Forecasting Significant Incidents in Gas Fields

Test Case: Barnett Shale, Fort Worth, Texas

byJerry Lobdill, physicist and Ch. E.

(ret.)

One Picture is Worth...

Significant Incidents (SI) A US DOT term meaning an incident

involving any of: $50,000 in damage or more Fire Explosion Injury Death

The RRC collects mandatory reports of SI’s for the US DOT

Purpose of Study Use Significant Incident historical

data to quantify the risk associated with urban gas drilling and production.

Apply findings to the City of Fort Worth (Barnett Shale)

Barnett Shale Gas Well Density 2007

Proposed Statistic Average Significant Incident Rate

per 1000 gas wells per unit time. This is scalable to a field of any

size.

History of Barnett Shale Play Play covers about 15 counties First wells drilled in the northern

rural region in the 1990s By June 2008 there were 7766 wells First wells in Fort Worth area drilled

in 2001 As of last week 2008 a total of 1376

well permits had been issued in FW

Factors Affecting SI Rate No. producing wells Miles of gathering pipeline Population density Regulation Maintenance/Inspection Age of Field

Population Density vs SI Rate Certain kinds of human activity

increase the SI Rate above that experienced in rural settings.

The historical SI data available are mostly for non-urban areas.

Fort Worth has 2333 people/sq. mi. Our forecasts will be conservative.

The Effect of Regulation on SI Rate Regulations do not imply safety. They are the result of a tug of war

between profit and safety. Profit interests are strongest. Regulations are only as good as the

enforcement budget. Use modern TX RRC

Regulation/enforcement in this study.

Effect of Maintenance/Inspection, Age Regular inspection should

minimize SIs. Inspection without corrective

maintenance will not prevent SIs. As gas field ages maintenance and

inspection receive short shrift. Our forecasts will be conservative.

Wells and Pipelines in and Near Tarrant County, 2007

Analysis Summary There were 9 SI’s from 2004-2007

in the Barnett Shale. Statistical analysis shows Fort

Worth will have (conservatively) a “significant incident” about every 6 months on average when full production is achieved (3000 wells).

The Barnett Shale Data

Number of Incidents vs Number of Wells

Barnett Shale Incidents, 2004-2007

y = 5.45066E-04x + 4.47961E-01

R2 = 6.32528E-01

0

1

2

3

4

5

0 1000 2000 3000 4000 5000 6000 7000

No. Wells

Nu

mb

er o

f In

cid

ents

/ ye

ar

Mathematically Assuming only that the SIs are independent

events... The probability that there are exactly k SIs in a

period of t months when the average rate is SIs per month is given by the Poisson distribution.

The equation is

Simulated Timeline, 3000 Wells—One Replication

Maximum time between Significant Incidents for this replication is about 17.6 months.

Event Timeline, Poisson Process, Average rate =1/6

0

1

0 12 24 36 48 60 72 84 96 108 120 132 144 156

Number of months

SI Rate Implications for Fort Worth Property insurance against gas

damage will be mandatory. Home values will go down (for

sales, but not for taxes) PITI will escalate. Population will decrease. Taxes will go up. Bond ratings will decline.

In Fort Worth Today... High Impact drilling is routinely

permitted. For-profit gas companies are given

eminent domain power to seize private property for pipeline ROW.

City, State claim impotence.

Conclusions Drillers and their allies in local government

ignore the public safety aspects of shale bed gas drilling today.

The public cannot afford to accept this rosy view of life in an urban gas field.

As new shale bed field projects begin, citizens should use this analytical tool to forecast the SI rate and demand restriction of pipeline and drilling site locations to industrial zones.