Method for real-time determination of gas content in coal seam using drill cuttings in drilling site

Abstract

The present application belongs to the field of coalbed methane exploitation, and specifically relates to a method for real-time calculation of coalbed gas content by using drill cuttings in a drilling site. The method comprises the following steps: weighing a sample desorption tank; measuring the time for planned collected drill cuttings to reach a drilling mud discharge outlet from a well bottom; obtaining sample quality; simultaneously, measuring the time for collected drill cuttings to be loaded into the desorption tank from the drilling mud discharge outlet; calculating a loss time and a loading time ratio; testing the drill cuttings sample; calculating the loss time ratio; selecting a corresponding loading time ratio curve according to the calculated loading time ratio, and finding a loss gas volume ratio corresponding to a point of the loss time ratio on the loading time ratio curve; heating the desorption tank to obtain residual gas quantity; obtaining dry ash-free basis quality of the sample; calculating water quality in the sample; calculating desorption gas quantity and residual gas quantity per unit mass of the sample; calculating loss gas quantity; calculating loss gas quantity per unit mass of the sample; and calculating coalbed gas content.

Description

Technical Field

[0001] This invention belongs to the field of coalbed methane extraction, specifically a method for determining the gas content of coal seams in real time using drill cuttings at the drilling site. Background Technology

[0002] Coalbed methane (CBM) content is a crucial basis for exploration and optimization of CBM blocks both domestically and internationally. Currently, there are two main methods for determining CBM content: direct experimental measurement and indirect measurement. Direct experimental methods yield relatively accurate data, but require replacing conventional drilling tools with coring tools to obtain samples, resulting in significant costs and a long experimental cycle. Indirect methods primarily involve downhole measurement of coalbed methane pressure, laboratory determination of adsorption constants, and industrial analytical indicators, using the Langmuir equation to calculate the CBM content. However, indirect methods often result in relatively larger errors in CBM content measurements.

[0003] In the context of cost reduction and efficiency improvement, there is an urgent need to research a new method for determining the gas content of coal seams in order to obtain more accurate and comprehensive gas content data while reducing input costs. Coal cuttings are debris generated by drill bits breaking through rock formations at the drilling site. Coal cuttings are a type of debris that is inevitably produced during the drilling process, and their acquisition does not affect normal drilling operations or require the replacement of drilling tools. Therefore, developing a method suitable for real-time determination of coal seam gas content using drill cuttings at the drilling site is a pressing issue that needs to be addressed. Summary of the Invention

[0004] To address the problems of high cost, long cycle time, and low accuracy in obtaining coal seam gas content, this invention provides a method suitable for real-time determination of coal seam gas content using coal cuttings at the drilling site.

[0005] This invention adopts the following technical solution: a method for determining the gas content of coal seams in real time using drill cuttings at drilling sites, comprising: S100: Weigh the sample desorption vessel and obtain the mass m1; S200: Cuttings sample collection, the time t2 for the cuttings collected according to the metering plan to reach the drilling mud outlet from the bottom of the well; S300: Collect rock cuttings at the drilling mud outlet, quickly wash them to remove mud impurities, and weigh the washed sample in a sample desorption tank to obtain the mass m2. The mass of the sample is obtained by m2-m1=m3. At the same time, measure the time t3 from when the collected rock cuttings are collected from the drilling mud outlet to when the rock cuttings are put into the desorption tank. S400: Calculate the loss time t1 and the filling time ratio a1; S500: Test rock cuttings samples to obtain the desorbed gas volume V. 解 And read the desorption time t4; S600: Calculate the time loss ratio a2; S700: In the intersection chart of the time loss ratio and the gas loss ratio, select the corresponding filling time ratio curve according to the calculated filling time ratio a1, and find the point of the time loss ratio a2 on the filling time ratio curve that corresponds to the gas loss ratio a3. S800: Heats the desorption vessel and detects the gas volume to obtain the residual gas volume V. 残 ; S900: The sample is removed from the desorption tank and dried at low temperature to obtain the dry weight of the sample m4. At the same time, in order to eliminate the influence of the remaining impurities that have not been washed away on the data, the dried sample needs to be subjected to industrial analysis to obtain the dry ash-free mass of the sample m5. S1000: Calculate the mass of water in the sample using m3-m4=m6; S1100: Use V 解 / m5=Q1 to calculate the desorbed gas volume per unit mass of the dry, ash-free sample, using V 残 / m5=Q2 is used to calculate the residual gas volume per unit mass of the dry, ash-free sample. S1200: Calculate the gas loss V 损 Loss of gas volume V 损 =a3 ×V 解 ×[(m5 / m6) / 100]; S1300: Use V 损 / m5=Q3 calculates the gas loss per unit mass of the dried, ash-free sample; S1400: Calculate the coalbed methane content Q, Q=Q1+Q2+Q3.

