tools for assessing stray gas migration: a case study in ... · tools for assessing stray gas...
TRANSCRIPT
![Page 1: Tools for Assessing Stray Gas Migration: A Case Study in ... · Tools for Assessing Stray Gas Migration: A Case Study in Pennsylvania Seth Pelepko, P.G. & Stew Beattie PADEP: Bureau](https://reader034.vdocuments.net/reader034/viewer/2022050117/5f4de6a342fb636289063920/html5/thumbnails/1.jpg)
Tools for Assessing Stray Gas Migration: A Case Study in
Pennsylvania
Seth Pelepko, P.G. & Stew Beattie
PADEP: Bureau of Oil and Gas Planning & Program Development
Stray Gas Incidence & Response Forum
July 25, 2012
Cleveland, OH
![Page 2: Tools for Assessing Stray Gas Migration: A Case Study in ... · Tools for Assessing Stray Gas Migration: A Case Study in Pennsylvania Seth Pelepko, P.G. & Stew Beattie PADEP: Bureau](https://reader034.vdocuments.net/reader034/viewer/2022050117/5f4de6a342fb636289063920/html5/thumbnails/2.jpg)
• Defining Background in Absence of Pre-Drill Samples: A Multiple Regression Model
• Transitioning from a One-Dimensional Analysis to a Three-Dimensional Analysis: Evaluating Data Trends and Building a 3D Site Conceptual Model
• GIS Applications: Topographic Position Index (TPI), Surface Modeling, and the ArcScene Environment
• Lessons Learned and Improvements Moving Forward
Presentation Outline
![Page 3: Tools for Assessing Stray Gas Migration: A Case Study in ... · Tools for Assessing Stray Gas Migration: A Case Study in Pennsylvania Seth Pelepko, P.G. & Stew Beattie PADEP: Bureau](https://reader034.vdocuments.net/reader034/viewer/2022050117/5f4de6a342fb636289063920/html5/thumbnails/3.jpg)
Dependent Variable: Predrill Methane for Years Three and Four (n = 307) Add %’s
Defining Background in Absence of Pre-Drill Samples: A Multiple Regression Model
Site Size: Background Area: 172 sq. mi. Stray Gas Site: 10.5 sq. mi.
(81.0%)
(9.0%)
(1.0%)
(2.0%)
(6.5%)
(0.5%)
![Page 4: Tools for Assessing Stray Gas Migration: A Case Study in ... · Tools for Assessing Stray Gas Migration: A Case Study in Pennsylvania Seth Pelepko, P.G. & Stew Beattie PADEP: Bureau](https://reader034.vdocuments.net/reader034/viewer/2022050117/5f4de6a342fb636289063920/html5/thumbnails/4.jpg)
Independent Variables Considered
• Surface Elevation
• Bottomhole Elevation
• Topographic Position Index (TPI)
• Gas Well Distribution
• Gas Show Density (0 to 500 feet and 0 to 1000 feet)
• Depth to Tully
• Longitude
• Latitude
• % Sand (0 to 500 feet and 0 to 1000 feet)
• Sample Date
• Gas well production for first period of reporting
Defining Background in Absence of Pre-Drill Samples: A Multiple Regression Model
![Page 5: Tools for Assessing Stray Gas Migration: A Case Study in ... · Tools for Assessing Stray Gas Migration: A Case Study in Pennsylvania Seth Pelepko, P.G. & Stew Beattie PADEP: Bureau](https://reader034.vdocuments.net/reader034/viewer/2022050117/5f4de6a342fb636289063920/html5/thumbnails/5.jpg)
Surface Elevation and Bottomhole Elevation (n = 307)
Defining Background in Absence of Pre-Drill Samples: A Multiple Regression Model
![Page 6: Tools for Assessing Stray Gas Migration: A Case Study in ... · Tools for Assessing Stray Gas Migration: A Case Study in Pennsylvania Seth Pelepko, P.G. & Stew Beattie PADEP: Bureau](https://reader034.vdocuments.net/reader034/viewer/2022050117/5f4de6a342fb636289063920/html5/thumbnails/6.jpg)
Topographic Position Index (TPI) (USGS 10 m DEM) (Weiss, 2001)
Defining Background in Absence of Pre-Drill Samples: A Multiple Regression Model
![Page 7: Tools for Assessing Stray Gas Migration: A Case Study in ... · Tools for Assessing Stray Gas Migration: A Case Study in Pennsylvania Seth Pelepko, P.G. & Stew Beattie PADEP: Bureau](https://reader034.vdocuments.net/reader034/viewer/2022050117/5f4de6a342fb636289063920/html5/thumbnails/7.jpg)
