SERVICES FOR THE OIL & GAS INDUSTRY
Software allows to model, interpret, simulate and predict oil or gas well and reservoir behavior, fast and efficiently.
UniTest® PTA allows to create PVT fluid, reservoir and wellbore models that quick and easy pressure transient analysis.
From this models, the user can generate combinations, and make comparative studies varying parameters of each model, for example: OD of tubing, Damage, Initial Pressure, etc. UniTest® PTA offers wide comparison range of parameters.
- Pressure Transient Analysis
- Optimization and Non-linear Regression
- Dynamic Nodal Analysis
- IPR and Outflow Calculations
- Multiphase Flow
- Compositional Model
- Three Phase Model
- Sensitivity
- Pressure Transient Analysis
Allows well testing analysis through simulation, considering petrophysics reservoir properties, it's shape and special characteristics (fractures, faults, limits, etc.), as well as PVT fluid properties.
Input information can be loaded (pressure, temperature and rates logs) from surface or bottom hole taken data by multiple sensors. Analyzing data a simulation model and matching can be defined.
Simulation it's done evaluating diffusivity equation in each block of generated grid. Simulator uses different grids for each model in order to enhance analysis in certain types of reservoirs.
- Optimization and Non-linear Regression
The program has a non-linear optimizer to adjust parameters of each model to real data.
Parameters to be used as real and model properties to optimize can be chosen, being able to optimize more than one property each time and chose difference level of numerical range in each optimization jump.
Where property doesn't surpasses certain values, adjustment range can be specified . Also you can choose the interval at which data to simulate it's taken.
- Dynamic Nodal Analysis
Reservoir, wellbore and piping composed system it's analyzed in well testing. It's operation comprehension implies every component analysis and dynamic relation between them.
There are interpretation models for each component that can be adjusted with measured data for each case. Traditional method of well testing considers instantaneously constant rate during draw-down, and instantaneously zero flow during build-up. On the other hand, traditional nodal analysis simplifies reservoir behavior to a steady state.
However, solving models dynamically, significant advantages are obtained:
- Adjustment improvement of each model, eliminating needs to assume premises.
- Validate acquired data, identifying zones in which simulation it isn't compatible with some measurement.
- Reduce uncertainty in results when using multiple criteria and convergent measurements.
- Increase each measurement value as control points of the simulation.
The system is divided into three sections, which it's behavior will be described by:
- Reservoir models.
- Flow models into tubing and/or casing.
- Surface flow models (Choke).
This models can be concatenated in series so that the output of one model can be the input of the other one, and are dynamically and jointly solved.
Presenting acquired measurements with simulation results in specialized graphs, the validity of each model can be evaluated.
- IPR and Outflow Calculations
In well's IPR calculation, the error of considering pseudo-steady state behavior of the system it's also repeated. UniTest® enable actual and future well IPR calculation, simply specifying production time at which calculation it's wanted to be done.
Also allows outflow curves calculations, considering choke effect and pipeline geometry.
- Multiphase Flow
UniTest%reg; allows the use of multiphase flow classical correlations such as Poettman & Carpenter or Beggs & Brill.
It also includes recent advances in multiphase flow calculation: mechanistic models. These models allow pressure drop calculation, differentiating between flow patterns (bubble, annular, mist, slug, etc.) from 0 to 90° tilt.
- Compositional Model
Using equations of state to describe hydrocarbons behavior inside the reservoir or piping gives better approaches than using fixed PVT curves or simply constants properties.
Thermodynamic UniTest® simulator allows to obtain all thermodynamics parameters as well as the usual laboratory curves (PV, Bo, Rs, etc.) from fluid composition.
For gases, development described in AGA#8 (American Gas Association) report it's available to be used, which is an equation of 5th order status.
For liquids and gases, simulator applies Peng-Robinson equation of state with necessary modifications for better liquid density predictions.
- Three Phase Model
Software can consider flow of all fluids in reservoir: oil, gas and water. It calculates saturation profile distribution an consider three fluids flow to define bottom hole general behavior.
- Sensitivity
This is a very powerful tool of UniTest® to make comparisons by varying parameters. It allows to fixed stop a channel (the simulated channel), chose the variable channel and the number of cases in which this channel will be evaluated. It's possible to make sensitivity in every model, reservoir, pipeline or PVT.
UniTest® PTA's Technical References
Correlations
UniTest® has many correlations to use as complementary tools in the study of a particular case.
PVT (Oil)
Correlations are used to obtain parameters such as Bo, Rs, Bubble Point, Density and Viscosity of Oil, etc.
Beggs & Robinson SPE 5434
"Estimating the Viscosity of Crude Oil Systems"
Beggs, H.D., and Robinson, J.R., JPT (Sept., 1975) pp. 1140-1141.
GlasO SPE 8016
"Generalized Pressure-Volume-Temperature Correlations"
GlasO, O., JPT (May, 1980) 785-95.
Khan SPE 15720
"Viscosity Correlations for Fluid Physical Property Prediction"
Khan, S.A., M.S. Thesis, The University of Petroleum & Minerals (1985).
Lasater SPE 957
"Bubble Point Pressure Correlation"
Lasater, J.A., Trans., AIME (1958) 213, 379.
Marhoun SPE 13718
"PVT Correlations for Middle East Crude Oils"
Al-Marhoun, M. A., JPT (May, 1988) 650-66.
