope of the cubic function;

[0029] Based on the curve characteristics of the cubic function, the slope value with a depth ratio exceeding 50% is selected as the main trend of the function. The extreme slope value is generally used as the main trend of the function to achieve a depth ratio exceeding 50%. If this cannot be achieved, adjustments can be made based on actual conditions.

[0030] According to the slope relationship of the function, the depth of the slope extreme value is deduced as

[0031] (IV), in, h is the well depth of the extreme slope,

[0032] The extreme slope and main trend value of the function are

[0033] (V);

[0034] (VI).

[0035] Furthermore, in step f, based on the main trend values ​​of the gas logging ascending function and the gas logging descending function of each sandstone reservoir, the trend slope ratio is calculated as equation (VII):

[0036] R =∣ k 上升 / k 下降 ∣ (VII).

[0037] Furthermore, in step g, the trend slope ratios of the sandstone reservoirs in the selected oil test sections are integrated and combined with the corresponding oil test results to assign corresponding fluid properties to each sandstone reservoir. Based on the principle of maximizing the coincidence rate, a discriminant value is selected as the formation fluid property discrimination criterion, thus forming a discrimination method. Based on the selected discrimination criterion, the formation fluid properties of the sandstone reservoirs in the new well can be determined while drilling. Specifically, through steps b-g, the trend slope ratios of the sandstone reservoirs in the new well are calculated and combined with the discrimination criterion to produce a discrimination result.

[0038] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0039] First, this invention functions the gas logging curve as a function of well depth, more objectively displaying its changing trends. This significantly improves the usability of gas logging data and lays an important foundation for subsequent trend analysis and data processing. This method is more objective and accurate than existing standardization and correction methods, which all process gas logging data based on well depth. These methods are all based on data from the same well depth, independent of well depth.

[0040] Second, the present invention uses the functionalized gas logging curves through standardization, trend analysis, and extreme value transformation to obtain a formula for calculating the main trend of the function. This effectively avoids the subjectivity of human judgment and makes the conclusion more objective and accurate. Compared with the existing technology of using gas logging curves to identify formation fluid properties, this method is more objective. The existing method mainly summarizes the depth-varying characteristics of the gas logging curve when drilling into a water-producing layer, and uses this as a basis to identify formation fluid properties through human observation and empirical judgment. This method is too subjective, resulting in a large discrepancy between the final identification results and the actual results. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a graphical representation of the curve function of the gas measurement ascending section and the gas measurement descending section in the fourth step of Example 2.

[0042] Figure 2 This is the step 7 in Example 2 where the discrimination value is selected with the maximum matching rate. DETAILED DESCRIPTION

[0043] The present invention will be further described in detail below with reference to the examples, but the embodiments of the present invention are not limited thereto.

[0044] Example 1

[0045] This embodiment is the most basic implementation method, which is a method for discriminating formation fluid properties using gas logging curve morphology functions, and relates to the field of geological evaluation while drilling technology, including the following steps:

[0046] a. Collect the logging data and oil test information of the wells that have been tested in the study area, and select the test sections based on the test results;

[0047] b. Extract the gas testing data of the corresponding gas testing display section according to the screened oil testing section;

[0048] c. Standardize the drilling time and displacement of the total hydrocarbons in the extracted gas logging data;

[0049] d. Taking a single set of sandstone reservoirs as a benchmark, the data before the normalized total hydrocarbon peak is taken as the gas logging ascending section, and the data after the total hydrocarbon peak is taken as the gas logging descending section. The gas logging ascending section and gas logging descending section data are respectively fitted with a cubic function to the well depth to obtain the gas logging ascending function and gas logging descending function;

[0050] e. Based on the trend of the cubic function slope, select the value with a depth coverage rate exceeding 50% as the main trend of the function;

[0051] f. Calculate the trend slope ratio based on the main trend values ​​of the gas logging ascending function and the gas logging descending function of each sandstone reservoir;

[0052] g. Integrate the trend slope ratios of each sandstone reservoir and establish a discrimination standard based on the corresponding oil testing conclusions to form a discrimination method.

