Method for discriminating properties of formation fluid by gas logging curve morphological function

Abstract

The invention discloses a method for distinguishing formation fluid properties through a gas logging curve morphological function, and relates to the technical field of geological evaluation while drilling, in the scheme, gas logging data is used for functionalizing the well depth, a function main trend calculation formula is established through standardization processing, trend analysis and extreme value transformation, the trend slope ratio is calculated, and the gas logging curve morphological function is obtained. According to the method, a judgment standard is established and a judgment method is formed by utilizing trend slope ratio differences of gas logging curves corresponding to sandstone reservoirs containing different fluids, and then the judgment method is used for performing while-drilling judgment on formation fluid properties of new well sandstone reservoirs, so that the problem that the fluid properties of low-pressure, high-bound-water and thin-layer sandstone reservoirs in the Sulige region are difficult to judge while drilling is effectively solved; the formation fluid property while drilling judgment coincidence rate reaches 89.3% and is obviously higher than the coincidence rate of an existing chart method and other judgment methods, and the judgment result is more reliable.

Description

Technical Field

[0001] The invention relates to the technical field of geological evaluation while drilling, and in particular to a method for determining 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, which is widely used and has good results.

[0003] However, for the main target layers of the Sulige area, the Box 8 and Mountain 1 sandstone reservoirs, due to their low pressure, high bound water, and thin layer characteristics, the temperature, conductivity, and chloride ion parameters change very little or even do not change during the drilling process of the aquifer, and the parameter response rate is less than 10%, which cannot be effectively used for the identification of formation fluid properties while drilling. At the same time, due to the lack of obvious gas-water boundaries in the sandstone reservoirs, coupled with the low pressure and thin layer characteristics of the sandstone reservoirs, the gas logging curve shows the characteristics of rapid rise and fall as a whole, and the gas logging characteristics of aquifers, which first drop rapidly and then slowly, will not appear.

[0004] Since the formation fluid property response characteristics of commonly used logging parameters such as temperature, conductivity, chloride ion, and gas logging display 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 not ideal, and the discrimination compliance rate is generally around 70%, which is significantly low.

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

[0006] The purpose of the present invention is to provide a method for discriminating formation fluid properties by using a gas logging curve morphology function, which functions the gas logging data to the well depth, establishes a function main trend calculation formula through standardization processing, trend analysis and extreme value transformation, and calculates the trend slope ratio. By using the difference in trend slope ratios of gas logging curves corresponding to sandstone reservoirs containing different fluids, a discrimination standard is established to form a discrimination method, and the formation fluid properties obtained by the discrimination method are reliable.

[0007] The present invention is achieved through the following technical solutions: A method for determining formation fluid properties using a gas logging curve morphology function comprises the following steps: 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 according to the oil test conclusions; b. Extract the gas testing data of the corresponding gas testing display section according to the selected oil testing section; c. Standardize the drilling time and displacement of all 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 the gas logging descending section data are respectively fitted with the well depth by cubic function to obtain the gas logging ascending function and the gas logging descending function; e. According to the trend of the slope change of the cubic function, the value with depth coverage exceeding 50% is selected 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, combine with the corresponding oil testing conclusions to establish the discrimination criteria and form a discrimination method.

[0008] Furthermore, in step a, oil testing sections in which multiple sets of sandstone reservoirs are tested at the same time and the oil testing conclusions are single fluid and oil testing sections in which only one set of sandstone reservoirs is tested are screened out from the tested wells to match the formation fluid properties corresponding to the sandstone reservoirs in the oil testing sections.

[0009] Furthermore, in step b, the gas testing data of the gas testing display section is extracted as a whole based on a single set of sandstone reservoirs from the screened oil testing section.

[0010] Furthermore, 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 the drilling time and displacement of the total hydrocarbons in the extracted gas logging data is as follows: 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 It is the 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.

[0011] Furthermore, in step c, the standard displacement is 20-30 L / s, and the standard drilling time is 5-10 min / m.

[0012] 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 standardization is used as the boundary, and the standardized total hydrocarbon curve is divided into a gas logging ascending section and a gas logging descending section. The data of the gas logging ascending section and the gas logging descending section are respectively fitted with a cubic function with the well depth, and the gas logging ascending function and the gas logging descending 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 depth of the well, a , b , c , d are the coefficients of the fitting formula.

[0013] 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.

[0014] Furthermore, in step e, according to the cubic function obtained by fitting, the function slope is obtained as equation (III), k=3a × H 2 +2b × H+ c (III), among which, k is the slope of the cubic function; According to the curve characteristics of the cubic function, the slope value with a depth ratio of more than 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 of more than 50%. If it cannot be achieved, it can be adjusted according to the actual situation. According to the function slope relationship, the well depth of the slope extreme value is deduced as (IV), where h is the well depth of the extreme slope, The extreme slope and main trend value of the function is (V); (VI).

[0015] Furthermore, in step f, according to 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).

