Page 10 - Geothermal Energy Systems Exploration, Development, and Utilization

VIII Contents
3.5.1.3 Critical Formations/Fault Zones 138
3.5.1.4 Hydrocarbon Bearing Formations 138
3.5.1.5 Permeabilities 138
3.5.2 Well Design 139
3.5.2.1 Trajectory 139
3.5.2.2 Casing Setting Depths 139
3.5.2.3 Casing Sizes 139
3.5.2.4 Casing String Design 140
3.6 Drilling a Well 142
3.6.1 Contract Types and Influence on Project Organization 142
3.6.1.1 Turnkey Contract 142
3.6.1.2 Meter-contract 143
3.6.1.3 Time-based Contract 143
3.6.1.4 Incentive Contract 143
3.6.2 Site Preparation and Infrastructure 144
3.6.2.1 General 144
3.6.2.2 Excavating and Trenching 144
3.6.2.3 Environmental Impact (Noise, Pollution Prevention) 144
3.6.3 Drilling Operations 144
3.6.4 Problems and Trouble Shooting 145
3.7 Well Completion Techniques 148
3.7.1 Casing (Please Refer Also to ‘‘Casing String Design’’) 148
3.7.1.1 Allowance of Vertical Movement of Casing 148
3.7.1.2 Pretensioning 148
3.7.1.3 Liner in Pay Zone (Slotted/Predrilled) or Barefoot Completion 150
3.7.2 Wellheads, Valves and so on 150
3.7.3 Well Completion without Pumps with Naturally Flowing Wells 151
3.7.4 Well Completion with Pumps 152
3.8 Risks 152
3.8.1 Evaluating Risks 153
3.8.1.1 Poor or Wrong Geological Profile Forecast 153
3.8.1.2 Poor Well Design 153
3.8.2 Technical Risks 154
3.8.2.1 Failure of Surface Equipment 154
3.8.2.2 Failure of Subsurface Equipment 154
3.8.3 Geological–Technical Risks 155
3.8.4 Geological Risks 157
3.8.5 Geotectonical Risks 159
3.9 Case Study Groß Sch¨ onebeck Well 159
3.10 Economics (Drilling Concepts) 162
3.10.1 Influence of Well Design on Costs 164
3.10.1.1 Casing Scheme 164
3.10.1.2 Vertical Wells versus Deviated Wells 165
3.11 Recent Developments, Perspectives in R&D 165
3.11.1 Technical Trends 165