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ABSTRACT System standardisation is acknowledged to be one area which can significantly reduce the life cycle costs for any project This paper looks at subsea control systems, specifically the Norsk Hydro Troll Olje Project in the light of previously defined objectives INTRODUCTION The subject of standardisation for subsea control systems has been broached several times This review takes as its starting point the paper presented at Subsea Control and Data Acquisition (1992) otled "Standardisation of Subsea Control Systems" Since that time, the first deliveries to the Troll Olje project have taken place and we are in a position to evaluate some of the theories and practicalities in the light of a "real life" project The alternatives of a "Company Standard" or "Vendor Standard" both have drawbacks, however the use of commercially available products which have been pre-qualified seems to be a path that several vendors and oil companies might like to consider Since the system suppliers are in continual competition in the world market, the prices should be market driven and a monopoly situation is less likely to occur. The "market" is governed by oil companies and they have different views and requirements which may make standardisation more difficult to achieve We will show the areas where "standardisation" is reasonably easy to achieve and look at the more difficult topics such as the Subsea Electronic Module (SEM) where the challenge is greater The Starting Point for Standardisation In late 1991, Norsk Hydro started presenting their views to various subsea control vendors with the intention of having some "standardisation" in place when the Troll Olje subsea control package came out for tender There were some general function requirements and some specific equipment requirements :-an electrohydraulic system was desirable, subsea communication would be superimposed on the power cables; it would be possible to modify subsea software from topside, subsea software was to be written in a high level language, Subsea Control Unit (SCU) would be an integral part of the DISCOS (Distributed Supervision, Control and Safety) system, Hydraulic Power Unit (HPU) would be part of the normal topside equipment, Emergency Shutdown (ESD) would be obtained by means of a system physically separated and different from the Process Shutdown (PSD) system, Xmas tree Instrumentation would not influence the workover frequency, Interfaces should be standardised and resolved by the various subcontractors With these requirements as a base, and a range of pre-qualified components, the subsea control vendors were asked to quote against a well tried solution using "standard" components Norsk Hydro had all the experience of TOG1 and previous projects to hand when reviewing the various solutions and components, and were able to ensure that known pitfalls were avoided The GEC-Marconi Oil & Gas (G-MOG) solution was to fit the pre-qualified components into an existing and tried solution which has evolved over many projects "A move towards subsea control system standardisation?" This is the question we will now attempt to answer
ABSTRACT The enhanced reliability and downsizing of electronic equipment in general, together with the increasing power of microprocessors and the use of Industry Standard Protocols, has now opened up more than ever before the opportunity for Subsea Instrumentation Systems, to utilise Standard Instrument and Control equipment INTRODUCTION The current exploitation of marginal oil and gas fields has resulted in the use of more cost effective methods of production, such as subsea wellheads. Control and Instrumentation just as in any other oil and gas installation, has a major role to play in the success of such applications. However, what should be a straight forward and simple application of a small DCS/SCADA System IS often complicated and over engineered to compensate for the perceived harsh environment into which the equipment is being placed, especially that which is being located subsea in actual fact, there are many propriety elements of such a DCS/SCADA System available today which, due to the state of current technology and Quality Assurance, are together suitable for such applications without recourse to over specified and therefore excessively expensive solutions. Whilst providing due consideration to the problems of Subsea/Topsides monitoring and control applications the use of PC workstations, PC based process control software packages, dual high security communications and remote intelligent I/0, can provide for a highly featured, secure and cost effective system. Moreover, the established use of Smart transmitters which communicate digitally has meant that the ‘reading’ of Process values can now be made at the topsides terminal with a much greater degree of accuracy than via a conventional Analogue card Also possible with Smart sensors are enhanced self diagnostics and the ability remotely re-range and recalibrate the transmitters from the topsides terminal. This paper will examine just such a system and provide an overview of what can be achieved simply and effectively EQUIPMENT OVERVIEW In considering any Subsea Monitoring and Control System, there are three main elements, the Subsea equipment, the Communication equipment and the Topsides Monitoring and Control