Coal Reservoir Gas Content Correction Based on Coalbed Methane Well Production Data

doi:10.19657/j.geoscience.1000-8527.2022.026

Abstract

Abstract:

It is found that the cumulative production of coalbed methane wells in some coalbed methane (CBM) blocks (Qinshui basin: Panzhuang and Panhe CBM blocks; Ordos basin: Baode CBM block) is far greater than the original calculated geological proven reserve.This phenomenon has made a challenge on the calculated geological reserve by volume method, and put forward a new way for the overall increase of geological reserve.In the CBM reserve calculation by volume method, the accuracy of gas-bearing area and gas content, as well as the heterogeneity of coal density and thickness would all affect the accuracy of reserve parameters.Due to the limitation of coring and analysis, errors are common exist in the calculation of gas content.In this study, a minimum critical gas content calculation method (Critical Minimum Method) was proposed, based on the production data and coal isothermal adsorption experimental data from CBM wells in the Ordos and Qinshui basins.Then, the calculated critical minimum gas content was compared with the measured gas content, according to the direct measurement method proposed by the United States Bureau of Mines (USBM) and the Smith-Williams method.The geologic controlling mechanism of the D-value between the gas contents (based on USBM and Critical Minimum Method) was also analyzed.The results show that in the medium-low to medium-high coal ranks (R_o= 0.7%-2.1%), the gas content calculated by the Critical Minimum Method is generally higher than that by the USBM and Smith-Williams method.The Critical Minimum Method shows strong adaptability in this coal rank range.In the range of high coal ranks (R_o=2.1%-2.8%), the results by Critical Minimum Method can serve as mutual support with the coring sample measurement results.Generally, the D-value between these two gas contents (based on USBM and Critical Minimum Method) is affected by the pore/fracture development characteristics in different coal ranks, coal structure development, gas saturation, and escape time of the coring process.The D-value is positively correlated with the porosity and permeability, coal structure development, gas saturation and escape time.In addition, for the CBM wells with no cores collected, drilling cuttings can be used for isothermal adsorption parameters measurement.Gas content of coal reservoir can be obtained by the Critical Minimum Method, which can provide a data basis for further CBM exploration and development.

Key words: gas content, critical minimum gas content, correction method, production data, coalbed methane

CLC Number:

P618.1
TE155

YAN Taotao, GUO Yilin, MENG Yanjun, CHANG Suoliang, JIN Shangwen, KANG Lifang, FU Xinyu, WANG Qingqing, ZHAO Yuan, ZHANG Yu. Coal Reservoir Gas Content Correction Based on Coalbed Methane Well Production Data[J]. Geoscience, 2022, 36(05): 1360-1370.