[0053] In this example, gas logging data was functionalized against well depth. A formula for calculating the main trend of the function was established through standardization, trend analysis, and extreme value transformation. The trend slope ratio was then calculated. By leveraging the differences in trend slope ratios between gas logging curves corresponding to sandstone reservoirs containing different fluids, a discrimination criterion was established, resulting in a method that has a high degree of match with actual formation fluid properties.

[0054] Example 2

[0055] This embodiment takes the tight sandstone reservoirs of He 8 and Shan 1 sections in the Sulige area as an example, and uses the gas logging curve morphology function to discriminate the formation fluid properties to further illustrate this solution for easier public understanding.

[0056] The method for determining formation fluid properties using the gas logging curve morphology function specifically includes the following steps:

[0057] The first step is to collect the logging data, well logging data and oil test information of the tested wells in the study area, and screen the test sections based on the oil test conclusions:

[0058] Oil testing of the He 8 and Shan 1 sandstone reservoirs in the Sulige area typically covers multiple sandstone bodies, typically one to three, and employs segmented perforation followed by overall testing. The testing often concludes that gas and water are produced simultaneously. From the wells tested, we screened out sections where multiple sandstone reservoirs were tested simultaneously and the results indicated a single fluid, as well as sections where only one sandstone reservoir was tested. The fluid properties of the sandstone reservoirs within the test sections were then matched.

[0059] Step 2: Extract the gas testing data of the corresponding gas testing display segment based on the oil testing segment selected in the first step:

[0060] From the screened test oil sections, the gas testing data of the gas testing display section is extracted as a whole based on a single set of sandstone reservoirs. That is, if there is only one gas testing display, the data is extracted from the beginning to the end of the display; if there are two gas testing displays, the data is extracted from the beginning of the first gas testing display to the end of the second gas testing display.

[0061] The third step is to standardize the drilling time and displacement of the total hydrocarbons in the extracted gas logging data.

[0062] Engineering parameters have a great influence on gas logging parameters, which in turn seriously affect the results of gas logging curve functionization. It is necessary to standardize two key parameters, drilling time and displacement. The standardization formula for drilling time and displacement is formula (I):

[0063] TG 标准 = TG × V / V 标准 × t / t 标准 (I),

[0064] In formula 1, TG 标准 is the standard total hydrocarbon; V is the displacement; V 标准 For standard displacement; t For drilling time; t 标准 is the standard drilling time. The selection of standard displacement and standard drilling time is determined by the average value of the sandstone section in the study area.

[0065] The standard displacement and drilling time are determined by the average values ​​of the sandstone sections in the study area. Generally, the standard displacement is 20-30 L / s and the standard drilling time is 5-10 min / m.

[0066] The fourth step is to use the aforementioned single set of sandstone reservoirs as the benchmark, with the total hydrocarbon base value at the beginning of the gas logging display as the starting point, the total hydrocarbon recovery value at the end of the gas logging display as the ending point, and the total hydrocarbon peak value after normalization as the boundary, and divide the normalized total hydrocarbon curve into the gas logging rising section and the gas logging falling section. The data of the gas logging rising section and the gas logging falling section are respectively fitted with a cubic function to the well depth, and the gas logging rising function and the gas logging falling function are obtained as the relationship (II),

[0067] TG 标准 =a × H 3 + b × H 2 c × H + d Formula (II),

[0068] in, H For the well depth, a 、 b 、 c 、 d are the fitting formula coefficients.

[0069] If the same set of sandstone reservoirs contains two gas logging displays, the two displays are merged to extract the gas logging ascending segment data of the first gas logging display and the gas logging descending segment data of the second gas logging display;

[0070] If the gas logging section shows a thicker section and a longer peak duration, extract the gas logging ascending section data to the first near-peak point, where the total hydrocarbon value exceeds 85% of the total hydrocarbon value at the peak point. Extract the gas logging descending section data starting from the last near-peak point.

[0071] In this embodiment, the curve function reference of the gas logging ascending section and the gas logging descending section of the study area is Figure 1 .

[0072] Step 5. Based on the slope change trend of the cubic function obtained above, select the value with depth coverage exceeding 50% as the main trend of the function.

