Dynamic displacement is an unconventional well killing method in which killing fluid is injected and gas is discharged simultaneously. The determination of the maximum injection rate of killing fluid and the control of casing pressure of wellhead are the key to the success of well killing. In this paper, a mathematical model of the dynamic displacement method is established based on the fact that the bottom hole pressure is maintained to be constant during the killing fluid injection process, the mass conservation is satisfied during the gas discharge process, and the modified Drosos fluid generic correlation is satisfied during the fall process of the killing fluid. By comparing the calculated maximum injection rate of killing fluid with the Ramtahal experimental data, the error is only 7. 0% and 0. 1 % when the casing inner diameter is 152 mm without drilling string in the casing and the drilling string outer diameter is 51 mm, which can be applied to the calculation of killing fluid by dynamic displacement method. The model is used to analyze the effect of different factors on the maximum injection displacement of killing fluid and the influence of casing pressure on wellhead. The results show that the maximum killing fluid injection rate goes up with the drill string eccentricity and surface tension, which means the casing pressure is decreased faster and the less killing time is needed. On the other side, the maximum killing fluid injection rate goes down with gas volume and viscosity, which means the casing pressure is decreased slower and more killing time is needed.

With average Ø244. 5 mm casing setting depth of 5 045 m in Panyu oilfield extended reach wells(ERWs) , which have features such as long open hole with high hold inclination, high friction factor in open hole with multi-interbed, narrow safety window of drilling fluid density in fault location which tend to cause fracture downhole loss in 244. 5 mm casing running process. Currently, casing floatation collar technology was chiefly used in ERWs, which may have disadvantage risks such as floatation collar failure, limited measurements to deal with casing stuck and so on. In light of reality such as shallow true vertical depth(TVD) and long extended hole section in Panyu oilfield ERWs, a rotating casing running technology with full-floatation was presented to avoid those risks. In this paper, technical principle was analyzed and key technologies such as over drive system, stress check of casing string and the selection of casing flotation package were introduced entirely. The effects of this technique were elaborated. Through 6 of Ø244. 5 mm extended-reach wells applications, the results show that, during the rotating running of casing with full-floatation, decrease casing string load, increase hook load safety factor, run casing string through tight section smoothly and get through fault safely without downhole loss, differential stuck and other downhole complications. All ERWs′ Ø244. 5 mm casing string were set at designed depth.

For deep water drilling, the amount of the drilling load impedes the further improvement of drilling depth, the riserless drilling technology may be the key to open the door. Compared with conventional riser drilling method for calculating the drilling load, the drilling load calculation method for riserless drilling technology has carried on the preliminary discussion, and in view of the rig equipped with riserless drilling technique, the hook load and variable load values have been calculated. The calculation results show that the variable load is obviously reduced after the drilling platform has been equipped with riserless drilling technology, and the advantage of the drilling technology is more obvious as the depth of the operation is deeper. Research results show that with the increasing exploration depth, after the rig is equipped with riserless drilling technology can minimize the hull size, reduce drilling costs, after the old platform is equipped with no riser drilling technology, it can be applied in the deep-water drilling to save construction cost.