Sub-system We shall take each of the above In turn and briefly examine proprietary equipment which can be used In the Subsea environment, with little or no changes other than application specification engineering SUBSEA INTERFACE EQUIPMENT This category of equipment can be broken down into three sub-headings, Primary Transducer, Electronic Interface and Communications Taking each of the above in turn we will look at what is currently commercially available, as follows Primary Transducer - Conventional There is currently available a multitude of conventional transducers suitable for installation In some extremely harsh environments - far more onerous than can be found in the relatively stable environment of a Subsea Instrument housing Such transducers can be chosen, not only for their particular Interface characteristic se, pressure, temperature, flow, but also chosen for their reliability, quality and construction medium i e stainless steel, flameproof, etc Such transducers provide Industry standard outputs such as 4–20mA, voltage and milli-volt signals which can be "read" by virtually all I/O proprietary input/output equipment
SPE Members Abstract Numerical simulation of miscible displacement experiments in fractured porous media was carried out to analyze the data. It was found that both the location and the magnitude of the fracture permeability heterogeneity were the main factors in determining the miscible displacement efficiency. The stripping of solute from matrix to fracture, which is caused by the permeability variation in the fracture, significantly increases the recovery efficiency. By taking the fracture permeability heterogeneity into account, the experiments were successfully simulated. Introduction The initial (also the maximum) gravity drainage rate, qo of a homogeneous rock matrix for an immiscible process is (1) In Eq. 1, is the threshold capillary pressure, and L is the height. Other symbols are defined in the Nomenclature. Assumptions made in the derivation of Eq. 1 include infinite gas mobility. In fractured porous media comprised of matrix blocks and fracture network, the initial (also the maximum) gravity drainage rate does not exceed that of the unfractured porous media, provided the fracture storage is negligible. After the initial period, due to the contrast in capillary pressures of the matrix and the fracture, the gravity drainage rate of the fractured media is less than that of the unfractured media. For zero capillary pressure, Eq. 1 reduces to. The critical rate for frontal instability (viscous fingering) in a homogeneous medium is given by. Therefore, the maximum drainage rate is less thanprovided the displacing fluid has a negligible viscosity. In the experiments presented in Ref. 5, even when the rate of injection or production exceeded the critical rate, an efficient displacement was achieved. The main reason for such high recovery efficiency is a pronounced crossflow mechanism between the fracture medium and the matrix blocks. The primary objective of this work is to analyze the laboratory measurements reported in Ref. 5 and to investigate the mechanism which results in a very pronounced crossflow of fluids between the matrix and the fractures. EFFECT OF FRACTURE HETEROGENEITY Ref. 5 provides data on miscible displacement tests for different fluids at various injection rates (different V/V the critical velocity, and for a unit cross sectional area) in the two-, three- and twelve-slab assembly. The data reveal that the recovery performance in these tests are more efficient than in the corresponding experiments of Thompson and Mungan, performed at the same V/Vc. The effluent concentration is small after the primary breakthrough, then gradually increases to about 1 PV of injection. This characteristic is completely different from the data of Thompson and Mungan, which show a sharp primary breakthrough, plateau of solvent cut for a long period of time, then a sharp secondary breakthrough. P. 603^
A Partially Scaled Physical Model of Cyclic Steam Stimulation for Recovery of Oil and Bitumen
Frauenfeld, T.W.J. (Alberta Research Council) | Kimber, K.D. (Alberta Research Council) | Sawatzky, Ron (Alberta Research Council) | Purewal, Gurdeep (Alberta Research Council) | Drake, Ken (Alberta Research Council)
Abstract Cyclic steam stimulation is the most widely used thermal recovery process for Alberta heavy oils and bitumen. This is a complex process where bitumen production is a result of the interaction of several mechanisms. Such a process may be studied by numerical models and by physical models. Physical models of a petroleum recovery process are a useful adjunct to numerical models. Physical models may be used to validate numerical simulations, and may also be used to study process for which the mathematical formulations are not well defined. A partially scaled physical model was used in this study, in order to evaluate available numerical simulators and to study mechanisms involved in the process. In order to design and construct a partially scaled physical model of a cyclic steam stimulation, the important mechanisms must first be defined. The approach used was to run partially scaled lab models of the process, each of which scaled different mechanisms, and compare the model results with those of the prototype. This study compared 2 models, one built using the criteria