Prediction of cavity growth rate during underground coal gasification using multiple regression analysis

Abstract

During underground coal gasification (UCG), whereby coal is converted to syngas in situ, a cavity is formed in the coal seam. The cavity growth rate (CGR) or the moving rate of the gasification face is affected by controllable (operation pressure, gasification time, geometry of UCG panel) and uncontrollable (coal seam properties) factors. The CGR is usually predicted by mathematical models and laboratory experiments, which are time consuming, cumbersome and expensive. In this paper, a new simple model for CGR is developed using non-linear regression analysis, based on data from 11 UCG field trials. The empirical model compares satisfactorily with Perkins model and can reliably predict CGR.

Fault Reactivation Can Generate Hydraulic Short Circuits in Underground Coal Gasification—New Insights from Regional-Scale Thermo-Mechanical 3D Modeling

“…In order not to overestimate ground surface subsidence and stresses in 3D models as discussed by Adhikary et al [30], UCG reactor growth is considered to occur simultaneously in 50-m steps along the pre-defined UCG channels, determined by an average gasification front progress of 1 m/day. The selected reactor growth rate is in good agreement with the empirical model presented by Najafi et al [12], allowing for predication of UCG reactor growth rates under various operational and geological boundary conditions. Data published on previous field-scale UCG activities exhibit reactor growth rates varying from 0.35 to 1.2 m/day.…”

“…Especially thermo-mechanical effects and/or fault reactivation may introduce potential migration pathways for hazardous environmental contaminants, mainly composed of organic and inorganic pollutants [4,9,11]. Site-specific coupled thermo-mechanical processes occurring in rocks adjacent to a deep UCG reactor are generally not well known in the field, because of the difficulty to quantify all occurring chemical reactions during the UCG process and their effects on UCG reactor size and shape [12]. Current knowledge on these processes is mainly based on laboratory experiments [13][14][15][16][17][18][19][20][21][22][23] and a few successful UCG field trails.…”

“…Since the 1930s, more than 50 pilot-scale UCG operations have been carried out worldwide. These developments have been concentrated in the former Union of Soviet Socialist Republics (USSR), Europe, U.S., South Africa, Australia and China and were predominantly undertaken at shallow depths, e.g., at Angren (110 m) in Uzbekistan, Chinchilla (140 m) in Australia, and Hanna (80 m) and Hoe Creek (30-40 m) in the U.S. [3,7,12,[24][25][26].…”

Effect of Oxygen - Air Ratio on the Gasification of Mui Basin Coal Using Fixed-Bed Gasifier

“…Countries with low per capita energy consumption experience low per capita gross domestic products (GDP) [1]. Coal is the largest fossil fuel resource in the world [and many countries use coal for energy production due to its availability, reliability, and relative low cost [2,3]. In the year 2017, coal provided 35% -40% of the global electricity generation [4,5].…”

Prediction of Steam Jacket Dynamics and Water Balances in Underground Coal Gasification

“…The rate of reactor growth depends on a number of factors, some of which can be controlled, such as the rate of air or steam injection, as well as the geological boundary conditions affected by the chemo-thermo-hydro-mechanical properties of the coal and its overburden [17][18][19][20][21].…”