渝东南构造复杂区常压页岩气生产特征及开发技术政策

doi:10.11743/ogg20210119

摘要/Abstract

摘要：

针对渝东南构造复杂区常压页岩气压力系数低、吸附气占比高、地应力复杂及压裂形成复杂缝网难度大等地质特点，在60余口页岩气水平井钻探成果和生产特征分析基础上，总结了常压页岩气生产规律，划分了生产阶段，明确了产能主控因素，提出了开发技术政策。结果表明：常压页岩气生产具有初期以排液为主，产气量较低，随着返排率增大，产气量不断增大，后期产量逐渐稳定，产量递减慢，单位压降产气量较高，单井可采储量较小的特点。可划分为纯液、过渡、稳定生产和低压排采等4个阶段，不同阶段生产特征受地层压力系数影响明显：压力系数越高，纯液生产时间越短，见气返排率降低；在过渡阶段，返排率越低，气液平衡时间越长；在稳定生产阶段，产气能力越强，单位压降产量和单井可采储量越高。产能主要受地层压力系数和有效改造体积控制，其中有效改造体积主要受控于最优靶窗钻遇率、水平段长、水平段方位以及压裂改造规模等，压力系数越高，最优靶窗钻遇率越高，水平段长越长，压裂改造规模越大，越利于提高单井产量和最终经济可采储量。在上述认识基础上，提出了渝东南构造复杂区页岩气开发技术优化政策和配套的压裂工艺参数，以指导常压页岩气效益开发。

关键词: 生产特征, 产能影响因素, 开发技术政策, 常压页岩气, 龙马溪组, 渝东南构造复杂区

Abstract:

The normal-pressure shale gas reservoirs in some structurally complex areas of southeastern Chongqing is characterized by low pressure coefficient, high proportion of adsorbed gas and complex in-situ stress.Difficulties in forming complex fracture networks in these reservoirs are also frequently experienced during frac operations.Based on the analysis of drilling results and production characteristics of more than 60 horizontal shale gas wells in the areas, we summarized the production law, delineated the production stages, clarified the main factors controlling production capacity, and proposed an optimized technology combination for the reservoir development.It shows that the reservoirs produce mainly fracturing fluids with only a small amount of gas during the initial stage after fracturing and start to yield more gas as the flowback rate of frac fluids increases.At the later stage, gas production gradually stabilizes (depletes slowly) but features relatively high gas production per MPa of pressure drop and limited reserve covered by single wells.The whole production process can be divided into four stages: the liquid (flowback fluid only) stage, transition stage, stable production stage and low-pressure gas drainage stage.The formation pressure coefficient plays a critical role in all of the stages.During the liquid stage, higher pressure coefficient helps to shorten the liquid producing time and to initiate gas production when the flowback rate is still low.In the transition stage, it maintains a longer gas-liquid equilibrium time at lower flowback rate.In the stable production stage, it ensures a stronger gas production capacity that yields more gas with each unit of pressure drop and recover more reserves from a single well.Apart from formation pressure coefficient, the productivity of the reservoirs after fracturing operations is also conditioned by the stimulated reservoir volume (SRV) of frac operations.SRV is in turn controlled mainly by optimal hit ratios of target window, length and orientation of laterals and stimulated areas.Higher formation pressure coefficient and optimal target window drilling rate, longer lateral length, and wider stimulated areas generally signify higher single-well production and more commercially recoverable reserves.Given the above-mentioned understandings, we put forward an optimized technology combination and related fracturing parameters for the normal-pressure shale gas development in the complex areas of southeastern Chongqing.