[0006] In step S100, the desorption vessel is designed to hold 1000g of coal sample.

[0007] Step S200 includes: placing colored fine sand into the wellhead inlet position, using a timer to measure the time it takes for the fine sand to travel from the wellhead to the drilling mud outlet along with the drilling mud. This time is the time it takes for the fine sand to travel from the wellhead to the bottom of the well and then back to the wellhead. Therefore, this time is divided by 2 to obtain the time t2 for the planned rock cuttings to travel from the bottom of the well to the drilling mud outlet.

[0008] In step S300, t3 is less than 2 minutes.

[0009] In step S400, the lost time t1 = the time t2 for the cuttings to reach the drilling mud outlet from the bottom of the well + the time t3 for the cuttings to be loaded into the desorption tank from the drilling mud outlet; the loading time ratio a1 = t3 / t1.

[0010] In step S600, the time loss ratio a2 = 10 × (t1 / t4).

[0011] In step S800, the heating temperature is 90°C.

[0012] Compared with existing technologies, this invention obtains the gas content of rock cuttings through experimental measurement, and calculates the constants and formulas for calculating the gas content of coal seams by inversion. It achieves the goal of obtaining samples without drilling and coring, and can obtain continuous and stable gas content data in areas with complex geological structures, large differences in gas content, and low coring density. This can effectively reduce the investment in exploration wells and improve the accuracy of reserve evaluation. Attached Figure Description

[0013] Figure 1 This is a cross-plot of the time loss ratio and the gas loss ratio. In the figure: the horizontal axis represents the time ratio of lost gas, the vertical axis represents the volume ratio of lost gas, and the curve represents the filling time ratio curve. The filling time ratio of the curve from bottom to top is 0.02-0.30, with an interval of 0.02. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] A method for determining the gas content of coal seams in real time using coal cuttings at drilling sites includes the following steps: S100: First, select a desorption vessel that can hold 1000g of coal sample. Then, clean the sample desorption vessel and dry it at high temperature to remove moisture. Finally, weigh the desorption vessel to obtain the mass m1 of the desorption vessel.

[0016] S200: Place the colored fine sand into the wellhead at the wellhead inlet position. Use a timer to measure the time it takes for the fine sand to travel with the drilling mud from the wellhead to the drilling mud outlet. Since this time is the time it takes for the fine sand to travel from the wellhead to the bottom of the well and then back to the wellhead, divide this time by 2 to get the time t2 for the planned rock cuttings to travel from the bottom of the well to the drilling mud outlet.

[0017] S300: Collect approximately 800g of cuttings from the drilling mud outlet, quickly wash them to remove mud and other impurities, and then weigh the washed sample in a sample desorption container to obtain the mass m2 (approximately 2.6kg). The sample mass is then calculated as m2 - m1 = m3. Simultaneously, use a timer to measure the time t3 from the time the collected cuttings are collected at the drilling mud outlet to the time they are placed in the desorption container. This process should not exceed 2 minutes; that is, t3 should be less than 2 minutes.

[0018] S400: Calculate the time loss t1 and the filling time ratio a1. Time loss t1 = Time t2 for cuttings to reach the drilling mud outlet from the bottom of the well + Time t3 for cuttings to be loaded into the desorption tank from the drilling mud outlet. Filling time ratio a1 = t3 / t1.