[0016] Furthermore, in step g, 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 formation fluid property discrimination standard according to the principle of maximum compliance rate to form a discrimination method. According to the selected discrimination standard, the formation fluid properties of the sandstone reservoir of the new well can be discriminated while drilling, that is, through steps b to g, the trend slope ratio of the sandstone reservoir of the new well is calculated, and the discrimination result is obtained in combination with the discrimination standard.

[0017] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. In the present invention, the gas logging curve is functionalized to the well depth, which more objectively shows the changing trend of the gas logging curve, greatly improves the availability of gas logging data, and lays an important foundation for subsequent trend analysis and data processing. Compared with the existing standardization processing, correction processing and other methods, it is more objective and accurate. These processing methods are all equal to the well depth for the processing of gas logging data. This type of processing method is based on the data of the same well depth, and the processing method is independent of the well depth.

[0018] 2. In the present invention, based on the gas logging curve after functionalization, the main trend calculation formula of the function is obtained through standardization processing, trend analysis and extreme value transformation, which effectively avoids the subjectivity of human judgment and makes the conclusion more objective and accurate. Compared with the technology of using gas logging curves in the identification of formation fluid properties in the prior art, this method is more objective. The existing method mainly summarizes the changing characteristics of the gas logging curve at depth when drilling into a water-producing layer, and uses this as the basis to identify the formation fluid properties through human observation and experience judgment. This method is too subjective, resulting in a large gap between the final identification result and the actual result. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] 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.

[0020] Figure 2 This is the step 7 in Example 2 where the discrimination value is selected with the maximum matching rate. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0022] Example 1 This embodiment is the most basic implementation method, a method for determining formation fluid properties using a gas logging curve morphology function, which relates to the technical field of geological evaluation while drilling, and includes the following steps: 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 according to the oil test conclusions; b. Extract the gas testing data of the corresponding gas testing display section according to the selected oil testing section; c. Standardize the drilling time and displacement of all 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 the gas logging descending section data are respectively fitted with the well depth by cubic function to obtain the gas logging ascending function and the gas logging descending function; e. According to the trend of the slope change of the cubic function, the value with depth coverage exceeding 50% is selected 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, combine with the corresponding oil testing conclusions to establish the discrimination criteria and form a discrimination method.

[0023] In this embodiment, the gas logging data is functionalized to the well depth, and the main trend calculation formula of the function is established through standardization, trend analysis and extreme value transformation, and the 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, and the result has a high matching rate with the actual formation fluid properties.

[0024] Example 2 This embodiment takes a certain dense sandstone reservoir in the Box 8 and Mountain 1 sections of the Sulige area as an example, and uses the gas logging curve morphology function to determine the formation fluid properties, to further illustrate this solution and facilitate public understanding.

[0025] The method for determining the formation fluid properties by the gas logging curve morphology function specifically comprises the following steps: 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 select the test sections according to the oil test conclusions: The oil testing of the sandstone reservoirs in the He 8 and Shan 1 sections in the Sulige area generally covers multiple sets of sand bodies, usually 1 to 3 sets, and adopts the method of segmented perforation and overall oil testing, and the oil testing conclusions are mostly gas and water co-production. From the tested wells, the oil testing sections where multiple sets of sandstone reservoirs were tested and the oil testing conclusions were single fluid and the oil testing sections where only one set of sandstone reservoirs was tested were selected to match the formation fluid properties corresponding to the sandstone reservoirs in the oil testing sections.

[0026] Step 2: Extract the gas test data of the corresponding gas test display segment according to the oil test segment selected in the first step: From the screened test oil sections, taking a single set of sandstone reservoirs as the benchmark, the gas testing data of the gas testing display section are extracted as a whole, that is, if there is only one section of gas testing display, it is extracted from the beginning to the end of the display; if there are two sections of gas testing display, it is extracted from the beginning of the first section of gas testing display to the end of the second section of gas testing display.

[0027] The third step is to standardize the drilling time and displacement of all hydrocarbons in the extracted gas logging data.

[0028] Engineering parameters have a great influence on gas testing parameters, which in turn seriously affect the results of gas testing curve functionalization. It is necessary to standardize two key parameters, drilling time and displacement. The standardization formula for drilling time and displacement is formula (I), TG 标准 = TG × V / V 标准 × t / t 标准 (I), In formula 1, TG 标准 is the standard total hydrocarbon; V is the displacement; V 标准 It is the 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.

[0029] The standard displacement and standard drilling time are determined by the average values ​​of the sandstone section in the study area. Generally, the standard displacement is 20~30L / s and the standard drilling time is 5~10min / m.

[0030] Step 4: Taking the aforementioned single set of sandstone reservoirs as the benchmark, taking the total hydrocarbon base value at the beginning of the gas logging display as the starting point, taking the total hydrocarbon recovery value at the end of the gas logging display as the end point, and taking the total hydrocarbon peak value after standardization as the boundary, the standardized total hydrocarbon curve is divided 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 the well depth by cubic function, 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 depth of the well, a , b , c , d are the coefficients of the fitting formula.

