Chapter Four - Shale Gas Production Technologies

页岩气开采技术

Shale Oil and Gas Handbook, 2017, Pages 123-152

Sohrab Zendehboudi, Alireza Bahadori

Abstract:Gas contained within shale reservoir rocks is classified as unconventional gas reservoirs because the shale formation has low permeability. The reservoir is challenging to produce due to the lack of interconnections of the pore spacing. The gas cannot easily flow to the well in an unconventional reservoir and for this reason, shale gas reservoirs were not considered to be economical. In recent years, research and development of new technologies has made it possible to produce shale gas in an economically feasible fashion. The two major breakthroughs for shale gas production were hydraulic fracturing and directional drilling, which are typically used in combination to provide enhanced recovery in the reservoir. With the emergence of the new, successful methodologies, shale gas production increased substantially. Aside from the challenges involved with extracting the gas from the reservoir, there are also operational limitations that must be considered before the gas can be sold as a commodity. One major consideration is the environmental impacts associated with the stimulation methods which tend to prevent shale gas production in some locations. Equipment design is also a necessary consideration as gas processing equipment will have specific requirements in order to operate safely and effectively. For example, a gas liquid separator is an essential piece of equipment required to coalesce the liquid out of the gas stream. This is important in protecting downstream equipment and achieving product purity specifications. Design considerations such as, type, size, and material must be accounted for to ensure successful operation. After production, the product gas must be properly transported to a client or stored at a facility. The intent of the product determines whether it will be transported for distribution or stored at a facility or depleted reservoir. The new technology has led to successful production, processing, and transportation of shale gas. Shale gas can now be considered an economically feasible resource and it is expected that its production will continue for years to come. North America, specifically the United States, has benefited substantially from the new enhanced recovery methodologies and shale gas has filled the void of natural gas in some locations.

Chapter Nine - Shale Oil Processing and Extraction Technologies

页岩油加工与开采技术

Shale Oil and Gas Handbook, 2017, Pages 321-356

Sohrab Zendehboudi, Alireza Bahadori

Abstract:The exploitation of oil shale involves mining, after which shale is directly burned to produce electricity or undergoes further processing. The two very common methods of surface mining, open-pit mining and strip mining, involve the removal of overlying material. In underground mining of oil shale, however, the removal of overlying material is very limited. For the extraction of the oil shale both in situ or ex situ processes are involved. In either case, the pyrolysis converts the kerogen of the oil shale into the condensable vapors, which after condensation are turned into synthetic crude oil and noncondensable gas (shale gas). Pyrolysis includes heating in the absence of air at a high temperature. Usually, this takes place between 450 and 500°C. The decomposition starts at a very low temperature of 300°C, and then proceeds more rapidly at a higher temperature.

Indicative energy technology assessment of UK shale gas extraction

英国页岩气开采指示能源技术评估

Applied Energy, Volume 185, Part 2, 1 January 2017, Pages 1907-1918

Geoffrey P. Hammond, Áine O’Grady

Abstract: There is at present much interest in unconventional sources of natural gas, especially in shale gas which is obtained by hydraulic fracturing, or ‘fracking’. Boreholes are drilled and then lined with steel tubes so that a mixture of water and sand with small quantities of chemicals – the fracking fluid – can be pumped into them at very high pressure. The sand grains that wedge into the cracks induced in the shale rock by a ‘perforating gun’ then releases gas which returns up the tubes. In the United Kingdom (UK) exploratory drilling is at an early stage, with licences being issued to drill a limited number of test boreholes around the country. However, such activities are already meeting community resistance and controversy. Like all energy technologies it exhibits unwanted ‘side-effects’; these simply differ in their level of severity between the various options. Shale gas may make, for example, a contribution to attaining the UK’s statutory ‘greenhouse gas’ emissions targets, but only if appropriate and robust regulations are enforced. The benefits and disadvantages of shale gas fracking are therefore discussed in order to illustrate a ‘balance sheet’ approach. It is also argued that it is desirable to bring together experts from a range of disciplines in order to carry out energy technology assessments. That should draw on and interact with national and local stakeholders: ‘actors’ both large and small. Community engagement in a genuinely participative process – where the government is prepared to change course in response to the evidence and public opinion – will consequently be critically important for the adoption of any new energy option that might meet the needs of a low carbon future.

Review of multi-scale and multi-physical simulation technologies for shale and tight gas reservoirs

页岩与致密气藏多尺度多物理模拟技术综述

Journal of Natural Gas Science and Engineering, In Press, Accepted Manuscript, Available online 30 November 2016

Lei Wang, Shihao Wang, Ronglei Zhang, Cong Wang, Yi Xiong, Xishen Zheng, Shangru Li, Kai Jin, Zhenhua Rui

Abstract:This paper provides a comprehensive literature review on the simulation techniques being developed in recent years for describing unique flow behaviors in shale and tight gas reservoirs. The advances in modeling gas flow and transport mechanisms during the primary and enhanced gas recovery processes are reviewed in detail. The capabilities of reservoir simulation tools are discussed in terms of mathematical treatment (finite difference, finite element, explicit/implicit scheme, sequentially and fully coupled schemes), fluid flow characteristics (Darcy and non-Darcy flow, desorption, Klinkenberg effect and gas slip flow, transitional flow, Knudsen diffusion), reservoir rock properties (pore size distribution, fractures, geomechanics), multidisciplinary coupling scheme (THM, THC, THMC), modeling scale, and computational efficiency. For pore-scale modeling of gas flow and transport in unconventional reservoir rocks, the numerical methods for generating pore network models and the procedure for constructing real 3D digital rocks are first explained. Then, the network modeling methods used for simulating slip and transitional flows in pore networks are introduced and compared. After that, existing lattice-Boltzmann models developed for slip flow simulation are illustrated. Along with the explanation, pros and cons of the models for pore-scale modeling have been identified. Overall, dwelling on the concerns and challenges in shale and tight gas reservoir simulation, current status, progress and bottlenecks of numerical simulation technologies are discussed and perspectives on future development of unconventional gas reservoir simulators are proposed.