Gas Well Distribution (n = 245)
Defining Background in Absence of Pre-Drill Samples: A Multiple Regression Model
![Page 8: Tools for Assessing Stray Gas Migration: A Case Study in ... · Tools for Assessing Stray Gas Migration: A Case Study in Pennsylvania Seth Pelepko, P.G. & Stew Beattie PADEP: Bureau](https://reader034.vdocuments.net/reader034/viewer/2022050117/5f4de6a342fb636289063920/html5/thumbnails/8.jpg)
Gas Show Density (0 to 500 feet, n = 89; and 0 to 1000 feet, n = 122)
Defining Background in Absence of Pre-Drill Samples: A Multiple Regression Model
![Page 9: Tools for Assessing Stray Gas Migration: A Case Study in ... · Tools for Assessing Stray Gas Migration: A Case Study in Pennsylvania Seth Pelepko, P.G. & Stew Beattie PADEP: Bureau](https://reader034.vdocuments.net/reader034/viewer/2022050117/5f4de6a342fb636289063920/html5/thumbnails/9.jpg)
Depth to Tully Limestone (n = 229)
Defining Background in Absence of Pre-Drill Samples: A Multiple Regression Model
N-S Extent of Water Supplies
N-S Extent of Gas Wells
A (S) A’ (N)
meters
met
ers
![Page 10: Tools for Assessing Stray Gas Migration: A Case Study in ... · Tools for Assessing Stray Gas Migration: A Case Study in Pennsylvania Seth Pelepko, P.G. & Stew Beattie PADEP: Bureau](https://reader034.vdocuments.net/reader034/viewer/2022050117/5f4de6a342fb636289063920/html5/thumbnails/10.jpg)
Depth to Tully Limestone (n = 229)
Defining Background in Absence of Pre-Drill Samples: A Multiple Regression Model
A (S) A’ (N)
meters
met
ers
?
?
![Page 11: Tools for Assessing Stray Gas Migration: A Case Study in ... · Tools for Assessing Stray Gas Migration: A Case Study in Pennsylvania Seth Pelepko, P.G. & Stew Beattie PADEP: Bureau](https://reader034.vdocuments.net/reader034/viewer/2022050117/5f4de6a342fb636289063920/html5/thumbnails/11.jpg)
Longitude and Latitude (n = 307)
Defining Background in Absence of Pre-Drill Samples: A Multiple Regression Model
S
W E
N
![Page 12: Tools for Assessing Stray Gas Migration: A Case Study in ... · Tools for Assessing Stray Gas Migration: A Case Study in Pennsylvania Seth Pelepko, P.G. & Stew Beattie PADEP: Bureau](https://reader034.vdocuments.net/reader034/viewer/2022050117/5f4de6a342fb636289063920/html5/thumbnails/12.jpg)
% Sand (0 to 500, n = 192; and 0 to 1000 feet, n = 192)
Defining Background in Absence of Pre-Drill Samples: A Multiple Regression Model
![Page 13: Tools for Assessing Stray Gas Migration: A Case Study in ... · Tools for Assessing Stray Gas Migration: A Case Study in Pennsylvania Seth Pelepko, P.G. & Stew Beattie PADEP: Bureau](https://reader034.vdocuments.net/reader034/viewer/2022050117/5f4de6a342fb636289063920/html5/thumbnails/13.jpg)
Model Results: Under-Predicting Methane
Defining Background in Absence of Pre-Drill Samples: A Multiple Regression Model
![Page 14: Tools for Assessing Stray Gas Migration: A Case Study in ... · Tools for Assessing Stray Gas Migration: A Case Study in Pennsylvania Seth Pelepko, P.G. & Stew Beattie PADEP: Bureau](https://reader034.vdocuments.net/reader034/viewer/2022050117/5f4de6a342fb636289063920/html5/thumbnails/14.jpg)
Model Results (Stepwise Regression)
• Most important variables for predicting dissolved methane are TPI (X1), latitude (X2), and bottomhole elevation (X3)
• Regression equation is:
ln(methane concentration + 1) = -130.923 - 1.192(ln(TPI+300) + 3.323(latitude) - 0.001(bottomhole elevation)
• Model was statistically significant and no assumptions were violated
• Goodness-of-fit was less than desirable – only 36% of variance explained
Where do we go from here?
