ENGINE Workshop 4 “Drilling cost effectiveness and feasibility of high- temperature drilling” July 2 -5 , 2007 The PT Borehole Simulator HEX-B2 Thomas Mégel Thomas Kohl GEOWATT AG Dohlenweg 28, CH-8050 Zürich 03/07/07 ENGINE Reykjavik Drilling Workshop 1
Introduction HEX-B2 Pressure / Temperature are key parameters in reservoir characterization Borehole Measurements are expensive and require a proper data quality control P/T downhole data can be imprecise under EGS conditions 03/07/07 ENGINE Reykjavik Drilling Workshop 2
Accuracy and Risk of Logging HEX-B2 Measurements in Boreholes: What goals should be achieved? How can the data be controlled? What happens during high flow rate experiments? Is accessibility in boreholes ensured? • High Temperature • Broken Casing • High Mineralization High Costs associated to data acquisition Logging operation Cleaning boreholes from cable/squeezed instruments 03/07/07 ENGINE Reykjavik Drilling Workshop 3
New Possibility in Downhole Measurements HEX-B2 Requirements for data extrapolation to downhole conditions Require P/T information to travel from borehole head to bottom or vice versa Processes related to fluid density distribution are most critical Knowledge of • Physical processes in borehole • Geometrical layout of casing / cementing • Rock matrix parameters New technological developments Make use of use for new computer power 03/07/07 ENGINE Reykjavik Drilling Workshop 4
New pT- Simulator HEX-B2 HEX-B2 HEX-B2 Wellheads GPK2/GPK3 wellhead data borehole model GPK3 03/07/07 ENGINE Reykjavik Drilling Workshop 5
New pT- Simulator HEX-B2 HEX-B2 Model parameters: Input parameters/Physical processes: Dynamic wellhead data 1. Wellhead pressure 2. Injection rate 3. Fluid temperatur Wellhead data: c (1) 4. Fluid NaCl-molality • Initial pressure p(z,t) tmp(z,t) c (2) Dynamic properties and processes implemented p(z,t) Borehole data: • Heat exchange with rock mass tmp(z,t) • Casing diameters • Fluid heat capacity (T, NaCl-mol) • Wall roughness • Fluid density (T, NaCl-mol, p) • MD-TVD • Buoyancy forces in the borehole c (3) • Fluid losses into rock • Friction forces borehole/casing • Initial NaCl-molality • Fluid viscosity (T, NaCl-mol) • Fluid volume (T,p) Resul ults ts Rock mass data: • Thermal conductivity • Specific heat capacity c PT (z,t) Flow Exit • Initial temperature in borehole points c (i) + Injectiv tivity ty Index II (t) 03/07/07 ENGINE Reykjavik Drilling Workshop 6
Features of HEX-B2 HEX-B2 HEX-B2 3 Borehole model: 1 • Arbitrary borehole diameters • Well completion • Rock mass model • Borehole trajectory Processes in borehole: 2 • Navier-Stokes equation • Mass conservation • Pipe friction 1 • Advection (NaCl-mol, T) 2 • Fluid density (NaCl-mol, T, p) 4 • Fluid viscosity (NaCl-mol, T) • Fluid heat capacity (NaCl-mol, T) 3 Radial thermal diffusion (borehole completion and rock mass) 4 40% 20% Exit-/Entry points 4 At production: Inflow of T(t) and NaCl-mol(t) 03/07/07 ENGINE Reykjavik Drilling Workshop 7
Application of HEX-B2 HEX-B2 Possible modes Reservoir response from measured wellhead data • Pressure/flow rate BC at wellhead • Calculation of injectivity/productivity indices • Improvement of reservoir during stimulation • Variation of downhole temperature during production Calculation of scenarios from reservoir parameters • flow rate BC at wellhead; Reservoir parameters at bottom • Pressure profile • Production temperature • Failure pressure at shearing events near borehole • Optimization of production scenarios with thermosyphon effect (Buoyancy) • Design of well testing parameters 03/07/07 ENGINE Reykjavik Drilling Workshop 8
Procedure for Application HEX-B2 Calibration of HEX-B2 Model Provide necessary borehole/rock parameters Calibrate model on existing dataset Preparatory Phase Monitoring of wellhead data (pressure, temperature, molality) Evaluate transient effects from earlier tests Calculation phase Set reference depth Calculate injectivity/productivity indices Perform sensitivity analysis 03/07/07 ENGINE Reykjavik Drilling Workshop 9
