WO2018044133A1 - Method for selecting decline curve method in accordance with cumulative production increase rate index in unconventional gas field - Google Patents

Abstract

The present invention relates to a method having presented an index for selecting a decline curve method in ultimate recovery and cumulative production prediction in an unconventional gas field and, more specifically, to a method capable of selecting a decline curve method by using a cumulative production increase rate index in an unconventional gas field such that the decline curve method can be used by using the index during productivity evaluation and productivity prediction for economic analysis in the development of the unconventional gas field. According to the present invention, the method for selecting a decline curve method in accordance with a cumulative production increase rate index in an unconventional gas field comprises: a data collection step of acquiring data through daily output production data from actual field data; a step of calculating a cumulative production increase rate index by using the data acquired in the data collection step; a step of selecting a decline curve method by means of a value calculated from the cumulative production increase rate index; and predicting the cumulative production and ultimate recovery of an unconventional gas field by using the selected decline curve method.

Description

Decline curve selection method according to cumulative output growth rate indicator in non-traditional gas field

The present invention relates to a method for suggesting an index for selecting a decay curve method for predicting ultimate value and cumulative production in non-traditional gas fields. More specifically, the present invention provides an index for productivity evaluation and productivity prediction for economic analysis in developing non-traditional gas fields. It is a method to select the decay curve method using the cumulative output growth rate indicator in non-traditional gas field to use the decay curve method.

Shale gas is being actively produced due to the recent economic development due to the development of hydraulic fracturing and horizontal drilling technology, and commercial production is being carried out mainly in North America where pipelines and natural gas infrastructure are developed. Generally, reserve assessments and productivity predictions for production oil fields are performed through production data analysis or reservoir simulation. The analysis of production data is divided into production transition flow analysis, Decline Curve Analysis (DCA), and mass balance method. The double decay curve analysis method is used to predict future production behavior using only time and yield, and is widely used because it is possible to quickly calculate yield and estimated ultiate recovery (EUR) using a simple program in the field.

However, in the case of initial shale wells, the decay trend of production data varies according to the flow characteristics. Generally, the production decline rate indicator is used to select the decline curve analysis, but the actual field data is highly volatile and it is difficult to select a constant decline rate.

In addition, the prior art for predicting ultimate yield and cumulative production in the oil field is US Patent Publication US 2015-0331976, US Patent Publication US 2013-0346040 and US Patent Publication US 2014-0136111.

However, conventionally, the production decay rate index is used to predict ultimate value and cumulative production using the decay curve method, and this index is volatilized due to reasons such as production interruption due to oil well maintenance when analyzing the decay method at actual production sites. Because of this and the decay rate is not constant, the conventional decay curve analysis method has a limitation in selecting a variable in accordance with the judgment of the engineer (expert), in addition to the disadvantage that the uncertainty component increases by that amount.

As described above, when the decay curve method is used to predict ultimate value and cumulative production in the non-traditional gas field, the decay rate is not constant due to volatility due to oil well maintenance or production interruption in actual production sites. In order to solve the problems of the conventional production decay curve analysis method, in which the judgment of an engineer (expert) is involved when performing the analysis, the reservoir properties or the oil well such as, for example, the cumulative yield growth index It is desirable to provide a new decay curve analysis method that uses output and time data without much data such as complete data. However, there are no indicators or methods that satisfy all of these requirements.

Therefore, there is little volatility and it is possible to simulate a certain trend of production decline, a new indicator that can be applied irrespective of the reservoir properties and oil well completion method conditions is required, the present invention is a heterogeneous hydraulic fracturing leveling by using the cumulative output growth rate indicator This study studied the method of deciding the appropriate decay curve analysis method according to the trend of production decline through analysis of shale gas well simulation data and field data.

The present invention has been made to solve the above problems, in the case of using the Arps empirical formula when performing the productivity analysis using the decay curve method for predicting future productivity, such as cumulative production or ultimate value in non-traditional gas field In addition to the problem of large production forecasting errors, the decay rate indicator when applying the decay curve method causes volatility due to oil well maintenance or production interruption at actual production sites, resulting in uneven decay rates. In order to solve the problem that the judgment of engineers (experts) should be involved when using the decay curve method, the decay curve method is selected according to the cumulative yield growth index when predicting the ultimate value and cumulative yield in the non-traditional gas field using the cumulative yield growth index. It is to provide a way to predict productivity through the method.