developed by Pujol and Boberg, the other built using criteria developed by Kimber (Kimber #2). The former model scaled the relationship between pressure drive forces and gravity forces, while the latter scaled pressure drive forces and fluid expansion. The experimental results were compared to numerical simulations of both models and of a field scale prototype reservoir. The experimental and numerical results indicated that gravity the presence of non-condensable gasses and capillary forces were significant forces influencing oil production in the lab models. Capillary forces were less significant in the field scale simulations. The Pujol and Boberg model produced a better representation of cyclic steam stimulation than did the Kimber #2 model. Fracture dynamics and related effects were not represented. This type of a model is applicable to heavy oil reservoirs where there is sufficient initial fluid mobility to establish injectivity without fracturing. P. 593^
- North America > United States (1.00)
- North America > Canada > Alberta (0.90)
- North America > Canada > Alberta > Western Canada Sedimentary Basin > Alberta Basin > Cold Lake Field > Clearwater Formation > 995053 2D Cold Lake 2-10-63-2 Well (0.99)
- North America > Canada > Alberta > Western Canada Sedimentary Basin > Alberta Basin > Cold Lake Oil Sands Project > Clearwater Formation (0.98)
SPE Members Abstract Numerical simulation of multicomponent adsorption (such as in foam-forming surfactants, lignosulfonate, polymer/surfactants, etc.) is still at an early stage. Mathematical models of multicomponent adsorption and desorption in a surfactant/rock system have not yet been well developed. In this paper, a mathematical model for multicomponent adsorption, based on surface excess theory, is presented. The mathematical model is validated through more than 30 experimental runs under a wide range of operating conditions. Several multicomponent mixtures were used in the experimental runs to observe the effects of surfactant concentration, chemical slug size, flow rate, rock properties, salinity of the surfactant solution, and temperature. With the application of lignosulfonate as a sacrificial adsorbate, the amount of surfactant adsorption can be reduced significantly. Polymersurfactant solution flooding system is a economical way to increase the efficiency of chemical injection. Polymer has beneficial effects on surfactant adsorption though polymer itself still has strong adsorption at the solid/liquid interface relative to surfactant. Numerical simulation results showed excellent agreement with experimental data. Introduction The phenomenon of adsorption and desorption at solid/liquid interface is of major importance in the process of enhanced oil recovery with the application of surfactant. More recently, foam-forming surfactants have been used in remediating contaminated soils foam-forming surfactants have been used in petroleum industry for enhanced oil recovery. Some simulation research had been made with regards to the processes of surfactant flooding. The behavior of surfactant under various conditions had been studied by different researchers. Adsorption is one of the main mechanisms for surfactant loss in any process that uses surfactants. Laboratory study and field tests indicated that surfactant loss by adsorption could be significantly reduced reflushing lignosulfonate as a sacrificial adsorbate. Different mechanisms of surfactant adsorption have been recognized and adsorption modeling were made with good results Surfactant adsorption at the solid/liquid interface can be modeled with either a Langmuir-type model or a surface excess model. The Langmuir equation was used in simulating adsorption and desorption of some chemical floodings in enhanced oil recovery. For a thermodynamically consistent study, the surface excess theory is more suitable to model surfactant adsorption and desorption at the solid/liquid interface. P. 615^
Abstract In this paper we examine factors influencing the characteristics of slightly sub-miscible gas displacement of oil in a heterogeneous system. 2D fine grid compositional solutions are obtained using a fast simulator, MORE, on a Cray YMP computer for a stochastically generated heterogeneity distribution. It is shown that only four pseudo-components are needed to represent the phase behavior adequately and that although fairly low interfacial tensions are obtained, there is not a discernible need to modify the immiscible relative permeabilities. Comparisons are made with heterogeneous results based on the simpler first contact miscible assumptions often used in two-component high resolution simulations of viscous fingering. The fully compositional flow is less unstable than its miscible counterpart, but it is found that the latter can be made to reproduce a compositional solution through reducing the mobility ratio from M = 20 to M = 5. A method for determining this effective mobility ratio is described. Cases with gravity give moderate agreement using M = 5, provided an ad hoc adjustment is also made to the gravity number. Introduction The intention of this work is to obtain a better understanding of how phase behavior, adverse viscosity ratio, viscous fingering, heterogeneity and gravity interact in compositional modeling of gas displacement processes. One of the difficulties in understanding such problems arises