彭水及邻区龙马溪组页岩气常压形成机制

doi:10.13809/j.cnki.cn32-1825/te.2020.01.002

摘要/Abstract

摘要：

彭水及邻区龙马溪组页岩气藏在地质历史时期存在过超压现象,但现今为常压,发生了由超压向常压的转变。通过抬升过程中地层压力演化模拟,揭示龙马溪组泥页岩在抬升过程中发生了超压破裂,产生裂缝,导致页岩气散失和超压释放。依据泥页岩覆压渗透率测试分析数据,认为当龙马溪组泥页岩裂缝面上所受的正应力大于15 MPa,即埋深大于1 000 m时裂缝将发生闭合。但裂缝闭合程度受泥页岩超固结比（OCR）影响,处于脆性带之下的泥页岩,OCR相对小,裂缝闭合程度相对高,超压可能未完全释放,现今仍然维持一定程度的超压;处于脆性带之上的泥页岩,OCR越大,裂缝闭合程度越差,对页岩气保存不利,容易导致超压完全释放,变为常压。泥页岩的OCR与地层流体压力系数之间具有显著的相关性,OCR比越大,越趋于常压。

关键词: 页岩气, 常压, 超固结比, 脆性, 裂缝闭合

Abstract:

The shale gas reservoirs in Longmaxi formation in Pengshui and its adjacent areas were overpressured in geological history, but nowadays they transformed into normal pressure. Through the simulation of formation pressure evolution in the uplifting process, it is revealed that Longmaxi shale was fractured under excessive pressure in this process, resulting in shale gas loss and therefore overpressure release. By overburden pressure permeability test, it is found that when the normal stress on the mudstone fracture surface of Longmaxi formation is more than 15 MPa, that is to say, when the buried depth is more than 1 000 m, the cracks will be closed, but the degree of fracture closure is affected by overconsolidation ratio（OCR） of shale. For the mudstone or shale under the brittle zones, OCR is relatively small, the closure degree of fracture is relatively high, the overpressure may not be completely released, and a certain degree of overpressure is still maintain. But for those above the brittle zones, the lager the OCR, the worse the fracture closure degree, and it is apt to cause the overpressure released completely, finally transit to normal pressure state. There is a significant correlation between OCR and the pressure coefficient of the formation fluid, that is, the higher the OCR ratio, the more normal the pressure will tend to be.

Key words: shale gas, normal pressure, overconsolidation ratio, brittleness, fracture closure

中图分类号:

TE122

袁玉松,方志雄,何希鹏,李双建,彭勇民,龙胜祥. 彭水及邻区龙马溪组页岩气常压形成机制[J]. 油气藏评价与开发, 2020, 10(1): 9-16.

YUAN Yusong,FANG Zhixiong,HE Xipeng,LI Shuangjian,PENG Yongmin,LONG shengxiang. Normal pressure formation mechanism of Longmaxi shale gas in Pengshui and its adjacent areas[J]. Reservoir Evaluation and Development, 2020, 10(1): 9-16.