[0073] According to the cubic function obtained by fitting, the slope of the function is the relationship (III),

[0074] k=3a × H 2 +2b × H+ c (III), Where k is the slope of the cubic function;

[0075] Based on the characteristics of the cubic function curve, select the slope value that accounts for more than 50% of the depth as the function's main trend. Based on existing data, using the extreme slope value as the function's main trend generally achieves a depth share of more than 50%. If this is not possible, adjust the value based on actual conditions.

[0076] According to the slope relationship of the function, the well depth of the slope extreme value is deduced as:

[0077] h=-b⁄3a (IV)

[0078] In formula IV, h is the well depth of the extreme slope.

[0079] The extreme slope and main trend value of the function are

[0080] (V);

[0081] (VI).

[0082] Step 6: Based on the main trend values ​​of the gas logging ascending function and the gas logging descending function of each sandstone reservoir, the trend slope ratio is calculated as equation (VII):

[0083] R =∣ k 上升 / k 下降 ∣ (VII).

[0084] Step 7: Integrate the trend slope ratios of each sandstone reservoir and establish a discrimination standard based on the oil test results to form a discrimination method:

[0085] The trend slope ratio of the sandstone reservoir in the selected oil test section is integrated, and the corresponding fluid properties are assigned to each set of sandstone reservoirs in combination with the corresponding oil test conclusions. The discrimination value is selected as the discrimination standard for the formation fluid properties according to the principle of maximum compliance rate to form a discrimination method. Figure 2 The discrimination criteria obtained in this embodiment are: gas layer: R<1.1; aquifer (gas-water layer and water layer): R≥1.1.

[0086] Step 8. Based on the selected discrimination criteria, the formation fluid properties of the new well sandstone reservoir can be identified while drilling. That is, through steps b to g, the trend slope ratio of the new well sandstone reservoir is calculated, and the discrimination result is obtained in combination with the discrimination criteria.

[0087] The present invention functions gas logging data against well depth, establishes a formula for calculating the main trend of the function through standardization, trend analysis, and extreme value transformation, and calculates the trend slope ratio. By utilizing the differences in the trend slope ratios of gas logging curves corresponding to sandstone reservoirs containing different fluids, a discrimination standard is established, forming a discrimination method. This method effectively addresses the difficulty in while-drilling fluid property discrimination in low-pressure, high-bound-water, and thin-layer sandstone reservoirs in the Sulige area. Tests have shown that the compliance rate for while-drilling formation fluid property discrimination using this method reached 89.3%, significantly exceeding the compliance rate of existing discrimination methods such as the plate method.

[0088] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for discriminating formation fluid properties using gas logging curve morphology functions, characterized in that: The following steps are involved: a. Collect the logging data and oil test information of the wells that have been tested in the study area, and select the test sections based on the test results; b. Extract the gas testing data of the corresponding gas testing display section according to the screened oil testing section; c. Standardize the drilling time and displacement of the total hydrocarbons in the extracted gas logging data; d. Taking a single set of sandstone reservoirs as a benchmark, the data before the normalized total hydrocarbon peak is taken as the gas logging ascending section, and the data after the total hydrocarbon peak is taken as the gas logging descending section. The gas logging ascending section and gas logging descending section data are respectively fitted with a cubic function to the well depth to obtain the gas logging ascending function and gas logging descending function; e. Based on the trend of the cubic function slope, select the value with a depth coverage rate exceeding 50% as the main trend of the function; f. Calculate the trend slope ratio based on the main trend values ​​of the gas logging ascending function and the gas logging descending function of each sandstone reservoir; g. Integrate the trend slope ratios of each sandstone reservoir and establish a discrimination standard based on the corresponding oil test results to form a discrimination method for while-drilling identification of the formation fluid properties of the sandstone reservoir in the new well.

2. The method for discriminating formation fluid properties using gas logging curve morphology functions according to claim 1, characterized in that: In step a, multiple test sections in which multiple sandstone reservoirs were tested simultaneously and the test conclusions were that a single fluid was present, as well as test sections in which only one sandstone reservoir was tested, were selected from the tested wells to match the formation fluid properties corresponding to the sandstone reservoirs in the test sections.