Key words: production characteristics, factor affecting productivity, optimized development technology, normal-pressure shale gas, Longmaxi Formation, structurally complex area in southeastern Chongqing

中图分类号:

TE321

何希鹏,卢比,何贵松,等. 渝东南构造复杂区常压页岩气生产特征及开发技术政策[J]. 石油与天然气地质, 2021, 42(1): 224-240. doi: 10.11743/ogg20210119 Xipeng He,Bi Lu,Guisong He,et al. Production characteristics and optimized development technologies for normal-pressure shale gas in the structurally complex areas of southeastern Chongqing[J]. Oil & Gas Geology, 2021, 42(1): 224-240. doi: 10.11743/ogg20210119

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类别	评价参数	涪陵地区	南川地区	武隆地区	彭水地区
沉积特征	优质页岩厚度/m	38~40	30~35	32~35	24~25
地化特征	TOC/%	3.0~4.0	3.1~3.6	4.0~5.0	3.0~3.5
地化特征	R_o/%	2.65	2.58	2.62	2.63
岩矿特征	石英含量/%	40~50	45~50	55~65	40~50
岩矿特征	粘土含量/%	25~40	25~40	15~30	20~38
储集特征	孔隙度/%	4.0~6.0	3.5~4.0	4.5~5.0	2.5~3.5
储集特征	裂缝发育情况	高角度缝相对不发育	高角度缝及层理缝发育	高角度缝及层理缝发育	高角度缝及层理缝发育
保存条件	地层压力系数	＞1.50	1.10~1.35	1.05~1.15	0.90~1.10
赋存特征	吸附气占比/%	25~40	40~55	45~60	50~60
应力特征	最大水平主应力/MPa	50~70	50~95	30~70	30~70
应力特征	水平应力差异系数	0.08~0.12	0.10~0.12	0.22~0.25	0.22~0.36

主要指标		压力系数
主要指标		0.9~1.0	1.0~1.1	1.1~1.3	1.3~1.4
地质特征	水平段中深/m	2 000~2 500	2 800~3 300	3 000~3 300	2 800~3 800
压裂改造	水平段长/m	1 000~1 400	1 200~1 500	1 500~2 000	1 600~1 900
	总液量/m³	16 000~21 000	34 000~47 000	43 000~53 000	37 000~43 000
	总砂量/m³	800~1 300	1 200~2 100	2 000~2 400	1 300~1 700
	施工排量/(m³·min^-1)	10~14	14~16	16~18	16~18
试气情况	无阻流量/(10⁴ m³·d^-1)	3~10	7~15	15~30	20~45
试气情况	稳定日产气/(10⁴ m³)	2~3	3~4	4~6	6~10
试采情况	套压5 MPa时累产气/(10⁴ m³)	800~1 500	1 500~2 500	2 500~4 000	4 000~8 000
	套压5 MPa时返排率/%	50~80	25~40	20~25	10~20
	初期年递减率/%	20~25	25~30	30~35	35~45
	单位压降产气量/(10⁴ m³·MPa^-1)	40~60	80~120	120~150	150~240
	EUR/(10⁸ m³)	0.35~0.50	0.50~0.70	0.70~0.90	0.90~1.20

生产阶段	压力系数	0.9~1.0	1.0~1.1	1.1~1.3	1.3~1.4
纯液阶段	生产时间/d	10~15	0~10	< 1	< 1
	日产液量/m³	120~500	90~120	60~90	20~60
	阶段返排率/%	5.0~15.0	2.0~5.0	0.5~2.0	< 0.5
过渡阶段	生产时间/d	>150	50~150	5~10	0~5
	日产气量/(10⁴ m³)	2~3	3~4	4~10	6~10
	阶段返排率/%	15.0~40.0	5.0~15.0	2.0~10.0	0.5~5.0
稳定阶段	日产气量/(10⁴ m³)	2~3	3~4	4~10	6~10
	阶段递减率/%	20~25	25~30	30~40	>40
	单位压降产气量/(10⁴ m³·MPa^-1)	40~60	80~120	120~150	>150
	阶段累产气量/(10⁴ m³)	700~1 000	1 000~2 500	2 500~4 500	4 500~8 000
低压排采阶段	日产气量/(10⁴ m³)	1.0~1.5	1.5~2.0	3.0~5.0	4.0~6.0
	阶段递减率/%	5~10	10~20	20~30	25~35
	单井EUR/(10⁸ m³)	0.35~0.50	0.50~0.70	0.70~0.90	0.90~1.20