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参考文献 26

[1]	何希鹏, 高玉巧, 唐显春 , 等. 渝东南地区常压页岩气富集主控因素分析[J]. 天然气地球科学, 2017,28(4):654-664.
	HE X P, GAO Y Q, TANG X C , et al. Analysis of major factors controlling the accumulation in normal pressure shale gas in the southeast of Chongqing[J]. Natural Gas Geoscience, 2017,28(4):654-664.
[2]	董大忠, 王玉满, 李新景 , 等. 中国页岩气勘探开发新突破及发展前景思考[J]. 天然气工业, 2016,36(1):19-32.
	DONG D Z, WANG Y M, LI X J , et al. Breakthrough and prospect of shale gas exploration and development in China[J]. Natural Gas Industry, 2016,36(1):19-32.
[3]	聂海宽, 汪虎, 何治亮 , 等. 常压页岩气形成机制、分布规律及勘探前景——以四川盆地及其周缘五峰组—龙马溪组为例[J]. 石油学报, 2019,40(2):131-143.
	NIE H K, WANG H, HE Z L , et al. Famation mechanism, distribution and exploration prospect of normal pressure shale gas reservoir: A case study of Wufeng-Longmaxi Famation in Sichuan Basin and its periphery[J]. Acta Petrolei Sinica, 2019,40(2):131-143.
[4]	李双建, 袁玉松, 孙炜 , 等. 四川盆地志留系页岩气超压形成与破坏机理及主控因素[J]. 天然气地球科学, 2016,27(5):924-931.
	LI S J, YUAN Y S, SUN W , et al. The formation and destroyment mechanism of shale gas overpressure and its main controlling factors in Silurian of Sichuan Basin[J]. Natural Gas Geoscience, 2016,27(5):924-931.
[5]	方志雄, 何希鹏 . 渝东南武隆向斜常压页岩气形成与演化[J]. 石油与天然气地质, 2016,37(6):819-827.
	FANG Z X, HE X P . Formation and evolution of normal pressure shale gas reservoir in Wulong Syncline, Southeast Chongqing, China[J]. Oil & Gas Geology, 2016,37(6):819-827.
[6]	NYGARD R, GUTIERREZ M, BRATLI R K , et al. Brittle-ductile transition, shear failure and leakage in shales and mudrocks[J]. Marine and Petroleum Geology, 2006,23(2):201-212.
[7]	YUAN Y S, JIN Z J, ZHOU Y , et al. Burial depth interval of the shale brittle-ductile transition zone and its implications in shale gas exploration and production[J]. Petroleum Science, 2017,14(5):637-647.
[8]	李士祥, 施泽进, 刘显阳 , 等. 鄂尔多斯盆地中生界异常低压成因定量分析[J]. 石油勘探与开发, 2013,40(5):528-533.
	LI S X, SHI Z J, LIU X Y , et al. Quantitative analysis of the Mesozoic abnormal low pressure in Ordos Basin[J]. Petroleum Exploration and Development, 2013,40(5):528-533.
[9]	SWARBRICK R E, OSBORNE M J . Mechanisms that generate abnormal pressures: An overview[J]. AAPG Memoir, 1998,70:13-34.
[10]	王瑀辉, 袁玉松 . 含烃盐水包裹体PVTsim模拟的一种简化方法及应用[J]. 石油地质与工程, 2018,32(5):40-43.
	WANG Y H, YUAN Y S . Hydrocarbon brine inclusions PVTsim simulation: A simplified method and application[J]. Petroleum Geology and Engineering, 2018,32(5):40-43.
[11]	米敬奎, 杨孟达, 刘新华 . 利用PVTsim计算鄂尔多斯盆地上古生界砂岩储层中包裹体的捕获压力[J]. 湘潭矿业学院学报, 2002,17(3):22-26.
	MI J K, YANG M D, LIU X H . Calculation to trapping pressure of inclusions occurring in upperpaleozoic sandstone reservoir from the Ordos basin using PVTsim method[J]. Journal of Xiangtan Mining Institute, 2002,17(3):22-26.
[12]	RICKMAN R, MULLEN M J, PETRE J E. A practical use of shale petrophysics for stimulation design optimization: All shale plays are not clones of the Barnett Shale[C]// paper SPE-115258-MS presented at the SPE Annual Technical Conference and Exhibition, 21-24 September 2008, Denver, Colorado, USA.
[13]	LABANI M M, REZAEE R . The importance of geochemical parameters and shale composition on rock mechanical properties of gas shale reservoirs: a case study from the Kockatea Shale and Carynginia Formation from the Perth Basin, Western Australia[J]. Rock Mechanics and Rock Engineering, 2015,48(3):1249-1257.
[14]	WANG F P, GALE J F . Screening criteria for shale-gas systems[J]. Gulf Coast Assoc Geol Soc Trans, 2009,59:779-793.
[15]	邹才能, 董大忠, 王社教 , 等. 中国页岩气形成机理、地质特征及资源潜力[J]. 石油勘探与开发, 2010,37(6):641-653.
	ZOU C N, DONG D Z, WANG S J , et al. Geological characteristics, formation mechanism and resource potential of shale gas in China[J]. Petroleum Exploration and Development, 2010,37(6):641-653.
[16]	聂海宽, 包书景, 高波 , 等. 四川盆地及其周缘下古生界页岩气保存条件研究[J]. 地学前缘, 2012,19(3):280-294.
	NIE H K, BAO S J, GAO BO , et al. A study of shale gas preservation condition for the Lower Paleozoic in Sichuan Basin and its pheriphery[J]. Earth Science Frontiers, 2012,19(3):280-294.
[17]	李双建, 周雁, 孙冬胜 . 评价盖层有效性的岩石力学实验研究[J]. 石油实验地质, 2013,35(5):574-578.
	LI S J, ZHOU Y, SUN D S . Rock mechanic experiment study of evaluation on cap rock effectiveness[J]. Petroleum Geology & Experiment, 2013,35(5):574-578.
[18]	BABANOURI N, NASAB S K, BAGHBANAN A , et al. Overconsolidation effect on shear behavior of rock joints[J]. International Journal of Rock Mechanics and Mining Sciences, 2011,48(8):1283-1291.
[19]	NYGÅRD R, GUTIERREZ M, BRATLI R K , et al. Brittle-ductile transition, shear failure and leakage in shales and mudrocks[J]. Marine and Petroleum Geology, 2006,23(2):201-212.
[20]	MARK R P T, RICHARD R H, RICHARD E S , et al. Origin of overpressure and pore- pressure prediction in the Baram province, Brunei[J]. AAPG Bulletin, 2009,93(1):51-74.
[21]	朱贺, 汪佳, 施坤 , 等. 泥岩裂缝性储层应力敏感性实验研究[J]. 科学技术与工程, 2011,11(35):8862-8864.
	ZHU H, WANG J, SHI K , et al. Experimental study on pressures sensibility of fractured shale reservoir[J]. Science Technology and Engineering, 2011,11(35):8862-8864.
[22]	解习农, 刘晓峰, 胡祥云 , 等. 超压盆地中泥岩的流体压裂与幕式排烃作用[J]. 地质科技情报, 1998,17(4):59-64.
	JIE X N, LIU X F, HU X Y , et al. Hydrofracturing and associated episodic hydrocarbon expulsion of mudstones in overpressured basin[J]. Geological Science and Technology Information, 1998,17(4):59-64
[23]	郝芳, 董伟良 . 沉积盆地超压系统演化、流体流动与成藏机理[J]. 地球科学进展, 2001,16(1):79-85.
	HAO F, DONG W L . Evolution of, fluid flow and petroleum accumulation in overpressured systems in sedimentary basins[J]. Advance In Earth Sciences, 2001,16(1):79-85
[24]	HARWOOD R J . Oil and Gas Generation by Laboratory Pyrolysis of Kerogen[J]. AAPG, 1977,61(12):2082-2102.
[25]	席斌斌, 腾格尔, 俞凌杰 , 等. 川东南页岩气储层脉体中包裹体古压力特征及其地质意义[J]. 石油实验地质, 2016,38(4):473-479.
	XI B B, TENG G E, YU L J , et al. Trapping pressure of fluid inclusions and its significance in shale gas reservoirs, southeastern Sichuan Basin[J]. Petroleum Geology & Experiment, 2016,38(4):473-479.
[26]	高键, 何生, 易积正 . 焦石坝页岩气田中高密度甲烷包裹体的发现及其意义[J]. 石油与天然气地质, 2015,36(3):472-480.
	GAO J, HE S, YI J Z . Discovery of high density methane inclusions in Jiaoshiba shale gas field and its significance[J]. Oil & Gas Geology, 2015,36(3):472-480.

