### 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 wire line 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 ConfigurationWFL/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) Example of Multi - Finger Caliper Survey Multi -finger Imaging 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.