Application of high density drilling fluid technique in Bashituo oil gas field

formation intruded seriously by salt bed, wellbore instability, high temperature in downhole, within high pressure layers and leakage were all made the drilling difficult in Bashituo oil gas field. A set of high density drilling fluid suitable for this area was developed to settle the problem by optimizing the bentonite concentration, High temperature resisting additive agent and weighting agent. The density of this system can reach up to 2.20 gram per centimeter while temperature can get as high as 160 degree. The drilling fluid was used in field experiment in Well BK8H and has gained well results due to thermal stability, inhibitive character and resisting pollution. During the treatment in Well BK8H, the fluid system performed well, no accident and other complex situation happened downhole. Due to this, salt bed with 400 meters was drilled though smoothly, and the enlargement rate of re-drilling well was 2.33percent, besides, the drilling cycle of this well was shorter than that of the similar well in the same area. All these illustrates that the high density drilling fluid system meet the drilling requirement under complex conditions in Bashituo blocks.