Study On Optimization Design Of Hydraulic Parameters In Ultra-deep Well Drilling Engineering

Deep, ultra-deep wells have already been an important approach to exploit oil and gas resource with incremental demands of world energy. Under high temperature and high pressure(HTHP) condition in ultra-deep well drilling, many difficulties may be encountered, the most important thing is the efficiency of the hydraulic power is very low, among which drilling fluid density could not dealt with as a constant. Since HTHP have an important effect on density, viscosity, yield stress of drilling fluid which are key factors to precisely calculate friction pressure loss in well-bore for utmost improving hydraulic power utilities. In the paper, well temperature profile was study firstly, then the influence rules of temperature and pressure on drilling fluid density and rheologies were conducted in lab. On the above basis, a mathematic model for calculating frictional pressure loss of water base drilling fluid during ultra-deep well drilling was established. A primary study on optimization design of hydraulic parameters in ultra-deep well drilling. Main achievements and conclusions are following:(1)Influence coefficients are different for different types of drilling fluid.(2)Temperature and pressure influencing on drilling fluid density and rhyologies are performed in lab. The results shows temperature and pressure have obvious effect on drilling fluid density, and influence coefficient of rheologies are mainly temperature. The plastic viscosity of drilling fluid decreases exponentially with the increment of temperature.(3)A mathematical model for calculating frictional pressure loss were established. Compared with field test datum, error range is within 3 percent.(4)A primary study on optimization design of hydraulic parameters in ultra-deep well drilling. The method of minimum displacement should be used in the optimization design of hydraulic parameters in ultra-deep well drilling.