[0019] S500: Rock cuttings samples were tested using a conventional desorption method to obtain the desorbed gas volume V. 解 And read out the duration of this process, which is the deaspiration time t4.

[0020] S600: Calculate the time loss ratio a2, where a2 = 10 × (t1 / t4).

[0021] S700: Cross plot of loss time ratio and loss gas volume ratio ( Figure 1 In the process, select the corresponding filling time ratio curve according to the calculated filling time ratio a1, and find the point of loss time ratio a2 on the filling time ratio curve, which corresponds to the loss gas volume ratio a3.

[0022] S800: The desorption vessel is heated to 90°C, and the gas volume is measured to obtain the residual gas volume V. 残 .

[0023] S900: The sample is removed from the desorption vessel and dried at low temperature to obtain the dry weight of the sample m4. At the same time, in order to eliminate the influence of the remaining impurities that have not been washed away on the data, the dried sample needs to be subjected to industrial analysis to obtain the dry ash-free mass of the sample m5.

[0024] S1000: Calculate the mass of water in the sample using m3-m4=m6.

[0025] S1100: Use V 解 / m5=Q1 to calculate the desorbed gas volume per unit mass of the dry, ash-free sample, using V 残 / m5=Q2 is used to calculate the residual gas volume per unit mass of a dry, ash-free sample.

[0026] S1200: Calculate the gas loss V 损 Loss of gas volume V 损 =Loss gas volume ratio a3 ×V 解 ×[(m5 / m6) / 100].

[0027] S1300: Use V 损 / m5=Q3 is used to calculate the desorbed gas volume per unit mass of a dry, ash-free sample.

[0028] S1400: Calculate the coalbed methane content Q, Q=Q1+Q2+Q3.

[0029] Taking the YL-L1 horizontal well in Yongle South as an example, on June 21, 2021, directional drilling was carried out on the horizontal section of the R1 main branch of the YL-L1 well. Five samples were taken on site, and the gas content was calculated as follows: Example 1: S100: First, select a desorption container that can hold 1000g of coal sample. Then, clean the sample desorption container and dry it at high temperature to remove moisture. Finally, weigh the desorption container and obtain the mass m1 of the desorption container as 1890g.

[0030] S200: Place the colored fine sand into the wellhead at the wellhead inlet position. Use a timer to measure the time it takes for the fine sand to travel from the wellhead to the drilling mud outlet along with the drilling mud. Since this time is the time for the fine sand to travel from the wellhead to the bottom of the well and then back to the wellhead, divide this time by 2 to get the planned time t2 for the rock cuttings to travel from the bottom of the well to the drilling mud outlet, which is 21 minutes.

[0031] S300: Collect approximately 800g of cuttings from the drilling mud outlet, quickly wash them to remove mud and other impurities, and then weigh the washed sample in a sample desorption container to obtain the mass m2 (2607g). The mass m2 - m1 = m3 is then used to obtain the sample mass as 717g. Simultaneously, a timer is used to measure the time t3 (1.8min) from the time the collected cuttings leave the drilling mud outlet to the time the cuttings are placed in the desorption container.

[0032] S400: Calculate the time loss t1 and the filling time ratio a1. Time loss t1 (22.8 min) = Time t2 (21 min) for cuttings to reach the drilling mud outlet from the bottom of the well + Time t3 (1.8 min) for cuttings to be loaded into the desorption tank from the drilling mud outlet. Filling time ratio a1 = t3 / t1 = 0.08.

[0033] S500: Rock cuttings samples were tested using a conventional desorption method to obtain the desorbed gas volume V. 解 (2871.3cm) 3 ), and read the duration of this process, which is the deaspiration time t4 (1550 min).

[0034] S600: Calculate the time loss ratio a2, where a2 = 10 × (t1 / t4) = 0.15.

[0035] S700: Cross plot of loss time ratio and loss gas volume ratio ( Figure 1 In the calculation, select the corresponding filling time ratio curve according to the filling time ratio a1 (0.08), and find the point of loss time ratio a2 (0.15) on the filling time ratio curve to find the loss gas volume ratio a3 (0.15).