Figures/Tables 10

Fig.1 Sketch location map of the CBM study block

Table 1 Basic sample parameters from each CBM block

区块	样品号	埋深/m	煤体结构	含气量 /(cm³·g^-1)	R_o/%	孔隙度/%	渗透率 /10^-3μm²	镜质组/%	惰质组/%	壳质组/%
临兴	LX1-1	1 090.40	碎裂	6.63	0.71	4.67	0.30	72.32	8.59	19.09
	LX1-2	1 088.52	碎裂	4.43	0.70	4.67	0.30	—	—	—
	LX1-3	1 092.15	碎裂	5.92	0.73	4.67	0.30	—	—	—
	LX1-4	1 086.52	碎裂	4.48	0.72	4.67	0.30	—	—	—
	LX1-5	1 084.11	碎裂	3.15	0.72	4.67	0.30	47.47	15.86	36.67
	LX2-2	893.73	—	4.04	0.92	5.96	0.19	60.40	19.80	19.80
	LX2-3	899.83	—	3.94	0.90	5.96	0.19	50.82	18.81	30.37
	LX2-4	888.48	—	2.60	0.94	5.96	0.19	64.49	17.65	17.86
	LX2-5	896.15	—	4.55	0.95	5.96	0.19	76.97	13.88	9.15
	LX2-6	886.45	—	3.15	0.96	5.96	0.19	77.18	16.17	6.65
	LX3-4	977.18	碎裂	5.51	0.80	12.58	0.62	17.22	54.74	28.04
柳林	LL4-1	579.66	碎裂	6.62	1.25	0.52	0.64	75.60	24.40	0
	LL4-3	640.65	碎裂	10.25	1.50	0.74	0.06	76.80	23.20	0
	LL5-1	560.45	碎粒	6.63	1.69	—	0.16	—	—	—
	LL5-2	577.30	碎粒	6.71	1.65	—	0.06	—	—	—
	LL5-3	632.43	碎粒	7.59	1.66	—	0.10	—	—	—
	LL6-1	870.80	碎粒	6.49	1.66	5.65	1.39	55.20	11.20	33.60
	LL6-2	882.45	碎粒	7.07	1.65	4.76	0.14	12.70	8.30	79.00
	LL7-3	623.85	碎裂	9.35	—	7.5	0.42	56.80	30.30	12.90
	LL8-1	954.80	原生	9.40	1.45	4.95	—	73.70	12.40	13.90
	LL8-2	964.40	原生	8.75	1.54	4.81	0.07	61.50	26.30	12.20
	LL8-4	973.10	碎裂	8.63	1.56	4.86	0.21	83.80	8.50	7.70
韩城	HC1-2	504.86	碎粒	5.63	1.92	—	—	98.24	1.76	0
	HC1-4	534.29	碎粒	9.10	1.93	—	—	82.29	17.71	0
	HC1-6	534.59	碎粒	7.14	1.93	—	—	87.60	12.40	0
	HC2-3	1 051.67	碎裂	9.14	2.12	—	0.24	—	—	—
	HC2-5	1 066.58	碎裂	12.19	2.06	—	0.24	—	—	—
	HC2-8	1 068.38	碎裂	11.28	2.12	—	0.24	—	—	—
安泽	AZ1-3	1 047.18	原生	23.62	2.72	3.38	0.10	85.30	14.70	0
	AZ1-7	1 049.70	原生	22.69	2.87	1.32	0.10	81.60	18.40	0
	AZ2-1	1 419.05	碎裂	15.21	2.02	0.72	0.02	79.40	20.60	0
	AZ2-4	1 427.30	碎裂	16.11	2.06	2.10	0.02	70.00	30.00	0
	AZ5-2	970.70	碎裂	15.67	2.12	3.95	0.09	80.70	19.30	0
	AZ5-4	971.40	碎裂	15.16	2.10	4.76	0.09	79.60	20.40	0