from the fact that in a multi-contact process leading to miscibility, the two phases move quickly towards equality in composition, so that density and viscosity contrasts are substantially reduced. However, at positions away from the mixing zone, the injected and in situ phases retain their original contrasts in properties. This led to the Todd and Longstaff method for modeling viscous fingering in such systems, where the problem is represented in terms of a mixing rule with effective properties for the phases. This formulation neglects phase behavior and is based on the hypothesis that the system behaves very similarly to a first contact miscible process. More recent studies have indicated that multi-contact processes do not generally attain miscibility (see for example Ref. 2) and that dispersion effects can lead to sub-miscible behavior with some detrimental effects on oil displacement. Another factor relates to heterogeneity, where it is becoming increasingly evident that reservoir heterogeneity has a strong effect on fingering patterns, although the magnitude of the adverse viscosity ratio also strongly influences the behavior. The correct way to adjust the Todd and Longstaff mixing parameter for heterogeneity is poorl;y understood. Because heterogeneity forces the displacing fluid to take preferred paths, the sweep characteristics are very different from the homogeneous case, and the assumptions of uniform mixing within large grid blocks are often highly erroneous. For these reasons, the alpha-correction procedures were introduced by Barker and Fayers into compositional modeling to compensate for the non-uniformities in phase behavior and component transport associated with the use of large grid blocks. In the present studies, we set up a "mildly" heterogeneous problem and study the attributes of the various ways discussed above of representing its behavior under nearly miscible displacement. P. 547^
SPE Members Abstract This paper presents a method for lowering the permeability of thief zones in oil reservoirs to improve recovery during waterflood operations. The method consists of preheating the thief zone around the injection or production well by injecting hot water or steam and then injecting a hot, saturated chemical solution. If the chemical has a lower solubility at reservoir temperature than at injection temperature, cooling within the formation will result in the precipitation of solids in the pore spaces. Several chemicals were identified as having a suitable temperature-dependent solubility with a low environmental toxicity, including potassium carbonate and sodium borate. The porosity and permeability reduction from temperature-dependent precipitation of these chemicals was then experimentally determined and a correlation between the permeability and porosity reduction was obtained. A theoretical analysis of this promising new process and how it can be applied are also presented. Introduction It is often desirable to plug geological formations to limit or prevent fluid flow. Cases where such plugging may be desirable include heterogeneous oil reservoirs that have high-permeability thief zones and hazardous waste sites that have a potential for leaching soluble wastes. Various methods to deliberately plug geologic formations have been proposed. In one method very small solid particles are injected to bridge across pore spaces 1. The injection of solid particles, however, is only effective in changing the permeability close to the point of injection. In another method, chemically incompatible fluids are injected into formations and allowed to mix. The use of gels has also been proposed. The permeability change from gels, however, is a function of the fluid viscosity rather than of a physical change in the matrix flow path. A number of methods have been presented to model chemical dissolution and precipitation reactions in porous media. These models, however, have not adequately addressed the corresponding reductions in porosity and permeability and their subsequent effect of fluid flow. These models could, in principle, be modified to predict the reduction in porosity by adding a volume balance to the pore space. Several theoretical models have been presented on ways to estimate the reduction in permeability following chemical precipitation. The simplest approach to modeling the permeability of a porous medium is to treat the medium like a bundle of capillary tubes. The "capillary tube model" is developed from Poiseuilles' equation for flow through a single tube. The permeability, K, of a porous medium using this model can be expressed as (1) where "x" is the average spacing between tubes, and is the porosity. P. 539^