[0036] S800: The desorption vessel is heated to 90°C, and the gas volume is measured to obtain the residual gas volume V. 残 (150.62cm) 3 ).

[0037] S900: Remove the sample from the desorption vessel and dry it at low temperature to obtain the dry weight of the sample m4 (714.12g). At the same time, in order to eliminate the influence of the remaining impurities that have not been washed away on the data, the dried sample needs to be analyzed industrially to obtain the dry ash-free mass of the sample m5 (627.52g).

[0038] S1000: Calculate the mass of water in the sample (2.88g) using m3-m4=m6.

[0039] S1100: Use V 解 / m5=Q1 Calculate the desorbed gas volume per unit mass of the dry, ash-free sample (4.58m). 3 / g), using V 残 / m5=Q2 Calculate the residual gas volume per unit mass of the dried, ash-free sample (0.24m). 3 / g).

[0040] S1200: Calculate the gas loss V 损 Loss of gas volume V 损 =Loss gas volume ratio a3 ×V 解 ×[(m5 / m6) / 100]=938.44 cm 3 .

[0041] S1300: Use V 损 / m5=Q3 Calculate the gas loss per unit mass of sample under dry, ash-free conditions (1.50m³). 3 / g).

[0042] S1400: Calculate the coalbed methane content Q, Q = Q1 + Q2 + Q3 = 6.32m 3 / g.

[0043] The measured total gas content per unit mass of the core was 6.38 cm³. 3 / g, deviation 0.9%.

[0044] Example 2: S100: First, select a desorption vessel that can hold 1000g of coal sample. Then, clean the sample desorption vessel and dry it at high temperature to remove moisture. Finally, weigh the desorption vessel and obtain the mass m1 of the desorption vessel as 1820g.

[0045] S200: Place the colored fine sand into the wellhead at the wellhead inlet position. Use a timer to measure the time it takes for the fine sand to travel from the wellhead to the drilling mud outlet along with the drilling mud. Since this time is the time it takes for the fine sand to travel from the wellhead to the bottom of the well and then back to the wellhead, divide this time by 2 to get the planned time t2 for the rock cuttings to travel from the bottom of the well to the drilling mud outlet, which is 26 minutes.

[0046] S300: Collect approximately 800g of cuttings from the drilling mud outlet, quickly wash them to remove mud and other impurities, and then weigh the washed sample in a sample desorption container to obtain the mass m2 (2578g). The mass of the sample is then calculated as m2 - m1 = m3, yielding a final mass of 758g. Simultaneously, a timer is used to measure the time t3 (1.6min) from the collection of the cuttings from the drilling mud outlet to their placement in the desorption container.

[0047] S400: Calculate the time loss t1 and the filling time ratio a1. Time loss t1 (27.6 min) = time t2 (26 min) for cuttings to reach the drilling mud outlet from the bottom of the well + time t3 (1.6 min) for cuttings to be loaded into the desorption tank from the drilling mud outlet. Filling time ratio a1 = t3 / t1 = 0.06.

[0048] S500: Rock cuttings samples were tested using a conventional desorption method to obtain the desorbed gas volume V. 解 (2496.2cm) 3 ), and read the duration of this process, which is the deaspiration time t4 (1730 min).

[0049] S600: Calculate the time loss ratio a2, where a2 = 10 × (t1 / t4) = 0.16.

[0050] S700: Cross plot of loss time ratio and loss gas volume ratio ( Figure 1 In the calculation, select the corresponding filling time ratio curve according to the filling time ratio a1 (0.06), and find the point of loss time ratio a2 (0.16) on the filling time ratio curve, which corresponds to the loss gas volume ratio a3 (0.15).

[0051] S800: The desorption vessel is heated to 90°C, and the gas volume is measured to obtain the residual gas volume V. 残 (178.68cm) 3 ).

[0052] S900: Remove the sample from the desorption vessel and dry it at low temperature to obtain the dry weight of the sample m4 (755.58g). At the same time, in order to eliminate the influence of the remaining impurities that have not been washed away on the data, the dried sample needs to be subjected to industrial analysis to obtain the dry ash-free mass of the sample m5 (571.51g).