[0031] 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 section thickness is large and the peak duration is long, the extraction of gas logging ascending section data ends at the first near-peak point, and the near-peak point total hydrocarbon value exceeds 85% of the peak point total hydrocarbon value. Extraction of gas logging descending section data starts from the last near-peak point.

[0032] 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 .

[0033] Step 5. According to the slope change trend of the cubic function obtained above, select the value of depth coverage exceeding 50% as the main trend of the function.

[0034] According to the cubic function obtained by fitting, the function slope is the relationship (III), k=3a × H 2 +2b × H+ c (III), where k is the slope of the cubic function; According to the characteristics of the cubic function curve, the slope value with a depth ratio of more than 50% is selected as the main trend of the function. Combined with the existing data, the slope extreme value can generally reach a depth ratio of more than 50% when used as the main trend of the function. If it cannot be achieved, it can be adjusted according to the actual situation.

[0035] According to the function slope relationship, the well depth of the slope extreme value is: h = -b⁄3a (IV) In Formula IV, h is the well depth of the extreme slope.

[0036] The extreme slope and main trend value of the function is (V); (VI).

[0037] Step 6: According to the main trend values ​​of the gas logging rising function and the gas logging falling function of each sandstone reservoir, the trend slope ratio is calculated as equation (VII): R =∣ k 上升 / k 下降 ∣ (VII).

[0038] Step 7: Integrate the trend slope ratios of each sandstone reservoir, establish the discrimination criteria based on the oil testing conclusions, and form a discrimination method: 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 of 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.

[0039] 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.

[0040] The present invention functions the gas logging data with respect to the well depth, establishes the main trend calculation formula of the function through standardization, trend analysis and extreme value transformation, and calculates the trend slope ratio. 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. This method effectively solves the problem of difficulty in while-drilling discrimination of fluid properties in low-pressure, high-bound water and thin-layer sandstone reservoirs in the Sulige area. After testing, the compliance rate of while-drilling discrimination of formation fluid properties using this method reached 89.3%, which significantly exceeded the compliance rate of existing discrimination methods such as the plate method.

[0041] 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 protection scope of the present invention.

Claims

1. A method for determining 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 according to the oil test conclusions; b. Extract the gas testing data of the corresponding gas testing display section according to the selected oil testing section; c. Standardize the drilling time and displacement of all 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 the gas logging descending section data are respectively fitted with the well depth by cubic function to obtain the gas logging ascending function and the gas logging descending function; e. According to the trend of the slope change of the cubic function, the value with depth coverage exceeding 50% is selected 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, combine with the corresponding oil test conclusions to establish a discrimination standard, and form a discrimination method for while-drilling discrimination of the formation fluid properties of the sandstone reservoirs of new wells.

2. The method for discriminating formation fluid properties by using gas logging curve morphology function according to claim 1, characterized in that: In step a, oil testing sections in which multiple sets of sandstone reservoirs are tested and the oil testing conclusions are single fluid and oil testing sections in which only one set of sandstone reservoirs is tested are selected from the tested wells to match the formation fluid properties corresponding to the sandstone reservoirs in the oil testing sections.

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

4. The method for discriminating formation fluid properties by using gas logging curve morphology function according to claim 3 is characterized by: 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 the drilling time and displacement of the total hydrocarbons in the extracted gas logging data is as follows: 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 It is the 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 by using gas logging curve morphology function 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 determining formation fluid properties by using gas logging curve morphology function according to claim 4, characterized in that: In step d, the above-mentioned 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 standardization is used as the boundary, and the standardized total hydrocarbon curve is divided into a gas logging ascending section and a gas logging descending section; the data of the gas logging ascending section and the gas logging descending section are respectively fitted with the well depth by a cubic function, and the gas logging ascending function and the gas logging descending 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 depth of the well, a , b , c , d are the coefficients of the fitting formula.

7. The method for determining formation fluid properties by using gas logging curve morphology function according to claim 6, characterized in that: 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 section thickness is large and the peak duration is long, the gas logging ascending section data is extracted to the end of 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. The gas logging descending section data is extracted starting from the last near-peak point.

8. The method for discriminating formation fluid properties by using gas logging curve morphology function according to claim 6, characterized in that: In step e, according to the cubic function obtained by fitting, the function slope is obtained as equation (III), k=3a × H 2 +2b × H+ c (III), among which, k is the slope of the cubic function; According to the curve characteristics of the cubic function, the slope value with a depth ratio of more than 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 of more than 50%. If it cannot be achieved, it can be adjusted according to the actual situation. According to the function slope relationship, the well depth of the slope extreme value is deduced as (IV), where h is the well depth of the extreme slope, The extreme slope and main trend value of the function is （Ⅴ）； （Ⅵ）。 9. The method for discriminating formation fluid properties by using gas logging curve morphology function according to claim 8, characterized in that: In step f, according to 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 determining formation fluid properties by using gas logging curve morphology function according to claim 9, characterized in that: In step g, the trend slope ratio of the sandstone reservoir in the screened 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, and a discrimination method is formed for the while-drilling discrimination of the formation fluid properties of the sandstone reservoir in the new well.

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