Diagnosis of Well Production Operations on the Basis of Nonparametric Criteria of Production Data Variations

Abstract

The relevance of application of different parametric indices of time series variations, such as variance, variation coefficient, normalized deviation, Theil's criteria, etc., for assessment of technological processes is analyzed in this work.

Different nonparametric criteria of time series variations are suggested that allow diagnosis of changes in the conditions of the process analyzed, when application of other criteria are incorrect or inappropriate.

The applicability and simplicity of realization of nonparametric criteria for practical engineering calculations in analysis of multifractal and chaotic fluctuations are shown.

The applicability of the suggested criteria of time series variations for early diagnosis of qualitative changes in behavior of dynamic systems is proven on model examples as well as on practical examples of oil and gas production.     

Application of Fractal Analysis of Time Series in Oil and Gas Production

Abstract

The peculiarities of fractal characteristics' calculations for time series are described in this article. It was suggested an algorithm for calculation of fractal dimension for time series. This method differs from the covering method, considering only the Y coordinate and possessing high accuracy and rapidity of convergence on a limited number of measurements, compared to the method of covering. The criteria of early diagnosis for changes in the condition of hydrodynamic processes that do not vary by fractal dimension have been recommended.

The presented method is applicable for practical engineering calculations with self-affine, chaotic data, usually with a relatively limited number of measurements. It is quite a simple method for calculation of fractal dimensions and the algorithm can be easily realized. The applicability of the proposed algorithm for fractal dimension calculation and early diagnosis criteria of qualitative changes in the behavior of various dynamic systems has been tested both on simulated as well as practical examples of oil and gas production.     

THE PRODUCTION OF SYNTHETIC FUELS FROM NIGERIAN TANBAND BITUMEN

ABSTRACT

Synthetic fuels are expected to become a major source of energy supply in the future and major sources of synthetic fuels will be coal, shale oil and tar sand.

This paper presents an investigation of hydrotreating using a batch process for bitumen from Nigerian oil sand. The chatacteriistics in conversion of asphaltencs were studied. Various ananlyses were performed to obtain the properties of the bittemen before and after conversion to synthetic crude, e.g., changes of heteroatoms such as sulphur decreases of asphaltics, viscosity add specific gravity, and increases of distillate yield.

The process liquid fuel streams that are highly aromatic. The data suggest that the use of hydrogen causes stabilization of reactive intermediates rather than saturation of thermal products.     

A DETAILED CHEMICAL ANALYSIS OF CHANGES TO BITUMEN PRODUCED BY THE IN SITU COMBUSTION PROCESS AT THE OXYGEN WOLF LAKE PROJECT,ALBERTA PART 2: DISTILLATION CUTS AND CHROMATOGRAPHIC FRACTIONS

ABSTRACT

The detailed chemical changes in bitumen brought about over a one year period by an in situ combustion process in an oil sands reservoir have been investigated. The analytical data for the distillation cuts and chromatographic fractions from a core sample and a number of produced oil samples revealed significant changes as a result of the recovery process, particularly for the naphtha and middle distillate cuts. The residue cut did not exhibit any increase in heteroatom or asphaltene content. None of the changes to the produced oil samples would be expected to negatively impact on the subsequent upgrading process. The relationship between the observed changes to the fractionated oil samples and the dynamics of the in situ combustion process are discussed.     

A Mechanistic Model for Predicting Frictional Pressure Losses for Newtonian Fluids in Concentric Annulus

Abstract

A mathematical model is introduced estimating the frictional pressure losses of Newtonian fluids flowing through a concentric annulus. A computer code is developed for the proposed model. Also, extensive experiments with water have been conducted at Middle East Technical University, Petroleum and Natural Gas Engineering Department Flow Loop and recorded pressure drop within the test section for various flow rates. The performance of the proposed model is compared with computational fluid dynamics (CFD) software simulated annulus flow section and various criteria such as crittendon, hydraulic diameter and slot flow approximation as well as experimental data. The results showed that the proposed model and experimental results are in good agreement for almost all cases when compared with the other criteria and CFD software. Also, the proposed model could estimate the frictional pressure losses for both laminar and turbulent flow regimes within an error range of ±10%.     

