页岩油体积压裂后合理焖井时间模拟研究

doi:10.13809/j.cnki.cn32-1825/te.2024.05.010

摘要/Abstract

摘要：

针对页岩油藏压裂开发过程中，焖井效果井间差异大、焖井有效性和时效性不明确等问题，建立了考虑裂缝闭合、油水渗吸置换以及压裂液滞留多效应协同的压裂—焖井—生产一体化数值模型，并验证了模型的可靠性，探究了页岩油井压后焖井期间地层油水运移规律以及合理焖井时间。研究结果表明：①焖井期间地层油水运移特征在时间上呈现阶段性变化，依次可分为裂缝闭合、渗吸置换和能量平衡3个主控阶段，同时也在空间上与水力裂缝的复杂程度密切相关；②在毛管渗吸作用下，适当延长焖井时间有利于压裂井初期见产，但压裂液在基质中的滞留量增多也会加剧油相相渗伤害，结合累增油量变化规律，明确了合理焖井时间宜在30~45 d；③考虑真实工况对焖井作用的影响，提出了以“压裂+焖井时间”作为焖井优化的指标，提高时间效益的同时可以减少井间差异。研究提出了体积压裂水平井焖井作用评价方法和模拟流程，其结果对页岩油压裂后合理焖井时间优化具有指导作用。

关键词: 页岩油, 体积压裂, 合理焖井时间, 裂缝闭合, 渗吸置换, 数值模拟

Abstract:

To address issues such as the significant variance in shut-in effects between wells and the unclear effectiveness and timeliness of shut-ins during fracturing in shale formations, a numerical model integrating fracturing, shut-in, and production processes was developed. This model considers the synergistic effects of fracture closure, oil-water imbibition replacement, and fracturing fluid retention. The model's reliability was verified through simulations, exploring the oil-water migration law in the formation during the shut-in period of shale oil fractured wells and determining the optimal shut-in duration. Research indicates that: ① The oil-water migration characteristics during well shut-in undergo phased changes over time, which can be categorized into three main control stages: fracture closure, imbibition replacement, and energy balance. Additionally, these migration laws are closely related to the complexity of hydraulic fractures in space. ② Under the influence of capillary imbibition, extending the shut-in time appropriately benefits the initial production of fractured wells. However, an increase in fracturing fluid retention within the matrix can also exacerbate oil phase permeability damage. Based on the law of change in incremental oil volume, a reasonable shut-in time is identified to be between 30 to 45 days. ③ Considering real working conditions, “fracturing & well shut-in time” is proposed as an indicator for optimizing well shut-in, which aims to improve time efficiency and reduce differences between wells. This paper proposes an evaluation method and simulation workflow for assessing the well shut-in effects of volume fractured horizontal wells, offering valuable guidance in optimizing the reasonable shut-in time for shale oil fractured wells.

Key words: shale oil, volume fracturing, reasonable shut-in time, fracture closure, imbibition replacement, numerical simulation

中图分类号:

TE357

廖凯,张士诚,谢勃勃. 页岩油体积压裂后合理焖井时间模拟研究[J]. 油气藏评价与开发, 2024, 14(5): 749-755.

LIAO Kai,ZHANG Shicheng,XIE Bobo. Simulation of reasonable shut-in time for shale oil after volume fracturing[J]. Petroleum Reservoir Evaluation and Development, 2024, 14(5): 749-755.

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参数名称	上隔层数值	含油层数值	下隔层数值
地层压力/MPa	37	37	37
地层厚度/m	20	20	20
孔隙度/%	3	11	3
渗透率/10^-3 µm²	0.001	0.010	0.001
初始含水饱和度/%	70	20	70
水平最小主应力/MPa	54	52	56
水平最大主应力/MPa	60	58	62
杨氏模量/GPa	40	27	40
泊松比	0.35	0.25	0.35
抗拉强度/MPa	3.45	3.45	3.45
天然裂缝密度/（条/m）	0.15	0.15	0.15

参数名称	数值	参数名称	数值
簇间距/m	10	施工排量/（m³/min）	14
滑溜水黏度/（mPa·s）	5	压裂液总量/m³	1 300
冻胶液黏度/（mPa·s）	200	滑溜水比例/%	40

裂缝尺寸	各段微地震解释数据	各段微地震解释数据平均值	单段裂缝模拟值
裂缝半长/m	60~189	116.4	125.3
裂缝带宽/m	50~140	93.6	89.7
裂缝高度/m	33~68	50.7	44.6