In addition, another object of the present invention, when using the production decline rate in the analysis of the decay curve method to predict the productivity as described above because the actual production data variability occurs because the decay rate is not constant judgment of the engineer (expert) In order to solve the problems of the decay curve selection and productivity prediction methods of the conventional non-traditional gas field which had this required disadvantage, the engineer's judgment is made by using the cumulative yield growth index using only the production data and the time data acquired in the field. It is designed to replace the production decay rate indicator that should be intervened, so that the decay curve method can be selected using the cumulative output growth rate indicator in non-traditional gas fields configured to be applied irrespective of reservoir properties and well-completed data. It is to provide.

In addition, another object of the present invention, by using the cumulative output growth rate indicator that can be applied irrespective of the reservoir properties and well completion data as described above, it is possible to replace the production decline rate indicator and the judgment of the engineer (expert) Instead of declining production rates to be intervened, this study aims to provide a method of predicting productivity through the decay curve selection method according to the cumulative output growth rate indicators when predicting ultimate value and cumulative production in non-traditional gas fields.

Technical problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned above will be clearly understood by those skilled in the art from the following description. Could be.

In the non-traditional gas field according to the present invention, the method of selecting the decay curve method according to the cumulative production growth rate indicators includes: a data collection step of acquiring data through daily output production data from actual field data; Calculating a cumulative production growth rate indicator using the data obtained in the data collection step; Selecting a decay curve method based on a value calculated from the cumulative yield increase index; And predicting the cumulative production amount and the ultimate value of the non-traditional gas field using the selected decay curve method.

By the means for solving the above problems, the present invention when predicting the non-traditional gas field ultimate value and cumulative production of the non-traditional gas field productivity prediction using the cumulative production growth rate indicator configured to reduce the error generated by using the existing Arps empirical formula By providing the method of selecting the production decline curve analysis method, it is possible to solve the shortcomings of the selection method by using the reservoir property data or the well completion method data that are difficult to obtain in actual field and have high uncertainty, and it is generated by using the widely used production decline rate. As the volatility of actual production data is so severe that the decay rate is not constant, it is possible to solve the problem of selecting the decay curve method when calculating the ultimate value and cumulative production of the prior art, which has the disadvantage of involving the judgment of engineers (experts).

In addition, according to the present invention, when using the decay curve method in the production prediction as described above, the decay curve method is selected according to the reservoir properties or the oil well completion conditions when selecting the analysis method, but the data used for this is obtained in the field The method of selecting the decay curve method when predicting ultimate yield and cumulative yield, which consists of a system that selects the decay curve method using the cumulative yield growth index that can only be analyzed with production data over time to solve the problem of high uncertainty that is difficult to do. This provides an alternative to the production decay rate indicators that require the judgment of engineers (experts) when analyzing traditional Arps decay curves.

1 is a flow chart showing a method of selecting a decay curve method according to the cumulative output growth rate indicator in the non-traditional gas field

2 is a comparison of production decline index between field data and simulation data.

3 is a comparison of cumulative output growth rate indicators of field data and simulation data.

4 is a productivity prediction analysis simulation according to the production trend of shale gas well

5 is an analysis graph according to the cumulative output growth rate classification

6 is a comparison of the decay curve method when the cumulative output growth rate is 0.5% in the Canadian A basin shale gas field.

7 is a comparison of the decay curve method when the cumulative output growth rate is 0.25% in the Canadian A basin shale gas field.

8 is a comparison of the decay curve method when the cumulative output growth rate is 0.5% in the US B-branch shale gas field

9 is a comparison of the decay curve method when the cumulative output growth rate of 0.25% in the US B basin shale gas field

Specific matters including the problem to be solved, the solution to the problem, and the effects of the present invention as described above are included in the embodiments and drawings to be described below. Advantages and features of the present invention, and methods for achieving them will be apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings.

