SZ36-1油田注聚井和聚驱受益油井堵塞物的组成及成因对比分析

Comparisons of component and formation mechanism of blockages in polymer flooding injection well and response well in SZ36-1 oilfield

关键词:  渤海油田  聚合物驱油  注聚受益油井  含聚堵塞物

Key words:  Bohai oilfield  polymer flooding  polymer flooding response well  polymer-contained blockage

摘要:

随着注聚开发的进行,SZ36-1油田的部分受益油井中出现了含聚堵塞物,导致了产能下降。采用多种表征手段对比分析了注聚井和受益油井堵塞物的组成,发现在所采集到的样品中,受益油井堵塞物以无机垢为主,无机垢/有机垢质量比为4.0~5.5,远大于注聚井的0.25~0.75,受益油井和注聚井中无机垢分别主要为Fe₂O₃和CaCO₃,有机垢则均为部分水解聚丙烯酰胺。对比分析了注聚井和受益井中无机垢和有机垢的成因,重点分析了受益油井堵塞物的成因:在受益油井的近井地带,酸化作业后的残酸含有大量Fe³⁺,与聚合物驱替液相遇后,液体pH值上升,形成Fe(OH)₃沉淀,氧化后即形成Fe₂O₃无机垢；驱替液中降解后的聚合物在酸性条件下会选择性地与Fe³⁺通过配位作用,形成水不溶的聚合物交联物,即形成有机垢。分析结果可为注聚井和注聚受益油井的针对性解堵以及预防注聚受益油井堵塞提供依据。

Abstract:

As the development of polymer flooding, polymer contained blockage was appeared and the oil well production was decreased in SZ36-1 oilfield. In this paper, the components of blockage in polymer flooding injection well (PFIW) and response well (PFRW) were compared by several characterization methods firstly. The inorganic scale was the main substance in collected samples, the mass ratio of inorganic scale and organic scale in PFRW blockage was 4.0-5.5, which was much larger than that of PFIW (0.25-0.75). The inorganic scale mainly was Fe₂O₃ in PFIW and and CaCO₃ in PFIW, and the organic scale was partially hydrolyzed polyacrylamide. Then, the formation mechanisms of inorganic scale and organic scale in PFRW and PRIW were investigated, especially the formation mechanism of blockage in PFRW was studied. In the area which was close to the response oil well, there was a lot of Fe³⁺ in residual acid solution after the acidification operation, and when it was mixed with polymer flooding solution, Fe(OH)₃ was formed as the pH increased and Fe₂O₃ blockage was formed after the oxidation. In addition, the cross-linked polymer blockage which was organic scale, was formed by the selective coordination between polymer and Fe³⁺ when the degraded polymer was mixed with Fe³⁺ solution in acid condition. The results in this paper are helpful for the targeted removal of plugging in PFRW or PRIW and preventive blockage in PRIW.