Drilling fluid technology for protecting low pressure reservoir

Based on the analysis of Huatugou oilfield's geographic conditions, rock properties and reservoir characteristics and according to the evaluation of reservoir sensitivity, the formulation of drilling/completion fluids technology to protect low pressure reservoir were determined. The fluids include free solid formate drilling fluid, free solid or low solid clay strongly inhibitive polymer drilling fluid and micro foam drilling fluid. Field application showed that the three fluids have good effects on improving ROP and reservoir protection with their stable properties and strong inhibitions to shale's hydrous disintegration and expansion. And by using it, drilling engineering requirements were satisfied and under well accidents such as shrinkage and pipe sticking were prevented. Comparing with zwitterionic polymer drilling fluid by which the oil production is only 3.83 t/d on the same usage condition, the average increment of oil production is 0.26～1.74 t/d.