Page 382 - Fundamentals of Gas Shale Reservoirs

362 GAS SHALE CHALLENGES OVER THE ASSET LIFE CYCLE

• Reduce corrosion, scaling, and bacterial contamination
in wells and facilities
Ex p n • Install artificial lift if required
Exploration
• Protect the environment

17.2.5 Rejuvenation Phase Objectives—Recommended
Rejuvenation Appraisal Practices
ti
• Evaluate wells for Re‐frac candidates and then
Asset life cycle implement Refracs
• Analyze field for redevelopment potential—infill
drilling

17.3 EXPLORATION PHASE DISCUSSION
Produc
Production n Development
Devel ment
The life cycle starts with the exploration and then appraisal
phases (which are similar in many respects) where the oper-
ator begins to obtain an understanding of the reservoir
FIGURE 17.1 The shale gas asset life cycle (Source: Baker Hughes). aspects of these unique shale formations. It has been said by
other authors that there is not really an exploration phase,
• Begin to characterize the reservoir with exploration wells because shales are continuous formations and their locations
• Determine the initial economic value and reservoir are known. The objective is to locate the part of the formation
potential/evaluate that is more prolific (sweet spots) than the others.
A screening study is particularly important when entering
17.2.2 Appraisal Phase Objectives—Recommended a new basin or area. The primary purpose of the study is to
Practices identify the core areas, that is, locate the sweet spots. Well‐
by‐well production data indicate that shale formations
• Drill the appraisal wells and continue to characterize have small spots of very productive wells (sweet spots), sur-
the reservoir rounded by large areas of wells that produce far less gas
• Build reservoir model(s) for simulation or oil. Sweet spots are a function of total organic carbon
• Generate a field development plan (TOC), thermal maturity, thickness, gas in place (GIP),
• Validate the economics of the play/evaluate natural fractures, mineralogy, and field stress in the area.
• Consider a pilot project/evaluate Sweet geologic spots may not necessarily be sweet economic
spots. Also, if an area possesses most of these attributes, but
17.2.3 Development Phase Objectives—Recommended is not a favorable area in which to frac (mineralogy or
Practices stresses), it is not a sweet spot. It may sound trite, but develop
the sweet spots first, then go back to the less attractive areas
• Implement the field development plan or pilot (Kennedy et al., 2012a).
• Install surface production and export facilities,
including compression and pipelines 17.3.1 Screening Study—Current Practice
• Design wells and optimize drilling costs
• Refine and optimize the hydraulic fracturing and well- Most small operators in the United States do not conduct
bore completion designs (characterize the horizontal basin screening studies, especially in the established plays.
laterals) There is no doubt, however, that the major operators and
large independents have conducted such studies prior to
17.2.4 Production Phase Objectives—Recommended entering a new play area in the United States. From this
Practices author’s experience with National Oil Companies (NOCs)
and International Oil Companies (IOCs), they are all con-
• Monitor and optimize producing rates ducting or have conducted basin screening studies prior to
• Manage the water cycle—sourcing for drilling and entering international virgin areas that do not have any shale
fracturing water; lifting, treating, handling, storage, wells or existing production. Studies are known to exist in
and disposal of well flowback water China, Saudi Arabia, Argentina, Australia, and Mexico.