Optimization Assisted Asphaltene Deposition Modeling in Porous Media During a Natural Depletion Scheme

Abstract

Changes in thermodynamic properties such as pressure, temperature, and composition may result in asphaltene precipitation and deposition in porous media. In addition, asphaltene deposition can cause wettability alteration, permeability reduction, and ultimately a decrease in the productivity of a reservoir. Natural depletion is one of the most common processes of asphaltene deposition in which pressure changes destabilize the dissolved asphaltene in the oil and settle them onto the rock surface.

In this work, natural depletion experiments in consolidated core samples were performed under simulated reservoir conditions to obtain reliable data and analyze the asphaltene deposition mechanisms.

A mass balance equation, momentum equation, asphaltene deposition, and permeability reduction models were applied to model the process of permeability changes as a result of asphaltene deposition. MATLAB programming language was used to calculate the numerical form of the above equations iteratively. A genetic algorithm technique was employed as the optimization tool for history matching and determination of model parameters.

Modeling and optimization results showed an accurate match with measured data. Optimization confirmed that all major deposition processes (surface deposition, entrainment, and pore throat plugging) were effective in permeability changes. Calculation of precipitated asphaltene saturation by the introduced equation provides information on the volume fraction of porous media that was evaded by the precipitated asphaltene particles.     

SOLID STATE 13C NMR STUDY OF THERMALLY UPGRADED LOW RANK COALS

ABSTRACT

The results of solid-state ¹³C NMR study aimed at evaluating the chemical changes and extent of upgrading achieved in the thermal treatment of two western Canadian low rank coals are discussed. The coals were thermally treated at varying temperatures (200 - 500°C) using different process media (nitrogen, steam and products of combustion)

Apparent aromaticity of the two coals was increased after the thermal treatment and increased with treatment temperature. Significant chemical changes, such as loss of the protonated aromatic carbons, quaternary carbons in alkylated rings and aliphatic ethers, were observed at 400°C and above. Condensation and polymerization of the chemical components were also evident. The effect of process medium was found to depend on the coal feed and the treatment temperature.     

EFFECT OF PYRITIC SULFUR AND MINERAL HATTER ON ORGANIC SULFUR REMOVAL FROM COAL

Abstract

The perchloroethylene coal cleaning process uses perchloroethylene as the solvent to remove both organic and inorganic forms of sulfur without any significant loss to its calorific value. The process removes these forms of sulfur in two sequential unit steps. The objective of this investigation was to determine the exact sequence of operations in the Process. Hence, organosulfur was removed before and after depyriting and demineralizing the coal. The extent of total sulfur as well as organic sulfur removal were compared in both cases. It was found that the desulfurization is more efficient when organosulfur is extracted before pyritic sulfur and not vice versa, in the sequential removal of organic and inorganic forms of sulfur. The data presented in this paper reestablishes a fact that the mineral matter content in coal is quintessential to its organosulfur extractability.     

Performance Evaluation of Cyclic Pressure Pulsing in a Depleted,Naturally Fractured Reservoir with Stripper-Well Production

Abstract

We present a parametric study on the operational parameters of cyclic pressure pulsing with N₂ and CO₂. We aim to develop a better understanding of how operational parameters affect the process performance in a shallow, naturally fractured, and depleted reservoir of the Big Andy Field in eastern Kentucky. The study includes analyses of various design parameters such as the injection rate, lengths of injection and soaking periods, cycle rate limits, and number of cycles. Incremental oil production, peak oil rate, and net present value (NPV) are considered as the performance criteria. Analyses have been performed using a single-well, dual-porosity, compositional reservoir model.     

