随着XJ油田气井开采的深入,气井能量逐步下降,积液问题越发突出,严重影响气井有效生产。为了气井有效生产及制定合理工作制度,明确气井井筒压力损失规律、选择准确的计算模型对实际积液气井稳产意义很大。本文通过实际气井生产数据,结合实测井筒压力数据,通过编程计算优选出适用KM区块的井筒压力计算模型并进行了检验,针对影响气井井筒压力损失的因素进行了敏感性分析。结果表明:Mukherjee & Brill模型的适用性最好,预测准确性最高;气井产水时压力损失为不产水气井的2倍,可见产水量是造成井筒压力损失的重要原因,产水量大时井筒摩阻损失占据主导地位;不同水气比情况发现,且当水气比比达到2 m 3/10 4 m 3时,井筒压力损失的近80%;井径越大,气体携液能力越差,导致压力损失越大。为降低压力损失,提高气井产能,需要对气井实施及时排液以及排液采气措施。本文研究结果可对现场气井增产措施的实施提供一定指导。 With the deepening of gas well exploitation in XJ oilfield, the energy of gas wells has gradually decreased, and the problem of liquid accumulation has become more and more prominent, which seriously affects the effective production of gas wells. In order to effectively produce gas wells and formulate a reasonable working system, it is of great significance to clarify the wellbore pressure loss law of gas wells and select an accurate calculation model for the stable production of actual liquid-accumulating gas wells. In this paper, based on the actual gas well production data, combined with the wellbore pressure data, the wellbore pressure calculation model suitable for the KM block is optimized and tested by programming calculation, and the sensitivity analysis is carried out for the factors affecting the wellbore pressure loss of gas wells. The results show that the Mukherjee & Brill model has the best applicability and the highest prediction accuracy; when the gas well produces water, the pressure loss is twice that of the non-water-producing gas well. It can be seen that the water production is an important cause of the wellbore pressure loss. When the water production is large, the wellbore Friction loss dominates; it is found that under different water-gas ratios, and when the water-gas ratio reaches 2 m 3/10 4 m 3, the wellbore pressure loss accounts for nearly 80%; the larger the well diameter, the worse the gas liquid-carrying ability, resulting in greater pressure loss. In order to reduce the pressure loss and improve the productivity of gas wells, it is necessary to implement timely liquid drainage and gas production measures for gas wells. The results of this study can provide some guidance for the implementation of field gas well stimulation measures.
随着XJ油田气井开采的深入,气井能量逐步下降,积液问题越发突出,严重影响气井有效生产。为了气井有效生产及制定合理工作制度,明确气井井筒压力损失规律、选择准确的计算模型对实际积液气井稳产意义很大。本文通过实际气井生产数据,结合实测井筒压力数据,通过编程计算优选出适用KM区块的井筒压力计算模型并进行了检验,针对影响气井井筒压力损失的因素进行了敏感性分析。结果表明:Mukherjee & Brill模型的适用性最好,预测准确性最高;气井产水时压力损失为不产水气井的2倍,可见产水量是造成井筒压力损失的重要原因,产水量大时井筒摩阻损失占据主导地位;不同水气比情况发现,且当水气比比达到2 m3/104 m3时,井筒压力损失的近80%;井径越大,气体携液能力越差,导致压力损失越大。为降低压力损失,提高气井产能,需要对气井实施及时排液以及排液采气措施。本文研究结果可对现场气井增产措施的实施提供一定指导。
气井产水,井筒积液,压降模型,压力损失,水气比
Wenmin Ma1, Meilin Hu2, Quanlong Li3, Xiuwu Wang1*
1Department of Chemical Engineering, Kunming University of Science and Technology, Kunming Yunnan
2Yunnan Gas Safety Technology Research Institute Co., Ltd., Kunming Yunnan
3Yunnan Kuoxin Registered Safety Engineer Office Co., Ltd., Kunming Yunnan
Received: Aug. 13th, 2022; accepted: Sep. 15th, 2022; published: Sep. 23rd, 2022
With the deepening of gas well exploitation in XJ oilfield, the energy of gas wells has gradually decreased, and the problem of liquid accumulation has become more and more prominent, which seriously affects the effective production of gas wells. In order to effectively produce gas wells and formulate a reasonable working system, it is of great significance to clarify the wellbore pressure loss law of gas wells and select an accurate calculation model for the stable production of actual liquid-accumulating gas wells. In this paper, based on the actual gas well production data, combined with the wellbore pressure data, the wellbore pressure calculation model suitable for the KM block is optimized and tested by programming calculation, and the sensitivity analysis is carried out for the factors affecting the wellbore pressure loss of gas wells. The results show that the Mukherjee & Brill model has the best applicability and the highest prediction accuracy; when the gas well produces water, the pressure loss is twice that of the non-water-producing gas well. It can be seen that the water production is an important cause of the wellbore pressure loss. When the water production is large, the wellbore Friction loss dominates; it is found that under different water-gas ratios, and when the water-gas ratio reaches 2 m3/104 m3, the wellbore pressure loss accounts for nearly 80%; the larger the well diameter, the worse the gas liquid-carrying ability, resulting in greater pressure loss. In order to reduce the pressure loss and improve the productivity of gas wells, it is necessary to implement timely liquid drainage and gas production measures for gas wells. The results of this study can provide some guidance for the implementation of field gas well stimulation measures.
