Kevin Randall

GISWR Term Project

Fall 2006

 

 

Introduction

 

Coalbed methane (CBM) is produced from the Ferron Sandstone Member of the Mancos Shale Formation in the Drunkards Wash, Helper, and Buzzard Bench gas fields, located in the northwestern portion of the Colorado Plateau physiographic province in central Utah (Figure 1) (Montgomerey et al, 2001). CBM is typically produced by pumping water from the coalbed, lowering the hydrostatic pressure of the reservoir desorbing the methane from the fracture surfaces, which then flows as a free gas to the well bore. Water pumped from the Drunkards Wash, Helper, and Buzzard Bench fields is very high in total dissolved solids (TDS), particularly sodium and chloride, and is considered by the U.S. EPA to be a hazardous waste (Rice, 1999). It is disposed of by injecting it primarily into the Navajo Sandstone and to a lesser extent the Kayenta, Wingate and Shinarump Formations, at depths ranging from 4,558 to 8,218 feet below the surface, as a means of permanent storage. Concern has been expressed by several local government entities in the area regarding the disposal methods of this hazardous material and the possibility of contamination of overlying freshwater aquifers.  

                  

 

 

The purpose of this research is to determine the fate of salt-water injected into deep aquifers, primarily the Navajo Sandstone, in the Drunkards Wash, Helper, and Buzzard Bench coal-bed methane gas fields.  The objectives of the study are to: gather and analyze water samples from a representative number of salt-water disposal wells and shallow water-supply wells for major and minor ions, as well as other chemical constituents which are not necessary to mention for this GIS term project, and to determine if the subsurface structures allow for the migration of disposal waters into upper freshwater aquifers or are acting as a cap on the disposal waters.

 

Groundwater Collection Methods

 

            Water samples were taken from deep salt-water disposal wells with the permission and assistance provided by the respective petroleum corporations; namely Anadarko Petroleum, ConocoPhillips, and XTO Energy. Twenty deep salt-water disposal wells were initially identified as candidates for chemical sampling based on records filed with the Utah Division of Oil, Gas and Mining.  However, it was later determined that nine of these wells were located so far to the northwest of the shallow water-supply wells that it is unlikely that the salt-water being injected into these wells could ever reach any of the shallow wells.  For this reason, it was decided that only eleven of the twenty deep salt-water disposal wells would be sampled.  Unfortunately, two of these eleven wells are no longer operating, so only nine deep salt-water disposal wells were sampled

           

            Twenty-four shallow water-supply wells were identified as candidates for chemical sampling based on permit applications filed with the Utah Division of Water Rights.  Of these, only four were sampled. As for the other twenty, nine could not be sampled, seven were never drilled, and four were destroyed.

 

Groundwater Chemistry

 

            The following table contains selected results from the major and minor ions data for the freshwater wells. Values reported are in mg/L.

 

Freshwater wells

 

 

Well #

pH

Na

Cl

TDS

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1

7.22

117.4

94.6

842.58

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4

7.26

3382

7619

11336.9

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

20

7.23

224.7

69.1

1594.5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

29

6.87

193

77.6

1298.78

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The following table contains the same major and minor ions data from the salt water disposal wells for comparison with the freshwater data:

 

Salt Water Disposal Wells

 

 

 

Well #

pH

Na

Cl

TDS

 

 

 

 

 

 

 

SWD-1

7.76

2609

1535

4278.12

 

 

 

 

 

 

 

SWD-2

7.64

2588

1575

4297.92

 

 

 

 

 

 

 

SWD-4

7.67

3133

3287

6593.02

 

 

 

 

 

 

 

D-3

7.9

2684

3525

6366.68

 

 

 

 

 

 

 

D-4

7.57

2400

2422

4954.95

 

 

 

 

 

 

 

D-7

7.68

4037

9974

14244.1

 

 

 

 

 

 

 

D-14

7.53

2960

3789

6897.84

 

 

 

 

 

 

 

F-2

7.08

3720

8347

12370.2

 

 

 

 

 

 

 

H-1

7.48

4106

1117

5586.72

 

 

 

 

 

 

 

 

            Well #4 from the freshwater table is highlighted in yellow to demonstrate the two-orders of magnitude increase in total dissolved solids (TDS) when compared with the three other freshwater wells. The TDS value for this well lies within the range of values found for TDS of all of the salt-water disposal wells.

