Anticipating the Energy Crunch – Extracting Tight and Unconventional Gas
Is this realistic? Well, let us take a look as the actual volumes of natural gas endowment. The USGS 2000 global petroleum assessment estimates ‘conventional gas’ endowment from 216 petroleum provinces at approximately 11,600tcf. This volume is conservative as it does not include reserve growth, unconventional gas (tight gas, shale gas, coal-bed methane and natural gas hydrates) or offshore gas provinces with water depths greater than 2,000m in some petroleum provinces and 4,000m in others. A method called variable shape distribution (VSD) indicates that for the 937 petroleum provinces that exist throughout the world, the endowment is over 15,000tcf.
The GFREE team examination of ‘unconventional gas’ indicates an endowment of over 15,000tcf for tight gas, 10,000tcf for shale gas and 5,000tcf for coal-bed methane. As a result, the estimated global conventional and unconventional gas endowment, without reserve growth, is a gigantic 45,000tcf – enough to satisfy the world’s energy needs for several decades.
In the case of tight formations, natural gas is generated
somewhere else (most likely in a shale) and migrates to the tight formation, where it is trapped and stored in inter-particle, slot and microfracture porosity.
It is important to understand some of the key differences between tight gas, shale gas and coal-bed methane formations. In the case of shales, the gas is generated in the shale and remains in the shale, i.e. the shale is both source rock and reservoir rock. In this instance, part of the gas is stored in inter-particle porosity, part is in natural microfractures and part is adsorbed in kerogen within the shale. Production of formation water is not generally an issue in shale gas. In coal-bed methane, the coal is, as in the case of shale, source and reservoir rock, and the gas is adsorbed in the coal. However, most of the time de-watering from natural fractures (usually called cleats in the coal-bed methane industry) might pose an environmental hazard. However, there are some instances where water is not present in the cleats and methane is obtained from the moment the wells go on production.
In the case of tight formations, natural gas is generated somewhere else (most likely in a shale) and migrates to the tight formation, where it is trapped and stored in inter-particle, slot and microfracture porosity. If the gas is trapped in continuous tight accumulations there is no water leg and no water production (except for vapour water). When gas is trapped in regular structural and stratigraphic traps with very low permeability (tight formations), water production can become a very important operational, environmental and economic issue.
One of the most fascinating issues about the above gargantuan volumes, in addition to lasting for several decades, is the fact that, with some creativity, natural gas can pave the way towards a non-fossil economy.
102
We have developed what we call the ‘2030 – 1/3 forecast’ using a global energy market (GEM) model. It indicates that, by 2030, one- third of global energy needs will be met by natural gas, one-third by liquids and one-third by solids. We represent the GEM model by a pentagon. The top of the pentagon (corner 1) corresponds to historical energy consumption and forecast future energy consumption. The next corner (2) is associated with the historical and forecast future fraction contributed by each primary energy source. Corner 3 represents actual and forecast consumption rates of each source. The question is whether there is enough oil, gas and other resources to supply the rates forecast for the period considered in this study. This is answered in the next corner (4), which describes estimated energy resource availability by plotting recoverable petroleum volumes versus the number of recognised petroleum provinces around the world. The final corner (5) corresponds to a cumulative long-run supply curve, which presents the production costs of the world’s recoverable volumes of hydrocarbons. Detailed analysis of this pentagon leads the GEM model to corroborate the large natural gas endowment discussed above.
The GEM indicates that the only market share that will keep increasing beyond 2030 is the one provided by natural gas. The per cent contribution of oil to the global energy mix peaked around 1975 and has been declining ever since. The solid contribution has remained more or less stable. On the other hand, the natural gas contribution has been increasing steadily. Given the large endowment discussed above, and GFREE research on this subject, it is reasonable to anticipate that this increase will continue into the foreseeable future.
An important item not usually considered in our industry is the hydrogen-to-carbon ratio (H/C), a good proxy for environmental quality, which increased steadily from 1850 to 1970, then the ratio stabilised. The H/C ratio helps to explain the benefits of natural gas as compared with other fossil fuels. Natural gas is the cleanest fossil fuel that can be burned: four atoms of hydrogen for one atom of carbon, or an H/C ratio of 4:1. Compare this with the average H/C ratio for oil of 2:1, for coal 0.5:1 and for wood, agricultural residues and animal dung 0.1:1. Just a comparison of these ratios demonstrates that that natural gas is healthier for the environment compared with other fossil fuels.
Our GEM model indicates that by 2030 the H/C ratio will start
increasing again. The net result will be a relative decrease in CO2 going into the atmosphere. Since natural gas will last for several decades, it will provide plenty of time for society to substitute a non-fossil energy
source that will lead to a decrease in CO2 emissions. Furthermore, this decarbonisation will result in more convenience and cleanliness throughout the world.
In one of the scenarios we have studied, the CO2 peak would occur in the second half of this century; it would then decline as envisaged
in the GFREE’s ‘low and zero carbon initiative’.
Is it doable? Three years ago, before coming to the University of Calgary, I had my doubts. However, after a three-year interaction with youngsters working on these and other problems I feel comfortable asserting that is certainly achievable. Without question we are in good hands for the future. n
EXPLORATION & PRODUCTION – VOLUME 8 ISSUE 1
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140 |
Page 141 |
Page 142 |
Page 143 |
Page 144 |
Page 145 |
Page 146 |
Page 147 |
Page 148