井名	现今埋深/m	最大古埋深/m	OCR	志留系压力系数实测值	志留系压力系数预测值	误差
PY1	2 153	6 243	2.70	0.96	1.05	0.09
HY1	2 162	6 461	3.00	1.01	0.99	0.02
PY3	3 021	6 216	2.10	1.05	1.21	0.16
DY1	2 050	5 045	2.50	1.15	1.10	0.05
LY1	2 832	5 831	2.10	1.20	1.21	0.01
SY1	3 467	5 462	1.57	1.30	1.43	0.13
NY1	4 405	5 700	1.29	1.40	1.59	0.19
JY1	2 409	5 708	2.20	1.45	1.18	0.27
JS1	4 985	6 904	1.40	1.67	1.52	0.15
DY2	4 359	6 354	1.27	1.78	1.61	0.17

井名	志留系底界最大埋深/m	志留系底界现今埋深/m	脆性带底界/m	保存条件
HY1	6 461	2 162	2 485	较差
PY1	6 243	2 153	2 401
DY1HF	5 545	2 050	2 132
LY1	5 831	2 832	2 242	较好
JY1	5 708	2 409	2 195	较好
DY2HF	6 354	4 359	2 443	好

岩样编号	长度/cm	直径/cm	温度/ ℃	气体黏度/（mPa·s）	造缝前渗透率/10^-3μm²	造缝后渗透率/10^-3μm²
泥-1	3.933	2.487	12	0.017 78	0.002 769	19.503
泥-2	3.239	2.490	12	0.017 78	0.003 701	33.433
泥-3	3.284	2.502	12	0.017 78	0.003 466	18.176
泥-4	2.544	2.493	12	0.017 78	0.003 687	23.588

泥-1		泥-2		泥-3		泥-4
围压/MPa	渗透率/10^-3 μm²	围压/MPa	渗透率/10^-3 μm²	围压/MPa	渗透率/10^-3 μm²	围压/MPa	渗透率/10^-3 μm²
1.00	19.503 000	1.0	33.433 00	1.0	18.176 000	1.0	23.588 000
3.20	9.889 109	9.05	5.639 825	5.4	7.249 812	10.1	12.915 430
5.15	4.742 773	11.5	3.237 930	8.35	2.961 592	12.2	9.766 560
7.15	3.837 527	14.0	1.447 781	11.2	1.574 693	15.2	6.350 846
10.25	2.090 685	19.9	0.443 591	15.2	0.785 671	20.6	2.338 490
15.40	0.832 936	25.2	0.220 236	20.1	0.395 021	25.5	1.168 620
24.98	0.248 925	29.9	0.130 036	25.2	0.238 413	30.4	0.646 946
34.70	0.093 078	39.4	0.056 493	29.9	0.153 105	38.9	0.263 671
44.00	0.042 680	49.8	0.026 599	39.4	0.068 022	50.0	0.108 952
59.50	0.016 512	58.0	0.016 027	50.2	0.032 018	60.0	0.056 485
				59.6	0.021 513

地层层位	样品编号	轴向应力/MPa	围压/MPa	温度/℃	峰值强度/MPa	弹性模量/GPa	泊松比	内聚力C/MPa	内摩擦角Φ/（°）
龙马溪组	1142-3	40.25	1.92	17	38.33	3.54	0.11	11.0	30.0
	1142-38	61.01	7.65	25	53.36	3.48	0.12
	1142-15	93.32	15.49	35	77.83	5.03	0.20
	1142-21	126.35	31.06	55	95.29	6.09	0.22
	1142-46	147.08	48.16	75	98.92	5.33	0.29