Analysis of Drilling Fluid Circulating Pressure Loss in Hole Annulus for Microhole Drilling
The microhole drilling (MHD) technology is one of cutting-edge drilling technologies with wellbore diameter less than 88.9 mm and taking coiled tubing (CT) as drilling string to deliver the bottomhole assembly to drill ahead. The normal circulation of drilling fluid is affected because of huge annulus drilling fluid circulating pressure loss (ADFCPL) caused by small diameter wellbore, narrow hole annulus and deep well. For three flow regimes of power-law fluid in MHD, the computing models of ADFCPL are built by analyzing the relationships among annulus drilling fluid parameters according to power law fluid flow state equation. The ADFCPL with different flow rate, CT diameter, well depth, eccen- tricity and so on is calculated for the hole annulus of MHD. The calculation results show that: in 89mm diameter MHD, the ADFCPL is huge. It increases with the increase of outer diameter of CT and average flow rate of drilling fluid, and in- creases linearly with the increase of well depth, and decreases with the increase of eccentricity. The bigger the hole annu- lus is, and the lower the flow rate is, the less the impact of eccentricity acts on the ADFCPL is. Thus, the ADFCPL can be reduced by decreasing the outer diameter of CT and the average flow rate of drilling fluid in hole annulus. Only low flow rate can be used to drill deep well. The research results may be useful for MHD parameter selections related to the ADFCPL.
STUDY ON THE PRESSURE LOSS LAWS IN MICRO HOLE CIRCULATORY SYSTEM
By research,the computation model of pressure loss in the micro hole coiled tubing and annulus was obtained.The pressure loss in the unbent and helix coiled tubing,and in the annulus under different hole depth and delivery capacity was calculated according to mathematical model and parameter presumed,and the regularity for change curve between the pressure loss and other parameters was obtained.The curve indicate,under the same flow rate,along with increase of the hole depth(length),the pressure loss in the unbent and helix coiled tubing,and in the annulus linear increases;if the flow rate increases,the pressure loss in the unbent and helix coiled tubing,and in the annulus of the same length also increases.The pressure loss in the helix tubing is far large than the unbent tubing under the same length.The total pressure drop of coiled tubing will decline along with the increase of hole depth.
HYPERGOLIC REACTION MECHANISMS OF CATALYTICALLY PROMOTED FUELS WITH ROCKET GRADE HYDROGEN PEROXIDE
Abstract The coupling of the physical and chemical processes controlling the ignition delays (τ ign ) of hypergolic propellants complicates the direct analysis of the transient ignition processes. The transport properties of both the propellants and the ambient gas, and the heat of vaporization and reaction affect τ ign and must be considered experimentally. Furthermore, since hypergolic ignition occurs, by definition, on contact, the mechanics of initial contact and subsequent mixing can affect τ ign and must also be considered. Experimental results from a study of the hypergolic ignition of a catalytically promoted fuel with rocket grade hydrogen peroxide (RGHP) are presented. Statistical analysis of the experimental data was conducted to evaluate the relative effects of RGHP concentration, initial ambient pressure, and the ambient gas on τ ign . At RGHP concentrations of less than 92% in water, stable ignition was difficult to achieve. At sufficiently high Lewis number, an oscillatory ignition process is observed. A phenomenological model comprising mixing, RGHP decomposition, fuel heating and vaporization, and auto-ignition is presented and compared to the experimental results.