低产煤层气井无机矿物泡排酸蚀解堵特性

Inorganic mineral plugging removal characteristics by acid etching and foam drainage in low-producing coalbed methane well

  • 摘要: 煤层气开发中无机矿物堵塞容易导致煤层气井低产,严重制约煤层气井的连续稳定排采与产量,酸蚀溶解是高效清理无机矿物的有效手段之一。基于无机矿物的多组分酸液溶蚀试验,考虑泡排作用对无机矿物的润湿携带效果,研究了起泡剂复配酸液解堵剂对低产煤层气井无机矿物的泡排酸蚀解堵特性。结果表明:氢氟酸对以硅酸盐岩为主要成分的无机矿物的溶蚀效果较盐酸与乙酸最佳,酸液质量分数超过12%对无机矿物溶蚀率增长不显著。多组分酸较单组份酸对无机矿物溶蚀率更高,普遍达40%~80%。当复配解堵剂中起泡剂质量分数小于0.6%时,随起泡剂浓度增长,溶液表面张力、溶液与无机矿物表面接触角均逐渐减少,泡排作用下泡沫越绵密,起泡能力逐渐增加,泡沫半衰期逐渐延长,泡沫携粉含量越高。当起泡剂质量分数超过0.6%后,复配解堵液表面张力呈紊乱趋势,泡沫稳定性变差。十二烷基二甲基胺乙内酯(BS-12)泡沫体系泡径大较脂肪醇聚氧乙烯醚(AEO)泡沫体系泡径大小不均对泡沫半衰期影响更为严重。由于十二烷基葡萄糖苷(APG)复配酸液表面张力最小,泡沫稳定绵密且对无机矿物润湿性最好,选取耐酸性强的非离子型表面活性剂APG作为起泡剂复配酸液为优选的溶蚀无机矿物解堵剂。泡排作用促进无机矿物溶蚀率少量增长,酸液浓度对泡沫稳定性、泡沫半衰期起抑制作用,泡沫携带排出的无机矿物粒径越小,粒径范围越窄。

     

    Abstract: The blocking of inorganic minerals in coalbed methane development will cause the low production of coalbed methane well, which will seriously restrict the continuous and stable production of coalbed methane well. Acid dissolution is an effective means to clean up inorganic minerals. Based on the experiment of multi-component acid dissolution of inorganic minerals, combined with the wetting and carrying effect of foam drainage on inorganic minerals, the inorganic mineral plugging removal characteristics by acid etching and foam drainage in low-production coalbed methane wells were studied. The results indicate that hydrofluoric acid has better dissolution effect on inorganic minerals with silicate rock as the main component than hydrochloric acid and acetic acid. The dissolution rate of inorganic minerals does not increase significantly when the acid concentration exceeds 12%. The multi-component acid has higher dissolution rate of minerals than single component acid, generally reaching 40%-80%. When the concentration of foaming agent is less than 0.6%, the surface tension of the solution and the contact angle between the solution and inorganic minerals gradually decrease with the increase of the concentration of foaming agent. Under the action of foam discharge, the foam becomes denser, the foaming ability gradually increases, the foam half-life gradually prolongates, and the foam powder carrying content is higher with the increase of the concentration of foaming agent. When the concentration of foaming agent exceeds 0.6%, the surface tension tends to be disturbed and the foam stability becomes worse. The large bubble diameter of BS-12 foam system has more serious influence on the foam half-life than that of AEO foam system. The surface tension of APG compound acid is minimal with the stable and dense foam, and it has the best wettability to inorganic minerals. APG as non-ionic surfactant with strong acid resistance is selected as the foaming agent, compound with acid is the preferred solution to etch inorganic minerals. Foam drainage promotes the dissolution rate of inorganic minerals to increase slightly, and the acid concentration inhibited the stability and foam half-life, with the smaller particle size of inorganic minerals discharged from the foam and the narrower particle size range.

     

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