FIRE FLOOD RECOVERY PROCESS EFFECTS UPON HEAVY OIL PROPERTIES

ABSTRACT

Heavy oil produced under primary and fire flood conditions was fractionated and analyzed to determine the changes occurring in the oil as a result of the recovery process. Oil produced under primary conditions showed a gradual increase in density, viscosity and other properties over time indicating fractionation during flow through the formation

Oil produced under fire flood conditions showed a decrease in viscosity and density and other properties as a result of the products of thermal cracking of the oil. GC-MS analyses indicate the formation of smaller straight chain alkanes and small aromatics molecules     

Aquathermolysis of heavy oil in reservoir conditions with the use of oil-soluble catalysts: part III – changes in composition resins and asphaltenes

Abstract

This paper discusses aquathermolysis process of heavy crude oil from Boca de Jaruco reservoir, which is developed by CSS method. The catalysts based on cobalt, nickel, iron and cupper are used to intensify the in-situ conversion processes. The active form of catalysts generates after steam injection. The third part of paper discusses conversion of resins and asphaltenes. The influence of thermo-catalytic conditions and composition of catalysts are also studied. The destruction of resins and asphaltenes are observed after thermocatalytic treatments. The changes in composition of resins and asphaltenes are revealed by IR-spectroscopy data.     

Predicting the response of explosives to attack by high-density shaped-charge jets

Abstract

Predicting an explosive's response to jet attack would appear to be difficult due to the complex nature of the projectile. Consequently it is surprising that such a simple criterion as that obtained by Held (v²D = constant) seems to be adequate in describing the initiation boundary of a given explosive under such circumstances. This paper discusses the complexity of jet impacts and compares experimental data with initiation boundaries formed by more regular projectiles. It appears that round-nosed rods, spheres and some jets form one class of projectile while flat-nosed rods form another. Both classes of projectile obey the v²D criterion, which is shown to approximate to the critical energy criterion. Such an approximation enables predictions to be made about the effect of jet density on the initiation boundary and gives estimated values of such boundaries for explosives tested only by plate or rod impacts. Some suggestions are made as to why such simple initiation criteria work, but the nature of jet formation also leads to a warning about placing too much reliance on such predictions for charge demolition, since small changes in tip geometry may precipitate drastic changes in apparent charge sensitivity.     

Development of risk assessment techniques for use in the field of explosives and ammunition

Abstract

Criteria for estimating the risks involved with ammunition and explosives are presented against a background of the public's perception of risk. The criteria are presented in terms of a three band approach separated by two threshold risk levels. The upper and lower bands represent unacceptable and trivial risk situations respectively, whilst the middle band represents a region in which the risk levels must be reduced to as low a level as is reasonably practicable.

Individual Risk criteria are presented for three groups of people: the workforce necessarily exposed to risk in the course of their daily work, those members of the workforce who do not need to be exposed to risk in order to do their work and the general public. In the case of Societal Risk only one set of criteria are presented on the basis that when a major incident involving large numbers of casualties occurs the public reaction does not discriminate in its perception of horror between members of the general public and members of the workforce. In addition to preserving life it is suggested that criteria are required to preserve stocks in situations where life itself may not be at risk. For this it is recommended that the propagation of initial initiation or explosion to other munitions nearby by sympathetic detonation should be prevented, as far as possible, by the maintenance of the current separation distances for magazines, updated where necessary as new knowledge becomes available and new explosives and munitions are developed.

The present tentative proposals are compared with quantitative risk evaluation criteria proposed in other countries and in other industries.     

Modified Screening Criteria of Potential Asphaltene Precipitation in Oil Reservoirs

Abstract

In this article, the De Boer method, the most widely used screening criteria for potential asphalt precipitation, is modified by specifying separate plots for each reservoir. The solubility parameter, which is the most important parameter in this method, is calculated by using the concept of refractive index. Accuracy of the predictions was confirmed by the colloidal instability index, asphaltene–resin ratio, and asphaltene instability trend techniques. Finally, the applicability of this approach was checked using six real cases of Iranian reservoirs. These cases were chosen to include oils with different API gravity, asphaltene content, and extremities (severe to no problem).     

A new ignition criterion based upon a critical thermal energy density

Abstract

It has long been known that various ignition criteria of energetic materials have been limited in applicability to small regions. In order to explore the physical nature of ignition, we calculated how much thermal energy per unit mass of energetic materials was absorbed under different external stimuli. Hence, data of several typical sensitivity tests were analyzed by order of magnitude estimation. Then a new concept on critical thermal energy density was formulated. Meanwhile, the chemical nature of ignition was probed into by chemical kinetics.

Finally, it was considered that perhaps the critical thermal energy density was an important characteristic parameter for energetic material ignition.     

