Page 26 - Fundamentals of Gas Shale Reservoirs

6 GAS SHALE: GLOBAL SIGNIFICANCE, DISTRIBUTION, AND CHALLENGES

Legend
Assessed basins with
resource estimate
Assessed basins without
resource estimate
Countries within scope of report
Countries outside scope of report

FIGURE 1.3 Map of 48 major shale basins in 32 countries (from EIA, 2011b).

1.4.2.1 EIA Global Resource Estimation Methodology reflected in the calculation of “risked GIP” and the
The resource estimates presented by the EIA in the global subsequent calculation of TRR. The TRR values presented
shale gas review were calculated using a basin‐by‐basin by the EIA effectively correlate with the TRR zone defined
approach, using the following methodology: by Dong et al. (2013).
1. Conducting preliminary geological and reservoir char­ 1.4.2.2 EIA USA Resource Estimation Methodology The
acterization of shale basins and formation(s) resource estimates provided by the EIA for individual US
2. Establishing the areal extent of the major gas shale shale gas plays were assessed using a comparable method to
formations (i.e., specific to certain shale formations that adopted for the global resources assessment. However,
within a basin) the main difference is that production data (i.e., well recovery
3. Defining the prospective area for each gas shale data) was used to support the estimate. This reflects the fact
formation that many US shale gas plays are in a production phase, with
4. Estimating the total gas in‐place (GIP) approximately 25,000 producing wells in 2007, (Vidas and
Hugman, 2008), whilst the rest of the world is still largely in
5. Estimating the risked shale GIP, accounting for the the exploration phase.
following: The resource estimates quoted represent a TRR for each
• Play success probability factor shale gas play, although they do reduce the gas already pro­
• Prospective area success risk factor duced. The TRR for this source effectively correlates with
6. Calculating the TRR of shale gas in terms of Tcf. On a the TRR zone defined by Dong et al. (2013).
“by region” average, this value was generally between
24 and 29% of GIP. 1.4.2.3 Rogner Resource Estimation Methodology The
Rogner study (1997) provides shale gas resource data for
Naturally, the accuracy of the estimate is a function of Russia and the Middle East. Rogner states that the estimates
the availability and quality of data, but this is generally presented are very speculative as a result of the lack of data.