Hydraulic refracturing: theory and models

HYDRAULIC REFRACTURING: THEORIES & MODELS

JERSON ORLANDO BECERRA
DANIEL URIBE VILLEGAS

NATIONAL UNIVERSITY OF COLOMBIA MEDELLIN
FACULTY OF MINAS
SCHOOL OF PROCESSES AND ENERGY
MEDELLIN
SEMESTER 02 / 2010
HYDRAULIC REFRACTURING: THEORIES & MODELS

JERSON ORLANDO BECERRA
DANIEL URIBE VILLEGAS

Thesis submitted to obtain a degree in:
Bachelor science in PetroleumEngineering

Director
GUILLERMO ARTURO ALZATE ESPINOSA

NATIONAL UNIVERSITY OF COLOMBIA
FACULTY OF MINAS
SCHOOL OF PROCESSES AND ENERGY
MEDELLIN
SEMESTER 02 / 2010

Abstract

Since the decade of 20s when charges of dynamite were commonly exploited into the wells to increase the production oil rates, the well stimulation has become a solution to increase the production oil rate, overcomethe formation damage, or even as alternative to produce an unconventional reservoir with a very low permeability.
Refracture treatments are often applied in wells that have previously been fractured. The performance of these treatments has been observed to be highly variable with some wells underperforming while others are restored to initial production rates. A procedure for the selection ofcandidate wells that will improve the odds of a successful treatment is needed. This work presents guidelines based on a poroelastic model that allow an operator to select candidate wells, choose the timing of the refracture operation in the life of the well, consult history and models that rules the operation, and finally some field practices and experience.
INDEX
Abstract 3
LIST OF FIGURES. 51. History of hydraulic fracture 6
1.1 The beginning 6
1.2 Basic fracture modeling 6
1.3 Hydraulic fracture modeling 8
1.4 Reservoir response to a fracture 9
1.5 Three generations 11
1.5.1 The first generation: damage bypass 11
1.5.2 The second generation: massive fracturing 11
1.5.3 The third generation: tip-screenout treatments 11
1.6 Re-fracturing 12
2. Models andsensible variables 12
2.1 Hydraulic fracturing models (classics) 12
2.1.1 PKN 12
2.1.2 KGD 14
2.1.3 Net fracturing pressure 14
2.1.4 Dimensionless Fracture Capacity (CFD). 15
2.2 Refracturing 2D model 16
2.2.1 Reorientation Mechanism 16
2.2.2 Dimensionless Parameters 2D 17
2.2.3 Isotropic Point 18
2.2.4 Dimensionless toughness and refracture path. 19
2.3 Refracturing 3D models. 202.3.1 Dimensionless parameters 3D 20
2.4 Sensible variables. 21
2.4.1 Shear Modulus Contrast Effect 21
2.4.2 Production Rate Sensitivity 21
2.4.3 Deviatoric Stress Sensitivity 22
2.4.4 Viscosity 22
2.4.5 Proppant selection 22
2.4.6 Sand concentration 22
2.4.7 Effect of Pay Zone Thickness 3D 23
3. Field cases 23
3.1. Clinton sand formation 24
3.1.1 Case study 1. Margaretmiller #3. 24
3.1.2 Case study 2. L. H. Luman#2. 24
3.1.3 Case study 3. Florence coble#2. 24
3.1.4 Case study 4. James coackley#1. 25
3.2. Refracs in the Oak hill (Cotton valley) field 25
3.2.1 Well 10. 25
3.2.2 Well 4. 26
3.2.3 Well 5. 26
3.2.4 Well 8. 27
3.3. North Westbrook Unit 29
3.4. Devonian formation, Crane County, Texas 31
3.4.1 Well 1. 33
3.4.2 Well 2. 33
3.4.3 Well3. 33
3.5. Richland count, Montana 33
3.5.1 Refracture procedure 34
3.5.3 Post-Refracture Treatment Performance. 38
4. Well candidates & methodology selection 40
4.1. Completion Efficiency (CE) 40
4.2. Comprehensive approach and key factors to restimulation candidate identification 41
4.3. Restimulation criteria and guidelines 41
4.3.1 Evaluation of the actual performance 424.4. Optimization of hydraulic fracture design - candidate selection 43

LIST OF FIGURES.
Fig1.1. KGD fracture. 9
Fig1.2. PKN fracture. 9
Fig 1.3. McGuire and Sikora (1960) curves for folds of increase (J/Jo) in a bounded reservoir of area A (acres). 10
Fig 2.1. log-Iog plot developed after Prats of the steady-state folds of increase versus Relative Conductivity 15
Fig 2.2....