Study on bonding strength performances and improved method of coalbed methane well cementation in coal reservoir

In order to solve the problems of poor well cementation quality at the seam section caused by the poor hydrophilic wettability of coal surface,different type surfactants and silane coupling agents were optimized as the wettability modifier of coal surface. The wettability modification,interface bonding strength and other improved effects of coal surface were tested and studied. The test evaluation was conducted on the rheological performance,setting time,compressive strength and other influence law of the cement slurry with wettability modifer.The study results showed that the surfactant and silane coupling agent both could effectively improve the hydrophilic wettability of coal surface,but the silane coupling agent could not improve the interface bonding strength of the coal. Because the hydrolysis of the silane coupling agent would produce the Si-OH groups,which could adsorb on the cement partical surfaces to form the wrapping layer,and stopping the further contract between the cement and water,the silane coupling agents would have a high retarder effect and would not be favorable to the interface bonding of the seam. The anionic surfactant with the ether and sulfate would have no retarder side effect to the cement,and a good compatibility with the cement slurry.So that the anionic surfactant could obviously improve the interface bonding strength (1.71 MPa) of the seam and the optimum concentration of surfactant was optimized as 0.3 %.