Factors influencing the productivity and technology optimization of horizontal wells for moderately deep coalbed methane in the northern Zhengzhuang block

Authors

ZHANG Cong, Huabei Oilfield Shanxi Coalbed Methane Exploration and Development Branch of PetroChina, Changzhi 046000, ChinaFollow
LI Kexin, Huabei Oilfield Shanxi Coalbed Methane Exploration and Development Branch of PetroChina, Changzhi 046000, ChinaFollow
JIA Huimin, Huabei Oilfield Shanxi Coalbed Methane Exploration and Development Branch of PetroChina, Changzhi 046000, China
ZHANG Wuchang, Huabei Oilfield Shanxi Coalbed Methane Exploration and Development Branch of PetroChina, Changzhi 046000, China
YANG Ruiqiang, Huabei Oilfield Shanxi Coalbed Methane Exploration and Development Branch of PetroChina, Changzhi 046000, China
LI Jun, Huabei Oilfield Shanxi Coalbed Methane Exploration and Development Branch of PetroChina, Changzhi 046000, China
WANG Qi, Huabei Oilfield Shanxi Coalbed Methane Exploration and Development Branch of PetroChina, Changzhi 046000, China
HOU Weiming, The Second Logging Branch of PetroChina Bohai Drilling Engineering Co., Ltd., Renqiu 062550, China

Abstract

[Objective] Hydraulic fracturing of vertical wells was adopted during the early production of moderately deep coalbed methane (CBM) of the northern Zhengzhuang block in the Qinshui Basin, generally yielding low productivity and inefficiency. In contrast, single-casing fracturing of horizontal wells has increased the single-well production to 10‒50 times that of vertical wells, establishing horizontal wells as the dominant development well type. However, the horizontal wells differ greatly in CBM production. This study aims to determine the factors influencing the productivity of horizontal wells using staged fracturing for moderately deep CBM in the northern Zhengzhuang block and improve the production performance. [Methods] To this end, based on the production practice using horizontal wells in the northern Zhengzhuang block, combined with geological characteristics and engineering parameters, this study analyzed the dominant factors governing the productivity of horizontal wells for moderately deep CBM and proposed targeted suggestions for efficient production of horizontal wells. The results indicate that the productivity of horizontal wells using single-casing fracturing is influenced by both geological and engineering factors. [Results and Conclusions] The effects of geological conditions are as follows: (1) Moderately deep reservoirs exhibit significantly higher gas saturation than shallow reservoirs, generally boasting high resource enrichment. (2) Horizontal wells with high productivity are primarily distributed in gentle areas with low structural curvature. (3) There is a positive correlation between the number of perforation sections in primary coal seams and the gas production performance of horizontal wells. (4) The horizontal principal stress differences in the study area range from 8 to 16 MPa and increase with burial depth, posing challenges in the formation of complex fracture networks. This is the cause of the low gas production performance in the early stage. The effects of engineering conditions on the productivity of horizontal wells include: (1) The optimal gas production performance occurred when the included angle between the orientation of the wellbore trajectory and the azimuth of the maximum horizontal principal stress varied from 60° to 90°, with the average stable gas production rate of horizontal wells reaching up to 9700 m³/d. (2) Longer horizontal sections of horizontal wells were associated with higher stable gas production of coal seams. (3) The pumping bridge plug and clustering perforation fracturing technology yielded significantly higher gas production performance of horizontal wells than tubing fracturing, with the stable gas production increasing significantly with the fracturing scale. Among fracturing parameters, the fracturing fluid injection rate produced more significant controlling effects on fracture stimulation. Specifically, the stable gas production rate of a horizontal well was less than 2000 m³/d when the injection rate was less than 7 m³/min, increased gradually when the injection rate increased to 8‒10 m³/min, remained stably between 10000 and 12000 m³/d when the injection rate remained at 10‒12 m³/min, and exceeded 18000 m³/d when the injection rate increased to 16‒18 m³/min. Finally, based on optimal geological parameters such as gas-bearing properties, structural curvature, coal structure, and in-situ stress, along with optimal engineering parameters like horizontal section length, fracturing section number, the fracturing fluid volume and proppant volume for single-stage fracturing, fracturing fluid injection rate, and proppant concentration, this study analyzed the dominant factors influencing the productivity of horizontal wells for moderately deep CBM using grey relational analysis. The results indicate that coal structure and fracturing scale are the primary factors influencing the productivity of horizontal wells. Therefore, the principal methods for enhancing the productivity of horizontal wells through hydraulic fracturing for moderately deep coal seams in the study area include increasing the drilling rate and placement efficiency of primary coal seams, as well as further enhancing the fracturing fluid injection rate and fracturing scale.

