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.
An Analysis of The Flow Resistance in Coiled Tubing Wound Around A Reel, In Microhole Drilling
Microhole drilling (MHD) is a new frontier drilling technology in which the diameter of wellbore is less than 88.9mm and coiled tubing (CT) is used as drill string. The CT wound around reel for MHD has small bending radius and large length to result in large circulating flow resistance and affect normal MHD circulation. The calculation model for curvature radius and length of CT wound around reel are established by analyzing the relationships among the various geometrical parameters of the reel system. The calculation model is combined with Dean number and power-law fluid state equation to put forward the calculation model for the flow resistance in CT wound around reel (CTFR), which takes into changes of the parameters such as flow rate & density of drilling fluid, inner diameter & length of CT and the reel diameter. The calculation result shows that CTFR is considerably affected by the diameter & length of CT and drilling fluid flow rate. CTFR increases rapidly with reducing of the CT diameter and increasing of the CT length and drilling fluid flow rate. Simultaneously, it is significantly affected by the circulation drilling fluid density in CT. With increasing of circulating drilling fluid density, CTFR increases significantly. The higher the flow rate is, the larger the CTFR increment is. The research results may be useful for MHD parameter selections related to CTFR.
APPLICATION OF SATELLITE PHOTOGRAPHS IN A MORPHOTECTONIC STUDY OF THE CENTRAL ALBORZ, IRAN
This paper introduces a study of morphotectoni c structure in the Central Alborz Basin, Mazandaran province of Iran (about 1200 square kilometer), using Russian KFA-1000 satellite photography and sequential air photographs. The KFA-1000 metric camera has better ground resolution than SPOT and LANDSAT for the whole of the study area. Results are provided from one pair of 30×30 cm. photos, which provided easy interpretation and better results than other data. Areas identified from these images as being of significance were examined in greater detail through the use of aerial photographs (at scales of 1:5000, 1:10000 and 1:60000 were available).