           

            With a TDS value this high in a freshwater well, there arise questions of contamination from fluid migration between the Navajo Sandstone (the disposal aquifer) and overlying freshwater aquifer(s). Proof of contamination could have serious consequences for all petroleum companies involved as well as the state, including cessation of gas production and disposal water injection until further evidence is proven or disproven, and all royalties paid to the state of Utah would cease. Royalties paid to the state of Utah have been significant such as 1999 royalties in the sum of $26.4 million dollars (Montgomery et al., 2001). With such severe consequences, it is necessary to establish what the source is for such a high TDS value.

 

            There are two possible sources for this groundwater having high TDS as observed: 1) Contamination, via fluid migration from disposal waters injected into the Navajo Sandstone or 2) dissolution of soluble minerals found within the geologic formation in which the well is completed.

 

            Recent literature searches from before disposal waters were injected into the Navajo Sandstone imply that one particular geologic formation, the Upper Blue Gate shale member of the Mancos Shale, contains soluble salts and is attributed to high TDS in other wells. Freshwater well #4 which contains high TDS, is completed in this formation and may be accountable for the high TDS which would help rule out the possibility of contamination from salt-water disposal.

 

This is where GIS will be useful: I have found a study, from the late 1970’s, which shows several different rivers and streams in this study area and the change in TDS along the length of those rivers/streams. It may be useful to document where these rivers and streams cross surficial outcrops of the Upper Blue Gate shale member of the Mancos Shale, and compare that to the increasing TDS along the length of the river/stream. This will serve as further evidence in my argument that the high TDS in groundwater is indeed attributed to the soluble minerals found in this geologic formation because surface waters also increase in TDS as they pass over this same geologic formation.

 

Questions to answer or Goals using GIS

 

1.      Display locations of wells for both freshwater and salt-water disposal wells.

2.      Document sampling locations along rivers/streams and display TDS.

3.      Quantify the length of channel flowing into the main river/stream that crosses over the Upper Blue Gate (UBG) shale between sampling points.

4.      Quantify the area of sub watersheds, that cut through the UBG shale and which contribute to the main river/stream between sampling points, where possible.

 

Methods

 

Gather DEMs, topographic maps, shaded hill slope relief maps, NHD stream data, and geologic maps.

 

http://seamless.usgs.gov/

 

http://nhd.usgs.gov/data.html

 

http://geology.utah.gov/maps/gis/index.htm

 

http://agrc.its.state.ut.us/

 

 

            Geologic maps were somewhat difficult to come by. I found the Huntington 30’x 60’ map on the Utah Geological Survey (UGS) website, which is one of four GIS ready geologic maps made available to the public, fortunately in my field area. The Price 30’ x 60’ geologic map I had to order a CD from the UGS, and the Nephi 30’ x 60’ geologic map I also found on CD through the Utah State University Library Special Collections department. As for the fourth geologic map, the Manti 30’ x 60’, it is only available in analog format (hard copy) and has yet to be digitized into a GIS ready version.

 

            The first goal is relatively simple, displaying the locations of the wells which were sampled for the previously mentioned chemical constituents. This I felt would be most effective using topographic maps and shaded hill slope relief maps, which I made each layer somewhat transparent. The shaded hill slope relief map is 50% transparent and the topographic map is 25% transparent.  The fresh-water wells are represented by the blue circle with white, underlined name labels, and the salt-water disposal wells are represented by the red triangles with the black name labels. Well #4 of the fresh-water wells is in the middle of the field area, less than one kilometer from fresh-water well #20.

