PVT EMPIRICAL MODELS FOR SATURATED OMANI CRUDE OILS

Pressure-volume-temperature (PVT) properties are critical to reservoir as well as production engineers, in particular. PVT properties could be determined experimentally. But, experiments are time consuming and costly. Moreover, laboratory PVT analysis does not consider the variations of PVT properties with respect to temperature since they are measured at reservoir temperature at the time of sampling. For that matter, the data is not benefitable. But, even if experimental analysis is done, it is difficult to obtain representative results to develop a new field. To tackle the above and other related problems, relying on sound PVT emperical correlations would be the ultimate solution. In this work, the intent is to develop stochastic models for PVT properties pertaining to Omani crude oils since it is believed that such correlations are scarce and not very precise. The empirical equations are developed for saturated Omani crude oils. The correlations are tested and validated. The empirical equations evaluation and assessment are done against existent experimental data and published correlations.     

On business process monitoring using cross-flow coordination

This paper presents an approach for monitoring the execution progress of business processes. The monitoring focuses on the exceptions that could arise during this execution and, hence, could make the processes fail if not handled properly and timely. The approach relies on three flows known as control, communication, and navigation. The control flow connects tasks together with respect to a certain business logic. The communication flow captures the messages exchanged between persons/machines when they perform tasks of processes. Finally, the navigation flow captures the interactions between specialized networks that offer solutions to exceptions. These networks are built upon relations between tasks, between persons, and between machines. The coordination of control, communication, and navigation flows focuses on both the actions that are taken and the messages that are exchanged when handling exceptions. A system demonstrating flow development and coordination is, also, presented in the paper.     

MATRIX AND CEMENT EFFECTS ON RESIDUAL OIL SATURATION IN SANDSTONE FORMATIONS: A NEURAL NETWORK APPROACH

Abstract

Residual oil in sandstone is affected by mineral composition, clay matrix and cementing material. Matrix minerals affect the affinity of a fluid to spread on a rock surface significantly and in turn controls the fluid distribution within the pore spaces. At the interface between the rock surface and the contacting fluid, electrical charges are in the origin of the extent of phase wetness. Available framework grains, a dominant component of rock matrix, affect porosity and, hence, amounts of rock preferential wetness. Cement, clay matrix and quartz overgrowth, which make up for the rest of the grain population in a rock, influence wetness and, therefore, amounts of residual oil. In this paper, spectro-electromicroscopy (SEM) point-count technique in conjunction with neural network analysis were used to determine the effect of certains rock parameters on the amounts of residual oil following waterflooding operations. Using artifcial neural network, the intent was then to predict the extent of residual oil in sandstone rocks given limited information about rock matrix, cementing material and primary porosity.     

SELECTIVE COMPLETION FOR HORIZONTAL WELLS DRILLED IN A FRACTURED OMANI RESERVOIR

Reservoir simulation sensitivity analysis and unit technical cost analyses are used in order to determine the optimum well performance of a horizontal well that is selectively completed in one of the fractured Omani reservoirs. A black-oil model representing one heavily fractured Omani field was used in the analysis with a match box-like reservoir structure. The fractures are taken as thin streaks penetrating the reservoir vertically with high permeability along X, Y and Z- directions. Matrix block permeability values are drastically lower than those characterizing fracture block permeability.

Eclipse 100 black-oil simulator was used throughout the study to analyze the effect of fracture frequency and to obtain the optimum completion by investigating different isolation length for fractured horizontal producers, injectors and both producers and injectors.

The sensitivity analysis involves building numerous models for 2mD, 10mD and 50mD. That is because the range of permeability in the field is not very well defined. But, it is thought to be in the above selected range.

The objective being to determine the optimum completion that gives the best performance associated with the lowest cost after several selective completion options are tested for different fracture frequency and for different type of wells (producers, injectors or both).     

Mobilizing Condensate in Gas Reservoirs–A Numerical Simulation Study

Abstract

A mechanism of a commingled Huff 'n Puff cycles of gas cross flow from a highly pressurized lower formation into a depleted upper formation has proven to be effective in reducing gas-well productivity losses due to near-wellbore condensate dropout. Compositional simulation was used to evaluate the performance of gas wells hampered by liquid dropout and to assess ways of producing the gas field. As a result of liquid re-vaporization the study shows that an appropriate scheduling of huff 'n puff shut-in and production cycles lead into a decline of in-situ liquid dropout and an increase in surface liquid recovery.     

