New insights into the hydroquinone (HQ)–hexamethylenetetramine (HMTA) gel system for water shut-off treatment in high temperature reservoirs

Aiming at water shut-off in high temperature reservoirs, the hydroquinone (HQ)–hexamethylenetetramine (HMTA) gel system was studied. The gelation performance and effects of various parameters were systematically evaluated. With increase of the concentrations and temperature, gelation time decreases and gel strength increases. In addition, gelation rate and gel strength were enhanced on adding acid. Moreover, the gel system shows good salt tolerance. The thermal stability measurement indicates that the gel can maintain stability up to 140 °C. Uniformly distributed three-dimensional network structure was formed in the gel. At last, the gelation mechanism was proposed, illuminating the detailed gelation process clearly.

The microstructure of the gel was analyzed by the environmental scanning electron microscopy (ESEM). From the ESEM micrographs, uniformly distributed three-dimensional network structure is observed. Polymer chain bunches with thickness of several micrometers to tens of micrometers, connecting with a node, surround the pores forming a three-dimensional network structure. In the structure, the amide groups (CONH2) from the polymer crosslink with the hydroxyl groups (CH2OH) from the cross-linkers, which contributes to the uniformly porous mesh-like network structure. The uniformly porous network structure is conducive to perfect water holding capacity, which contributes to low water separating proportion and good stability of the gel system.Figure optionsDownload as PowerPoint slide