Calculating Length and Percent of the Wellbore in Zone

Calculating the length and percent of the wellbore that is in the target zone can be useful parameters to help understand why some wells produce anomalously high or low initial potential volumes or production volumes. These parameters when combined with mapping and cross section software can visualize the information and provide greater understanding of the reservoir and its economic potential. GVERSE Geomodeling introduces this technology within the geomodel and cross section capabilities of the software.

Below is a map view of a Barnett Shale field producing from multiple horizontal wells.

The target zone is between the Barnett MFS surface and the Basal Barnett as shown in GVERSE Petrophysics below. This zone maximizes the amount of the competent lithologic components of sandstone, limestone, and dolomite to enhance the brittleness and storage capacity of the reservoir.

Calculating the Length and Percent of the Wellbore in the Zone on a Cross Section
The cross section below shows the wellbore mostly within the target zone between the Barnett MFS and the Basal Barnett (yellow stippled pattern).

The length and percent of the wellbore in the zone can be calculated within a single cross section or over the wells on a map. In this case, the length and percent of the wellbore in the zone is calculated over the well in this cross section by selecting “Calculate Well(s) in Zone” from the right-click context menu.. The definition of the zone is derived from the Barnett Target definition in ZoneManager. The zone definition can also be defined by the Geosurface Model (GSM) zones or by explicitly selecting the surfaces within the geomodel. The beginning of the length and percent calculation can either be the top of the zone, a user defined angle of the wellbore, or by an MD.

Pressing the Calculate button initiates the process and generates the report.

In this case, the length in zone is 2690.5 feet and the percent in zone is 95.24%.

Calculating the Length and Percent of the Wellbore in the Zone from a Map View
The procedure starts by selecting the wells or a group of well from the map view in GVERSE Geomodeling. The utility to calculate the length and percent of the wellbore in the zone is accessed on the right click context menu by selecting “Calculate Well(s) in Zone” option. A well list is presented where the user can select all of the wells or a subset to calculate. More wells can be added from a WellBase well list by pressing the Add button.

Pressing the Calculate button initiates the calculation process and report generation. An error log is created for wells that cannot be used in the calculation.

The report screen presents the list of the wells where calculations were possible and the Zone Name, Start, Zone Top, Zone Base, and the Length and Percent of the wellbore in the selected zone.

The report can be copied to the clipboard or saved as a tab, space, or comma delimited text file. In this case it is written to the Barnett Target zone in ZoneManager.

In ZoneManager, the IP for the wells has been extracted from WellBase and placed in a column in the Barnett Target zone spreadsheet along with the length and percent of wellbore in the zone calculated from GVERSE Geomodeling.

Once the data is in ZoneManager, it is possible to conduct a number of analytical procedures such as attribute calculations, data statistics, data histograms, creation of WellBase or IsoMap layers, and cross plots. In this case a cross plot of the Length of the wellbore in the zone is plotted against the Barnett Shale IP for the well. By examining the distribution of the data and calculating a curve fit to the data, the relationship between the length of the wellbore in the zone and the IP can be better understood.

Notice the data point at the upper left of the cross plot. This well point indicates that even though the well has a short length of the wellbore in the zone, it is producing at a high rate, a result that is not expected. By selecting the well data point on the cross plot, the well can be opened in WellBase to confirm the IP data.

After confirming the IP rate in WellBase is correct, the well can be highlighted in GVERSE Geomodeling to examine the location of the well in relationship to other wells and the Barnett Shale structural surface.

The highlighted well can be opened in a cross section view to examine the wellbore geometry as it relates to the target zone.

Notice that a large percentage of the wellbore length is just above the Barnett MFS surface and therefore out of the target zone. This being the case, it looks to be that a significant percent of the IP volume is coming from the zone above the current target zone and therefore would be a zone for future development.

LMKR GeoGraphix and GVERSE applications provide the user with comprehensive tools for analyzing reservoir character, structure, and their relationship to production. These tools can add value to any field development program and provide insight into enhance recovery and future field development.