致密凝析气藏压裂伤害及返排控制技术
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摘要
四川盆地部分凝析气藏测试产量难以达到地质预期,为了提高凝析气藏压后效果,以L气藏为研究对象,在储层伤害性评价及凝析油伤害机理研究的基础上,分析了A井返排率和产能低的主要原因,提出了低渗透凝析气藏控压返排技术。研究结果表明:(1)低渗透凝析气藏伤害主要是水锁伤害和凝析油伤害,其中凝析油对渗透率伤害达到90%以上,应该尽量避免;(2)提出了致密凝析气藏压后返排控制技术,当井底压力高于露点压力时,在临界出砂流量下快速排液,当井底压力接近露点压力时,控制返排速度保证井底压力高于露点压力;(3)根据临界出砂流速计算模型及喷嘴压降损失模型编制了计算软件,初步形成了凝析气藏控压返排现场应用技术。该技术成果在L气藏B井进行了先导试验,现场应用效果表明:压后返排率较邻井提高157%,无阻流量提高53%,增产效果显著。该技术成果对于低渗透凝析气藏难动储量的有效动用具有一定的指导意义。
For several condensate gas reservoirs, Sichuan Basin, their tested yield seems impossible to come up to geological expectation. For the purpose of increasing fracturing effect, on the basis of evaluation on reservoir damage and damage mechanism of condensate oil, we analyzed the main causes on lower flowback rate and deliverability in A well, L gas reservoirs,and developed one technology of flowback with pressure control for condensate gas reservoirs with low permeability. Results show that (1) for these reservoirs, there are two damages individually from water lock and condensate oil. Attempt to avoid the condensate-oil damage to permeability achieving over 90%;(2) through the technology of flowback with pressure control, fluid may be drained under critical sand flow rate when bottomhole pressure is higher than dowpoint pressure whereas flowback rate may be controlled to ensure bottomhole pressure larger than dewpoint pressure when bottomhole pressure is close to dewpoint pressure; and (3) based on one calculation model of critical sand flow rate and another model of nozzle pressure-drop loss, a kind of software was developed to be applied to many pressure-control flowback domains in condensate gas reservoirs. This achievement has been used in a pilot test in B well of L reservoirs. Test results demonstrate that after fracturing, compared with adjoining wells, its flowback ratio increases by 157%,53% for openflow, respectively, indicating an obvious stimulation effect. Moreover, this achievement is significant for effective producing immovable reserves in condensate gas reservoirs with low permeability.
For several condensate gas reservoirs, Sichuan Basin, their tested yield seems impossible to come up to geological expectation. For the purpose of increasing fracturing effect, on the basis of evaluation on reservoir damage and damage mechanism of condensate oil, we analyzed the main causes on lower flowback rate and deliverability in A well, L gas reservoirs,and developed one technology of flowback with pressure control for condensate gas reservoirs with low permeability. Results show that (1) for these reservoirs, there are two damages individually from water lock and condensate oil. Attempt to avoid the condensate-oil damage to permeability achieving over 90%;(2) through the technology of flowback with pressure control, fluid may be drained under critical sand flow rate when bottomhole pressure is higher than dowpoint pressure whereas flowback rate may be controlled to ensure bottomhole pressure larger than dewpoint pressure when bottomhole pressure is close to dewpoint pressure; and (3) based on one calculation model of critical sand flow rate and another model of nozzle pressure-drop loss, a kind of software was developed to be applied to many pressure-control flowback domains in condensate gas reservoirs. This achievement has been used in a pilot test in B well of L reservoirs. Test results demonstrate that after fracturing, compared with adjoining wells, its flowback ratio increases by 157%,53% for openflow, respectively, indicating an obvious stimulation effect. Moreover, this achievement is significant for effective producing immovable reserves in condensate gas reservoirs with low permeability.
引文
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[12]钟烨,邓燕,等.压裂气井防支撑剂回流技术研究[J].重庆科技学院学报(自然科学版),2011,13(1):70-72.
[2]Carvajal G A,Danesh A,Jamiolahmady M et al.The Impact of Pertinent Parameters on the Design of Hydraulic Fracturing in Gas Condensate Reservoirs[C].(SPE 94074)Society of Petroleum Engineers,2005.
[3]Al-anazi H A,Abdulbaqi D M,Habbtar A H et al.Successful implementation of horizontal multi-stage fracturing enhanced gas production in heterogeneous&tight gas-condensate reservoirs:case studies[C].(SPE 161664)Society of Petroleum Engineers,2012.
[4]沈海超,胡晓庆.非均质低渗凝析气藏压裂后低效原因分析及改进措施研究[J].特种油气藏,2012,19(2):116-119.
[5]冯虎,吴晓东,李明志,等.凝析气藏压裂返排参数对气井产能的影响[J].石油勘探与开发,2006,33(1):83-86.
[6]吴亚红,张士诚,吴亚生.低渗凝析油气藏压裂优化设计和产量预测[J].天然气工业,2005,33(1):84-87.
[7]王和琴,刘长印,张国英.桥口地区凝析气藏压裂效果影响因素分析[J].特种油气藏,2004,11(2):53-55.
[8]杨正友.白庙、桥口凝析气田适应性压裂工艺研究及应用[J].油气井测试,2007,16(1):60-61.
[9]Mianmo Meng.Investigation on the Variation of Shale Permeability with Spontaneous Imbibition Time:Sandstones and Volcanic Rocks as Comparative Study[J].Journal of Natural Gas Science and Engineering 27(2015).
[10]杨继盛,刘健仪.采气实用计算[M].北京:石油工业出版社,1995:101,120-122.
[11]任山,慈建发.考虑动态滤失系数的压裂井裂缝闭合及返排优化[J].中国石油大学学报(自然科学版),2011,35(3):103-104.
[12]钟烨,邓燕,等.压裂气井防支撑剂回流技术研究[J].重庆科技学院学报(自然科学版),2011,13(1):70-72.