Keywords

Qinshui Basin, northern Zhengzhuang block, moderately deep coalbed methane (CBM), horizontal well fracturing, fracturing scale, fracturing fluid injection rate

DOI

10.12363/issn.1001-1986.23.09.0594

Recommended Citation

ZHANG Cong, LI Kexin, JIA Huimin, et al. (2024) "Factors influencing the productivity and technology optimization of horizontal wells for moderately deep coalbed methane in the northern Zhengzhuang block," Coal Geology & Exploration: Vol. 52: Iss. 6, Article 4.
DOI: 10.12363/issn.1001-1986.23.09.0594
Available at: https://cge.researchcommons.org/journal/vol52/iss6/4

Reference

[1] 杨秀春，徐凤银，王虹雅，等. 鄂尔多斯盆地东缘煤层气勘探开发历程与启示[J]. 煤田地质与勘探，2022，50(3)：30−41.

YANG Xiuchun，XU Fengyin，WANG Hongya，et al. Exploration and development process of coalbed methane in eastern margin of Ordos Basin and its enlightenment[J]. Coal Geology & Exploration，2022，50(3)：30−41.

[2] 贾慧敏，胡秋嘉，樊彬，等. 沁水盆地郑庄区块北部煤层气直井低产原因及高效开发技术[J]. 煤田地质与勘探，2021，49(2)：34−42.

JIA Huimin，HU Qiujia，FAN Bin，et al. Causes for low CBM production of vertical wells and efficient development technology in northern Zhengzhuang Block in Qinshui Basin[J]. Coal Geology & Exploration，2021，49(2)：34−42.

[3] 闫霞，徐凤银，聂志宏，等. 深部微构造特征及其对煤层气高产“甜点区” 的控制：以鄂尔多斯盆地东缘大吉地区为例[J]. 煤炭学报，2021，46(8)：2426−2439.

YAN Xia，XU Fengyin，NIE Zhihong，et al. Microstructure characteristics of Daji Area in East Ordos Basin and its control over the high yield dessert of CBM[J]. Journal of China Coal Society，2021，46(8)：2426−2439.

[4] 张懿，朱光辉，郑求根，等. 中国煤层气资源分布特征及勘探研究建议[J]. 非常规油气，2022，9(4)：1−8.

ZHANG Yi，ZHU Guanghui，ZHENG Qiugen，et al. Distribution characteristics of coalbed methane resources in China and recommendations for exploration research[J]. Unconventional Oil & Gas，2022，9(4)：1−8.

[5] 张村，宋子玉，赵毅鑫. 2010—2020年国际煤层气开采发展趋势的文献计量分析[J]. 西安科技大学学报，2022，42(3)：484−492.

ZHANG Cun，SONG Ziyu，ZHAO Yixin. A bibliometric analysis of trends in international coalbed methane exploitation for the period 2010—2020[J]. Journal of Xi’an University of Science and Technology，2022，42(3)：484−492.

[6] 郑民，李建忠，吴晓智，等. 我国主要含油气盆地油气资源潜力及未来重点勘探领域[J]. 地球科学，2019，44(3)：833−847.

ZHENG Min，LI Jianzhong，WU Xiaozhi，et al. Potential of oil and natural gas resources of main hydrocarbon–bearing basins and key exploration fields in China[J]. Earth Science，2019，44(3)：833−847.

[7] 高玉巧，李鑫，何希鹏，等. 延川南深部煤层气高产主控地质因素研究[J]. 煤田地质与勘探，2021，49(2)：21−27.