SPE Members Abstract There is increasing concern among domestic-operators for reducing water production as fields mature. A new polymer gel, with several unique advantages over conventional gelling systems, has been developed which could serve as a water shut-off agent. The gel forms in place when a freshwater solution of a water-soluble polymer (hydroxypropylcellulose, HPC) and a surfactant (sodium dodecyl sulfate, SDS) mixes with brine. While conventional gels use a chemical initiator or activator, often a heavy metal like chromium, to form the gel, the new HPC/SDS gel uses the salinity of the connate brine to initiate immediate gel formation The low-viscosity freshwater HPC/SDS solution injects easily into core material. Upon mixing with the connate brine, a stable high-viscosity gel forms that effectively reduces brine permeability by over 95% in both linear and radial sandstone corefloods. The gel viscosity was measured at about 70,000 centipoise. Permeability reduction is maintained, both in the forward and reverse flow direction, even after several pore volumes of brine flow. In a parallel coreflood test, the gel diverted 90% of the fractional flow of brine. Introduction Significant water production is a serious problem faced with increasing frequency by producers. While this problem can arise for several reasons, production from high-permeability, watered-out streaks or channels during waterflooding operations is a common cause. Additionally, fluids injected into one zone, because of permeability variations, tend to channel to zones of higher permeability, resulting in poor vertical conformance. The injected water thus bypasses the oil-bearing zones. Many processes have been proposed and developed to reduce preferential channeling through high-permeability zones. P. 529^
- Energy > Oil & Gas > Upstream (1.00)
- Materials > Chemicals > Commodity Chemicals > Petrochemicals (0.46)
Moradi-Araghi, Ahmad, Phillips Petroleum Co. SPE Member Abstract Earlier reports from our laboratory described a number of thermally-stable water-soluble polymers which tolerate extensive aging times in brines with high salinity and hardness levels at temperatures up to 149 C (300 F). These polymers can be crosslinked with phenol and formaldehyde crosslinking system to produce stable gels under hostile environment conditions typically defined as temperatures higher than 167 F (75 C) and brine hardness levels above 2000 ppm. The resulting gels can be used for profile modification and water shutoff treatments under hostile environment conditions. In one paper we proposed a mechanism for the gelation of acrylamide containing polymers. This mechanism postulates the formation of salicyl alcohol as an intermediate through the condensation of phenol and formaldehyde. P. 483^
- Energy > Oil & Gas > Upstream (1.00)
- Materials > Chemicals > Commodity Chemicals > Petrochemicals (0.66)
- Production and Well Operations > Well Intervention > Water shut-off (0.54)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery > Waterflooding (0.48)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Flow in porous media (0.48)
- Well Drilling > Drilling Fluids and Materials > Drilling fluid selection and formulation (chemistry, properties) (0.42)
Abstract The influence of pH, temperature, and gelation delaying ligands on the stability of Cr(III) complexes in bulk solution and on Cr(III) propagation in porous media has been investigated for acetate, glycolate, and malonate complexes of Cr(III). For a given complex, Cr(III) instability to hydrolysis and Cr(III) retention increase with increasing pH and temperature. The chemical nature of the gelation delaying ligands bound to Cr(III) and their concentration in the solution have a profound influence on the resistance of the Cr(III) complex to hydrolysis and on Cr(III) retention. Thus, whereas the Cr(III) acetate crosslinker, by itself, propagates poorly at elevated temperature, addition of sodium glycolate to the solution markedly reduces retention. We show that Cr(III) retention in sandstone cores can be virtually eliminated at 90 C by appropriate formulation of the gel-formiag solution. Other experiments establish that Cr(III) precipitation at elevated temperature is reversible in the presence of polymer and that significant accumulation of the Cr(III) precipitate can have a negative impact on injectivity. Introduction Economic factors and environmental considerations have made water management a key issue for operators in the 1990's. Technical solutions that offer the possibility to reduce the amount of produced water, and thereby maintain or recover well profitability, command particular interest. Polymer gel treatments have been employed for this purpose, with varying degrees of success, for nearly three decades. Recent, impressive field results obtained with gels have played an important role in the current revival of interest in this technology. Greater attention devoted to the identification of suitable candidate wells and to treatment design have been key factors in the recent successes achieved with polymer gels. An important role has also been played by the introduction of new gel-forming fluids (hereafter referred to in this paper as "gelants") based on the use of Cr(III) acetate and acrylamide polymers, which provide improved reliability in the field while resolving toxicity problems associated with some of the earlier formulations. The short gelation times of Cr(III) acetate/polymer compositions at elevated temperature, however, limit their application to lower temperature reservoirs. An important industrial objective therefore is to develop gelants that permit the extension of these gel treatments to hot reservoirs. We have reported recently the development of a family of new Cr(III)/polymer compositions that provide excellent control over, and wide flexibility in programing, gelation times to temperatures as high as l50 C. P. 505^
- Research Report (0.46)
- Overview (0.34)
- Geology > Mineral (0.69)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.35)