American Oil and Gas Reporter - May 2015 - 93

SpecialReport: Gas Compression Technology
and oil flow data from HPS. These numbers can be incomplete and misleading.
The GORs shown in Table 2 were calculated from the predicted oil flows and cumulative gas production. The total GOR
for the well that uses total gas capture and
final oil volumes (third column) is almost
50 percent higher than the typical GOR
(first column). Inaccurate GOR data can
mislead facility engineers into underdesigning individual well equipment as well
as downstream gathering lines, compression and gas processing facilities.

requirements.
The equipment required to recover
flash gas is expensive, adding both cost and
complexity to production operations. Some
unconventional oil plays have simply
flared produced gas, but regulations in
states such as North Dakota now require
operators to capture certain percentages of
overall produced gas. The good news is that
flash gas and vapor recovery can have a

positive impact on production economics.
Table 4 shows the production values of
the main gas (HPS) and flash gases
(LP/VRT) for the three D-J Basin oils at
a flash gas basis pressure of 75 psig. It also
includes relative values of each of these
streams, based on dry gas and natural gas
liquids prices for the Rocky Mountain area.
While the flash gases from heavier oils with
lower GORs provide only 3-6 percent of

Example Simulations

Table 3 presents summaries of simulations using PVT data for three oils in the
Denver-Julesburg Basin. The oils were selected on the basis of the PVTs of reported stock tank API gravities (61.3, 49.6 and
35.8 degrees for oils A, B and C, respectively). Oil B is the same as used for the
alkane/PIONA comparison in Table 2.
Process simulations were run for each of
these oils based on the same design parameters:
* Total oil production of 458.9 bbl/d;
* HPS temperatures and pressures of
90 degrees and 112 psia (100 psig), and
LPS temperatures and pressures of 120 degrees and 37 psia (25 psig);
* VRT pressure of 15 psia (3 psig);
* Storage tank/ECD pressure of 12
psia (0 psig); and
* 350 Mcf/d of gas lift for oils B and
C, with no gas lift required for oil A.
Table 3 shows the simulation results
calculated on a single-well basis (values
for larger multiwell pads are an arithmetic
multiple of these values times the number
of wells feeding a facility). The wide range
(about 1,200 percent) in HPS production
highlights the differences in GOR. In contrast, LPS gas volumes from oil production vary by only 25 percent. The design
for flash gas handling equipment is obviously strongly dependent on total oil
production and significantly less dependent on GOR. This allows facilities engineers to simplify the design of gas handling facilities, sizing equipment based on
predicted oil production rates.
Although these simulations are for the
D-J Basin, oils produced in other basins
show similar trends. The flash vapor handling requirements vary much less between
different oils than the HPS gas handling
MAY 2015 93

American Oil and Gas Reporter - May 2015

Table of Contents for the Digital Edition of American Oil and Gas Reporter - May 2015