2012-12-12_REVISION - P2010026 (3)

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5.2 Development Details 5.2.1 Drilling The ELHT well pattern (Figure 2) consists of three horizontal heater wells and one inclined observer /producer well to provide pressure control. In addition to heating the formation during the heating phase, heater wells will also be used to control pressure in the immediate vicinity of the heater. The surface location for these wells will be in the northeast quadrant of the East RDD lease (Figure 2). None of the wells will be converted for dual use and no leaching is anticipated as the main objective for the ELHT pilot is to measure the response of the reservoir to heating (principally looking for the development of heater "hot spots "). All wells will be drilled, cased, and cemented prior to heater installation and ICP activities. Figure 6 shows a subsurface view of ELHT wells. Drilling operations will require 3 or more months. A dedicated drilling pad will be built and used for this pilot. As shown of Figure 2, the surface location of the conductors will be located less than 500 ft from the lease boundary but the down hole well trajectory during drilling will place the heated section or interval away from the property boundary in the central portion of the lease. As such, the ELHT testing will not affect any resource at or near the lease boundary. Well specifications and additional details for well construction are discussed in Section 6B.4. Five hydrology monitoring wells were installed in 2009 in the northeast quadrant of the RDD Lease (hydrology well pad 138) as part of the EAST RDD. Data from these wells are being collected as part of the East RDD and provide baseline water quality in the near downgradient area that is also applicable to the ELHT. An additional groundwater monitor well (135 -4 -298) was installed near the East RDD Pilot pattern with surface location approximately 60 ft NE of the East RDD pilot pattern. Elsewhere in the basin, Shell has drilled, tested, and sampled a considerable number of hydrology wells. These are discussed in the sections on hydrology and baseline water chemistry in this NOI Modification. The existing groundwater monitoring wells associated with the EAST RDD are sufficient for monitoring during the ELHT. As such, no additional hydrology wells will be drilled as part of the ELHT. 5.2.2 Nahcolite /Sodium Availability Assessment It is important to assess the impact of the heating process on the viability of sodium recovery when heating near rich nahcolite beds. Only one of the three heater wells is drilled in a zone containing significant nahcolite: • Heater 1 (2220 ft depth *) — 25.4 wt% Nahcolite (drilled near Greeno Bed) • Heater 2 (2300 ft *) — 0.8 wt% Nahcolite • Heater 3 (2400 ft) — 0.3 wt% Nahcolite (drilled in the illitic interval). The ELHT pilot does not include a pre - leaching phase in which sodium is recovered. Instead, to assess the impact that heating will have on sodium recovery, Shell proposes to recover a core across the heat - affected zone near Heater 1 after the completion of the heating and production phase and prior to commencement of well abandonment activities. The core is expected to drill through (1) a virgin nahcolitic zone above the heated interval, (2) an upper nahcolite /soda ash transition zone, (3) 4