MATRIX AND CEMENT EFFECTS ON RESIDUAL OIL SATURATION IN SANDSTONE FORMATIONS: A NEURAL NETWORK APPROACH

Residual oil in sandstone is affected by mineral composition, clay matrix and cementing material. Matrix minerals affect the affinity of a fluid to spread on a rock surface significantly and in turn controls the fluid distribution within the pore spaces. At the interface between the rock surface and the contacting fluid, electrical charges are in the origin of the extent of phase wetness. Available framework grains, a dominant component of rock matrix, affect porosity and, hence, amounts of rock preferential wetness. Cement, clay matrix and quartz overgrowth, which make up for the rest of the grain population in a rock, influence wetness and, therefore, amounts of residual oil. In this paper, spectro-electromicroscopy (SEM) point-count technique in conjunction with neural network analysis were used to determine the effect of certains rock parameters on the amounts of residual oil following waterflooding operations. Using artifcial neural network, the intent was then to predict the extent of residual oil in sandstone rocks given limited information about rock matrix, cementing material and primary porosity.     

Gas-Condensate Reservoir Pseudo-relative Permeability Derived by Pressure-Transient Analysis. Incorporation of Near-Wellbore Effects

Gas-condensate reservoirs exhibit a near-wellbore complex behavior due to the existence of a two-phase system when pressure drops below dew point. In analyzing well-testing data, a single-phase approach is only valid for well condition above dew point, whereas a multi-phase pseudo-pressure approach is widely adopted for a gas reservoir operating below dew-point. This article utilizes the pseudo-pressure approach, for analyzing well-test data in gas-condensate reservoirs producing below the dew-point pressure, to generate Corey exponents for relative permeability in order to determine near-wellbore representative relative permeability that history matches the actual well-testing data.     

Pressure-Volume-Temperature Empirical Formulations for Undersaturated Omani Oils

Pressure-Volume-Temperature (PVT) empirical correlations result from analysis of experimental data collected from laboratory measurements of phase behavior properties of hydrocarbon systems. The correlations are only applicable for the tested hydrocarbons. They could nevertheless be used to predict PVT properties of similar hydrocarbons with pressures and temperatures falling within the measurements' data range.

The developed correlations are mostly, local, some are “region-bound” and a few are global. Regional and global correlations are used with caution. The reason being that hydrocarbon systems from different regions have different composition and paraffinicity, regardless of comparable temperature and pressure ranges. As a result and due to a complex geology resullting from unique depositional environments of most Omani reservoirs, a local correlation to derive PVT properties for Omani crude oils is needed.

The correlations could also be used to supplement PVT experiments often time consuming and extremely costly. In this paper, the developed correlations are derived for undersaturated Omani black-oil.     

ESTABLISHING PVT CORRELATIONS FOR OMANI OILS

ABSTRACT

An adequate knowledge of any reservoir fluid PVT properties is essential for most types of petroleum calculations. These calculations include amount of oil in the reservoir, production capacity, variations in produced gas-oil ratio during the reservoir's production life, calculation of recovery efficiency, reservoir performance, production operations and the design of production facilities. PVT properties can be measured experimentally by using collected bottom-hole or surface samples of crude oils. But, the experimental determination of PVT is time consuming and very costly. In addition, even with the availability of PVT analyses, it is often necessary to extrapolate the data to field and/or surface conditions through the use of empirical correlations. Furthermore, geological and geographical conditions are considered very critical in the development of any correlation. But, universal correlations are difficult to develop. That is why correlations for local regions, where crude properties are expected to be uniform, is a reasonable alternative. In this study, experimental PVT data for North and South Oman crudes, statistical and artificial neural network (ANN) analyses are used to develop reliable PVT correlations. Comparisons with previously published correlations are presented.     

SELECTIVE COMPLETION FOR HORIZONTAL WELLS DRILLED IN A FRACTURED OMANI RESERVOIR

ABSTRACT

Reservoir simulation sensitivity analysis and unit technical cost analyses are used in order to determine the optimum well performance of a horizontal well that is selectively completed in one of the fractured Omani reservoirs. A black-oil model representing one heavily fractured Omani field was used in the analysis with a match box-like reservoir structure. The fractures are taken as thin streaks penetrating the reservoir vertically with high permeability along X, Y and Z- directions. Matrix block permeability values are drastically lower than those characterizing fracture block permeability.

Eclipse 100 black-oil simulator was used throughout the study to analyze the effect of fracture frequency and to obtain the optimum completion by investigating different isolation length for fractured horizontal producers, injectors and both producers and injectors.

The sensitivity analysis involves building numerous models for 2mD, 10mD and 50mD. That is because the range of permeability in the field is not very well defined. But, it is thought to be in the above selected range.

The objective being to determine the optimum completion that gives the best performance associated with the lowest cost after several selective completion options are tested for different fracture frequency and for different type of wells (producers, injectors or both).