[0053] S1000: Calculate the mass of water in the sample (2.42g) using m3-m4=m6.

[0054] S1100: Use V 解 / m5=Q1 Calculate the desorbed gas volume per unit mass of the dry, ash-free sample (4.37m). 3 / g), using V 残 / m5=Q2 Calculate the residual gas volume per unit mass of the dried, ash-free sample (0.31m). 3 / g).

[0055] S1200: Calculate the gas loss V 损 Loss of gas volume V 损 =Loss gas volume ratio a3 ×V 解 ×[(m5 / m6) / 100]=884.26 cm 3 .

[0056] S1300: Use V 损 / m5=Q3 Calculate the gas loss per unit mass of sample under dry, ash-free conditions (1.55m 3 / g).

[0057] S1400: Calculate the coalbed methane content Q, Q = Q1 + Q2 + Q3 = 6.23m 3 / g.

[0058] The measured total gas content per unit mass of the core was 6.38 cm³. 3 / g, deviation 2.4%.

[0059] Example 3: S100: First, select a desorption vessel that can hold 1000g of coal sample. Then, clean the sample desorption vessel and dry it at high temperature to remove moisture. Finally, weigh the desorption vessel and obtain the mass m1 of the desorption vessel as 1794g.

[0060] S200: Place the colored fine sand into the wellhead at the wellhead inlet position. Use a timer to measure the time it takes for the fine sand to travel from the wellhead to the drilling mud outlet along with the drilling mud. Since this time is the time for the fine sand to travel from the wellhead to the bottom of the well and then back to the wellhead, divide this time by 2 to get the planned time t2 for the rock cuttings to travel from the bottom of the well to the drilling mud outlet, which is 29 minutes.

[0061] S300: Collect approximately 800g of cuttings from the drilling mud outlet, quickly wash them to remove mud and other impurities, and then weigh the washed sample in a sample desorption container to obtain the mass m2 (2617g). The mass of the sample is then calculated as m2-m1=m3, yielding a final mass of 823g. Simultaneously, a timer is used to measure the time t3 (1.9min) from the collection of the cuttings from the drilling mud outlet to their placement in the desorption container.

[0062] S400: Calculate the time loss t1 and the filling time ratio a1. Time loss t1 (30.8 min) = time t2 (29 min) for cuttings to reach the drilling mud outlet from the bottom of the well + time t3 (1.9 min) for cuttings to be loaded into the desorption tank from the drilling mud outlet. Filling time ratio a1 = t3 / t1 = 0.06.

[0063] S500: Rock cuttings samples were tested using a conventional desorption method to obtain the desorbed gas volume V. 解 (2861.8cm) 3 ), and read the duration of this process, which is the deaspiration time t4 (1627 min).

[0064] S600: Calculate the time loss ratio a2, where a2 = 10 × (t1 / t4) = 0.18.

[0065] S700: Cross plot of loss time ratio and loss gas volume ratio ( Figure 1 In the calculation, select the corresponding filling time ratio curve according to the filling time ratio a1 (0.06), and find the point of loss time ratio a2 (0.18) on the filling time ratio curve, which corresponds to the loss gas volume ratio a3 (0.16).

[0066] S800: The desorption vessel is heated to 90°C, and the gas volume is measured to obtain the residual gas volume V. 残 (187.78cm) 3 ).

[0067] S900: Remove the sample from the desorption tank and dry it at low temperature to obtain the dry weight of the sample m4 (819.72g). At the same time, in order to eliminate the influence of the remaining impurities that have not been washed away on the data, the dried sample needs to be analyzed industrially to obtain the dry ash-free mass of the sample m5 (721.04g).

[0068] S1000: Calculate the mass of water in the sample (2.28g) using m3-m4=m6.

[0069] S1100: Use V 解 / m5=Q1 Calculate the desorbed gas volume per unit mass of the dry, ash-free sample (3.97m). 3 / g), using V 残 / m5=Q2 Calculate the residual gas volume per unit mass of the dried, ash-free sample (0.26m). 3 / g).

