Water locking damage evaluation and prevention countermeasures of tight sandstone gas reservoir in Hangjinqi area

The article makes a study on Palaeozoic sandstone reservoir of Hangjinqi area in Ordos basin.Combined with the reservoir engineering geological characteristics of the work area,indoor core water lock damage analysis and phase permeability experiment have been carried out.The effects of permeability,porosity and irreducible water saturation on water locking damage have been analyzed.The experimental results show that the water locking damage degree is of negative correlation with permeability and irreducible water saturation,and positively related to the reservoir illite content.The water locking degree of Taiyuan,Shanxi formations is obviously stronger than that of Shihezi formation,with the damage rate of over 40%.The spontaneous imbibitions and the effect of natural fractures strengthen the absorption of water lock damage reservoir.Therefore,the corresponding prevention measures have been put forward,namely controlling the scale of fracturing,reducing water facies reservoir contact time,adding waterproof lock agent,liquid nitrogen to reduce the water locking damage.