Woffl /ˈwɑː.fəl/ is a Python library for numerical modeling of subsurface jet pump oil wells.
Use the package manager pip to install woffl.
pip install wofflDefining an oil well in woffl is broken up into different classes that are combined together in an assembly that creates the model. The classes are organized into PVT, Geometry, Flow and Assembly.
The PVT module is used to define the reservoir mixture properties. The classes are BlackOil, FormGas, FormWater and ResMix. BlackOil, FormGas and FormWat are the individual components in a reservoir stream and are fed into a ResMix where the formation gas oil ratio (FGOR) and watercut (WC) are defined.
from woffl.pvt import BlackOil, FormGas, FormWater, ResMix
foil = BlackOil(oil_api=22, bubblepoint=1750, gas_sg=0.55)
fwat = FormWater(wat_sg=1)
fgas = FormGas(gas_sg=0.55)
fmix = ResMix(wc=0.355, fgor=800, oil=foil, wat=fwat, gas=fgas)A condition of pressure and temperature can be set on individual components or on the ResMix which cascades it to the different components. Different properties can then be calculated. For example with ResMix the streams mass fractions, volumetric fractions, mixture density, component viscosities and mixture speed of sound can be estimated.
fmix = fmix.condition(press=1500, temp=80)
xoil, xwat, xgas = fmix.mass_fract()
yoil, ywat, ygas = fmix.volm_fract()
dens_mix = fmix.rho_mix()
uoil, uwat, ugas = fmix.visc_comp()
snd_mix = fmix.cmix()If the reader wants to calculate the insitu volumetric flowrates, an oil rate needs to be passed after a condition. The method will calculate the insitu volumetric flowrate for the different components in cubic feet per second. For this method to be accurate, the watercut fraction defined should be to at least three decimal points. EG: 0.355 for 35.5%.
qoil, qwat, qgas = fmix.insitu_volm_flow(qoil_std=100)The inflow class is used to define the IPR of the oil well. Either a Vogel or straight line productivity index can be used for predicting the oil rate at a specific wellbore pressure. The inflow class is defined using a known oil rate, flowing bottom hole pressure and reservoir pressure. Oil rate is used instead of a liquid rate. The predicted oil rate can be used in conjuction with a ResMix to predict the flowing water and gas rates.
from woffl.flow import InFlow
ipr = InFlow(qwf=246, pwf=1049, pres=1400)
qoil_std = ipr.oil_flow(pnew=800, method="vogel")The WellProfile class defines the subsurface geometry of the drillout of the well. To define a WellProfile requires a survey of the measured depth, a survey of the vertical depth, and the jetpump measured depth. The WellProfile will then calculate the horizontal step out of the well as well as filtering the profile into a simplified profile.
from woffl.geometry import WellProfile
md_examp = [0, 50, 150,...]
vd_examp = [0, 49.99, 149.99,...]
wprof = WellProfile(md_list=md_examp, vd_list=vd_examp, jetpump_md=6693)Basic operations can be conducted on the wellprofile, such as interpolating using the measured depth to return a vertical depth or horizontal stepout.
vd_dpth = wprof.vd_interp(md_dpth=2234)
hd_dist = wprof.hd_interp(md_dpth=2234)The other benefit of the wellprofile is the ability to visual what the wellprofile looks like under the ground. Either the raw data or the filtered data can be plotted for visualization. The commands to use are below.
wprof.plot_raw()
wprof.plot_filter()The jetpump class defines the geometry of the jetpump. Currently only National pump geometries are defined. The pump is defined by passing a nozzle number and area ratio. Friction factors of the pumps nozzle, enterance, throat and diffuser are optional arguements.
from woffl.geometry import JetPump
jpump = JetPump(nozzle_no="12", area_ratio="B")The Pipe and Annulus class defines how large the tubing and casing are in the well. Currently only the tubing needs to be defined for solving the jetpump performance. Future work will incorporate the annular geometry to account for annular friction in the well.
from woffl.geometry import Pipe, Annulus
tube = Pipe(out_dia=4.5, thick=0.5)
case = Pipe(out_dia=6.875, thick=0.5)
annul = Annulus(inn_pipe=tube, out_pipe=case)Simple geometries of the Pipe and Annulus can be accessed, such as the hydraulic diameter and cross sectional area.
tube_id = tube.inn_dia
tube_area = tube.inn_area
ann_dhyd = annul.hyd_dia
ann_area = annul.ann_areaThe assembly module is used to combine the previously defined classes into a system that can be used for solving. The assembly code is still being developed and currently is a mix of classes and a few fuctions. The critical class is the BatchPump class, allowing multiple pumps to be run across a defined system.
from woffl.assembly import BatchPump
nozs = ["8", "9", "10", "11", "12", "13", "14", "15", "16"]
thrs = ["X", "A", "B", "C", "D", "E"]
well_batch = BatchPump(pwh=220, tsu=82, rho_pf=62.4, ppf_surf=2800, wellbore=tube, wellprof=wprof, ipr_su=ipr, prop_su=fmix)
jp_list = BatchPump.jetpump_list(nozs, thrs)
result_dict = well_batch.batch_run(jp_list)The results dictionary can be passed into a Pandas Dataframe and used for results analysis. A few simple functions have been written to easily visualize the results.
import pandas as pd
from woffl.assembly import batch_results_mask, batch_results_plot
df = pd.DataFrame(result_dict)
mask_pump = batch_results_mask(df["qoil_std"], df["total_water"])
batch_results_plot(df["qoil_std"], df["total_water"], df["nozzle"], df["throat"], mask=mask_pump)If the reader is interested in the physics and numerical modeling that went into woffl they should read the papers that are listed below. The paper by Merrill provies a good introduction to the basic method that is used. Cunningham set much of the foundational equations that are used in the modeling. The authors intend to publish a paper with a more detailed explanation in the future.
- Cunningham, R. G., 1974, “Gas Compression With the Liquid Jet Pump,” ASME J Fluids Eng, 96(3), pp. 203–215.
- Cunningham, R. G., 1995, “Liquid Jet Pumps for Two-Phase Flows,” ASME J Fluids Eng, 117(2), pp. 309–316.
- Merrill, R., Shankar, V., and Chapman, T., 2020, “Three-Phase Numerical Solution for Jet Pumps Applied to a Large Oilfield,” SPE-202928-MS, November 10, 2020.
- Himr, D., Habán, V., Pochylý, F., 2009, "Sound Speed in the Mixture Water - Air," Engineering Mechanics, Svratka, Czech Republic, May 11–14, 2009, Paper 255, pp. 393-401.