The present invention relates to a method for suggesting an index for selecting a decay curve method for predicting ultimate value and cumulative production in non-traditional gas fields. More specifically, the present invention provides an index for productivity evaluation and productivity prediction for economic analysis in developing non-traditional gas fields. It is a method to select the decay curve method using the cumulative output growth rate indicator in non-traditional gas field to use the decay curve method.

Hereinafter, a method of selecting the decay curve method according to the cumulative yield growth index in the non-traditional gas field will be described in detail with reference to the accompanying drawings.

First, the first step is a data collection step (S10). Specifically, the step of acquiring data and collecting data through the daily production data obtained over time from actual field data.

Next, the second step is to calculate the cumulative output growth rate indicator (S20). Specifically, the step of calculating the cumulative output growth rate indicator using the data obtained in the data collection step.

Unlike general gas wells, shale gas wells produce rapid declines in initial production and slow down late production trends. Therefore, it is necessary to apply the appropriate Decline Curve Analysis (DCA) according to the trend of production decline. Maley (1985) and Kupchenko (2008) conducted a study using the production decline rate as a factor for the production decline trend. The shale and dense gas wells are too small in late production, so the decline trend does not appear anymore. Production was overpredicted when applied. To improve this problem, we proposed the modified hyperbolic decay curve method that analyzes by changing the decay index value when the decay rate reaches a certain point using the decay rate limit index. Yu (2013) confirmed that the improved Duong's method was most accurate when the transmittance was less than 0.001md, and that the YM-SEPD method simulated the production trend best in the 0.1 ~ 0.001md reservoir layer. However, as shown in Fig. 2, the decay rate limit index may have a variable decay rate due to variability due to production stoppage due to oil well maintenance during site analysis, and the decay rate may not be constant. Uncertainty in the data is not applicable.

Therefore, there is a need for a quantitative and general indicator that can supplement the above problems. In the present invention, the cumulative yield growth index applicable to the reservoir properties and the well completion condition is proposed in Equation 1 below.

IG _p = cumulative output growth indicator

G _p (t _n ) = cumulative output value of n hours (day)

G _p (t _{n + 1} ) = cumulative output value of n + 1 hour (day)

The cumulative output growth rate indicator is less volatile according to the production data and the decay tendency is constant, so there is an advantage that it is easy to apply compared to the production decay rate. In addition, as shown in Figure 3, the simulation data and the actual field data compared with the cumulative output growth rate graph, the trend was confirmed that the trend is constant compared to the production decline rate.

Next, a third step is to select a decay curve method (S30). Specifically, the step of selecting the decay curve method based on the value calculated from the cumulative output growth rate indicator.

The decay curve method is a method of predicting future productivity based on past production data, and is one of the widely used productivity analysis techniques because it can be simply calculated as a graph of output over time using only production data. An empirical formula for predicting future production trends was proposed by analyzing the production history using the time, output, and cumulative output proposed by Arps (1945). The trend of production varies depending on the decay index. For traditional oil fields, the decay index value is the exponential decay curve (b = 0), the hyperbolic decay curve (0 <b <1), and the harmonic decay curve (b = 1). ) Is used.

The following describes a decay curve method suitable for non-traditional gas fields.

1) Superbolic Decline Method (1 <b <4)

In general, the hyperbolic equation of Arps in traditional gas wells shows a value between 0 and 1, but the hyperbolic decay curve shows more than 1 when the production decline is large and decreases later as Shale gas wells. Super Hyperbolic Decline: superbolic Therefore, when predicting the productivity of non-traditional gas reservoirs with very low permeability, future production trends are predicted by using the superbolic method applying the number of the decay index of the hyperbolic decay curve method in the transition flow section more than one (Kupchenko et al., 2008). However, since the decay index is between 0.5 and 1 in the flow zone where boundary-bound flow occurs, it is necessary to carry out production prediction analysis by changing the decay index value according to the flow zone, or appropriate production prediction analysis for various scenarios.