Keywords:Gas Well Water Production, Wellbore Fluid Buildup, Pressure Drop Model, Pressure Loss, Water to Gas Ratio
Copyright © 2022 by author(s) and Hans Publishers Inc.
This work is licensed under the Creative Commons Attribution International License (CC BY 4.0).
http://creativecommons.org/licenses/by/4.0/
随着气井开采的不断深入,地层能量逐渐降低,气井由于能量不足会出现积液的问题,积液会造成井筒压力损失增大,难以维持气井产能,严重的甚至会造成气井停产 [
对于气井井筒压力损失规律,大量学者在理论与室内实验展开了研究,并提出了多种井筒压降计算模型 [
本文开展了XJ油田气井压力损失的研究,结合现场测试数据,对比了不同模型压力预测的误差,优选了适用性最好的压降模型,研究了气井产水与不产水、水气比、井口压力以及不同管径条件下气井压力损失规律。研究结果为气井调整生产方案,延长气井有效生产年限提供指导,提高气藏最终采收率。
XJ油田气藏可采储量高,开发潜力大,但在气井生产后期,由于产水造成井底积液,严重影响气井的生产效益。XJ油田气藏生产区块有7个,共开发气井263口,但截至目前开井数仅157口,其中KM区块为主力生产区块,该区块总计开发气井150口,开井数为101口,采出程度为15.23%。
KM区块气藏分布受构造和岩性控制,火山岩气藏边底水普遍发育,受裂缝水窜的影响,通过分析气井生产数据,气井前期日产气量较高,但生产后期出水严重。气井一旦开始产水,由于液相的增加造成井筒压力损失大大增加,导致采气速度逐渐降低,井筒携液能力也会随之下降 [
井数/口 | 日产气/104 m3 | 日产水/m3 | 水气比/(m3/104 m3) | 油压/MPa | 套压/MPa | 流压/MPa | 压力损失/MPa |
---|---|---|---|---|---|---|---|
150 | 10.04 | 21.70 | 2.16 | 23.66 | 25.13 | 33.03 | 9.37 |
表1. KM区块气井生产数据
气井井底流压是井口压力、气柱重力、动能变化和摩擦造成压力损失的总和 [
产水气井井筒压力计算是根据多相流的能量守恒方程 [
d P d h = ρ m v m + d v m d h + g ρ m sin θ + f m ρ m v m 2 2 d (1)
式中:P为压力,MPa;h为垂向油管长度,m; ρ m 为气液混合密度,kg/m3;vm为气液混合流速,m/s;fm为摩阻系数,无量纲; θ 为管道的倾斜角度;d为管道内径,m;g为重力加速度,m/s2。
倾斜管柱持液率计算一般是基于水平管柱持液率进行修正,主要计算模型包括Beggs & Brill模型、Mukherjee & Brill模型。
Beggs & Brill水平管持液率计算公式为 [
H l ( 0 ) = a E l b N F r c (2)
E l = Q l Q l + Q g (3)
N F r = v 2 g d (4)
式中:Hl (0)为气液两相流持液率;E1为入口体积持液率;Ql、Qg为入口液相、气相体积流量;a、b、c为取决于流型的常数。
倾斜管持液率:
H l ( θ ) = φ H l ( 0 ) (5)
φ = 1 + C [ sin ( 1.8 θ ) − 1 3 sin 3 ( 1.8 θ ) ] (6)
C = ( 1 − E l ) ln [ d ( E l ) e ( N l w ) f ( N F r ) g ] (7)
式中: H l ( θ ) 为倾斜气液两相流的持液率; φ 为倾斜管校正系数; θ 为管柱倾斜角度; N l w 为液相粘度准数; N F r 为弗劳德数;d、e、f、g为流型参数。
