Numerical Analysis of the Gas Injection Rate in Z12V190 Diesel Tail Gas Drilling
Hou, Xuejun; Gao, Deli*; Shen, Zhonghou
Diesel tail gas drilling (DTGD) is a type of gas drilling, which uses diesel tail gas (DTG) as a circulating medium. Its cost is slightly higher than that of air drilling, but is cheaper than those of nitrogen drilling and natural gas drilling. When the reservoir is drilled with DTG, just as nitrogen and natural gas, the DTG will prevent the burning and blasting of oil and gas in the bottom hole. In order to reduce costs, the DTG is often used in drilling the reservoir, to prevent the underground explosion. This paper analyzes the composition of the Z12V190 diesel exhaust, calculates oxygen mass percentage (OMP), and diesel tail gas rates (DTGR). At the same time, some minimum gas injection rate (MGIR) formulae, using the minimum kinetic energy method, have been updated and illustrated by an example. The analysis results are as follows: the increasing of OMP leads to the increasing of DTGR, the increasing of diesel load and air intake resistance of diesel (AIROD) leads to the decreasing of OMP. The increasing of Critical Point (CP) pressure and CP drill pipe (DP) annulus section area rises the increasing of CP MGIR. Comparing the DTGR curves and MGIR curves, we find that the DTGD is suitable for low pressure shallow wells as well as deep wells, with the condition that the OMP in DTG must be less than 12%. For low-pressure oil fields in China, the DTGD is feasible.