页岩凝析气受限空间相态及开发特征研究

doi:10.13809/j.cnki.cn32-1825/te.2024.03.004

摘要/Abstract

摘要：

涪页10井的钻探获取了东岳庙段典型陆相页岩相关特征参数，其页岩储层介孔和大孔发育，非均质性较强，主要孔隙分布在10 nm左右。纳米孔中受限流体的临界参数偏移使得受限空间下凝析气的流体性质与常规室内实验测试结果存在差异。为更合理地开采页岩凝析气，结合室内相态实验、受限流体临界参数偏移计算和数值模拟，开展页岩凝析气相态特征分析和开采特征研究，明确凝析气的相态变化规律和开采特征。考虑临界参数偏移的凝析气相态特征计算表明：随着孔隙半径减小，体系组分的临界温度、临界压力降低，相图向左下收缩，露点压力降低，气相黏度降低，偏差因子增加，反凝析液饱和度逐渐降低。通过机理模型分析了临界参数偏移对衰竭开采效果的影响，结果表明：随着孔隙半径减小，天然气采收率基本不变，凝析油采收率逐渐增加，孔隙半径减小至10 nm，凝析油采收率增加9.93%。研究结果对页岩凝析气藏开发具有指导意义。

关键词: 页岩凝析气, 陆相页岩, 受限空间, 相态变化, 临界参数偏移, 开发特征

Abstract:

The exploration of Well-Fuye-10 in the Dongyuemiao section has provided valuable characteristic parameters of typical continental shale, revealing a reservoir with well-developed mesopores and macropores and significant heterogeneity. The predominant pore sizes are around 10 nm. Notably, deviations in the critical parameters of the confined fluids alter the condensate gas properties within these nanopores, differentiating them from conventional laboratory results. This study combines indoor phase state experiments, critical parameter migration calculations, and numerical simulations of confined fluids to analyze the phase state characteristics and extraction properties of shale condensate gas. The findings elucidate the phase state transformation and extraction dynamics of the condensate gas. Adjustments in the calculations for condensate gas phase characteristics to account for critical parameter offsets indicate that as pore radius decreases, there is a corresponding reduction in critical temperature and pressure of the system components. This results in a contraction of the phase diagram towards the lower left, a decrease in dew point pressure, reduced gas phase viscosity, an increase in deviation factor, and a gradual decrease in retrograde condensate saturation. Additionally, a mechanism model was employed to assess the impact of critical parameter shifts on depletion extraction effectiveness. Results demonstrate that while the recovery rate of natural gas remains relatively unchanged, the recovery rate of condensate oil shows a significant increase, rising by 9.93% as the pore radius decreases to 10 nm. These insights offer pivotal guidance for the development of shale condensate gas reservoirs, particularly in managing the unique phase behavior and optimizing recovery strategies.

Key words: shale condensate gas, continental shale, confined space, phase change, critical parameter offset, development characteristic

中图分类号:

TE372

汤勇,陈焜,胡小虎, 等. 页岩凝析气受限空间相态及开发特征研究[J]. 油气藏评价与开发, 2024, 14(3): 343-351.

TANG Yong,CHEN Kun,HU Xiaohu, et al. Phase behavior and development characteristics of shale condensate gas in confined space[J]. Petroleum Reservoir Evaluation and Development, 2024, 14(3): 343-351.

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组分	闪蒸气摩尔分数	闪蒸油摩尔分数	井流物摩尔分数	井流物质量分数
CO₂	0.198 8	0	0.185 6	0.283 0
N₂	0.424 7	0	0.396 6	0.384 8
C₁	81.870 9	0	76.436 9	42.473 5
C₂	10.468 5	0.299 0	9.793 6	10.202 0
C₃	3.855 6	0.334 5	3.621 9	5.533 4
iC₄	0.806 1	0.218 2	0.767 1	1.544 5
nC₄	1.132 4	0.541 2	1.093 1	2.200 9
iC₅	0.606 6	1.119 4	0.640 6	1.601 2
nC₅	0.428 8	1.143 4	0.476 2	1.190 2
C₆	0.207 6	5.586 2	0.564 6	1.682 0
C₇	0	10.915 3	0.724 5	2.409 4
C₈	0	16.185 7	1.074 3	3.982 1
C₉	0	11.875 3	0.788 2	3.303 9
C₁₀	0	9.700 6	0.643 8	2.988 8
C₁₁₊	0	42.081 4	2.793 0	20.220 4

孔隙半径/nm	临界温度/K
孔隙半径/nm	N₂—C₁	CO₂—C₃	iC₄—nC₄	iC₅—nC₅	C₆—C₉	C₁₀₊
非受限	196.98	50.87	144.89	191.15	240.45	446.48
100	196.25	322.61	415.89	461.74	510.56	713.73
40	195.14	320.49	412.67	457.92	506.04	704.93
30	194.53	319.31	410.89	455.8	503.53	700.06
20	193.31	316.97	407.34	451.58	498.54	690.39
10	189.68	310.01	396.78	439.05	483.73	661.82
5	182.52	296.33	376.13	414.57	454.84	606.65
2	161.97	257.33	317.82	345.76	374.05	457.08

孔隙半径/nm	临界压力/MPa
孔隙半径/nm	N₂—C₁	CO₂—C₃	iC₄—nC₄	iC₅—nC₅	C₆—C₉	C₁₀₊
非受限	4.59	4.73	3.74	3.38	3.05	1.59
100	4.58	4.71	3.72	3.36	3.03	1.58
40	4.55	4.68	3.69	3.33	3.01	1.55
30	4.54	4.66	3.67	3.32	2.99	1.55
20	4.51	4.63	3.64	3.29	2.96	1.53
10	4.42	4.53	3.55	3.20	2.87	1.46
5	4.26	4.33	3.36	3.02	2.70	1.34
2	3.78	3.76	2.84	2.52	2.22	1.01

孔隙半径/nm	天然气采收率/%	凝析油采收率/%
非受限	83.05	12.11
100	83.01	13.07
40	82.99	14.55
30	82.97	15.09
10	82.79	22.04