• Consider only confirmed thermogenic methane
• Consideration of other parameters or models (non-linear)
• Improved quality control/consistency for existing parameters
Conclusion:
• If 36% of variance can be explained with limited time and resources, there seems to be potential with this approach
Defining Background in Absence of Pre-Drill Samples: A Multiple Regression Model
![Page 15: Tools for Assessing Stray Gas Migration: A Case Study in ... · Tools for Assessing Stray Gas Migration: A Case Study in Pennsylvania Seth Pelepko, P.G. & Stew Beattie PADEP: Bureau](https://reader034.vdocuments.net/reader034/viewer/2022050117/5f4de6a342fb636289063920/html5/thumbnails/15.jpg)
• 1D: Simple linear regression model to examine dissolved- and free-phase methane time-series trends
• 2D: Shallow groundwater quality spatial and temporal trends
• 3D: Integrating gas well construction and MIT data with subsurface structure, water quality trends, and the time dimension
Transitioning from a One-Dimensional Analysis to a Three-Dimensional Analysis: Evaluating Data Trends and Building a 3D Site Model
![Page 16: Tools for Assessing Stray Gas Migration: A Case Study in ... · Tools for Assessing Stray Gas Migration: A Case Study in Pennsylvania Seth Pelepko, P.G. & Stew Beattie PADEP: Bureau](https://reader034.vdocuments.net/reader034/viewer/2022050117/5f4de6a342fb636289063920/html5/thumbnails/16.jpg)
![Page 17: Tools for Assessing Stray Gas Migration: A Case Study in ... · Tools for Assessing Stray Gas Migration: A Case Study in Pennsylvania Seth Pelepko, P.G. & Stew Beattie PADEP: Bureau](https://reader034.vdocuments.net/reader034/viewer/2022050117/5f4de6a342fb636289063920/html5/thumbnails/17.jpg)
Affordable and Accessible Tools:
• Topographic Position Index (TPI)
• Interpolation
– Natural Neighbor
– Kriging
• 3D Modeling and ArcScene
GIS Applications
![Page 18: Tools for Assessing Stray Gas Migration: A Case Study in ... · Tools for Assessing Stray Gas Migration: A Case Study in Pennsylvania Seth Pelepko, P.G. & Stew Beattie PADEP: Bureau](https://reader034.vdocuments.net/reader034/viewer/2022050117/5f4de6a342fb636289063920/html5/thumbnails/18.jpg)
Valley vs. Ridges
• Is there a methodology for exploring variability in the concentration of methane as a function of location, i.e., in valleys versus ridges, and how do we classify these zones?
GIS Applications
![Page 19: Tools for Assessing Stray Gas Migration: A Case Study in ... · Tools for Assessing Stray Gas Migration: A Case Study in Pennsylvania Seth Pelepko, P.G. & Stew Beattie PADEP: Bureau](https://reader034.vdocuments.net/reader034/viewer/2022050117/5f4de6a342fb636289063920/html5/thumbnails/19.jpg)
Topographic Position Index (TPI)
• The topographic position index reflects the difference in elevation between a focal cell and all cells in the neighborhood
• Geospatial tool developed by Andrew Weiss in 2001
GIS Applications
![Page 20: Tools for Assessing Stray Gas Migration: A Case Study in ... · Tools for Assessing Stray Gas Migration: A Case Study in Pennsylvania Seth Pelepko, P.G. & Stew Beattie PADEP: Bureau](https://reader034.vdocuments.net/reader034/viewer/2022050117/5f4de6a342fb636289063920/html5/thumbnails/20.jpg)
TPI
• Positive values indicate the cell is higher than its average surroundings while negative values mean it is lower
GIS Applications
![Page 21: Tools for Assessing Stray Gas Migration: A Case Study in ... · Tools for Assessing Stray Gas Migration: A Case Study in Pennsylvania Seth Pelepko, P.G. & Stew Beattie PADEP: Bureau](https://reader034.vdocuments.net/reader034/viewer/2022050117/5f4de6a342fb636289063920/html5/thumbnails/21.jpg)
Defining a Surface
• Interpolation
– Estimating values within the range of available data
• Extrapolation
– Predicting values of locations outside the range of available data
GIS Applications