Table 1 Basic sample parameters from each CBM block

区块	样品号	埋深/m	煤体结构	含气量 /(cm³·g^-1)	R_o/%	孔隙度/%	渗透率 /10^-3μm²	镜质组/%	惰质组/%	壳质组/%
临兴	LX1-1	1 090.40	碎裂	6.63	0.71	4.67	0.30	72.32	8.59	19.09
	LX1-2	1 088.52	碎裂	4.43	0.70	4.67	0.30	—	—	—
	LX1-3	1 092.15	碎裂	5.92	0.73	4.67	0.30	—	—	—
	LX1-4	1 086.52	碎裂	4.48	0.72	4.67	0.30	—	—	—
	LX1-5	1 084.11	碎裂	3.15	0.72	4.67	0.30	47.47	15.86	36.67
	LX2-2	893.73	—	4.04	0.92	5.96	0.19	60.40	19.80	19.80
	LX2-3	899.83	—	3.94	0.90	5.96	0.19	50.82	18.81	30.37
	LX2-4	888.48	—	2.60	0.94	5.96	0.19	64.49	17.65	17.86
	LX2-5	896.15	—	4.55	0.95	5.96	0.19	76.97	13.88	9.15
	LX2-6	886.45	—	3.15	0.96	5.96	0.19	77.18	16.17	6.65
	LX3-4	977.18	碎裂	5.51	0.80	12.58	0.62	17.22	54.74	28.04
柳林	LL4-1	579.66	碎裂	6.62	1.25	0.52	0.64	75.60	24.40	0
	LL4-3	640.65	碎裂	10.25	1.50	0.74	0.06	76.80	23.20	0
	LL5-1	560.45	碎粒	6.63	1.69	—	0.16	—	—	—
	LL5-2	577.30	碎粒	6.71	1.65	—	0.06	—	—	—
	LL5-3	632.43	碎粒	7.59	1.66	—	0.10	—	—	—
	LL6-1	870.80	碎粒	6.49	1.66	5.65	1.39	55.20	11.20	33.60
	LL6-2	882.45	碎粒	7.07	1.65	4.76	0.14	12.70	8.30	79.00
	LL7-3	623.85	碎裂	9.35	—	7.5	0.42	56.80	30.30	12.90
	LL8-1	954.80	原生	9.40	1.45	4.95	—	73.70	12.40	13.90
	LL8-2	964.40	原生	8.75	1.54	4.81	0.07	61.50	26.30	12.20
	LL8-4	973.10	碎裂	8.63	1.56	4.86	0.21	83.80	8.50	7.70
韩城	HC1-2	504.86	碎粒	5.63	1.92	—	—	98.24	1.76	0
	HC1-4	534.29	碎粒	9.10	1.93	—	—	82.29	17.71	0
	HC1-6	534.59	碎粒	7.14	1.93	—	—	87.60	12.40	0
	HC2-3	1 051.67	碎裂	9.14	2.12	—	0.24	—	—	—
	HC2-5	1 066.58	碎裂	12.19	2.06	—	0.24	—	—	—
	HC2-8	1 068.38	碎裂	11.28	2.12	—	0.24	—	—	—
安泽	AZ1-3	1 047.18	原生	23.62	2.72	3.38	0.10	85.30	14.70	0
	AZ1-7	1 049.70	原生	22.69	2.87	1.32	0.10	81.60	18.40	0
	AZ2-1	1 419.05	碎裂	15.21	2.02	0.72	0.02	79.40	20.60	0
	AZ2-4	1 427.30	碎裂	16.11	2.06	2.10	0.02	70.00	30.00	0
	AZ5-2	970.70	碎裂	15.67	2.12	3.95	0.09	80.70	19.30	0
	AZ5-4	971.40	碎裂	15.16	2.10	4.76	0.09	79.60	20.40	0

Fig.2 Principle diagram for coal sample gas content measurement of USBM method (modified after Kissel et al.[6])

Fig.3 Diagram of the VCF, STR and LTR parameters in Smith-Williams method (modified after Smith and Williams[7])

Fig.4 Phase division of typical CBM well production curve

Fig.5 Dynamic characteristics of pressure propagation in the different production stages (modified after Yan et al.[27])