Mukherjee & Brill倾斜管持液率计算公式:
H ( θ ) = exp ( − 0.3801 + 0.1299 sin θ − 0.1198 sin 2 θ + 2.343 N l 2 ) N w g 0.4757 N w l 0.2887 (8)
在气体稳定流动状态下,气井井筒压力损失主要有自身重力损失、动能损失以及摩阻损失三个方面。为了改善气井的生产效果,需要降低气井压力损失,但由于重力损失与动能损失难以改变,因此,研究的重点在于如何降低摩阻损失。在气井生产过程中的压力损失会造成消耗能量大,产能大幅降低。求解井筒压降一般采用Orkiszewski模型、Beggs & Brill模型、Mukherjee & Brill模型、Hasan模型以及拟单向流模型5种,但不同模型计算结果差异较大,优选准确性高的计算模型成为研究井筒压力损失的第一步。
通过收集KM区块生产气井的井底流压数据,并利用不同模型计算了井底流压,将计算结果与实测结果进行了对比,统计了不同模型计算结果的平均误差,结果如表2所示。表中展示的15口井的计算结果表明Mukherjee & Brill模型的预测误差最小,平均误差为9.3%,其次为拟单向流模型,但误差达到了17.9%,因此,针对KM区块气井,Mukherjee & Brill模型的预测准确性最高,适用性最好。
井号 | 井底流压实测结果与模型计算结果/MPa | |||||
---|---|---|---|---|---|---|
实测 | Orkiszewski | Beggs & Brill | Mukherjee & Brill | Hasan | 拟单相流 | |
K-1 | 8.04 | 8.45 | 11.81 | 9.25 | 11.04 | 10.28 |
K-2 | 14.50 | 23.48 | 25.65 | 14.33 | 20.69 | 9.81 |
K-3 | 11.62 | 28.47 | 11.13 | 10.87 | 23.89 | 8.84 |
K-4 | 19.95 | 38.86 | 24.85 | 20.28 | 28.67 | 23.21 |
K-5 | 47.70 | 32.93 | 38.47 | 36.27 | 34.75 | 43.85 |
K-6 | 11.15 | 9.07 | 15.15 | 9.78 | 14.38 | 8.24 |
K-7 | 10.45 | 15.16 | 14.35 | 13.57 | 14.69 | 14.82 |
K-8 | 21.08 | 20.49 | 26.62 | 25.02 | 23.59 | 23.94 |
K-9 | 30.58 | 46.47 | 37.97 | 30.95 | 35.05 | 28.38 |
K-10 | 25.10 | 38.69 | 38.53 | 29.09 | 25.08 | 26.18 |
K-11 | 38.66 | 60.03 | 44.43 | 39.52 | 48.94 | 35.21 |
K-12 | 28.40 | 45.45 | 38.92 | 29.29 | 37.32 | 24.83 |
K-13 | 28.38 | 34.19 | 34.60 | 29.64 | 30.81 | 24.56 |
K-14 | 34.98 | 34.70 | 37.37 | 35.64 | 32.97 | 36.50 |
K-15 | 35.37 | 34.05 | 40.01 | 34.72 | 35.44 | 45.14 |
平均误差 | 43.4% | 29.5% | 9.3% | 28.3% | 17.9% |
表2. 不同井井底流压预测结果
井筒压力损失的影响因素较多,重点考虑了气井产水、水气比、管径以及井口压力四个方面,利用优选的Mukherjee & Brill压降模型,研究不同影响因素的井筒压力损失,并分析了摩阻损失与重力损失变化规律。