Theoretical and Practical Aspects of Tertiary Hydrocarbon Migration

Abstract

Primary and secondary migrations are well defined terms in hydrocarbon reservoir genesis, as spontaneous hydrocarbon displacement from the source rock to the final trap. The fluid movement that occurs after reservoir abandonment defines the tertiary migration process. The result of the tertiary migration is a new saturation distribution within the reservoir and it is expected that in the most favorable cases, the production potential of some parts of the reservoir might be restored. The principles and factors involved in the tertiary migration process are examined and two successful production restarting projects in Romania are presented, as proof of the new concept effectiveness.     

A DETAILED CHEMICAL ANALYSIS OF CHANGES TO BITUMEN PRODUCED BY THE IN SITU COMBUSTION PROCESS AT THE OXYGEN WOLF LAKE PROJECT,ALBERTA PART 1: WHOLE OIL SAMPLES.

ABSTRACT

The detailed chemical changes in bitumen brought about over a one year period by an in situ combustion process in an oil sands reservoir have been investigated. Relative to a core sample, the fireflood-produced oils exhibited a significant reduction in density and viscosity which began early in the production cycle. This behaviour was correlated with a marked increase in material boiling in the naphtha and middle distillate ranges and a concomitant decrease in the residue cut. The sulfur and nitrogen contents in the produced oils decreased relative to the core sample. A reduction in the acid number of the produced oil samples was coupled with an increase in the oxygen content as the firefiood proceeded. The relationship between these changes and the dynamics of the in situ combustion process are discussed.     

The Importance of Asphaltene Content in Petroleum III—New Criteria for Prediction of Incompatibility in Crude Oil Blends

Abstract

Our previous results have shown that macroscopic properties of petroleum media may undergo abrupt changes caused by currently underinvestigated microscopic phase transitions in asphaltene nanocolloids. In particular, native crudes of diverse origin exhibit sharp viscosity and density peaking at phase boundaries, defined by specific asphaltene contents. We suggest that when these asphaltene contents are approached in blends of several crude oils, severe incompatibility may be observed; for example, massive appearance of solid sediments. New criteria for most incompatible and for most compatible blends are formulated in terms of grams per liter of asphaltene concentrations.     

The Lumping Kinetic Model for the Heavy Oil Catalytic Cracking MIP Process

Abstract

Based on the characteristics of heavy oil catalytic cracking and maximizing iso-paraffins (MIP) process, a 12-lumping kinetic model was developed in this article to simulate the MIP process. According to the published data from a commercial MIP process, 36 kinetic parameters of the model were determined by the stepwise method. The verification result with industrial data showed that the model could predict not only the distribution of products but also the quality of main products and describe the reaction rules of the MIP process correctly.     

An Experimental Investigation of Asphaltene Precipitation During Natural Production of Heavy and Light Oil Reservoirs: The Role of Pressure and Temperature

Abstract

Many oil reservoirs encounter asphaltene precipitation as a major problem during natural production. In spite of numerous experimental studies, the effect of temperature on asphaltene precipitation during pressure depletion at reservoir conditions is still obscure in the literature. To study their asphaltene precipitation behavior at different temperatures, two Iranian light and heavy live oil samples were selected. First, different screening criteria were applied to evaluate asphaltene instability of the selected reservoirs using pressure, volume, and temperature data. Then, a high pressure, high temperature filtration (HPHT) setup was designed to investigate the asphaltene precipitation behavior of the crude samples throughout the pressure depletion process. The performed HPHT tests at different temperature levels provided valuable data and illuminated the role of temperature on precipitation. In the final stage, the obtained data were fed into a commercial simulator for modeling and predicting purposes of asphaltene precipitation at different conditions. The results of the instability analysis illustrated precipitation possibilities for both reservoirs which are in agreement with the oil field observations. It is observed from experimental results that by increasing the temperature, the amount of precipitated asphaltene in light oil will increase, although it decreases precipitation for the heavy crude. The role of temperature is shown to be more significant for the light crude and more illuminated at lower pressures for both crude oils. The results of thermodynamic modeling proved reliable applicability of the software for predicting asphaltene precipitation under pressure depletion conditions. This study attempts to reveal the complicated role of temperature changes on asphaltene precipitation behavior for different reservoir crudes during natural production.