2) PLE method

Ilk et al. (2008) analyzed non-hyperbolic decay behavior in which the decay index was not constant in the graph that estimated the decay rate and decay index through production history analysis in dense gas fields. The reason behind the hyperbolic decline is suggested to be due to the presence of the transitional flow data, which are factors influencing the production decline rate and the decline index. The graph shows the decay rate of dense gas fields in the graph, which is different from the hyperbolic decay method, which follows the form of the power law that decays continuously for a long time. This is called the power function decay curve method (PLE). The advantage of this method is that it can be predicted in one way regardless of flow area when forecasting recoverable reserves and production data analysis of reservoirs where the production behavior by hydraulic fracturing is superior.

In Equation 3, n is the time index, q _i is the production when t = 0, D _∞ is the infinite rate of production decline rate D ₁ is the production decline rate when t = 1 and D _i is D ₁ / n to be. In the early stage of production, the PLE method was more consistent than the hyperbolic decay curve until the boundary effect flow occurred. However, the PLE method has the following disadvantages: First, there are four variables (n, q _i , D _∞ , D ₁ ) that need to be adjusted to match the production data. Secondly, it is difficult to determine the D _i variable, and the rate of change in initial production declines later. Third, when predicting recoverable reserves, the yield changes sensitively by adjusting the time index n. Lastly, when D _∞ is incorrectly selected in the initial production data, the late production deviation due to the variable adjustment is large.

3) Duong method

Lee and Wattenbarger (1996) show that the relationship between the yield and cumulative production of hydraulic fracturing reservoirs is shown in Equations 4 to 5, where n is 0.5 for linear flow of infinite conduction fracture and n is 0.25 for double linear flow. Said. Duong (2010) proposed a decay curve analysis method considering the initial production trend and the late trend of unstimulated rock bodies in multi-stage hydraulic fracturing in shale and dense gas fields. The ratio of the yield to the y-axis cumulative output and the x-axis time are shown in the log-log graph to show the trend of the straight line. The variables a and m can be easily derived from the slope and intercept of the specific graph. It can be expressed as Equation 7 below.

Yu et al. (2013) proposed a method for determining the variables of the Duong decay curve under various reservoir conditions where boundary effect flows occur. As a result of analyzing the linear relation by deriving the production history of various homogeneous hydraulic fracturing horizontal wells at various transmittances (0.1 ~ 0.0001md) through the reservoir model, the linear tendency is appeared when the reservoir transmittance is large (0.1 ~ 0.01md). In addition, when deriving recoverable reserves, it was found to be overestimated. In the case of low permeability (0.001 ~ 0.0001md), linear trends were observed, production history was consistent, and recoverable reserve errors were low.

4) YM-SEPD (Yu Modified-Streched Exponential Production Decline)

Valko's (2009) proposed Decech Curve Streched Exponential Production Decline (SEPD) expresses yields as potential recoveries ( _p ) and t, n, and τ variables based on the Exponential function, which represents 10,000 US Barnett shale wells. Verified by Valko and Lee (2010) improved SEPD in a way that is applicable to a wide range of dense and shale gas reservoirs. Potential recoveries and recoverable reserves in the SEPD equation are expressed as in Equations 8 to 9 below.

The recoverable reserve amount refers to the cumulative output when the production data is based on the minimum economic yield, which can be expressed by Equation 9 as the initial output q ₀ , two variables n and τ. If _p and cumulative output are plotted on the graph, the slope of the straight line is 1 and the recoverable amount can be derived from the value of x-intercept. Yu (2013) used the SEPD method to predict the productivity of Canadian dense gas fields, and the analysis shows that when the slope of the straight line is 1, it is out of production history and conservatively predicts. Yu et al. (2013) proposed the Yu Modified-SEPD (YM-SEPD) to solve the problem of the SEPD decay curve, which conservatively predicts productivity. As shown in Equation 10, when Ln (q / q (t)) and t are plotted on a log-log graph, a trend of a straight line is derived, and n and τ can be derived through slope and intercept. The proposed decay curve method was verified through simulation model and field data analysis to simulate multi-level hydraulic fracturing horizontal well.

Next, the fourth step is a step of predicting the cumulative production amount and the ultimate value of the non-traditional gas field (S40). Specifically, it is a step of predicting the cumulative production and the ultimate value of the non-traditional gas field using the selected decay curve method.

