Page 11 - Enhanced Oil Recovery in Shale and Tight Reservoirs
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CHAPTER ONE




              Introduction to shale and tight
              reservoirs




              Abstract

                 Preliminary definitions of shale and tight reservoirs are proposed after the definitions of
                 shale and tight reservoirs in the literature are summarized and discussed. There are no
                 widely agreed definitions of shale and tight formations. The definitions of shale oil and
                 oil shale are differentiated; the former is the oil that exists in shale, whereas the latter is
                 the rock that contains organic hydrocarbon materials. Shale and tight resources are
                 presented. Current production technologies are briefly introduced.

              Keywords: Oil shale; Shale; Shale oil; Shale resources; Tight formation.



                   1.1 Introduction
                   Oil production from shale and tight formations accounted for more
              than half of total U.S. oil production in 2015 (EIA, 2016). Such amount
              is expected to grow significantly as the active development of low perme-
              ability reservoirs continues. The current technique to produce shale oil is
              through primary depletion using horizontal wells with multiple transverse
              fractures. The oil recovery is less than 10% (Sheng, 2015d), or 3%e6%
              according to the EIA 2013 report (Kuuskraa, 2013). The oil recovery in
              tight formations is also low, e.g., 15%e25% (Kuuskraa, 2013). Clark
              (2009) showed that the results from several methods indicate that the
              most likely value for oil recovery factor in the Bakken shale is approximately
              7%. The North Dakota Council website states “With today’s best technol-
              ogy, it is predicted that 1%e2% of the reserves can be recovered.” (North
              Dakota Council, 2012). The oil recovery factor for each of 28 US tight
              oil plays is below 10% (Advanced Resources International, 2013). It is
              certain that a large percentage of the oil remains unrecovered without
              enhanced oil recovery methods. There is a big prize to be claimed in terms
              of enhanced shale and tight oil recovery. Therefore, this book is dedicated to
              the enhanced oil recovery (EOR) in shale and tight reservoirs.



              Enhanced Oil Recovery in Shale and Tight Reservoirs  © 2020 James Sheng.
              ISBN: 978-0-12-815905-7                  Published by Elsevier Inc.
              https://doi.org/10.1016/B978-0-12-815905-7.00001-3  All rights reserved.  1 j
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