Application of low content KCl drilling fluid in Sulige Gas Field

Severe borehole collapse occur easily in mudstone formations of Shiqianfeng Formation and Shihezi Formation of Sulige Gas Field, and troubles like hole collapse reaming, sticking, filling the hole and sidetracking often occur also. In view of the formation rock properties and characteristics of Sulige Gas Field, study was conducted on low content KCl drilling fluid; the inhibition and anti-collapse performance of the drilling fluid system is improved by maintaining 0.8%-1.0% of KCl in polysulfonate drilling fluid. Its application in two wells shows that this system has generated strong inhibition and clear sand specimen with no collapse and no obstructions in wiper trips; it has favorable performance in plugging and side-wall building and rheological property; the filter cake is smooth and tight and has stable performance; there is no discharge of drilling fluid; all of these properties satisfactorily meet the downhole service requirements and provide experiences for safe and efficient development of Sulige Gas Field.