不产水的气井井筒压力损失为举升压降损失与摩阻损失,由于纯气体密度小,压降损失小,另外,气体与管柱的摩擦因子较小,摩阻损失同样较低。利用模型计算不同产气量的井筒压力损失,结果如图1所示。不产水气井的井筒压力损失较小,均低于5 MPa;随着日产气量增大,压力损失较小幅度下降,且主要为重力损失,而摩阻损失基本可以忽略。
图1. 不产水气井的井筒压力损失
从模型角度看,气井产水量越大,持液率上升,同时压降损失增大;研究产液量与井筒压力损失的关系,控制产气量与井口压力不变,计算日产水量0.5~17 m3井筒压力损失,结果如图2所示。对比不产液气井井筒压力损失,在产液量较低时,井筒压力损失增大超过4 MPa,且以重力损失为主,主要由于产液极大的增加了气水混合密度;产水量增大,井筒持液率增大,需要消耗更大的能量才能将液体举升出井筒,也将导致井底压力提升;当日产水量超过13 m3时,由于气液两相间的摩阻急剧增大,井筒压力损失逐渐以摩阻损失为主。
图2. 产水气井的井筒压力损失
在产气量不变的情况下,水气比越大,表明产水量越高,造成井筒压力损失增大。计算了水气比为0.05~8 m3/104 m3的井筒压力损失,结果如图3所示。结果表明:水气比越高,液体产量越多,压力损失越大;水气比越低,液体产量越少,在相同产量的情况下,气体流量越快,气体携带液体时,液体将分散形成细小的液滴,气体的携带能力更强,摩阻变小,摩阻损失也会更低。当水气比低于2 m3/104 m3时,压力损失较小,但超过该值时,压力损失大幅提高,达到80%,且摩阻损失占据主导地位。
图3. 不同水气比的井筒压力损失
井筒直径与气体携液能力相关,在产量不变的情况下,井筒直径影响气体流量,当流量低于临界携液流量时,会造成井筒压力损失,井筒液体无法排除,影响气井生产。控制产量不变,选用了现场常用的5中油管尺寸,计算井筒压力损失,结果如图4所示。结果表明:管径越大,压力损失也越大,压力损失主要来源于重力损失,增大管径摩阻损失小幅提高。主要由于在产量相同的条件下,管径越小,流速越快,气体携液能力增强,造成的压力损失较小;反之,管径越大,气体携液能力大幅削弱,造成较大的能量损失。
图4. 不同管径的井筒压力损失
气井生产过程中,井口压力为井底压力减去压力损失,控制井口压力影响井底压力的大小。控制产气量、产水量不变,计算不同井口压力的井筒压力损失,结果如图5所示。井口压力越大,压力损失越大,其中重力损失占主导,而摩阻损失很小且变化较小;主要由于井口压力较大时,井底压力也较大,气液两相密度增大,重力损失大幅提高;另外,井口压力越大,则井底与井口的压差越小,气体携液能力越弱,井筒压力损失越大。
图5. 不同井口压力的井筒压力损失
结论:
1) KM区块气井产水量大,水气比高,井均井筒压力损失高达9.37 MPa;为了优选适合KM区块气井井筒压力计算模型,对比了气井实测数据与5种不同模型井底流压预测结果,优选Mukherjee & Brill模型,其预测误差仅9.3%,适用性好、准确度高。
2) 气井产水是井筒压力损失的主要原因,不产水气井的井筒压力损失较低,损失主要来源于重力损失;气井产水后压力损失明显增大,且产水量较大时,压力损失以摩阻损失为主。
3) 气井的井筒压力损失与气体携液能力相关,水气比越大,井筒的压力损失越大。为了降低井筒压力损失,可以通过优选油管尺寸、下入井下工具等措施,降低井筒压降,有效提高气井携液能力,达到提高气井采收率的目的。
建议:
1) 本文结合现场生产数据并优选模型研究了气井井筒压力损失规律,其模型适用于XJ油田,特别是KM区块,但研究方法以及研究得出的井筒压力损失规律可推广至更多的气藏。
云南省科技厅青年基金项目(KKSQ202005031)。
马文敏,胡镁林,李全龙,王修武. XJ油田产水气井井筒压力损失研究Study on Wellbore Pressure Loss in Gas Wells in XJ Oilfield[J]. 石油天然气学报, 2022, 44(03): 259-267. https://doi.org/10.12677/JOGT.2022.443034