WELL TESTING: INTERPRETATION METHODS

Transcription

1 GILLES BOURDAROT Engineer, Elf Aquitaine WELL TESTING: INTERPRETATION METHODS Translated from the French by Barbara Brown Balvet Center for PETROLEUM ENGINEERING AND PROJECT DEVELOPMENT 1998 EDITIONS TECHNIP 27 rue Ginoux Paris Cedex 15 ECOLE DU PETROLE ET DES MOTEURS IFPBSCHOOL

2 Contents Symbols and abbreviations 11 PRINCIPLE 17 Chapter 1 Principles of well testing Introduction Darcy's law Compressibility Diffusion equation Solving the diffusivity equation Compressible zone Radius of investigation Flow regimes Principle of superposition 31 Chapter 2 Wellbore storage Definition Naturally eruptive wells Pumping wells Orders of magnitude Pressure variations Bottomhole flow End of the wellbore storage effect 37 Chapter 3 Skin Definition Infinitesimal skin 39 G. BOURDAROT 5

3 3.3 Finite thickness skin Effective radius r Generalization of the skin concept 43 INTERPRETATION METHODS 45 Introduction 47 Chapter4 Conventional interpretation methods Drawdown test Pressure buildup: Homer's method Pressure buildup: MDH method After varying flow rates Simplification of the flow rate history Buildup radius of investigation 66 Chapter 5 Type curves Introduction Gringarten type curves Interpretation method Using type curves during buildup 75 Chapter 6 The derivative Representation Properties of the derivative The derivative as diagnostic tool Analysis with type curves Direct interpretation by means of the derivative Conclusion 89 RESERVOIR BOUNDARIES 91 Introduction 93 Chapter 7 Linear sealing faults Description The method of images 96 6 G. BOURDAROT

4 7.3 Conventional interpretation method Type curves: the derivative r 100 Chapter 8 Channels Description of flows Linear flow ' Conventional interpretation Bounded channels Pressure buildup with varying flow rates Pressure derivative, type curves 110 Chapter 9 Intersecting faults Conventional analysis Type curves; pressure derivative 114 Chapter 10 Constant pressure boundary Conventional interpretation method Type curves; derivative 121 Chapter 11 Closed reservoir Producing well, pseudosteady-state regime Shut-in well, average pressure 131 Chapter 12 Productivity index Definition Productivity index during the infinite-acting period Productivity index during the pseudosteady-state flow Real and theoretical PI 143 RESERVOIR ASPECTS 145 Chapter 13 Naturally fractured reservoirs Geometry Porosity Capacity Permeability Matrix-fracture exchange: X 153 G.BOURDAROT NIEDERS. STAATS-U.UNIV.- BIBLICTHEK G0TTINGEN

5 13.6 Analysis of flows Choosing between the pseudosteady-state and the transient interporosity flow models Type curve analysis Type curves derivatives Two examples of interpretation in a fractured reservoir 175 Chapter 14 Two-layer reservoirs Introduction Description of a two-layer reservoir The Bourdet model Testing a two-layer reservoir 184 WELL ASPECTS 191 Chapter 15 Partial penetration wells Introduction Flow around a partial penetration well Radial flow at the perforations Spherical flow Radial flow over the whole net thickness Extrapolated pressure, average pressure Pressure derivative Ambiguous interpretation Comparison with core samples Partial perforation and fractured reservoirs 206 Chapter 16 Slanted wells Introduction Flows and skin factor for slanted wells Influence of permeability ariisbtropy 211 Chapter 17 Artificially fractured wells Description of the fracture Flows around an artificially fractured well. Conventional interpretation methods Type curves, the derivative Type curves Conclusion 231 G.BOURDAROT

6 Chapter 18 Horizontal wells Description of a horizontal well Flows around a horizontal well. Conventional interpretation methods Type curves, the derivative 239 Chapter 19 Injection wells Description of an injection well Description of flows Type curves and derivative The objectives of testing an injection well 248 FLUID ASPECTS 251 Chapter 20 Gas wells Pseudopressure Deviation from Darcy's law Interpretation of a gas well test Presentation of absolute open-flow potential tests Conventional AOFP tests Interpretation of AOFP tests: Houpeurt's method Interpretation of absolute open-flow potential tests: empirical method Other test procedures 274 Chapter 21 Multiphase flows Introduction Perrine method hypotheses Perrine's method Productivity index of an oil well producing under the bubble point; Vogel's equation 287 INTERFERENCES 291 Chapter 22 Interference tests Presentation, particulars Interpretation methods in a homogeneous reservoir 294 G. BOURDAROT

7 22.3 Interference tests in fractured reservoirs Influence of flow rate history r Skin and wellbore storage effect Objective of interference tests, two examples 306 Chapter 23 Pulse tests Presentation Interpreting pulse tests: the Kamal and Brigham method 315 Practical units 325 References 327 Index G. BOURDAROT