Page 397 - Fundamentals of Gas Shale Reservoirs

CONCLUSIONS—RECOMMENDED PRACTICES 377
considered when the primary development in the sweet spots 7. Determine initial economic value and reservoir poten-
of the field has been or are nearing depletion. tial (should be accomplished by the operator).

Appraisal Phase
17.8 CONCLUSIONS—RECOMMENDED
PRACTICES 1. Drill appraisal wells. Number depends on a number
of considerations, but recommendation is to drill
A listing of the pertinent recommended practices (included both vertical (to continue to gather data to charac-
in this chapter’s discussion) to overcome an operator’s chal- terize the reservoir) and horizontal wells for testing
lenges in each phase of the asset life cycle of a shale gas well the completion and hydraulic fracturing design to
are shown in the following: determine potential producing rates from the frac
design/implementation.
Exploration Phase 2. Build reservoir models for simulation—start with the
geocellular (static) model and reservoir analysis tech-
1. Conduct basin/area screening study to identify core niques for shale.
area/sweet spots and for initial estimate of G/OIP. 3. Use the integrated multidisciplinary approach including
Recommended for new basins or new areas within a reservoir engineering (“shale engineering”), geology,
producing basin. petrophysics, geomechanics, geochemistry, and seis-
2. Conduct 3D seismic in new basins/areas to (i) mology for building models.
Identify areas of highest TOC using seismic imped- 4. Generate a field development plan to include well
ance, (ii) Increase understanding of natural fractures types, placement, attitude, direction (azimuth), and
using seismic attributes, (iii) provide azimuthal spacing (drainage area considerations).
anisotropy data related to natural fracture orientation 5. Shale wells should be drilled in the direction of
and/or horizontal stress anisotropy, and (iv) assist minimum horizontal stress, which maximizes access
in the identification of sweet spots using seismic to existing natural fractures so that the induced
cross‐plots. hydraulic fractures intersect the natural fractures in
3. Geophysical evaluation optimal workflow includes transverse manner near the wellbore creating more
a. Seismic rock properties complex fractures.
b. Azimuthal analysis 6. Based on the US experience and the characteristics of
c. Seismic analysis shale, a large number of development wells are
d. Stress estimate required to develop shale gas reservoirs.
e. Multiattribute/integration 7. Validate the economics of the play or consider
4. Begin to characterize reservoir by running specific conducting a pilot project to determine whether
logs and taking/analyzing cores in exploration and or not to continue into the development phase of
appraisal vertical wells the play.
5. Recommended logs include: conventional suite plus— 8. Pilot projects are conducted to prove commerciality
spectroscopy, pulsed neutron, and NMR for deter- and to determine the best technologies and optimum
mining mineralogy, porosity, O/GIP, optimum frac development plan.
and lateral placement locations, and log‐derived
mechanical properties to assist in frac design. Development Phase
6. Obtain cores conventional whole cores or sidewall 1. Implement the field develop plan or pilot project.
cores and analyze for calibrating logs and obtaining
true measured properties. Recommended analyses 2. Install surface production and export, compression,
should include porosity, permeability, saturations; gas pipelines facilities.
analysis to include adsorption/desorption isotherms 3. Design and drill wells; optimize drilling costs.
and isotopes; and triaxial compression testing for • Drill the lateral as flat as possible and perfectly
static elastic properties. A wide variety of technol- horizontal (not undulating), which can cause diffi-
ogies are used to examine the lithology and mineral culty running casing, and result in low spots that can
composition of shale. “Sample” for these analyses collect liquids causing hydrocarbon flow obstruc-
come from cuttings, rotary (SW) cores, conventional tion or liquid loading of gas wells.
core plugs, and whole core. These can often be • High‐build rate RSS can achieve “one‐run curve
combined and performed on the same sample. and lateral” wells (one BHA, one bit, one trip);