As a result of productivity prediction by applying the cumulative output growth rate indicator and the decay curve analysis method performed in the third step (S30), when the cumulative output growth rate is more than 0.25%, the Duong method is consistent with the production trend and the recoverable amount of reserve error is The smallest. In addition, when the cumulative output growth rate is less than 0.05%, the YM-SEPD method accurately simulates the production trend and confirms that the recoverable amount of storage error is small.

The cumulative production and ultimate value estimate of the non-traditional gas field was described in detail in the following simulation model analysis results.

G. Simulation model

As shown in FIG. 4, in the present invention, a heterogeneous multistage hydraulic fracturing horizontal well model was set up using a reservoir simulator to perform a productivity prediction analysis according to a production decline trend of shale gas wells. As shown in Table 1 below, the model has a horizontal length of 7,000 ft and a crushing step of 20 stages, a crushing length of at least 483 ft, a maximum of 1,129 ft, a storage layer thickness of 607 ft, a crushing gap of 350 ft, and a crushing permeability of 0.7 md. And the permeability of the rock body is 0.0004 md.

Horizontal length (ft)	7,000
Crushing stage	20
Crushing Length (ft)	483 (min.), 802 (mean), 1,129 (max)
Reservoir Thickness (ft)	607
Shredding Thickness (ft)	350
Shred Permeability (md)	0.7
Permeability of Rock Body (md)	0.0004

The production data used in the analysis is based on a minimum economic yield of 300 Mscf / day, with a total production period of about 25 years and a recoverable reserve (EUR) of 7.79 bcf. As shown in FIG. 5 (a), the analysis of production history shows that the transition flow period is 5.5 years and boundary effect flows have appeared since this point.

In addition, as shown in Table 2 below, eight cumulative output growth rate values are selected from the production data calculated through the simulation, and from that point, the productivity is predicted by Duong, Superbolic, PLE, and YM-SPED to compare with the simulation results. Sensitivity analysis was performed. Table 2 below shows the results of the calculation of the ultimate yield and simulation data in the cumulative output growth rate index.

	0.5% 120day (EUR, Bcf)	0.25% 230day (EUR, Bcf)	0.15% 375day (EUR, Bcf)	0.1% 550 day (EUR, Bcf)	0.075% 730 day (EUR, Bcf)	0.05% 1100day (EUR, Bcf)	0.04% 1340 day (EUR, Bcf)	0.03% 1750 day (EUR, Bcf)
Duong	7.1% (8.34)	5.0% (8.18)	35.6% (10.56)	38.0% (10.75)	52.5% (11.88)	65.5% (12.89)	65.5% (12.89)	65.7% (12.91)
Superbolic	46.5% (11.41)	54.0% (12.00)	57.3% (12.25)	58.0% (12.31)	62.1% (12.63)	74.5% (13.59)	74.6% (13.60)	75.6% (13.68)
PLE	-15.1% (6.61)	-13.4% (6.75)	-12.7% (6.80)	-9.6% (7.04)	-7.7% (7.19)	-3.7% (7.50)	-3.4% (7.53)	-4.2% (7.46)
YM-SEPD	-52.1% (3.73)	-36.6% (4.94)	-27.9% (5.62)	-25.5% (5.80)	-23.6% (5.95)	1.8% (7.93)	3.4% (8.06)	2.1% (7.95)
Simulation	(7.79)

As shown in FIG. 5 (b), the cumulative output growth rate used for the sensitivity analysis is 8 values (0.5 to 0.03%), which is expressed as a production period, at least 120 days (0.5%) to 1,750 days (0.03). %)to be.

As a result of analysis through the simulation data, the Duong method is the most suitable method when the cumulative output growth rate is 0.25%, the production tendency is consistent and the recoverable reserve error is the smallest, and YM-SPED is the cumulative output growth rate less than 0.05%. It was confirmed to be. Superbolic tended to be overestimated in the boundary effect flow as a result of the production trend analysis, and the production decline rate was about 30% lower, which was not suitable for late production simulation. In addition, the PLE method had the lowest mean error according to each cumulative output growth index, but it was difficult to analyze due to the large error caused by the selection of variables in the relational expression.

