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Theory of Gas Injection Processes

Peng-Robinson equation of state: 40 years through cubics

Condensate-to-gas ratio (CGR) plays an important role in sales potential assessment of both gas and liquid, design of required surface processing facilities, reservoir characterization, and modeling of gas condensate reservoirs. Field work and laboratory determination of CGR is both time consuming and resource intensive. Developing a rapid and inexpensive technique to accurately estimate CGR is of great interest. An intelligent model is proposed in this paper based on a feed-forward artificial neural network (ANN) optimized by particle swarm optimization (PSO) technique. The PSO-ANN model was evaluated using experimental data and some PVT data available in the literature. The model predictions were compared with field data, experimental data, and the CGR obtained from an empirical correlation. A good agreement was observed between the predicted CGR values and the experimental and field data. Results of this study indicate that mixture molecular weight among input parameters selected for PSO-ANN has the gr...

Prediction of Condensate-to-Gas Ratio for Retrograde Gas Condensate Reservoirs Using Artificial Neural Network with Particle Swarm Optimization

Evolving predictive model to determine condensate-to-gas ratio in retrograded condensate gas reservoirs

Rate Transient Analysis in Shale Gas Reservoirs with Transient Linear Behavior. (May 2009) Rasheed Olusehun Bello, B.Sc., University of Lagos, Nigeria; M.Sc., University of Saskatchewan, Canada Chair of Advisory Committee: Dr. Robert Wattenbarger Many hydraulically fractured shale gas horizontal wells in the Barnett shale have been observed to exhibit transient linear behavior. This transient linear behavior is characterized by a one-half slope on a log-log plot of rate against time. This transient linear flow regime is believed to be caused by transient drainage of low permeability matrix blocks into adjoining fractures. This transient flow regime is the only flow regime available for analysis in many wells. The hydraulically fractured shale gas reservoir system was described in this work by a linear dual porosity model. This consisted of a bounded rectangular reservoir with slab matrix blocks draining into adjoining fractures and subsequently to a horizontal well in the centre. The horizontal well fully penetrates the rectangular reservoir. Convergence skin is incorporated into the linear model to account for the presence of the horizontal wellbore. Five flow regions were identified with this model. Region 1 is due to transient flow only in the fractures. Region 2 is bilinear flow and occurs when the matrix drainage begins simultaneously with the transient flow in the fractures. Region 3 is the response

Rate Transient Analysis in Shale Gas Reservoirs with Transient Linear Behavior

A Direct Deconvolution or Convolution Algorithm for Well Test Analysis

The analytical theory of the buildup pressure response associated with the pretest stage of the repeat formation tester operation is given. Both an infinite system and the case of a reservoir layer bounded above and below by impermeable barriers are considered. The spherical flow analysis method for the infinite acting case yields the equivalent spherical permeability which is influenced by formation anisotropy. For the bounded case, 2 different types of spherical buildup are shown to occur and an analysis technique for each one is presented which yields the spherical permeability and an estimate of the layer thickness. In circumstances where radial cylindrical buildup is observable, in principle, the anisotropy may also be determined. A quantitative result relating the depth of investigation of the permeability measurement to the pressure gage resolution is given. Computer simulations of composite systems involving a filtrate-invaded zone around the well and an outer oil zone have shown how these affect the shape of buildup plots. Recommendations regarding the choice of water or oil physical properties in data analysis are made.

Interpretation Of The Pressure Response Of The Repeat Formation Tester

The influence of afterflow on transient pressure response has long been recognized in well test analysis. The typecurve approach based on the simplified model of a constant wellbore storage coefficient has attempted to assess afterflow effects from pressure data alone. The introduction of a new generation of production logging tools that can measure bottomhole flow (BHF) and pressure (BHP) simultaneously allows the afterflow in the well to be monitored at the surface. Consequently, the well test can be more rigorously interpreted by using a new form of variable rate analysis, and the shut-in time required to allow the detection of a straight line on the appropriate semilog plot (e.g., Horner, or Miller-Dyes-Hutchison (MDH)) is much reduced. The analysis of the pressure and flow data transmitted from the production logging device may be carried out at the wellsite in real time so that the test can be continued until the desired objectives are achieved. A field example shows how continuous BHF measurement during the wellbore storage period can improve the interpretation of a short-duration buildup test.

Interpretation of Pressure Buildup Test Using In-Situ Measurement of Afterflow

This study examines the invasion of a hydrocarbon bearing formation by drilling fluid filtrate, and investigates, with the aid of a numerical model, the significance of capillary forces on the resulting displacement. It is observed that in high permeability zones, capillary imbibition can draw filtrate into the formation faster than it is lost through the filtercake, which is assumed to control the fluid loss rate. On the basis of conclusions drawn from the numerical study, the phenomena of supercharging (the difference between the water phase pressure at the sandface and the undisturbed formation pressure) has been reanalysed, and an equation recognising supercharging as a two phase problem is presented. Depending on the character of the displacement, supercharging in a hydrocarbon zone can be enhanced or reduced due to the presence of mud filtrate. A field example is used to v

The Analysis of the Invaded Zone Characteristics and Their Influence on Wireline Log and Well-Test Interpretation

Etude par simulation en laboratoire du transfert de masse entre un gaz d'injection et l'huile d'une roche magasin. Le dispositif de simulation est decrit. L'equation d'etat de Schmidt-Wenzel est utilisee pour prevoir, avec plus de precision, la densite de la phase liquide et des correlations sont proposees afin de determiner le volume d'huile stocke dans la roche magasin. Les parametres d'interaction hydrocarbures/CH 4 N 2 ou CO 2 sont calcules en utilisant l'equation Peng-Robinson. La simulation du comportement des phases est appliquee a la prevision des conditions de misabilite de l'huile de stockage ou de l'huile d'une roche magasin lors de l'injection de CO 2 ou de N 2

George Stewart

Papers

A Direct Deconvolution or Convolution Algorithm for Well Test Analysis

Interpretation Of The Pressure Response Of The Repeat Formation Tester

Interpretation of Pressure Buildup Test Using In-Situ Measurement of Afterflow

The Analysis of the Invaded Zone Characteristics and Their Influence on Wireline Log and Well-Test Interpretation

Phase Behavior of Systems Comprising North Sea Reservoir Fluids and Injection Gases