[0070] S1200: Calculate the gas loss V 损 Loss of gas volume V 损 =Loss gas volume ratio a3 ×V 解×[(m5 / m6) / 100]=1636.95cm 3 .

[0071] S1300: Use V 损 / m5=Q3 Calculate the gas loss per unit mass of sample under dry, ash-free conditions (2.01m³). 3 / g).

[0072] S1400: Calculate the coalbed methane content Q, Q = Q1 + Q2 + Q3 = 6.24m³ 3 / g.

[0073] The measured total gas content per unit mass of the core was 6.38 cm³. 3 / g, deviation 2.2%.

[0074] Example 4: S100: First, select a desorption container that can hold 1000g of coal sample. Then, clean the sample desorption container and dry it at high temperature to remove moisture. Finally, weigh the desorption container and obtain the mass m1 of the desorption container as 1816g.

[0075] S200: Place the colored fine sand into the wellhead at the wellhead inlet position. Use a timer to measure the time it takes for the fine sand to travel from the wellhead to the drilling mud outlet along with the drilling mud. Since this time is the time for the fine sand to travel from the wellhead to the bottom of the well and then back to the wellhead, divide this time by 2 to get the planned time t2 for the rock cuttings to travel from the bottom of the well to the drilling mud outlet, which is 31 minutes.

[0076] S300: Collect approximately 800g of cuttings from the drilling mud outlet, quickly wash them to remove mud and other impurities, and then weigh the washed sample in a sample desorption container to obtain the mass m2 (2594g). The mass of the sample is then calculated as m2-m1=m3, yielding a final mass of 778g. Simultaneously, a timer is used to measure the time t3 (1.8min) from the time the collected cuttings leave the drilling mud outlet to the time they are placed in the desorption container.

[0077] S400: Calculate the time loss t1 and the filling time ratio a1. Time loss t1 (32.8 min) = time t2 (31 min) for cuttings to reach the drilling mud outlet from the bottom of the well + time t3 (1.8 min) for cuttings to be loaded into the desorption tank from the drilling mud outlet. Filling time ratio a1 = t3 / t1 = 0.06.

[0078] S500: Rock cuttings samples were tested using a conventional desorption method to obtain the desorbed gas volume V. 解 (2857.61cm) 3 ), and read the duration of this process, which is the deaspiration time t4 (1421 min).

[0079] S600: Calculate the time loss ratio a2, where a2 = 10 × (t1 / t4) = 0.22.

[0080] S700: Cross plot of loss time ratio and loss gas volume ratio ( Figure 1 In the calculation, select the corresponding filling time ratio curve according to the filling time ratio a1 (0.06), and find the point of loss time ratio a2 (0.22) on the filling time ratio curve, which corresponds to the loss gas volume ratio a3 (0.18).

[0081] S800: The desorption vessel is heated to 90°C, and the gas volume is measured to obtain the residual gas volume V. 残 (157.39cm) 3 ).

[0082] S900: Remove the sample from the desorption vessel and dry it at low temperature to obtain the dry weight of the sample m4 (775.28g). At the same time, in order to eliminate the influence of the remaining impurities that have not been washed away on the data, it is necessary to perform industrial analysis on the dried sample to obtain the dry ash-free mass of the sample m5 (623.83g).

[0083] S1000: Calculate the mass of water in the sample (2.72g) using m3-m4=m6.

[0084] S1100: Use V 解 / m5=Q1 Calculate the desorbed gas volume per unit mass of the dry, ash-free sample (4.58m). 3 / g), using V 残 / m5=Q2 Calculate the residual gas volume per unit mass of the dried, ash-free sample (0.25m³). 3 / g).

[0085] S1200: Calculate the gas loss V 损 Loss of gas volume V 损 =Loss gas volume ratio a3 ×V 解 ×[(m5 / m6) / 100]=1177.91cm 3 .

[0086] S1300: Use V 损 / m5=Q3 Calculate the gas loss per unit mass of sample under dry ash-free conditions (1.76m 3 / g).