3. The method for discriminating formation fluid properties using gas logging curve morphology functions according to claim 2, characterized in that: In step b, the gas logging data of the gas logging display section are extracted as a whole from the screened oil testing section, taking a single set of sandstone reservoirs as a benchmark.

4. The method for discriminating formation fluid properties using gas logging curve morphology functions according to claim 3, characterized in that: In step c, the total hydrocarbons in the extracted gas logging data are subjected to standardization processing of drilling time and displacement; The formula for normalizing drilling time and displacement of the total hydrocarbons in the extracted gas logging data is formula (I): TG 标准 = TG × V / V 标准 × t / t 标准 Formula (I), in, TG 标准 is the standard total hydrocarbon; V is the displacement; V 标准 For standard displacement; t For drilling time; t 标准 is the standard drilling time. The selection of standard displacement and standard drilling time is determined by the average value of the sandstone section in the study area.

5. The method for discriminating formation fluid properties using gas logging curve morphology functions according to claim 4, characterized in that: In step c, the standard displacement is 20~30L / s, and the standard drilling time is 5~10min / m.

6. The method for discriminating formation fluid properties using gas logging curve morphology functions according to claim 4, characterized in that: In step d, the aforementioned single sandstone reservoir is used as a benchmark, the total hydrocarbon base value at the beginning of the gas logging display is used as the starting point, the total hydrocarbon recovery value at the end of the gas logging display is used as the ending point, and the total hydrocarbon peak value after normalization is used as the boundary. The normalized total hydrocarbon curve is divided into a gas logging rising section and a gas logging falling section; the data of the gas logging rising section and the gas logging falling section are respectively fitted with a cubic function to the well depth, and the gas logging rising function and the gas logging falling function are obtained as the relationship (II), TG 标准 =a × H 3 + b × H 2 c × H + d Formula (II), in, H For the well depth, a 、 b 、 c 、 d are the fitting formula coefficients.

7. The method for discriminating formation fluid properties using gas logging curve morphology functions according to claim 6, characterized in that: In step d, if the same set of sandstone reservoirs contains two gas logging indications, the two indications are merged to extract the gas logging ascending segment data of the first gas logging indication and the gas logging descending segment data of the second gas logging indication; If the gas logging shows a thick section and the peak duration is long, the extraction of the gas logging ascending section data ends at the first near-peak point, and the total hydrocarbon value at the near-peak point exceeds 85% of the total hydrocarbon value at the peak point. When extracting the gas logging descending section data, start from the last near-peak point.

8. The method for discriminating formation fluid properties using gas logging curve morphology functions according to claim 6, characterized in that: In step e, based on the cubic function obtained by fitting, the function slope is obtained as equation (III), k=3a × H 2 +2b × H+ c （Ⅲ）, in, k is the slope of the cubic function; Based on the curve characteristics of the cubic function, the slope value with a depth ratio exceeding 50% is selected as the main trend of the function. The extreme slope value is generally used as the main trend of the function to achieve a depth ratio exceeding 50%. If this cannot be achieved, adjustments can be made based on actual conditions. According to the slope relationship of the function, the depth of the slope extreme value is deduced as （Ⅳ）， in, h is the well depth of the extreme slope, The extreme slope and main trend value of the function are （Ⅴ）； （Ⅵ）。 9. The method for discriminating formation fluid properties using gas logging curve morphology functions according to claim 8, characterized in that: In step f, based on the main trend values ​​of the gas logging ascending function and the gas logging descending function of each sandstone reservoir, the trend slope ratio is calculated as equation (VII): R =∣ k 上升 / k 下降 ∣ （Ⅶ）。 10. The method for discriminating formation fluid properties using gas logging curve morphology functions according to claim 9, characterized in that: In step g, the trend slope ratios of the sandstone reservoirs in the screened oil test sections are integrated, and the corresponding fluid properties are assigned to each set of sandstone reservoirs in combination with the corresponding oil test conclusions. The discrimination value is selected as the discrimination criterion for the formation fluid properties according to the principle of maximum compliance, forming a discrimination method for while-drilling discrimination of the formation fluid properties of the sandstone reservoirs in the new well.

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