アクリルアミド/AMPS共重合体のエマルジョン化と溶液化による掘削流体中の流体損失剤の比較

Comparison of an Emulsion- and Solution-Prepared Acrylamide/AMPS Copolymer for a Fluid Loss Agent in Drilling Fluid.

• Jingyuan Ma
• Boru Xia
• Peizhi Yu
• Yuxiu An

抄録

アクリルアミド系ポリマーは、その粘度範囲の広さと汎用性の高さから、油田の化学処理剤として広く使用されてきた。しかし、地層の複雑化に伴い、溶解性が悪く、温度、塩分、カルシウムに対する耐性が低いなどの欠点が徐々に露呈してきた。本論文では、アクリルアミド(AM)/2-アクリルアミド-2-メチル-1-プロパンスルホン酸(AMPS)共重合体を、それぞれ水溶液重合法と逆エマルジョン重合法により合成した。水溶液重合体(W-AM/AMPS)及び逆エマルジョン重合体(E-AM/AMPS)は、フーリエ変換赤外分光法(FTIR)、核磁気共鳴法(H NMR)、透過型電子顕微鏡法(TEM)、走査型電子顕微鏡法(SEM)及び粒度分析法を用いて特性を評価し、また、水溶液重合体(W-AM/AMPS)及び逆エマルジョン重合体(E-AM/AMPS)を用いて特性を評価した。また、レオロジー特性、ろ過特性、ナトリウムイオン(Na)及びカルシウムイオン(Ca)抵抗性を調べた。その結果、E-AM/AMPSはW-AM/AMPSに比べて4倍の溶解速度を示すだけでなく、時効前と時効後の両方で優れたせん断減肉性能を示すことがわかった。また、E-AM/AMPSを2wt%含有するベントナイト系は、W-AM/AMPSを2wt%含有するベントナイト系よりも濾過性に優れていた。さらに、E-AM/AMPSはNaやCaに対しても極めて高い耐性を示した。掘削流体中のE-AM/AMPSとW-AM/AMPSのレオロジー特性とろ過特性の間に大きな違いがあることは、2つの重合法によるポリマー微細構造の違いに起因すると考えられる。FTIRとH NMRの両方の結果から、E-AM/AMPSの分子基と分子鎖の間に水素結合が多く形成されており、その結果、E-AM/AMPSの架橋ネットワーク構造が形成されていることがTEMで観察された。この架橋ネットワーク構造がE-AM/AMPSの高粘度化を可能にし、ベントナイト粒子への吸着性を向上させ、優れたレオロジー挙動、濾過挙動を示した。また、E-AM/AMPS粉末は比表面積が高いため、水への溶解速度が速く、掘削流体の構成にかかる時間と手間を大幅に削減することができました。

Acrylamide polymers were widely used as oilfield chemical treatment agents because of their wide viscosity range and versatile functions. However, with the increased formation complexity, their shortcomings such as poor solubility and low resistance to temperature, salt, and calcium were gradually exposed. In this paper, acrylamide (AM)/2-acrylamide-2-methyl-1-propane sulfonic acid (AMPS) copolymers were synthesized by aqueous solution polymerization and inverse emulsion polymerization, respectively. The aqueous polymer (W-AM/AMPS) and the inverse emulsion polymer (E-AM/AMPS) were characterized by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (H NMR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and particle size analysis. The rheological properties, filtration properties, and sodium ion (Na) and calcium ion (Ca) resistance were investigated. The results showed that E-AM/AMPS not only had a dissolution speed 4 times faster than that of W-AM/AMPS but also had superior shear-thinning performance both before and after aging. The filtration property of the bentonite system containing 2 wt % E-AM/AMPS was also better than that of the bentonite system containing 2 wt % W-AM/AMPS. In addition, E-AM/AMPS also exhibited extremely high tolerance for Na and Ca. The huge difference between rheological and filtration properties of E-AM/AMPS and W-AM/AMPS in drilling fluid can be attributed to the differences in the polymer microstructure caused by the two polymerization methods. Both FTIR and H NMR results showed that more hydrogen bonds were formed between E-AM/AMPS molecular groups and molecular chains, which led to a cross-linked network structure of E-AM/AMPS which was observed by TEM. It was this cross-linked network structure that made E-AM/AMPS have a high viscosity and allowed it to be better adsorbed on bentonite particles, thus exhibiting excellent rheological and filtration behavior. In addition, E-AM/AMPS powder had a high specific surface area so that it can be dissolved in water faster, greatly reducing the time and difficulty of configuring drilling fluid.

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