GIS data modeling for well spot planning
Unit and Field Boundaries
A grouping of wells makes up a unit and a group of units makes up a field; the geologist develops
these units and fields. The grouping of the units and fields is typically done using a computer
aided drafting and design (CADD) system. The units and fields are typically digitized from a
map containing roads and other cultural features. Sometimes, they are digitized from georeferenced
aerial photographs. The units and fields are then imported into the GIS.
Figure 1: Well spots are represented as dots while the
units are contained within the Field. The Units have
been buffered.
The GIS database and anlaysis
The GIS database developed for this well spotting application contained the three base map layers
that have been previously described. The wells database contained fifteen attributes:
| API Number |
Field Name |
| Operator |
Well Name |
| Well Number |
State |
| County |
Date |
| Latitude |
Longitude |
| Depths |
The units database contained the following attributes: unit name, field name, and acreage. The
field layer merely contained the units.
Figure 2 shows a production field with wells represented
as points. The units are drawn as polygons with wells contained therein. The grouped units are
stored as a field. Figure 3 shows a group of wells with 1320' buffers. This buffer distance
reflects regulatory constraints on the number of wells that may be contained in a unit and the
density of the proximity of wells to one another. This analysis was conducted in the GIS using
attributes from the databases described above.
Figure 2: Buffered wells (circles) are superimposed over
units to depict well placement densities with reference
to units.
Figure 3: Geo-referenced image with well spots and
well buffers superimposed.
The units represented in figure 3 are buffered toward the inside to comply with further regulatory
constraints. Each unit is buffered 1320 feet to the inside of the unit. Buffering the units and
superimposing the well buffers on the units may also visually depict compliance with this
regulation. Well spots may be adjusted by using the GIS to select appropriate placement to
comply with regulations.
Output from the Geographix software has driven the GIS display and analysis to this point.
Buffering has taken place on the existing data. However, care must now be taken to determine
whether the placement of wells is appropriate with respect to the existing landcover. Traditional
methods of locating wells on the landscape have used field surveying with transits or GPS
equipment. This method requires considerable, expensive fieldwork. Geo-referenced aerial
imagery may reduce the need for this expensive fieldwork; however, it will not replace it. Since
all spatial data contained in the GIS is geo-referenced, the well spots, well buffers, and unit
buffers are readily superimposed onto geo-referenced imagery. Figure 3 depicts a digital image
with well spots and well buffers superimposed.
Inspecting the imagery with the superimposed well locations will identify areas where current
landuse and potential well spots might conflict. In the imagery, it is obvious that some of the
wells were already in place (white spots around the well spot symbols) while others were merely
in the planning phases (well spots with no surrounding white spots). The white scar on the
landscape surrounding a well spot is typically made by the placement of gravel around the well
head. Inspection of the imagery with superimposed well spots will provide the engineer the
opportunity to select alternate surface locations for wells that conflict with existing landuse.
Examples of this would include wells placed in roadways, ponds, and on urbanized structures.
Conclusions
Geo-referenced, digital imagery and GIS analysis may prove to be and invaluable addition to the
tool kit of the exploration engineer. The analytical processing provided in the GIS will augment
the analysis provided by conventional exploration software systems. In concert, the two tools
will allow the engineer the opportunity to make better-informed decisions and assist with the
compliance to regulatory agency criteria for well spotting.