In the following, a study comparing the simulation analysis results with field data was conducted. Field data used in the analysis is Canada A, US B shale gas field data, each reservoir data is shown in Table 3 below. The production period was 2.8 years and 10.2 years, respectively. The flow area analysis showed that Canada A production data is in the transition phase, and US B production data has occurred since eight years. As a result of the cumulative production growth rate, a certain trend can be derived to quantify the decline trend. Canada A production wells were compared with field data by predicting productivity from the point of time when the cumulative output growth rate was 0.5% (140 days for production period) and 0.25% (520 days for production period). Year) and 0.05% (production period of 2.9 years) to predict productivity.

parameter	Canada A	American B
horizontal well length (ft)	3,111	4,400
fracture stage	28	16
target depth (ft)	2,463	5,081
fracture spacing (ft)	110	270
initial production rate (Mscf / d)	25	27

N. Field data analysis result Canada A

Table 4 below shows the relative errors for the yield of Canadian A field data. As shown in FIG. 6, when the cumulative output growth rate was 0.5%, the Duong method was most consistent with the production trends compared to the other three decay curve methods, and the relative error on the output was calculated to be small as 1.35%. The PLE method and the YM-SPED conservatively predicted the production trend, and the relative errors were -6.37% and -8.08%, respectively. The relative error value of the superbolic method is 3.31% and compared with Duong, the decrease in production decreases slowly as the production period increases, and the actual yield and error tended to increase over time.

As shown in FIG. 7, when the cumulative production increase rate was 0.25%, the Duong method was found to have the best agreement with the production trend, and the relative error of the production was 0.16%, which was smaller than that of 0.5%. The PLE and YM-SPED methods had a smaller relative error than the cumulative output growth rate of 0.5% (-4.45%, -6.29%), but still predicted productivity conservatively. Superbolic showed that the cumulative output growth rate slowed down compared to Duong's method.

	Cumulative incline rate (0.5%)	Cumulative incline rate (0.25%)
Duong	1.35	0.16
Superbolic	3.31	5.58
PLE	-6.37	-4.45
YM-SPED	-8.08	-6.29

C. Field data analysis result USA B

Table 5 below shows the relative errors for US B field data output. As a result of analyzing the US B production data, as shown in FIG. 8, when the cumulative output growth rate is 0.25%, the Duong method excludes highly volatile periods (70-100 months) compared with the other three decay curve methods. The production trends were consistent. In addition, the relative error of output was the lowest at -1.56%. Both the PLE and YM-SPED methods conservatively predicted productivity, with relative errors of -13.40% and -17.22%, respectively. Superbolic showed a slow decline in production from the 20th month, resulting in overpredicted production, with a relative error of 7.79%. This result shows that Duong's method is consistent with the production trend and the lowest relative error when the cumulative output growth rate is 0.25%, similar to the Canadian A production well.

As shown in Fig. 9, when the cumulative production growth rate is 0.05%, the Duong and Superbolic methods have slowed the decay tendency after mid-production (60 months) compared to the other two decay curves, resulting in inconsistent production trends and overestimated relative errors. Were 7.31% and 11.63%, respectively. In the case of PLE, the initial production decline tends to be more conservative than YM-SPED, and the relative error is -5.92%. The YM-SPED had a relative error value of 0.04%, which was the most consistent among the four decay curves.

	Cumulative incline rate (0.5%)	Cumulative incline rate (0.25%)
Duong	-1.56	7.31
Superbolic	7.79	11.63
PLE	-13.40	-5.92
YM-SPED	-17.22	0.04

By the means for solving the above problems, the present invention when predicting the non-traditional gas field ultimate value and cumulative production of the non-traditional gas field productivity prediction using the cumulative production growth rate indicator configured to reduce the error generated by using the existing Arps empirical formula By providing the method of selecting the production decline curve analysis method, it is possible to solve the shortcomings of the selection method by using the reservoir property data or the well completion method data that are difficult to obtain in actual field and have high uncertainty, and it is generated by using the widely used production decline rate. As the volatility of actual production data is so severe that the decay rate is not constant, it is possible to solve the problem of selecting the decay curve method when calculating the ultimate value and cumulative production of the prior art, which has the disadvantage of involving the judgment of engineers (experts).

