Page 387 - Fundamentals of Gas Shale Reservoirs
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DEVELOPMENT PHASE DISCUSSION   367

                        Barnett  Fayetteville  Woodford  Marcellus  Haynesville  Eagle ford
                          44        32         22         410        75          21       TRR, Tcf
                        14,400     4,200      3,300      5,600      3,250       1,700     Wells 6-1-13
                        27,500    11,430      7,300     117,140    11,550       4,200     Wells required
                          1.6       2.8        3.0        3.5        6.5         5.0      EUR, Bcf
                             1400
                             1300
                             1200                                             Typical
                             1100                                        200–300 wells/1 Tcf
                             1000
                              900
                           Well count  700
                              800
                              600
                              500
                              400
                              300
                              200
                              100
                                -
                                    0.8      1.8      3.5      4.8      6.3      8.1     10.0 Bcf/well
                                                Ultimate gas recovery per well (Bcf)
                        FIGURE 17.4  Number of wells required to develop 1 tcf of gas (Updated from Kennedy et al., 2012b).




              Internationally, it has been observed that NOC operators   17.5.3  Design Wells and Optimize Drilling
            plan to take the approach of conducting a pilot program prior   Costs—Current Practice
            to full field development. In these virgin areas with very few   The early shale gas wells in the Barnett (discovery in 1981)
            wells or any offset wells to observe, this approach certainly   were mostly verticals. It was not until 2003 that there was a
            makes economic sense. Pilot programs are conducted to   total shift  to horizontal  wells for  developing shale  in the
            prove commerciality, and/or to define best technologies and   Barnett as well as all other US shale basins that followed.
            development plan. After conducting the pilot program, inter-  Now that the template has been set for shale gas drilling in
            national operators will stop to evaluate prior to taking the   the United States, service companies have been successfully
            decision to proceed with full field development.
                                                                 reducing drilling costs through optimized drilling and new
                                                                 technology. To date there have been approximately 150,000
            17.5  DEVELOPMENT PHASE DISCUSSION                   shale wells drilled in the United States. (It should be noted
                                                                 that some 10,000 of these wells were drilled in the old
            17.5.1  Implement the Field Development Plan           biogenic Antrim Basin, Michigan, and do not behave like
                                                                 the major shale thermogenic basins where today’s activity is
            In implementing a field development plan that includes a   centered.)
            large number of wells, an operator is cautioned not to   Listed in the following are some of the current typical
            become complacent and continue to allow the rig schedule   practices used for drilling horizontal wells:
            to totally drive the plan. Interim analyses should be under-
            taken to ensure that drilling and completion programs are     • Curve Section—Build rate is typically 6–8/100 ft.
            delivering wells with the expected initial potential (IP)‐
            producing rates.                                          • Optimum (and shorter) lateral lengths are now preferred
                                                                     over “longer lateral lengths.” Length of horizontal sec-
                                                                     tions varies from play to play, and ranges from 3000 to
            17.5.2  Surface Facilities                               6000 ft for shale gas.
            Surface facilities will not be discussed here. They are only     • Most operators convert to some form of oil‐based mud
            included in the life cycle for completeness and to ensure   (OBM) prior to drilling the curve and lateral.
            construction schedules match the timing of well completion     • Only a few wells in the United States are being drilled
            and availability.                                        with environmentally friendly water‐based mud (WBM).
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