DevPlan - Gas Workbook
This Spreadsheet is for evaluating gas prospects. It was developed by Jeff Baldauf and others and it has
been modified to make it more user-friendly and
improve the technical content. Steve Sills from AEPT is our main contact for modifying the spreadsheet but
Scott Wilson has also worked with us on parts
of the deliverability calculations. A depletion-drive material balance model is used to keep track of
reservoir pressure, field deliverability is tracked each
year, well deliverabilities are estimated using Winsnap output, and the spreadsheet keeps track of the
drilling schedule for the deliverability needed. The
data needed for facility cost estimation can be output as the first page of the Multi-cases sheet. This
spreadsheet is similar to the oil field development
spreadsheet but it needs some more work to make it easier to use. The input data for the spreadsheet are :
1. Gas Volumetrics Data: This data is shown in red in the Multi-cases sheet. The net pay, areal extent,
reservoir pressure, temperature, etc. needs to be
input. The program uses correlations to calculate Bg, z, and other gas parameters. The reservoir
abandonment pressure is used to calculate the recovery
factor.
2. Well Deliverability Data: The well deliverability data needs to be generated separately using the ARCO
nodal analysis program WINSNAP and then
entered into this spreadsheet in the well productivity tables. Winsnap can be downloaded from the net from
the AEPT Reservoir Development home page
at www-red.rrt.arco.com. The 2 major sensitivity parameters in the Winsnap runs are reservoir pressure and
wellhead pressure. The reservoir pressures
need to cover the range from original reservoir pressure to abandonment pressure. The spreadsheet needs 2
wellhead pressures sensitivities - the gas
production rates with the wellhead pressure before compressors are installed and the gas rates with the
reduced wellhead pressures after compression is
installed. The spreadsheet switches from one wellhead pressure to the other depending on the reservoir
pressure used for the installation of compression
(this option needs to be improved).
After the input data has been entered, the spreadsheet can keep track of wells, facilities and costs. The best
way to run the spreadsheet is to enter a
proposed field deliverability schedule in the Annual Prod BCF column. If the existing wells cannot meet
the field deliverability, the program adds new wells
to the drilling schedule. If the deliverability is kept too high, a very large number of wells could be needed
in one particular year. In that case, reduce the
field deliverability to get a reasonable drilling schedule. In general, the gas delivery contract will specify
the number of years that we need to supply a plateau
gas rate. In the example attached, the plateau rate is maintained for 4-5 years and the production declines
exponentially afterwards. You will need to
balance the deliverability, well spacing and costs to generate the optimum development plan.
This spreadsheet is a beta version and can be modified if needed.
The spreadsheet is available for PC platforms running Excel v5.0 or later.