Sensitivity Analysis of Thermodynamic Parameters in Gas-condensate Systems for Reserve Estimation by Means of Probabilistic Modeling

An improper sampling (non-representative) of reservoir fluid may introduce significant errors in reserve estimation. The process of verification and correction of PVT properties has been described, as well as, estimation of uncertainty of evaluation reserves based upon real geologic information. An analysis of vertical change of gas-condensate system composition in the thick geologic structures has been done. Compositional gradients influence saturation pressure (dew or bubble) and other fluid properties. This paper describes the complex phenomena related to mixing and segregation processes occurring during secondary migration and post-filling time of oil and gas-condensate system. The paper discusses the classical and non-equilibrium phenomena in the porous medium in presence of thermal gradient. The verification of PVT properties is based upon the reverse simulation processes using Tsai-Chen version of Peng-Robinson Equation of State. The regression procedure for correction of uncertain parameters in which density of stabilized condensate is the most important convergence criterion – has been applied. The sensitivity of other parameters (e.g. pay thickness, area, porosity, initial saturation of fluids) is included in the general procedure of global uncertainty reserves estimation. The analysis of typical parameter distribution has been made, based on a literature review. The Latin Hypercube Sampling has been used to final probabilistic simulation. Several examples of reserve estimations and their uncertainty have been done. The large impact of improper PVT on the condensate phase reserve estimation has been observed.

[1]  Stanislaw Nagy,et al.  Economic analysis of use of the early application CO2 and CO2 /N2- eor technology in Poland , 2008 .

[2]  S. Nagy,et al.  Analysis of Use of Low Quality Natural Gas to Improve Oil Recovery Factor , 2007 .

[3]  Abbas Firoozabadi,et al.  Thermodynamics of Hydrocarbon Reservoirs , 1999 .

[4]  F. Montel,et al.  Prediction of Compositional Grading in a Reservoir Fluid Column , 1985 .

[5]  F. Siddiqui.  Defining Fluid Distribution and Fluid Contacts for Dynamically Charged Reservoirs , 1999 .

[6]  M. P. Walsh,et al.  The New, Generalized Material Balance as an Equation of a Straight Line: Part 1 - Applications to Undersaturated, Volumetric Reservoirs , 1994 .

[7]  Reuven Y. Rubinstein,et al.  Simulation and the Monte Carlo method , 1981, Wiley series in probability and mathematical statistics.

[8]  V. Dieckmann,et al.  PVT and phase behaviour analysis in petroleum exploration , 1998 .

[9]  D. Peng,et al.  A New Two-Constant Equation of State , 1976 .

[10]  M. F. Hawkins,et al.  Applied Petroleum Reservoir Engineering , 1991 .

[11]  S. Nagy.  Capillary - adsorption effects in gas condensate systems in tight rocks - vertical variation of hydrocarbon composition , 2002 .

[12]  I. Prigogine,et al.  Book Review: Modern Thermodynamics: From Heat Engines to Dissipative Structures , 1998 .

[13]  P. D. Newendorp,et al.  Decision analysis for petroleum exploration , 1975 .

[14]  J. Dolson,et al.  The factors controlling the abundance and migration of heavy vs. light oils, as constrained by data from the Gulf of Suez. Part II. The significance of reservoir mass transport processes , 1998 .

[15]  B. Sage,et al.  Gravitational Concentration Gradients in Static Columns of Hydrocarbon Fluids , 1939 .