             

 

The next map shows the same fresh-water and salt-water disposal wells along with geologic maps of the field area.  The UBG shale is meant to stand out from the rest by displaying it in red. All other geologic formations are irrelevant for the accomplishment of the goals of this project.

 

           

            The next part of this project is to look at the rivers and streams that were sampled in the late 1970’s, before salt-water injection began. This particular study notes the change in TDS along the path of several rivers and streams within the study area.

 

  

Now let’s take a look at these sampling locations in relation to the UBG shale member by overlaying the geologic maps.

 

 

As mentioned previously, I was only able to obtain three of the four geologic maps that I wanted to use for this project. As this map makes clear, it would be difficult to accomplish the tasks of quantifying the tributary stream length that cuts through the UBG shale contributing to the main channels where the geologic map is missing. With this in mind I will only be able to complete the remaining goals on the Price River, the northern-most river.

 

After merging the geologic maps into one, I made the UBG shale a separate feature class for visualization purposes.

 

Now I am able to look at the tributary streams into the main channel that lie between the first sampling point (northern most/ TDS = 278) and the second sampling point (TDS = 479). This I have labeled Price1 as it is the first length of channel I am analyzing. This was made into its own selectable layer/feature class. After determining which tributary streams contribute to this length of the Price River I can also determine the catchments which I obtained from the NHDPlus website (see above for reference). Using the ‘Select by Location’ tool from the Selections drop down menu I was able to quickly determine the catchments associated with each reach along the Price River, which was also made to be its own selectable layer/feature class for each river reach. The length of tributary channel for this reach of the Price River  is 122.7 km, while the area of the catchments in mi2 is 139.8.

 

Four different reaches will be analyzed along the Price River, starting from the northern-most sampling points moving south, the first being called Price1 and Catch1 as mentioned previously. The next few maps will show the remaining reaches of the Price River with their associated tributary streams and catchments along with the lengths of tributary streams and areas of the catchments obtained from the statistics of the attribute table, which will be displayed using a table and graph.

 

PRICE1

                      

 

    

 

 

PRICE2

 

 

PRICE3

 

 

PRICE4

 

 

ALL TRIBUTARY STREAMS

Colors have been changed to make them stand out in comparison.

 

 

 

As there are five sampling locations along the Price River, and there are only 4 river reaches analyzed I decided to look at the change in TDS along a river reach for graphing purposes. Thus I subtracted 278 mg/L from each sampling point thus giving a   ∆ TDS along each river reach.

 

River Reach

∆ TDS

Stream length

Catchment area

Stream Length plus Upstream Lengths

Catchment Area plus Upstream Areas

Price1

201

122.7

139.8

122.7

139.8

Price2

1492

232.8

297.9

355.5

437.7

Price3

2522

172.7

212.5

528.2

650.2

Price4

2772

412.6

459.7

940.8

1109.9

 

 

            As can be seen from the table and graph, there is fairly linear trend between the increase in TDS and the increasing stream length and catchment area that crosses over the UBG shale. The first three points obviously demonstrate the greatest linearity, while the fourth point takes a significant jump in stream length/catchment area with a comparatively small increase in TDS.

 

            This application of GIS has been incredibly useful as delineating streams by hand or conducting field work to accomplish this type of task would have taken exponentially more time to complete.

 

References

Montgomery, S. L., Tabet, D.E., and Barker, C.E., 2001, Upper Cretaceous Ferron Sandstone: Major coalbed methane play in central Utah.  The American Association of Petroleum Geologists Bulletin, v. 85, no. 2, p.199-219.

 

Rice, C.A., 1999, Waters co-produced with coalbed methane from the Ferron Sandstone in east-central Utah: chemical and isotopic composition, volumes, and impacts of disposal (abs.).  Geological Society of America Annual Meeting, Abstracts with Programs, v. 31, abstract 6245.

 

Data obtained from the previously mentioned sources under the Methods section.