EPA Hydraulic Fracturing Workshop, March 10-11, 2011

Arlington, VA 22202

Theme 3: Mechanical Integrity

Pre & Post Well Integrity Methods for Hydraulically 

Fractured/Stimulated Wells

Talib Syed, P.E., TSA, Inc.

EPA HF Workshop March 10-11, 2011 

Arlington, VA TSA, Inc.
Courtesy, API 2009 2
Casing Setting and Design

• NORSOK 2004 lists factors to consider in casing design

- Casing must be designed to withstand tensile, burst and 

collapse loads

- Use safety factors (wear and tear) for casing 

deterioration 

- Axial and bending forces and shock load

- Casing design should also consider buckling, piston and 

thermal effects

• For refracturing candidates, eliminate any well as a 

candidate if there is any indication of gas migration to 

surface

EPA HF Workshop March 10-11, 2011 

Arlington, VA TSA, Inc.
Cementing Systems for Production/Injection Wells

• Portland cements generally used for oilfield 

service 

• Use of non-Portland specialty cements need 

additional steps in planning and execution phases

• Quality of the cementing operation critical for 

wellbore integrity – thoroughly circulate, effects 

of well deviation, use centralizers, SCP (sustained 

casing pressures) and causes

• Potential pathways for escape of fluids up-hole 

EPA HF Workshop March 10-11, 2011 

Arlington, VA TSA, Inc.
Cement Evaluation

• Two classes of sonic logging tools: (1) sonic (CBL/VDL) or SBT and (2) 

ultrasonic (USIT/CAST-V)

• Acoustic cement bond logs do not measure hydraulic seal but instead 

measure loss of acoustic energy as it propagates through casing. This loss 

of energy is related to the fraction of casing perimeter covered by cement

• The Ultrasonic Imaging Tool (USIT) is a continuously rotating pulse-echo 

type tool with nearly 100% coverage of the casing wall. The transducer 

(“sensor”) rotates, emitting and receiving signals reflected back from the 

casing wall. Preferable to run CBL with it for overall well integrity picture

• The Segmented Bond Tool (SBT) measures the quality of cement 

effectiveness, vertically and laterally around the circumference of the 

casing. The SBT measures 6 segments around the pipe and uses high 

frequency steered transducers mounted on 6 pads. Each of 6 motorized 

arms positions a transducer and receiver against the casing wall. SBT is 

usually run with VDL

EPA HF Workshop March 10-11, 2011 

Arlington, VA TSA, Inc.
Ultrasonic Imager (a) tool design and (b) transducer position 

(Smolen, 1996)

EPA HF Workshop March 10-11, 2011 

Arlington, VA TSA, Inc.
Example USIT Log 

EPA HF Workshop March 10-11, 2011 

Arlington, VA TSA, Inc.
Example SBT/VDL log 

EPA HF Workshop March 10-11, 2011 

Arlington, VA TSA, Inc.
EPA HF Workshop March 10-11, 2011 

Arlington, VA TSA, Inc.

Factors that Affect Cement 

Log Quality

• Micro-annulus, eccentralization, logging tool 

centralization, fast formations, lightweight cement, 

and cement setting time

• Good practice to pressure test the shoe after drilling 

out the surface and long string casing strings (FIT) and 

confirm zonal isolation at the casing shoe
• Internal MIT – Pressure test

• External MIT – confirm all fluids contained within wellbore and no 

upward flow behind casing, cement evaluation as discussed earlier 

– USIT/SBT-VDL/CAST-V and quality of cement job. Use of fluid 

confinement/channel logs: OA/WFL, RTS, Borax PNL, Temperature, 

Carbon Oxygen (CO) 

• Pressure tests at casing shoe (FIT/LOT/CIT) to verify zonal isolation

• Multi-finger caliper (MIT) surveys and magnetic thickness tools 

(MTT) to assess both internal and external condition of the tubular 

from corrosion and/or erosion impacts

Wellbore/Mechanical Integrity Methods 

EPA HF Workshop March 10-11, 2011 

Arlington, VA TSA, Inc.
Zonal Isolation and Casing Shoe Integrity

 Placement of cement completely around the casing and at the proper height 

(cement top) above the casing shoe is critical in achieving zone isolation and 

integrity

 Pressure tests to verify isolation at casing shoe include Formation Integrity 

Tests (FIT) (also called LOT – leakoff test) and Casing Integrity Tests (CIT). 

Pressure up inside the casing until pressure at shoe exceeds the maximum 

hydrostatic pressure expected at that point during subsequent drilling 

operations. Failure at shoe is usually due to contamination (from either original 

drilling mud or from displacement fluid) and is a result of poor cementing 

techniques rather than poor quality cements

EPA HF Workshop March 10-11, 2011 

Arlington, VA TSA, Inc.
Oxygen Activation/Water Flow Log/ Hydrolog/Spectra Flow Log

- Used to detect water flow or channels behind casing

- WFL is a dual burst TDT with a modified pulse sequence

- The WFL measurement technique and a WFL run on an injection well is 

shown.

Borax- PNL Log 

- Compares passes run before and after pumping a borax solution dissolved in 

warm water. A PNL indicates a significant Sigma value when boron is present. An 

example log run in Alaska is shown.

Ultrasonic Leak Detection Logs

- Can detect very small leaks, through multiple strings and can be run on wireline or on slick-line in memory mode.

EPA HF Workshop March 10-11, 2011 

Arlington, VA TSA, Inc.
EPA HF Workshop March 10-11, 2011 

Arlington, VA TSA, Inc.

Example Borax-PNL Log 

Ultrasonic Leak Detection

Tool Configuration
WFL/OA Log Measurement 

Technique (Smolen, 1996)

WFL Run on Injection Well

EPA HF Workshop March 10-11, 2011 

Arlington, VA TSA, Inc.
Magnetic Thickness 

Tool (MTT)

Multi-finger Imaging Example of Multi-Finger Caliper Survey 

Tool (MIT)

EPA HF Workshop March 10-11, 2011 

Arlington, VA TSA, Inc.
Thank You

Questions?

EPA HF Workshop March 10-11, 2011 

Arlington, VA TSA, Inc.