Multiscale modeling and optimization of coiled tubing acidizing in carbonate horizontal wells

doi:10.3969/j.issn.2096-1693.2025.03.016

Abstract

Abstract:

Coiled tubing drag acidizing is a commonly used diversion technique in carbonate reservoir horizontal wells. However, due to challenges such as long wellbore length, strong formation heterogeneity, and uneven damage distribution, predicting acidizing effectiveness remains uncertain. To address this, a radial dual-scale wormhole propagation model and a numerical model of coiled tubing drag acidizing were developed to simulate the evolution of acid etching patterns and the mechanism of damage removal under varying injection parameters. Field data from the X oilfield in Iraq were integrated for process optimization. Simulation results show that as the acid injection rate increases, acid etching morphologies evolve from conical pores to dominant wormholes, branched wormholes, and eventually uniform dissolution. Dominant wormholes require the least acid volume and exhibit the highest propagation efficiency. Wormhole length increases significantly with acid volume intensity, extending from 0.55 m to 1.42 m as intensity increases from 0.2 to 0.8 m³/m. Greater damage depth and lower permeability contrast lead to poorer acidizing outcomes. Based on the analysis, when the damage depth is less than 0.5 m, an injection rate of 0.5 m³/min and an acid intensity of 0.3~0.4 m³/m are recommended. For damage depths around 1 m, the recommended rate is 1 m³/min with an acid intensity of 0.4~0.7 m³/m. Field results confirm that combining coiled tubing drag acidizing with near-heel pinpoint injection can enhance well productivity by 2~5 times, outperforming other acid placement strategies. This study provides theoretical and practical guidance for optimizing acidizing parameters and operational design in carbonate long horizontal wells.

Key words: coiled tubing drag acidizing, wormhole morphology, acid volume per meter, pinpoint acid injection, process optimization

摘要： 连续油管拖动酸化是碳酸盐岩储层长水平井常用的酸液转向手段，然而受井筒跨度大、储层非均质性强及污染分布复杂等因素影响，其酸化效果难以准确预测。为此，本文建立了径向双尺度蚓孔扩展模型与现场尺度的连续油管酸化数值模型，系统模拟不同注酸参数下的酸蚀形态演化及酸化解堵规律，并结合伊拉克X油田现场数据开展实例分析。结果表明：随着注酸速率增加，酸蚀形态依次表现为锥形孔、主蚓孔、分支蚓孔及均匀溶蚀，其中主蚓孔突破所需酸量最少、扩展效率最高。蚓孔长度随用酸强度增大而显著增长，在0.2~0.8 m³/m范围内，长度从0.55 m增至1.42 m。地层污染深度越大、渗透率差异越小，酸化效果越差。模拟推荐：污染深度小于0.5 m时，采用注酸速率0.5 m³/min、用酸强度0.3~0.4 m³/m；污染深度约为1 m时，注酸速率提升至1 m³/min、用酸强度为0.4~0.7 m³/m。结合现场应用，采用“连续油管拖动酸化+近跟部加密点状注酸”的组合工艺可显著提升油井产能(2~5倍)，优于其他布酸方式。本研究为非均质碳酸盐岩长水平井的酸化参数优化与工艺设计提供了理论支持和工程参考。

关键词: 连续油管酸化, 蚓孔形态, 用酸强度, 点状注酸, 工艺优选

CLC Number:

LU Panpan, MOU Jianye, CHENG Yi, LUO Yang, LV Xiaoyi, SHEN-LI Chuheng. Multiscale modeling and optimization of coiled tubing acidizing in carbonate horizontal wells[J]. Petroleum Science Bulletin, 2025, 10(4): 747-761.

卢盼盼, 牟建业, 成一, 罗扬, 吕骁义, 谌李楚珩. 碳酸盐岩水平井连续油管酸化多尺度数值模拟与工艺优化[J]. 石油科学通报, 2025, 10(4): 747-761.

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URL: https://sykxtb.cup.edu.cn/EN/10.3969/j.issn.2096-1693.2025.03.016

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Figures/Tables 15

Fig. 1 Experimental results

Table 1 Simulation parameters of matrix acidizing

参数	数值	参数	数值
网格数(周向×径向)	360×200	反应速度常数/(m/s)	0.002
地层垂深/m	2300	地层温度/℃	75℃
油藏压力/MPa	22	扩散系数/( m²/s)	3×10^-9
初始比表面积/cm^-1	50	岩石密度/( kg/m³)	2650
平均孔隙度	0.2	井筒半径/m	0.1
地层平均渗透率/mD	10.8	酸液浓度	20 wt% HCl

Fig. 2 Morphology of acid etched wormhole at different acid injection rates

Fig. 3 Relationship between acid injection rate and pore volume multiple

Fig. 4 Length prediction of acid etched wormhole

Fig. 5 Schematic diagram of the distribution of contaminated depths and coiled tubing drag acidizing

Fig. 6 Initial formation conditions

Table 2 Simulation parameters for horizontal wells

参数	数值	参数	数值
水平井筒长度/m	1200	储层厚度/m	20
水平井方向的网格数	120	水平方向渗透率无因次关联长度	0.05
油藏压力/MPa	25	井筒直井/mm	152.4
地层平均渗透率/mD	10	孔隙度	0.2
地层综合压缩系数/(1/MPa)	0.004	原油粘度/()	1
蚓孔最优注入速度/(cm/min)	0.9	蚓孔扩展最优孔隙体积倍数	1.4
酸液密度/(kg/m³)	1080	水平井倾角/°	0
酸液浓度/%	20	注酸总量/m³	300/600

Fig. 7 Impact of damaged depth

Fig. 8 Impact of permeability contrast coefficient

Fig. 9 Impact of acid injection rate

Fig. 10 Impact of acid volume

Fig. 11 Optimization of different operation techniques

Fig. 12 Acid injection volume and acid intensity for different wells

Fig. 13 Production performance and daily oil production after coiled tubing drag acidizing in horizontal wells

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