AIPG Marcellus Shale Hydraulic Fracturing Conference

Discrete Fracture Network Models of Natural and Hydraulic FracturesNatural and Hydraulic Fractures

William Dershowitz and Thomas DoeWilliam Dershowitz and Thomas DoeGolder Associates

Redmond, WA

Talk Overview

Di t F t N t k M d l Discrete Fracture Network Models Stimulation of Natural Fractures by

Hydraulic FracturesHydraulic Fractures Microseismics and Critical Stress

B ildi d A l i H d f t Building and Applying a Hydrofracture DFN Model

Discrete Fracture Generation

O i t ti

Stochastic Inputs & Deterministic Features

Orientation

Si eSize

Intensity

kh

Defining the Fracture Permeability & Aperture

Fracture Set 1kh Storage aperture can be defined from

image logs and conventional logs;

Fracture Set 2kh

image logs and conventional logs; Hydraulic aperture needs to be defined

with respect to well tests and interference observations;observations;

Permeability defined from: Well test analysis;

A l i f d l d t Analysis of mud loss data; Dynamic simulation.

The stochastic nature of the DFN h th t th t i t fapproach means that the uncertainty of

these properties can be addressed.

Principal Stress & Hydraulic Fractures

Arrows show direction of maximum and minimum principalminimum principal stress.

Hydraulic fractures arehmin

Hydraulic fractures are represented in model as pink fractures.

This model is then combined with the natural fractures hmaxnatural fractures.

Mohr Circle Description of Stress

Effective Stress and Pore Pressure

Fracture Types

H d li F t Hydraulic FractureCreated by fracturing process

Inflated Natural Fractures Rough, Shear-Dilated Fractures Smooth, Non-Dilated Fractures Unaffected Fractures

Micro-Seismicity

Inflated Fractures

maxmax

Inflated Natural Fractures

Hydraulic Fracture

Account for Most Fluid

Roughness and Permeability

Rough Fracture Smooth FractureRough Fracture Smooth Fracture

roughness angle,

Significant T Increase Minor T Increase or Decrease

Natural Fracture Stimulation

Natural Fracture Stimulation

Simulation of Hydraulic Fracture by FracMan

Create Natural Fracture Network

Superpose grid with stress Superpose grid with stress and rock property data

Grow Hydrofracture Sneddon elastic crack Sneddon elastic crack

solution Balance Injection and

Hydrofrac VolumesInduced Hydraulic FracturePropped Natural FracturesNon-Inflated Critically-Stressed

Hydrofrac Volumes Modify Connected Natural

Fractures According to Type Non-Inflated Critically-Stressed

Natural FracturesType

Visualize Microseismicity on Critically Stressed Fractures

DFN example

0.01

0.1

1

10

orm

aliz

ed N

umbe

r

Fracture size data from seismic, well and outcrop data

Building the well scale DFN model up

Orientation data from Image logs

0.0001

0.001

1 10 100 1000 10000

Trace Length (meters)

No

g pfrom well data and geological understanding

from Image logs

Intensity data from Image logsage ogs

Area 2.8mi x 2.1mi

Frac Stage 1

Hydraulic fracture & inflated natural fractures

Shown without DFN

Material Balance Includes Hydrofrac and Inflated Fractures

Controls meshing size of fractures for volume and critical stress calculations

Controls pressure decay away from wellbore

Controls updating of the fracture apertures and resultant transmissivity

Determines the perm. improvement for the fractures

Frac Stage 1

Hydraulic fracture & critically stressedcritically stressed natural fractures (inflated & non-inflated)

Shown without natural fractures

Frac Stages 1-3

Stage 2

Stage 1

Hydraulic fracture system (Hydraulic fracture plus inflated natural f t )Stage 1 fracture)

Stage 2St 1

Stage 3g

Stage 1

Hydraulic fracture without inflated natural fractures

Frac Stages 1-3

Stage 2 Stage 1 Hydraulic fracture system (Hydraulic fracture plus critically t d f t i fl t d dstressed fractures - inflated and

noninflated)

Stage 2 Stage 1Stage 3

g g

Shown without inflated natural fractures

Modeling Microseismicity

Modeled MicroseismicMeasured Microseismic

Modeled and Measured

Modeled Microseismic with hydraulic fracture

Modeled and Measured Microseismic

Application

Calibrate model to Calibrate model to microseismic responses

Superpose “convex hull” to determine tributary drainage area

Apply to predict fracture Apply to predict fracture interactions in reservoir where there are no

i i i d tmicroseismic data