![Page 22: Tools for Assessing Stray Gas Migration: A Case Study in ... · Tools for Assessing Stray Gas Migration: A Case Study in Pennsylvania Seth Pelepko, P.G. & Stew Beattie PADEP: Bureau](https://reader034.vdocuments.net/reader034/viewer/2022050117/5f4de6a342fb636289063920/html5/thumbnails/22.jpg)
Interpolation: Natural Neighbor
• Natural Neighbor interpolates a value based on the closest subset of samples and weights them based on their proportionate area to the value being interpolated (Sibson,1981)
GIS Applications
![Page 23: Tools for Assessing Stray Gas Migration: A Case Study in ... · Tools for Assessing Stray Gas Migration: A Case Study in Pennsylvania Seth Pelepko, P.G. & Stew Beattie PADEP: Bureau](https://reader034.vdocuments.net/reader034/viewer/2022050117/5f4de6a342fb636289063920/html5/thumbnails/23.jpg)
• Kriging is an advanced, statistically-based procedure that estimates spatial variables and predicts surface trends using a technique in which the surrounding measured values are weighted to derive a predicted value for an unmeasured location (ESRI, 2012)
– Semivariogram: allows examination of spatial relationships between measured points
– Provides Cross-Validation: “how well” the model predicted unknown values
GIS Applications
![Page 24: Tools for Assessing Stray Gas Migration: A Case Study in ... · Tools for Assessing Stray Gas Migration: A Case Study in Pennsylvania Seth Pelepko, P.G. & Stew Beattie PADEP: Bureau](https://reader034.vdocuments.net/reader034/viewer/2022050117/5f4de6a342fb636289063920/html5/thumbnails/24.jpg)
3D Modeling and the ArcScene Environment
• The 3D environment permits visualization of a complex subsurface geological problem, e.g., stray gas migration
• By converting data to or compiling it in a suitable format it becomes easy to integrate surface and subsurface data to get a more complete picture
GIS Applications
![Page 25: Tools for Assessing Stray Gas Migration: A Case Study in ... · Tools for Assessing Stray Gas Migration: A Case Study in Pennsylvania Seth Pelepko, P.G. & Stew Beattie PADEP: Bureau](https://reader034.vdocuments.net/reader034/viewer/2022050117/5f4de6a342fb636289063920/html5/thumbnails/25.jpg)
3D Modeling and the ArcScene Environment
• ArcScene is a 3D visualization application that allows you to view GIS data in three dimensions (ESRI 2012)
GIS Applications
![Page 26: Tools for Assessing Stray Gas Migration: A Case Study in ... · Tools for Assessing Stray Gas Migration: A Case Study in Pennsylvania Seth Pelepko, P.G. & Stew Beattie PADEP: Bureau](https://reader034.vdocuments.net/reader034/viewer/2022050117/5f4de6a342fb636289063920/html5/thumbnails/26.jpg)
Lessons Learned and Improvements Moving Forward
A Proactive Approach and Progressive Thinking Matters • Improvements in data quality and management will facilitate the
construction of robust statistical and geological models • Some well-construction and operational practices are believed to have
exacerbated conditions at residential water supplies considered in the case study
• Data trends for a dynamic compound like methane may better be inferred
by examining monthly or quarterly averages • Passage of new well-construction regulations in February 2011 has been
accompanied by a decrease in the number of stray gas incidents • Multiple discussions and partnerships with research agencies, academia,
and industry are leading to improved operations throughout the Commonwealth of Pennsylvania
![Page 27: Tools for Assessing Stray Gas Migration: A Case Study in ... · Tools for Assessing Stray Gas Migration: A Case Study in Pennsylvania Seth Pelepko, P.G. & Stew Beattie PADEP: Bureau](https://reader034.vdocuments.net/reader034/viewer/2022050117/5f4de6a342fb636289063920/html5/thumbnails/27.jpg)
Thank You – Questions?
Seth Pelepko, P.G., LPG Well Plugging and Subsurface Activities Division 717.772.2199 ([email protected]) Stew Beattie, GIS/Information Specialist Well Plugging and Subsurface Activities Division 717.772.2199 ([email protected])