HORIZONTAL WELL

1. Increased exposure to the reservoir

2. Connect laterally discontinuous features

3. Changing the geometry of drainage

4. Extend field appraisal horizontally

 

Productivity Index = Hydrocarbon flow rate / p - pz (drawdown)

Rock Behavior:

The best direction to drill a horizontal well for optimum borehole stability is in the direction of the minimum horizontal insitu stress component.

 

Induced hydraulic fracture: always perpendicular to the minimum principal stress component

Natural fractures: perpendicular to the minimum principal stress component at the time the fracture was formed

Borehole breakout: Breakout aligns with horizontal stress directions

 

HOLE CLEANING

 

Indications of Cuttings Bed Buildup

1.      Decrease in cuttings volume at surface/ Decrease in mud consume

2.      Increased torque & drag (Not associated with hole geometry)

3.      Increased circulating pressure/ ECD

 

3 Pillars

1. Flow Rate for cuttings removal (Small cuttings more easily transported)

2. Rotary Speed (Avoid vibration / Minimum 1.5 RPM per inch of hole diameter to move cuttings)

3. Rheology

 

FORMATION DAMAGE

More exposure time during drilling operations

 

DIRECTIONAL SURVEYING

Tangential method

Radius of curvature method

Minimum curvature method (Current accepted)

Other methods

 

Geosteering: The ability to detect lithological and pore fluid changes before drilling them

Intercept Distance: 截距

 

Project Methodology

Phase 1: Database Assembly and Update; Shared Earth Model Creation

Phase 2: Macro-Well Planning in the Earth Model

Phase 3: Detailed Directional Engineering/Planning

Phase 4: Petrophysical Model Creation for Geosteering

Phase 5: Real-Time Geosteering Operations

Phase 6: Post-Well and Post-Pad Analysis

Back to Phase 1

 

HORIZONTAL COMPLETION GUIDELINES

 

1.      Reservoir rock & fluid characteristics

2.      Stability

3.      Isolation Needs

a)       Undesirable fluid production

b)       Stimulation

c)       Flow control

d)       Depleted fractures or sections

4.      Sand control

5.      Cost

 

HORIZONTAL WELL HYDRAULIC FRACTURING

 

New Issues Compared with Vertical Well:

1.      Fracture orientation is affected by well bore orientation

2.      Type of fracture (Longitudinal and Transverse)

3.      Isolation and limited entry to initialize fractures

4.      Number and spacing of fractures (efficiency of productivity)

5.      Complex fracture system in naturally fractured formation

 

Hydraulic Diagnostic Tools:

1.      Chemical Fracture Tracers

a)       Used to evaluate flowback and cleanup efficiency

b)       Mixed at a known concentration and injected throughout the frac fluid stages. Upon flowback, samples are collected and analyzed for tracer concentration

c)       Characteristics:

-        No react with other formation, tubular or frac fluids etc.

-        No degrade with temperature or time

-        Detectable at low concentrations

-        Environmentally safe to pump downhole

-        Soluble in water and do not concentrated upon leakoff

 

2.      Radioactive Tracers (Isotope, 同位素)

a)       Understand hydraulic fracture progression

3.      Production Logging

a)       Temperature Sensor

b)       Pressure Sensor

c)       Fluid Density

d)       Spinner

4.      Image & Sonic Logging

 

ACIDIZING OF HORIZONTAL WELLS

 

Matrix acidizing: near wellbore condition – skin

1.      In sandstone is very inefficient and should not be applied

2.      Carbonate can be acid stimulated successfully if designed right

3.      Formation heterogeneity is extremely important

 

Acidizing fracturing: reservoir contact – permeability