Table 2 Parameters for gas content calculation

区块	样品号	逸散时间/min	解吸25% 气量的时间 /min	兰氏压力/MPa	兰氏体积/ (cm³·g^-1)	初始见气流压/MPa
临兴	LX1-1	11.00	33.64	3.02	16.84	2.936
	LX1-2	12.50	110.00	2.81	14.26	2.936
	LX1-3	12.50	78.00	1.72	14.75	2.936
	LX1-4	16.00	51.00	2.59	17.35	2.936
	LX1-5	12.50	29.50	3.13	11.03	2.936
	LX2-2	—	—	2.55	12.50	1.682
	LX2-3	—	—	2.26	14.44	1.682
	LX2-4	—	—	2.06	11.55	1.682
	LX2-5	—	—	1.46	11.55	1.682
	LX2-6	—	—	2.31	12.67	1.682
	LX3-4	25.50		2.74	16.79	2.276
柳林	LL4-1	10.80	30.00	3.52	20.94	2.603
	LL4-3	8.13	81.00	1.67	25.53	2.603
	LL5-1	—	—	2.33	22.66	2.660
	LL5-2	—	—	1.40	20.48	2.660
	LL5-3	—	—	1.50	21.26	2.660
	LL6-1	12.60	42.00	2.33	22.81	1.960
	LL6-2	11.93	43.00	1.93	22.70	1.960
	LL7-3	—	—	1.84	17.08	4.700
	LL8-1	13.80	61.00	2.29	19.60	2.200
	LL8-2	11.51	43.00	2.55	19.48	2.200
	LL8-4	18.44	64.00	2.26	19.87	2.200
韩城	HC1-2	14.25	57.00	1.95	15.54	4.040
	HC1-4	10.40	170.00	2.49	25.81	4.040
	HC1-6	15.15	62.00	2.06	20.34	4.040
	HC2-3	13.00	18.00	2.04	25.89	2.650
	HC2-5	19.24	31.00	2.08	26.14	2.650
	HC2-8	10.82	18.00	2.17	29.40	2.650
安泽	AZ1-3	9.96	265.00	2.22	32.82	4.120
	AZ1-7	13.09	190.00	2.33	32.40	4.120
	AZ2-1	14.86	30.00	2.10	26.24	3.420
	AZ2-4	15.61	152.00	2.04	24.56	3.420
	AZ5-2	8.98	79.00	2.05	26.96	3.750
	AZ5-4	9.34	56.00	1.88	28.36	3.750

Table 3 Gas content results calculated by different methods

样号	含气量/(cm³·g^-1)			相对含气量测试差异/%			绝对含气量测试差异/(cm³·g^-1)
样号	V_U	$V S W$	V_C	V_C与V_U	V_C与 $V S W$	$V S W$ 与V_U	V_C与V_U	V_C与 $V S W$	$V S W$ 与V_U
LX1-1	6.63	6.80	8.30	25.21	22.08	2.50	1.67	1.50	0.17
LX1-2	4.43	4.88	7.29	64.48	49.31	9.22	2.86	2.41	0.45
LX1-3	5.92	6.75	9.30	57.11	37.87	12.25	3.38	2.55	0.83
LX1-4	4.48	5.55	9.22	105.76	66.00	19.32	4.74	3.67	1.07
LX1-5	3.15	4.18	5.34	69.48	27.75	24.63	2.19	1.16	1.03
LL4-1	6.62	8.45	8.90	34.46	5.37	21.63	2.28	0.45	1.83
LL4-3	10.25	11.21	15.55	51.72	38.76	8.54	5.30	4.34	0.96
LL6-1	6.49	8.04	10.42	60.58	29.66	19.25	3.93	2.38	1.55
LL6-2	7.07	8.49	11.44	61.78	34.76	16.70	4.37	2.95	1.42
LL8-1	9.40	9.50	9.60	2.17	1.09	1.05	0.20	0.10	0.10
LL8-2	8.75	8.90	9.02	3.11	1.37	1.69	0.27	0.12	0.15
LL8-4	8.63	9.10	9.80	13.57	7.71	5.16	1.17	0.70	0.47
HC1-2	5.63	6.77	10.48	86.16	54.78	16.86	4.85	3.71	1.14
HC1-4	9.10	9.68	15.97	75.50	64.95	6.02	6.87	6.29	0.58
HC1-6	7.14	8.52	13.47	88.63	58.15	16.16	6.33	4.95	1.38
HC2-3	9.14	14.12	14.63	60.06	3.58	35.28	5.49	0.51	4.98
HC2-5	12.19	13.20	14.65	20.15	10.96	7.65	2.46	1.45	1.01
HC2-8	11.28	15.40	16.16	43.30	4.96	26.75	4.88	0.76	4.12
AZ1-3	23.62	24.32	21.33	-9.70	-12.32	2.89	-2.29	-3.00	0.70
AZ1-7	22.69	23.99	20.70	-8.79	-13.72	5.40	-1.99	-3.29	1.30
AZ2-1	15.21	20.72	16.26	6.89	-21.53	26.58	1.05	-4.46	5.51
AZ2-4	16.11	17.47	15.38	-4.51	-11.96	7.80	-0.73	-2.09	1.36
AZ5-2	15.67	17.24	17.43	11.24	1.12	9.10	1.76	0.19	1.57
AZ5-4	15.16	17.39	18.89	24.60	8.64	12.81	3.73	1.50	2.23