GAO Yuqiao，LI Xin，HE Xipeng，et al. Study on the main controlling geological factors of high yield deep CBM in Southern Yanchuan Block[J]. Coal Geology & Exploration，2021，49(2)：21−27.

[8] 徐凤银，王成旺，熊先钺，等. 深部(层)煤层气成藏模式与关键技术对策：以鄂尔多斯盆地东缘为例[J]. 中国海上油气，2022，34(4)：30−42.

XU Fengyin，WANG Chengwang，XIONG Xianyue，et al. Deep(layer)coalbed methane reservoir forming modes and key technical countermeasures：Taking the eastern margin of Ordos Basin as an example[J]. China Offshore Oil and Gas，2022，34(4)：30−42.

[9] 姚红生，肖翠，陈贞龙，等. 延川南深部煤层气高效开发调整对策研究[J]. 油气藏评价与开发，2022，12(4)：545−555.

YAO Hongsheng，XIAO Cui，CHEN Zhenlong，et al. Adjustment countermeasures for efficient development of deep coalbed methane in southern Yanchuan CBM Field[J]. Petroleum Reservoir Evaluation and Development，2022，12(4)：545−555.

[10] 姚红生，陈贞龙，何希鹏，等. 深部煤层气“有效支撑” 理念及创新实践：以鄂尔多斯盆地延川南煤层气田为例[J]. 天然气工业，2022，42(6)：97−106.

YAO Hongsheng，CHEN Zhenlong，HE Xipeng，et al. “Effective support”concept and innovative practice of deep CBM in South Yanchuan Gas Field of the Ordos Basin[J]. Natural Gas Industry，2022，42(6)：97−106.

[11] 聂志宏，时小松，孙伟，等. 大宁–吉县区块深层煤层气生产特征与开发技术对策[J]. 煤田地质与勘探，2022，50(3)：193−200.

NIE Zhihong，SHI Xiaosong，SUN Wei，et al. Production characteristics of deep coalbed methane gas reservoirs in Daning–Jixian Block and its development technology countermeasures[J]. Coal Geology & Exploration，2022，50(3)：193−200.

[12] 李曙光，王成旺，王红娜，等. 大宁–吉县区块深层煤层气成藏特征及有利区评价[J]. 煤田地质与勘探，2022，50(9)：59−67.

LI Shuguang，WANG Chengwang，WANG Hongna，et al. Reservoir forming characteristics and favorable area evaluation of deep coalbed methane in Daning–Jixian Block[J]. Coal Geology & Exploration，2022，50(9)：59−67.

[13] 李培培，赵汝敏，杨松岭，等. 构造曲率与振幅曲率在地震资料解释中的应用[J]. 物探与化探，2013，37(5)：916−920.

LI Peipei，ZHAO Rumin，YANG Songling，et al. The application of structural curvature and amplitude curvature attribute to seismic interpretation[J]. Geophysical & Geochemical Exploration，2013，37(5)：916−920.

[14] 张群，孙四清，降文萍. 碎软低渗煤层煤矿区煤层气勘探开发关键技术及发展方向[J/OL]. 石油学报，2024：1–11. (2024-04-17). https://kns.cnki.net/kcms/detail/11.2128.TE.20240416.1653.012.html.

ZHANG Qun，SUN Siqing，JIANG Wenping. Key technologies and development direction of CBM exploration and development in coal mine area of fractured soft and low permeablity coal seams[J/OL]. Acta Petrolei Sinica，2024：1–11. (2024-04-17). https://kns.cnki.net/kcms/detail/11.2128.TE.20240416.1653.012.html.

[15] 徐刚，金洪伟，李树刚，等. 不同坚固性系数f值煤渗透率分布特征及其井下水力压裂适用性分析[J]. 西安科技大学学报，2019，39(3)：443−451.

XU Gang，JIN Hongwei，LI Shugang，et al. Distribution characteristics of coal seam permeability with different solidity coefficient f and applicability analysis of hydraulic fracturing of underground coal mine[J]. Journal of Xi’an University of Science and Technology，2019，39(3)：443−451.

[16] 孟召平，王宇恒，张昆，等. 沁水盆地南部煤层水力压裂裂缝及地应力方向分析[J]. 煤炭科学技术，2019，47(10)：216−222.