Petrosky & Farshad SPE 26644
"PVT Correlations for Gulf of Mexico Crude Oils"
Petrosky, G. E., Jr., MS thesis, U. of Southwestern Louisiana, Lafayette, LA (1990).
Standing
"A Pressure-Volume-Temperature Correlation for Mixtures of California Oils and Gases"
Standing, M. B., Drill. and Prod. Prac., API (1947) 275-87.
Vazquez & Beggs SPE 6719
"Correlations for Fluid Physical Property Prediction"
Vazquez, M. E. and Beggs H. D., JPT (June, 1980) 968-70.
Dindoruk & Christman SPE 89030
"PVT Properties and Viscosity Correlations for Gulf of Mexico Oils"
Birol Dindoruk and Peter G. Christman, Shell Intl. E&P Inc. (2004)
Lohrenz SPE 915
"Calculating Viscosities of Reservoir Fluids From Their Compositions"
John Lohrenz and Bruce G. Bray, Continental Oil Co., Charles R. Clark, U. of Kansas. (1964)
PVT (Gas)
Dranchuk & Abbou-Kassem
"Calculation of z-Factors for Natural Gases"
Dranchuk, P.M., and Abou-Kassem, J.H., Journal of Canadian Petroleum (Jul.-Sep. 1975) 14, 34-36.
Carr-Kobayashi-Burrows
"Viscosity of Hydrocarbon Gases Under Pressure"
Carr, N.L. Kobayashi, R., and Burrows, D.B., Trans., AIME (1954) 201, 264-272.
Lee-Gonzalez-Eakin
"The Viscosity of Pure Substances in the Dense Gaseous and Liquid Phases"
Lee, A.L., Gonzalez, M.H., and Eakin, B.E., JPT (Aug. 1966) 997-1000; Trans., AIME (1966) 234.
Optimización de Dranchuk & Abbou-Kassem y Lee-Gonzalez-Eakin:
SPE 75721: "Simplified Correlations for Hydrocarbon Gas Viscosity and Gas Density - Validation and Correlation of Behavior Using a Large-Scale Database"
F.E. Londono, R.A. Archer, and T.A. Blasingame, Texas A&M U.
PVT (Water)
McCain SPE 18571
"Reservoir-Fluid Properties Correlations, State of the Art"
W.D. McCain Jr., SPE, Cawley, Gillespie & Assocs. Inc.
Multiphase Flow
Ansari SPE 20630
"A Comprehensive Mechanistic Model for Upward Two-Fhase Flow in Wellbores"
Ansari, A.M., Sylvester, N.D., Sarica, C., Shoham, O. and Brill, J.P., SPE 20630 presented at the SPE 65th Annual Meeting, New Orleans, September 23-26, (1990), SPE Production Engineering, pp. 143-152 (May 1994).
Baxendell & Thomas SPE 2-PA
"The Calculation of Pressure Gradients in High Rate Flowing Wells"
Baxendell, P. B., CIA. SHELL de Venezuela, Thomas, R., CIA. SHELL de Venezuela, JPT (Oct. 1961), 1023.
Beggs & Brill SPE 4007
"A Study of Two Phase Flow in Inclined Pipes"
H. Dale Beggs, SPE-AIME, U. of Tulsa, James P. Brill, SPE-AIME, U. of Tulsa. 1973.
Fancher & Brown SPE 440
"Prediction of Pressure Gradients for Multiphase Flow in Tubing"
Fancher, G. H., and Brown, K. E., Trans. AIME (1963), 228, 59-69.
Gomez SPE 56520
"A Unified Mechanistic Model for Steady-State Two-Phase Flow in Wellbores and Pipelines"
L. E. Gomez, SPE, O. Shoham, SPE, and Z. Schmidt, SPE, The University of Tulsa, R. N. Chokshi, SPE, Zenith ETX Co., A. Brown, BP Exploration and T. Notrhug, StatOil.
Hagedorn Brown SPE 940
"Experimental Study of Pressure Gradient Occurring During Continuous Two-Phase Flow in Small Diameter Vertical Conduits"
Hagedorn, A.R. and Brown, K.E., JPT, pp. 475-484 (April, 1965).
Orkiszewski SPE 1546
"Predicting Two-Phase Pressure Drop in Vertical Pipes"
J. Orkiszewski, ESSO Production Research Co., SPE JPT (June 1967), 829-838.
Poettman & Carpenter
"The Multiphase Flow of Gas, Oil and Water Throuh Vertical Flow Strings with Application to the Design of Gas-Lift Installations"
Poettman, F. H., and Carpenter, P. G., API Drilling and Production Practices, 257-317 (1952).
Petalas & Aziz
"Development and Testing of a New Mechanistic Model for Multiphase Flow in Pipes"
Petalas, N. and Aziz, K., proceedings ASME, Fluid Eng. Division, 236, No. 1, pp. 153-159 (1996).
Equations of State
Peng-Robinson
"A New Two-constant Equation of State"
Peng, D.Y. and Robinson, D.B., 1976. Ind. Eng. Chem. Fundam., 15:58-64.
AGA#8
"Compressibility and Supercompressibility for Natural Gas and Other Hydrocarbon Gases"
American Gas Association, Transmission Measurement Committee Report No. 8