Table 3 Gas content results calculated by different methods

样号	含气量/(cm³·g^-1)			相对含气量测试差异/%			绝对含气量测试差异/(cm³·g^-1)
样号	V_U	$V S W$	V_C	V_C与V_U	V_C与 $V S W$	$V S W$ 与V_U	V_C与V_U	V_C与 $V S W$	$V S W$ 与V_U
LX1-1	6.63	6.80	8.30	25.21	22.08	2.50	1.67	1.50	0.17
LX1-2	4.43	4.88	7.29	64.48	49.31	9.22	2.86	2.41	0.45
LX1-3	5.92	6.75	9.30	57.11	37.87	12.25	3.38	2.55	0.83
LX1-4	4.48	5.55	9.22	105.76	66.00	19.32	4.74	3.67	1.07
LX1-5	3.15	4.18	5.34	69.48	27.75	24.63	2.19	1.16	1.03
LL4-1	6.62	8.45	8.90	34.46	5.37	21.63	2.28	0.45	1.83
LL4-3	10.25	11.21	15.55	51.72	38.76	8.54	5.30	4.34	0.96
LL6-1	6.49	8.04	10.42	60.58	29.66	19.25	3.93	2.38	1.55
LL6-2	7.07	8.49	11.44	61.78	34.76	16.70	4.37	2.95	1.42
LL8-1	9.40	9.50	9.60	2.17	1.09	1.05	0.20	0.10	0.10
LL8-2	8.75	8.90	9.02	3.11	1.37	1.69	0.27	0.12	0.15
LL8-4	8.63	9.10	9.80	13.57	7.71	5.16	1.17	0.70	0.47
HC1-2	5.63	6.77	10.48	86.16	54.78	16.86	4.85	3.71	1.14
HC1-4	9.10	9.68	15.97	75.50	64.95	6.02	6.87	6.29	0.58
HC1-6	7.14	8.52	13.47	88.63	58.15	16.16	6.33	4.95	1.38
HC2-3	9.14	14.12	14.63	60.06	3.58	35.28	5.49	0.51	4.98
HC2-5	12.19	13.20	14.65	20.15	10.96	7.65	2.46	1.45	1.01
HC2-8	11.28	15.40	16.16	43.30	4.96	26.75	4.88	0.76	4.12
AZ1-3	23.62	24.32	21.33	-9.70	-12.32	2.89	-2.29	-3.00	0.70
AZ1-7	22.69	23.99	20.70	-8.79	-13.72	5.40	-1.99	-3.29	1.30
AZ2-1	15.21	20.72	16.26	6.89	-21.53	26.58	1.05	-4.46	5.51
AZ2-4	16.11	17.47	15.38	-4.51	-11.96	7.80	-0.73	-2.09	1.36
AZ5-2	15.67	17.24	17.43	11.24	1.12	9.10	1.76	0.19	1.57
AZ5-4	15.16	17.39	18.89	24.60	8.64	12.81	3.73	1.50	2.23

Fig.6 Comparison of gas content results calculated by different methods in each CBM block

Fig.7 Geological controlling mechanism of D-value between two gas contents from USBM and Critical Minimum Method

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