Fracture Model Comparisons

This is a preliminary inventory and subjective comparison of fracturing models and their use and /or adaptability for PWRI. Additional models are being evaluated.

Summary of PWRI Model Capabilities

Capabilities	BPOPE	BP Spreadsheet	DE&S Model	Elf Model	Shell/ Maersk	Perkins and Gonzalez	PWFRAC	TerraFrac	Other Models
Wellbore Temperature Profile				3
Matrix Injection Before Fracturing	3	3	3	3
Thermal Stresses	3	3	3	3	3	3	3	3	3
Poroelastic Stresses	3	3	3	3	3	3	3	3	3
2-D Fracturing Model		3		3	3	3	3
P3D Fracturing Model			3
3-D Fracturing Model	3							3	3
Fully Coupled with Reservoir Model	3
Partially Coupled with Reservoir Model		3	3			3	3	3	3
Not Coupled with Reservoir Model				3	3
Multiple-Layer Formation	3	3	3					3	3
Variable Saturation in the Invaded Zone	3		3
Two Phase Flow	3		3	3
Changing Viscosity as a Function of Temperature	3	3	3	3			?	3	3
Secondary Fractures Considered						3
Damage	3	3	3	3	?	3	3
Internal formation damage considered	?	?				3
External Filter Cake Considered	3	3				3	3

Comparison of the Fracture Mechanics Engines

Model List	Fracturing Model			Fracture Criterion
	2D	P3D	3D
BPOPE			3	S.I.F.
BP Spreadsheet	3			S.I.F.
DE&S Model		3		Stress(?)
Elf Model	3			Stress
Shell/Maersk Model	3			S.I.F.
Perkins and Gonzalez	3			Stress
PWFRAC	3			S.I.F.(?)
TerraFrac			3	S.I.F.

  Case studies show that fracture height growth can be substantial in many cases (see for example, the cases presented by Elf for an offshore field in West Africa, and cases presented by Maersk for the Dan field). P3D or 3D fracturing models are required to simulate these PWRI induced fractures.

 : Fracture criterion based on fracture toughness and stress intensity factor is preferred as non-linear effects such as in soft formations can be modeled by adopting results from non-linear fracture mechanics.

  The intrinsic equations for the three-dimensional fracturing models in the BPOPE and TerraFrac are the same.

Comparison of the Reservoir Model

Model List	Coupled Reservoir Model			Two-Phase Flow	Saturation Computed	Temperature Computed
	No	Partially	Fully
BPOPE			3	3	3	3
BP Spreadsheet		3
DE&S Model			3	3	3	3
Elf Model		3
Shell/Maersk Model		3
Perkins and Gonzalez		3
PWFRAC		3
TerraFrac
MFRAC (Review in Progress)
VISAGE (Review in Progress)
WID (Review in Progress)

  The reservoir model in the BPOPE is a three-dimensional finite difference model for heat transfer and two-phase fluid flow.

  The reservoir model in the Duke model is a one-dimensional (perpendicular to the fracture face) finite difference model for heat transfer and two-phase fluid flow.

  Coupling between fracturing simulation and reservoir simulation is necessary in PWRI modeling.

Comparison of Fundamental Damage

Model List	Internal Damage	External Filter Cake	Compound Cake	Dynamic Filter Cake
BPOPE			3
BP Spreadsheet	?	?	3
DE&S Model	3	3		3
Elf Model			3
Shell/Maersk Model
Perkins and Gonzalez		3	3
PWFRAC	3	3		3
TerraFrac
MFRAC (Review in Progress)
VISAGE (Review in Progress)
WID (Review in Progress)

  Few models are available to characterize formation damage, both internal and external, due to solids and oil in water.

  When the velocity in the fracture width is sufficiently high, material on the surface of the filter cake can be dislodged and swept along the fracture (often known as dynamic filtration).

Model Descriptions

BPOPE	BP Spreadsheet
Duke Engineering Model	Elf Model
Shell / Maersk	Perkins and Gonzalez
PWFRAC	TerraFrac
Other Models

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