MENG Zhaoping，WANG Yuheng，ZHANG Kun，et al. Analysis of hydraulic fracturing cracks for coal reservoirs and in situ stress direction in Southern Qinshui Basin[J]. Coal Science and Technology，2019，47(10)：216−222.

[17] 张玉亭. 煤层分层地应力预测模型研究[J]. 非常规油气，2023，10(2)：115−120.

ZHANG Yuting. Prediction model study of coalbed layered in situ stress[J]. Unconventional Oil & Gas，2023，10(2)：115−120.

[18] 祝凌甫，伊丙鼎，曲秋扬，等. 基于Rhino精准曲面建模的常村煤矿原岩地应力场反演方法[J]. 矿业安全与环保，2021，48(5)：33−37.

ZHU Lingfu，YI Bingding，QU Qiuyang，et al. Inversion method of in situ stress field of Changcun Coal Mine based on Rhino precise surface modeling[J]. Mining Safety & Environmental Protection，2021，48(5)：33−37.

[19] 李叶朋，申建，杨春莉，等. 沁水盆地郑庄区块地应力发育特征及其地质意义[J]. 煤炭科学技术，2017，45(10)：176−181.

LI Yepeng，SHEN Jian，YANG Chunli，et al. Characteristics and its geological implication of ground stress in Zhengzhuang Block of Qinshui Basin[J]. Coal Science and Technology，2017，45(10)：176−181.

[20] 刘建，惠晨，樊建明，等. 鄂尔多斯盆地合水地区长6致密砂岩储层现今地应力分布特征及其开发建议[J]. 地质力学学报，2021，27(1)：31−39.

LIU Jian，HUI Chen，FAN Jianming，et al. Distribution characteristics of the present–day in situ stress in the Chang 6 tight sandstone reservoirs of the Yanchang Formation in the Heshui Area，Ordos Basin，China and suggestions for development[J]. Journal of Geomechanics，2021，27(1)：31−39.

[21] 郭广山，王海侨，刘松楠，等. 沁水盆地古交区块煤层气水平井产能影响因素分析[J]. 中国海上油气，2024，36(2)：110−118.

GUO Guangshan，WANG Haiqiao，LIU Songnan，et al. Analysis of factors influencing the productivity of horizontal wells in Gujiao coalbed methane block of Qinshui Basin[J]. China Offshore Oil and Gas，2024，36(2)：110−118.

[22] 杨帆，李斌，王昆剑，等. 深部煤层气水平井大规模极限体积压裂技术：以鄂尔多斯盆地东缘临兴区块为例[J]. 石油勘探与开发，2024，51(2)：389−398.

YANG Fan，LI Bin，WANG Kunjian，et al. Extreme massive hydraulic fracturing in deep coalbed methane horizontal wells：A case study of the Linxing Block，eastern Ordos Basin，NW China[J]. Petroleum Exploration and Development，2024，51(2)：389−398.

[23] 张聪，李梦溪，胡秋嘉，等. 沁水盆地南部中深部煤层气储层特征及开发技术对策[J]. 煤田地质与勘探，2024，52(2)：122−133.

ZHANG Cong，LI Mengxi，HU Qiujia，et al. Moderately deep coalbed methane reservoirs in the southern Qinshui Basin：Characteristics and technical strategies for exploitation[J]. Coal Geology & Exploration，2024，52(2)：122−133.

[24] 袁征，黄杰，袁文奎，等. 压裂裂缝长期导流能力衰退规律实验研究[J]. 非常规油气，2022，9(3)：78−82.

YUAN Zheng，HUANG Jie，YUAN Wenkui，et al. Experimental study on long term conductivity decline of hydraulic fracturing fracture[J]. Unconventional Oil & Gas，2022，9(3)：78−82.

[25] 杨松，刘晓，申建，等. 延川南气田近薄层煤层气开发实践及其示范意义[J]. 天然气工业，2023，43(8)：90−97.

YANG Song，LIU Xiao，SHEN Jian，et al. Development practice of near–thin bed CBM in the Yanchuannan gas field and its demonstration significance[J]. Natural Gas Industry，2023，43(8)：90−97.