Examples of HEX-B2: Soultz GPK3 Stimulation 2003 HEX-B2 HEX-B2 HEX-B2 calculation of injection 03/07/07 ENGINE Reykjavik Drilling Workshop 10
Examples of HEX-B2: Soultz GPK3 Stimulation 2003 HEX-B2 HEX-B2 Comparison with downhole data pT-probe shifted from 4544 MD to 4244 MD good fits with measured data reconstruction of failed pressure data at 4544 MD Data correction High Accuracy! 03/07/07 ENGINE Reykjavik Drilling Workshop 11
Examples of HEX-B2: Soultz GPK3 Stimulation 2003 HEX-B2 HEX-B2 DEMO 03/07/07 ENGINE Reykjavik Drilling Workshop 12
Examples of HEX-B2: Soultz GPK4 Stimulation 2004 HEX-B2 Completion of downhole PT-data 03/07/07 ENGINE Reykjavik Drilling Workshop 13
Examples of HEX-B2: Synthetic GPK2 Production Test HEX-B2 HEX-B2 Calculation of production without additional inflows Tdh = 190°C NaCl-mol = 5 03/07/07 ENGINE Reykjavik Drilling Workshop 14
Examples of HEX-B2: Synthetic GPK2 Production Test HEX-B2 HEX-B2 Calculation of production with assumed inflows Tdh = 190°C NaCl-mol = 5 inflows at -2200 MD inflows at -4500 MD 03/07/07 ENGINE Reykjavik Drilling Workshop 15
Examples of HEX-B2: Failure Pressure of Fractures HEX-B2 Near-borehole microseismicity GPK2 (2000): GPK3 (2003): Easting Easting 150 -350 -350 100 300 Northing 300 Northing 0 50 -100 -200 -400 -400 0 -300 200 200 Northin Northin -400 -50 100 100 -450 -450 0 0 -4500 -4500 -500 -500 -100 -100 -4550 -4550 -550 -550 -4600 -4600 -4650 -4650 -4500 -4500 -4700 -4700 -4600 -4600 -4750 -4750 -4800 -4800 -4700 -4700 -4850 -4850 -4900 -4900 -4800 -4800 -4950 -4950 -5000 -5000 -4900 -4900 -5000 -5000 First 24 h First 24 h r < 25 m r < 25 m r : 25 - 50 m r : 25 - 50 m r > 50 m r > 50 m 03/07/07 ENGINE Reykjavik Drilling Workshop 16
Examples of HEX-B2: Failure Pressure of Fractures HEX-B2 Near-borehole microseismicity Downhole pressure history GPK2 (2000): GPK3 (2003): Whole ole open hole section activated immediately Top-to to-down activation of open hole section Failure pressure of all intersecting fractures Failure pressure of intersecting fractures immediat ediately ly exceeded was exceeded slowly ly 03/07/07 ENGINE Reykjavik Drilling Workshop 17
Examples of HEX-B2: Failure Pressure of Fractures HEX-B2 Fracture failure pressure for GPK3 GPK3 (2003): Easting 150 -350 -350 100 50 -400 -400 0 Northin Northin -50 -450 -450 -4500 -4500 -500 -500 -4550 -4550 -550 -550 -4600 -4600 Depth + Time -4650 -4650 -4700 -4700 -4750 -4750 -4800 -4800 of near-borehole -4850 -4850 -4900 -4900 -4950 -4950 -5000 -5000 events + HEX-B2 Calculation of corresponding downhole pressures • Failure pressure from 52 - 60 MPa with TVD • Reflects depth-dependency of stress field • Range at a given depth: fracture orientation?! • Gradient of failure pressure: 5-10 10 MPa/400m 03/07/07 ENGINE Reykjavik Drilling Workshop 18
Examples of HEX-B2: Sensitivity Calculations HEX-B2 Steady-state pressure vs. Molality vs. productivity index Productivity Index 5 mol = 0% mol = 10% 4 mol = -10% PI [l/s/MPa] 3 2 1 0 150 160 170 180 190 200 T CS [°C] 03/07/07 ENGINE Reykjavik Drilling Workshop 19
Conclusions HEX-B2 HEX-B2 was used for interpretation of Soultz testing data Most useful features: Comparability of downhole pressure data • Different tests during exploration phase at variable flow rates • Extrapolation to arbitrary levels • Comparability of data Calculation of injectivity/productivity indices Correction and reconstruction of pT-data gaps Sensitivity calculation Scenario analysis for production temperature (heat loss in well, effect of inflow temperature,...) Accounting for effects of leaks in the casing (injection and production) Cost reduction for pT-downhole measurements 03/07/07 ENGINE Reykjavik Drilling Workshop 20
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