The Optimal Range of the Nitrogen-Injection Rate in Shale-Gas Well Drilling

Abstract

Given the downturn of natural-gas prices in North America, it is vitally important to reduce the cost of drilling shale-gas wells. Gas-percussion drilling with nitrogen gas recently has been used in shale-gas field development. It has increased footage capacity by approximately 60%. Because the rate of penetration (ROP) is fast in gas-percussion drilling, it requires injection of an adequate quantity of nitrogen gas to clean the hole. However, a high rate of gas injection often causes wellbore erosion and deviation problems. It is imperative to determine the optimal range of the nitrogen-gasinjection rate that can mitigate the problem.This paper presents an analytical method for predicting the optimal range of the nitrogen-gas-injection rate required to balance the borehole-cleaning and -integrity issues. The optimal gas-injection rate was sought between the minimal value required for hole cleaning and the maximal permissible value to avoid hole erosion. The minimal value was determined on the basis of Angel's kinetic-energy theory for cuttings removal modified with Charles' theory of particle-grinding energy. The maximum required value was estimated by use of the sonic flow criterion at the bit. Good consistency was observed between the predicted optimal range of gas-injection rate and field problem-free nitrogen-gas-injection rates. This paper provides drilling engineers a practical tool for designing the optimal range of nitrogen-gas-injection rate to cut shale-gas drilling cost.

New Development of Air and Gas Drilling Technology

“…The latter motivates us to develop a new mathematical model to determine the gas injection rate. Li et al [19] Drilling investigated the optimum range of nitrogen injection rate in shale gas well drilling. Chen et al [20] present a method for determining the minimum gas injection rate required for hole cleaning in horizontal gas drilling.…”

A new method for determining the minimum gas injection rate required for hole cleaning in horizontal gas drilling

“…Then numerous investigators were motivated to develop more accurate models. These models include those presented by McCray and Cole (1959), Schoeppel and Spare (1967), Capes and Nakamura (1973), Sharma and Crowe (1977), Ikoku et al (1980), Machado and Ikoku (1982), Mitchell (1983), Puon and Ameri (1984), Sharma and Chowdry (1984), Wolcott and Sharma (1986), Adewumi and Tian (1989), Supon and Adewumi (1991), Tian and Adewumi (1992), Guo et al (1994), Liu and Liu (2008), Samson et al (2012), Li et al (2013). Although the minimum required gas injection rates obtained from these models are more and more close to the field-applied minimum gas injection rate, currently there are few effective models to determine the exact minimum required gas injection rate of horizontal gas drilling, especially in a wide range of ROP (cuttings size).…”

Using Water to Control Water in Underbalanced Drilling With Nitrogen

“…Zhang et al (2012) investigated the effect of bottom hole temperature on rock failure in gas drilling. Li et al (2013) modified Angel's theory by adding the gas energy spent on particle grinding. Li et al (2013a) reported using flow diverting tools for reducing wellbore erosion in gas-drilling shale gas wells.…”

“…Li et al (2013) modified Angel's theory by adding the gas energy spent on particle grinding. Li et al (2013a) reported using flow diverting tools for reducing wellbore erosion in gas-drilling shale gas wells. Knowing that under-injection of gas often causes hole-cleaning problem, people tend to inject gas as much as the compressor can supply.…”