油田老区复杂地层长效防窜固井技术研究

Research on long-term anti-channeling cementing technology for complex formations in mature oilfield areas

摘要:

油田老区经长期注水、注聚开发，在多压力系统并存、油水层交错、聚合物污染、地层水侵的复杂工况影响下，固井水泥环完整性及层间密封长效性不足，油井无法直接投产或投产后层间窜流频发，严重制约老油田剩余油精细挖潜与长期稳产。为此，首先开展地层水侵、聚合物污染、虚泥饼滞留、顶替窜槽的实验与机理分析，明确主控因素，提出长效防窜固井关键技术对策；优选纳米液硅、触变剂，优化防窜参数，开发高效防水窜水泥浆体系；基于渗透溶胀和机械冲刷协同机制，开发双效复合冲洗液；确定有效防窜的环空压差标准（3~7 MPa），开发可调密度加重隔离液，设计压力补偿方法，建立全程压稳防窜技术；配套泥饼高效清除、关键层位强化居中等措施，形成复杂地层长效防窜固井技术。结果表明，某东部老油田一、二界面固井优质率大幅提升，薄隔层、水淹层等层段固井合格率由不足60%提升至100%，油井投产率由85%提升至100%，有效解决了油田老区水泥环长效密封不足的难题，为同类老油田分层细分开发提供了技术参考。

Abstract:

After long-term waterflooding and polymer injection development， the mature oilfield are subjected to the complex working conditions including coexisting multi-pressure systems， interleaved oil and water layers， polymer contamination and active formation water invasion， as a result， the integrity of the cement sheath and the long-term inter-zonal sealing performance were insufficient， and the oil wells cannot be put into production directly， or inter-zonal channeling frequently occurs after production， which severely restricts the fine exploration of remaining oil potential and long-term stable production in mature oilfields. In view of this， firstly， experiments and mechanism analysis are carried out on formation water invasion， polymer contamination， residual false mud cake， and displacement channeling to identify the main controlling factors and propose key technical countermeasures for long-term anti-channeling cementing. Nano-silicon fluid and thixotropic agent were selected， anti-channeling parameters were optimized， and an efficient water anti-channeling cement slurry system was developed. Based on the synergistic mechanism of permeation swelling and mechanical erosion， a dual-effect composite flushing fluid was developed. The effective anti-channeling annular pressure difference standard was determined to be 3~7 MPa， and an adjustable density heavyweight spacer fluid was developed， a pressure compensation method was designed， and a full-process pressure stabilization and anti-channeling technology was established. Supporting measures such as efficient mud cake removal and enhanced centralization of key layers were implemented to form a long-term anti-channeling cementing technology for complex formations. The results show that the high-quality rate of cementing for the first and second interfaces in an eastern mature oilfield has been significantly improved. The cementing qualification rate for thin interlayers and water-flooded zones has increased from less than 60% to 100%， and the oil well production rate has increased from 85% to 100%. This effectively solves the problem of insufficient long-term sealing of the cement sheath in mature oilfield areas， providing technical support for the layered subdivision development of similar mature oilfields.