CONDUCTING A STRAY GAS INVESTIGATION AND THE USE OF DOWNHOLE VIDEOGRAPHY AS AN INVESTIGATION TOOL

Tom Tomastik, Geologist Ohio Division of Oil and Gas

Resources Management

STRAY GAS INVESTIGATIONS

Stray gas investigations need to be accomplished with the highest level of experience and expertise

Must evaluate all potential sources of methane

Complete review of local geologic and hydrogeologic conditions

THE INVESTIGATION

Sampling events and protocols

Chain-of-custody Water well construction Aquifer identification Geology Oil and gas development Oil and gas well

construction, cementing, and plugging practices

WATER SAMPLING AND PROTOCOLS

Most shale play development is requiring pre-drill water sampling events

Sampling protocols need to be developed and followed

Chain-of-custody Lab analysis Geochemistry

WATER WELL CONSTRUCTION

Any stray gas investigation must evaluate all water well records in the area

Evaluate water well construction

Look for historic hydrocarbon issues

AQUIFER IDENTIFICATION, GROUNDWATER FLOW, AND WATER LEVEL

MAPS It is critical to identify the

different types of aquifers you are dealing with

Determine localized groundwater flow

Create historic and current potentiometric surface maps (water level maps) to evaluate aquifer conditions

LOCAL GROUNDWATER FLOW

GEOLOGICAL EVALUATION

It is very important to accurately determine local geologic conditions

Create appropriate geologic maps and cross sections

Identify and map surface geologic features that may influence stray gas migration

GEOLOGIC CROSS SECTION

LOCAL GEOLOGIC FEATURES – MEASURING FRACTURE ORIENTATION

REVIEW OF OIL AND GAS DEVELOPMENT IN THE AREA

Evaluate historic oil and gas development, well construction, and plugging methods

Then review modern and current oil and gas activity in the area

OIL AND GAS WELL CONSTRUCTION, CEMENTING PRACTICES, AND PLUGGING

METHODS

Evaluate historic and current oil and gas well construction and cementing practices

Plugging and abandonment methods

Potential oil and gas legacy issues

INVESTIGATION OF A STRAY GAS COMPLAINT

Geologists must collect and evaluate information regarding site specific hydrogeologic and geologic frameworks to develop an understanding of stray gas migration

Evaluate potential sources, driving mechanisms, and migration pathways

DOWNHOLE VIDEOGRAPHY

Since January of 2004, the Ohio Division of Oil and Gas Resources Management has found downhole videography an extremely valuable tool in evaluating stray gas investigations

GEOVISION COLOR DOWNHOLE VIDEO CAMERA

First Division Geovision camera is 2” in diameter

Second generation camera purchased is a Nano and is only 1-1/4” in diameter stainless steel

Can go to 600 feet in water

COLLECTING DOWNHOLE VIDEO DATA

It is very important to collect downhole video data for geologic information, water well construction, and stray gas zones

DOWNHOLE VIDEOGRAPHY AS AN INVESTIGATION TOOL

Water well construction details Water well maintenance – bacteria issues Aquifer identification and depths Stratigraphy – identifying rock lithology Identifying stray gas zones and migration

pathways

WATER WELL CONSTRUCTION ISSUES

WATER WELL MAINTENANCE

AQUIFER IDENTIFICATION

LITHOLOGY

STRAY GAS ZONE

FRACTURE IDENTIFICATON

ABANDONED UNDERGROUND MINE

DOWNHOLE VIDEOGRAPHY HAS ASSISTED IN:

Defining local geologic structure Identifying stray gas migration pathways Developing stray gas migration strategies Documenting stray gas sources

DEFINING LOCAL GEOLOGIC STRUCTURE

Downhole video camera has the ability to identify lithology and accurately pick geologic formation tops in water wells

Able to check accuracy of water wells records and correct errors

Can use this information to map local shallow bedrock geologic structures

LOCAL GEOLOGIC STRUCTURE

IDENTIFYING STRAY GAS SOURCES

The downhole video camera is able to accurately identify sources of stray gas in the water well borehole

Stray gas may not be readily apparent in water wells under static conditions

Water wells need to be pumped to drawdown the static water well to increase gas movement

By drawing the water level down, you are removing the hydrostatic weight of the water in the well, thus releasing more methane into the wellbore

DRAWDOWN OF WATER WELL

DIFFERENT SOURCES OF STRAY GAS IN WATER WELLS

Naturally-occurring stray gas in non-commercial quantities in shallow bedrock aquifers

Stray gas from exposed coal beds Stray gas from drilling into abandoned

underground coal mines Legacy oil and gas wells Bad cement jobs or well construction on current

oil and gas well development

NATURALLY-OCCURRING STRAY GAS IN SHALLOW BEDROCK

STRAY GAS FROM EXPOSED COAL SEAM

LEGACY OIL AND GAS PROBLEMS

CURRENT OIL AND GAS STRAY GAS PROBLEM – BAD CEMENT JOB

ON PRODUCTION CASING

AND THEN STRAY GAS PROBLEMS CAN LEAD TO THIS!

CONCLUSIONS

Downhole videography has played a critical role in assisting stray gas investigations in Ohio

Helps to identify stray gas sources Assists to determining stray gas migration

pathways Has been the main tool used in resolving

stray gas investigations

RECOMMENDATIONS

With continued shale play development, it is extremely important for regulatory agencies and the oil and gas industry to conduct through and professional stray gas investigations

It is crucial that we rely on good science to thoroughly explain the different sources of stray gas and dispel the myth that stray gas incidents are all directly related to hydraulic fracturing and shale play development

NOTHING LIKE COMING TO A COMPLETE STOP! QUESTIONS?