[0087] S1400: Calculate the coalbed methane content Q, Q = Q1 + Q2 + Q3 = 6.72m 3 / g.

[0088] The measured total gas content per unit mass of the core was 6.38 cm³. 3 / g, deviation 5.3%.

[0089] Example 5: S100: First, select a desorption vessel that can hold 1000g of coal sample. Then, clean the sample desorption vessel and dry it at high temperature to remove moisture. Finally, weigh the desorption vessel and obtain the mass m1 of the desorption vessel as 1809g.

[0090] S200: Place the colored fine sand into the wellhead at the wellhead inlet position. Use a timer to measure the time it takes for the fine sand to travel from the wellhead to the drilling mud outlet along with the drilling mud. Since this time is the time for the fine sand to travel from the wellhead to the bottom of the well and then back to the wellhead, divide this time by 2 to get the planned time t2 for the rock cuttings to travel from the bottom of the well to the drilling mud outlet, which is 34 minutes.

[0091] S300: Collect approximately 800g of cuttings from the drilling mud outlet, quickly wash them to remove mud and other impurities, and then weigh the washed sample in a sample desorption container to obtain the mass m2 (2636g). The mass m2 - m1 = m3 is then used to obtain the sample mass as 827g. Simultaneously, a timer is used to measure the time t3 (1.8min) from the time the collected cuttings leave the drilling mud outlet to the time the cuttings are placed in the desorption container.

[0092] S400: Calculate the time loss t1 and the filling time ratio a1. Time loss t1 (35.8 min) = Time t2 (34 min) for cuttings to reach the drilling mud outlet from the bottom of the well + Time t3 (1.8 min) for cuttings to be loaded into the desorption tank from the drilling mud outlet. Filling time ratio a1 = t3 / t1 = 0.05.

[0093] S500: Rock cuttings samples were tested using a conventional desorption method to obtain the desorbed gas volume V. 解 (2391.94cm) 3 ), and read the duration of this process, which is the deaspiration time t4 (1382 min).

[0094] S600: Calculate the time loss ratio a2, where a2 = 10 × (t1 / t4) = 0.26.

[0095] S700: Cross plot of loss time ratio and loss gas volume ratio ( Figure 1 In the calculation, select the corresponding filling time ratio curve according to the filling time ratio a1 (0.05), and find the point of loss time ratio a2 (0.26) on the filling time ratio curve, which corresponds to the loss gas volume ratio a3 (0.22).

[0096] S800: The desorption vessel is heated to 90°C, and the gas volume is measured to obtain the residual gas volume V. 残 (169.67cm) 3 ).

[0097] S900: Remove the sample from the desorption vessel and dry it at low temperature to obtain the dry weight of the sample m4 (825.16g). At the same time, in order to eliminate the influence of the remaining impurities that have not been washed away on the data, the dried sample needs to be subjected to industrial analysis to obtain the dry ash-free mass of the sample m5 (666.80g).

[0098] S1000: Calculate the mass of water in the sample (1.84g) using m3-m4=m6.

[0099] S1100: Use V 解 / m5=Q1 Calculate the desorption gas volume per unit mass of the dry, ash-free sample (3.58m). 3 / g), using V 残 / m5=Q2 Calculate the residual gas volume per unit mass of the dried, ash-free sample (0.25m³). 3 / g).

[0100] S1200: Calculate the gas loss V 损 Loss of gas volume V 损 =Loss gas volume ratio a3 ×V 解 ×[(m5 / m6) / 100]=1907.00cm 3 .

[0101] S1300: Use V 损 / m5=Q3 Calculate the gas loss per unit mass of sample under dry ash-free conditions (2.86m 3 / g).

[0102] S1400: Calculate the coalbed methane content Q, Q = Q1 + Q2 + Q3 = 6.69m 3 / g.

[0103] The measured total gas content per unit mass of the core was 6.38 cm³. 3 / g, deviation 4.9%.

[0104] In summary, the calculations show that the deviation between the real-time coal seam gas content obtained from drill cuttings at the drilling site and the average total gas content per unit mass measured in the core sample is 3.14%, which fully meets the data accuracy requirements in production. Therefore, the real-time coal seam gas content determination using drill cuttings at the drilling site has significant application value.