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[3]	沈骋, 任岚, 赵金洲, 陈铭培. 页岩岩相组合划分标准及其对缝网形成的影响——以四川盆地志留系龙马溪组页岩为例[J]. 石油与天然气地质, 2021, 42(1): 98-106, 123.
[4]	蔡全升, 陈孝红, 张国涛, 张保民, 韩京, 陈琳, 李培军, 李炎桂. 鄂西宜昌地区下古生界五峰组-龙马溪组页岩气储层发育特征与勘探潜力[J]. 石油与天然气地质, 2021, 42(1): 107-123.
[5]	陆亚秋, 梁榜, 王超, 刘超, 吉靖. 四川盆地涪陵页岩气田江东区块下古生界深层页岩气勘探开发实践与启示[J]. 石油与天然气地质, 2021, 42(1): 241-250.
[6]	霍建峰, 高健, 郭小文, 易积正, 舒志国, 包汉勇, 杨锐, 罗涛, 何生. 川东地区龙马溪组页岩不同岩相孔隙结构特征及其主控因素[J]. 石油与天然气地质, 2020, 41(6): 1162-1175.
[7]	洪剑, 唐玄, 张聪, 黄璜, 单衍胜, 郑玉岩, 谢皇长. 中扬子地区龙马溪组页岩有机质孔隙发育特征及控制因素——以湖南省永顺地区永页3井为例[J]. 石油与天然气地质, 2020, 41(5): 1060-1072.
[8]	聂海宽, 张柏桥, 刘光祥, 颜彩娜, 李东晖, 卢志远, 张光荣. 四川盆地五峰组-龙马溪组页岩气高产地质原因及启示——以涪陵页岩气田JY6-2HF为例[J]. 石油与天然气地质, 2020, 41(3): 463-473.
[9]	田鹤, 曾联波, 徐翔, 舒志国, 彭勇民, 毛哲, 罗兵. 四川盆地涪陵地区海相页岩天然裂缝特征及对页岩气的影响[J]. 石油与天然气地质, 2020, 41(3): 474-483.
[10]	高博乐, 潘仁芳, 金吉能, 张鉴, 赵圣贤, 鄢杰. 富有机质页岩微裂缝地震响应特征——以长宁示范区宁201井为例[J]. 石油与天然气地质, 2020, 41(2): 407-415.
[11]	郑和荣, 彭勇民, 唐建信, 龙胜祥, 刘光祥, 高波, 何希鹏, 王运海, 顾志翔. 中、上扬子地区常压页岩气勘探前景——以湘中坳陷下寒武统为例[J]. 石油与天然气地质, 2019, 40(6): 1155-1167.
[12]	肖佃师, 赵仁文, 杨潇, 房大志, 李勃, 孙星星. 海相页岩气储层孔隙表征、分类及贡献[J]. 石油与天然气地质, 2019, 40(6): 1215-1225.
[13]	庞小婷, 陈国辉, 许晨曦, 佟茂胜, 倪彬午, 包汉勇. 涪陵地区五峰组-龙马溪组页岩吸附-游离气定量评价及相互转化[J]. 石油与天然气地质, 2019, 40(6): 1247-1258.
[14]	赵日新, 卢双舫, 薛海涛, 田善思. 扫描电镜分析参数对定量评价页岩微观孔隙的影响[J]. 石油与天然气地质, 2019, 40(5): 1141-1154.
[15]	唐建信. 利用地震品质因子Q比例的分布特征预测南川页岩气藏保存条件[J]. 石油与天然气地质, 2019, 40(4): 930-937.