The Development Of An Environmentally Friendly Shale Inhibitor For Longmaxi Formation In Zhaotong Rigion

There exists a borehole instability problem in shale gas development process in long term,which has become a complex obstacle to shale oil and gas exploration and development.In the study,the shale samples of Longmaxi Formation from Zhaotong region were collected to study.Their clay mineral species,the dispersibility,swelling,wettability and microstructural properties that were characterized through X-ray diffraction and dispersibility linear expansion rate methods,and cation exchange capacity,wettability and soaking parameters.This shale wall instability mechanism has been researched to show that the Zhaotong shale formation is mainly composed of clay mineral and quartz,and with relatively high I/S mixed layer in clay mineral type but no pure montmorillonite.The shale is observed for microfracture development and easy to hydration expansion.These were main factors on the Zhaotong region borehole instability.Based on above data,polydimethyldiallyl-ammonium chloride was synthesized as shale chemical inhibitor for the shale wall instability.Polydimethyldiallyl-ammonium chloride chemical structure and shale inhibition performance were characterized and evaluated.It's molecular structure and relative molecular mass were analyzed via infrared spectroscopy,solid content determination and ubbelohde viscometer method.The amine shale inhibition performance was systematically evaluated by the experiments of pulp making rate,linear expansion rate,anti-swelling rate and rolling recovery rate.The results show that the amine inhibitors has good water solubility and environment-friendly whose shale inhibition is superior to that of conventional inhibitors such as KCl,amino inhibitors and small cation.Preparation of the amine drilling fluid system,the recovery rate and the expansion rate of shale in Zhaotong region were studied through the recovery rate and the linear expansion rate.The results show that the amine inhibitors can improve the recovery rate of shale cuttings by 11.68% and reduce the linear expansion rate of shale rock specimen by 15.85%,a reduction of the linear expansion that indicate this amine inhibitor could effectively inhibit shale hydration expansion in Zhaotong area.