[0105] The parameters mentioned above all refer to mass m (g), gas volume V (ml), gas volume Q per unit mass sample (ml / g), time t (s), and loss ratio a (dimensionless). Desorbed gas and residual gas acquisition methods are based on the national standard "Determination of Coalbed Methane Content (GB / T19559-2008)". Industrial analysis is based on the national standard "Industrial Analysis Methods for Coal (GB / T212-2001)".

[0106] The structures, proportions, sizes, etc., illustrated in the accompanying drawings of this specification are intended to complement the content disclosed in the specification, so as to enable those skilled in the art to understand and read them, and to limit the conditions under which the present invention can be implemented, and have substantial technical significance.

[0107] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for determining the gas content of coal seams in real time using drill cuttings at drilling sites, characterized in that, include: S100: Weigh the sample desorption vessel and obtain the mass m1; S200: Cuttings sample collection, the time t2 for the cuttings collected according to the metering plan to reach the drilling mud outlet from the bottom of the well; Step S200 includes: placing colored fine sand into the wellhead inlet position, using a timer to measure the time it takes for the fine sand to travel from the wellhead to the drilling mud outlet along with the drilling mud. This time is the time it takes for the fine sand to travel from the wellhead to the bottom of the well and then back to the wellhead. Therefore, this time is divided by 2 to get the time t2 for the planned rock cuttings to travel from the bottom of the well to the drilling mud outlet. S300: Collect rock cuttings at the drilling mud outlet, quickly wash them to remove mud impurities, and weigh the washed sample in a sample desorption tank to obtain the mass m2. The mass of the sample is obtained by m2-m1=m3. At the same time, measure the time t3 from when the collected rock cuttings are collected from the drilling mud outlet to when the rock cuttings are put into the desorption tank. S400: Calculate the lost time t1 and the filling time ratio a1; In step S400, the lost time t1 = the time t2 for the cuttings to reach the drilling mud outlet from the bottom of the well + the time t3 for the cuttings to be loaded into the desorption container from the drilling mud outlet; the loading time ratio a1 = t3 / t1; S500: Test rock cuttings samples to obtain the desorbed gas volume V. 解 And read the desorption time t4; S600: Calculate the time loss ratio a2; In step S600, the time loss ratio a2 = 10 × (t1 / t4). S700: In the intersection chart of the time loss ratio and the gas loss ratio, select the corresponding filling time ratio curve according to the calculated filling time ratio a1, and find the point of the time loss ratio a2 on the filling time ratio curve that corresponds to the gas loss ratio a3. S800: Heats the desorption vessel and detects the gas volume to obtain the residual gas volume V. 残 ; S900: Remove the sample from the desorption tank and dry it at low temperature to obtain the dry weight of the sample m4. Perform industrial analysis on the dried sample to obtain the dry ash-free mass of the sample m5. S1000: Calculate the mass of water in the sample using m3-m4=m6; S1100: Use V 解 / m5=Q1 to calculate the desorbed gas volume per unit mass of the dry, ash-free sample, using V 残 / m5=Q2 is used to calculate the residual gas volume per unit mass of the dry, ash-free sample. S1200: Calculate the gas loss V 损 Loss of gas volume V 损 =a3 ×V 解 ×[(m5 / m6) / 100]; S1300: Use V 损 / m5=Q3 calculates the gas loss per unit mass of sample under dry, ash-free conditions; S1400: Calculate the coalbed methane content Q, Q=Q1+Q2+Q3.

2. The method for determining the gas content of coal seams in real time using drill cuttings at the drilling site according to claim 1, characterized in that, In step S100, the desorption vessel is capable of holding 1000g of coal sample.

3. The method for determining the gas content of coal seams in real time using drill cuttings at the drilling site according to claim 1, characterized in that, In step S300, t3 is less than 2 minutes.

4. The method for determining the gas content of coal seams in real time using drill cuttings at the drilling site according to claim 1, characterized in that, In step S800, the heating temperature is 90°C.

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