In addition, according to the present invention, when using the decay curve method in the production forecast as described above, selecting the decay curve method in accordance with the storage properties or the completion conditions of the well when selecting the analysis method, but to obtain the data used in the actual field In order to solve the problem of difficulty and high uncertainty, the decay curve selection method when predicting ultimate yield and cumulative yield is composed of a system for selecting a decay curve method using the cumulative yield growth index which can be analyzed only with production data over time. By providing an alternative to the production decay rate indicators, the judgment of engineers (experts) should be involved in the traditional Arps decay analysis.

By the means for solving the above problems, the present invention when predicting the non-traditional gas field ultimate value and cumulative production of the non-traditional gas field productivity prediction using the cumulative production growth rate indicator configured to reduce the error generated by using the existing Arps empirical formula By providing the method of selecting the production decline curve analysis method, it is possible to solve the shortcomings of the selection method by using the reservoir property data or the well completion method data that are difficult to obtain in actual field and have high uncertainty, and it is generated by using the widely used production decline rate. As the volatility of actual production data is so severe that the decay rate is not constant, it is possible to solve the problem of selecting the decay curve method when calculating the ultimate value and cumulative production of the prior art, which has the disadvantage of involving the judgment of engineers (experts).

In addition, according to the present invention, when using the decay curve method in the production forecast as described above, selecting the decay curve method in accordance with the storage properties or the completion conditions of the well when selecting the analysis method, but to obtain the data used in the actual field In order to solve the problem of difficulty and high uncertainty, the decay curve selection method when predicting ultimate yield and cumulative yield is composed of a system for selecting a decay curve method using the cumulative yield growth index which can be analyzed only with production data over time. By providing an alternative to the production decay rate indicators, the judgment of engineers (experts) should be involved in the traditional Arps decay analysis.

As such, the technical configuration of the present invention described above can be understood by those skilled in the art that the present invention can be implemented in other specific forms without changing the technical spirit or essential features of the present invention.

Therefore, the above-described embodiments are to be understood as illustrative and not restrictive in all respects, and the scope of the present invention is indicated by the following claims rather than the detailed description, and the meaning and scope of the claims and their All changes or modifications derived from an equivalent concept should be construed as being included in the scope of the present invention.

[Description of the code]

S10. Data collection stage to obtain daily yield production data data from actual field data

S20. Computing the cumulative production growth rate indicator using the data obtained in the data collection step

S30. Selecting a decay curve method based on a value calculated from the cumulative output growth index;

S40. Predicting the cumulative production and the ultimate value of the non-traditional gas field using the selected decay curve method

Claims (5)

1. In the method of selecting the shale gas production decay curve method using the cumulative production growth rate index,

   A data collection step of acquiring daily yield production data data from actual field data;

   Calculating a cumulative production growth rate indicator using the data obtained in the data collection step;

   Selecting a decay curve method based on a value calculated from the cumulative yield increase index; And

   Estimating the cumulative production and ultimate value of the non-traditional gas field using the selected decay curve method;
2. The method of claim 1,

   The cumulative output growth index is a decay curve selection method according to the cumulative output growth index in the non-traditional gas field calculated by the following equation.

   

   IG _p = cumulative output growth indicator

   G _p (t _n ) = cumulative output value of n hours (day)

   G _p (t _{n + 1} ) = cumulative output value of n + 1 hour (day)
3. The method of claim 1,

   Decay curve method is an indicator of cumulative production growth in non-traditional gas field, which is selected from Super Hyperbolic Decline (Superbolic), Power Law Decay (PLE), Duong Decay Curve, and YM-SEPD Decay Curve. Decay curve selection method
4. The method of claim 1,

   The cumulative production and ultimate value of the non-traditional gas field prediction is,

   When the cumulative output growth rate is 0.5% and 0.25%, using the Duong decay curve method,

   If the cumulative output growth rate is less than 0.05%, the decay curve selection method according to the cumulative output growth rate in the non-traditional gas field using the YM-SEPD method
5. The method according to any one of claims 1 to 4,

   The recording medium in which the cumulative output growth rate indicator and the decay curve method can be recorded by a computer program.

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