bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Experimental Compositional Approach to Study Dynamic Miscibility in Nitrogen Injection in Light Crude Oil
Authors: Alcocer Charles F. 
Published: June 2014

SUMMARY
Laboratory research was conducted to study displacements of crude oil by high pressure nitrogen injection. The objective of this study was to design and build a physical reservoir model able to simulate reservoir temperature and make possible the collection of sampling during displacement to track the phase compositional changes taking place during the process of building up dynamic miscibility in high pressure nitrogen injection in light crude oil. The reservoir model was a stainless steel tube 125 feet long and 0.435 inches in diameter, packed with sand consolidated to give an average permeability of 930 md. The model was provided with five sampling valves to collect vapor samples during actual nitrogen displacement. Continuous sampling during displacement provided material for chromatographic compositional analysis, construction of profiles of component by component to establish their role in the building up of dynamic miscibility, construction of ternary diagrams to follow the process and way to predict the so-called multicontact miscibility in high-pressure nitrogen injection. Results of 4 dynamic tests are presented. All tests were performed above the minimum miscibility pressure using 42 API petroleum fluid. The analysis of the results shows very clearly that the composition approach to explain the three different zones that are created in a displacement of this nature is technically sound. The first zone was identified by analyzing produced fluids. The second zone was identified as a two-phase flowing zone and is the result of nitrogen being initially immiscible with reservoir light crude oil. Analysis of the shape of compositional profile curves suggested that vaporization is very strong at the beginning of the process and at the leading edge of the second zone. The slope of straight lines of composition profiles are direct consequence of vaporization rate. The third zone is one-phase flowing zone. If miscibility is built up it would be created in the leading edge of zone two of the displacement. This was the case for all tests run in this study.
Cement Bond Logging - A New Analysis to Improve Reliability
Authors: Gai H , Lockyear C F 
Published: June 2014

ABSTRACT
Since the CBL tool came into use over 30 years ago, Bond Index (BI) has been the most important parameter in interpreting a valid log. In recent years, more and more engineers started disbelieving the CBL because they found that the BI did not often tell the truth. Several investigators have been tackling this problem, but its complexity seems to have been overwhelming.
Fundamental studies have been carried out in the BP Research centre, Sunbury UK. It was found that the BI was obscured by the "engineering treatment" of attenuation rates which does not have correct theoretical grounds or physical intuition. This paper analyses BI and its related topics, and derives the Bond Percentage Index (BPI) which is accurate and reliable in predicting the bond conditions. It is concluded that BPI is the correct description of reality and BI, being derived on false basis, should be abandoned.
A Correlation for Miscible Flood Displacement Efficiency in the San Andres With NMR Relaxation
Authors: Hazlett R. D. , Furr M. J. , Navarro R. 
Published: June 2014

ABSTRACT
A set of San Andres crystalline dolomite cores was examined for the relationship between pore attributes discernible from NMR relaxation and miscible flooding displacement efficiency. A strong correlation was observed between the inferred abundance of long relaxation time components and laboratory measured residual oil to a multicontact miscible displacement process. NMR relaxation time distribution proved to be a simple, noninvasive, nondestructive indicator of flow performance in the 12 San Andres dolomite samples examined.
Spin-lattice relaxation measurements were conducted on clean, brine saturated core end pieces from plugs taken adjacent to those used for flow displacement studies. Sample data were deconvoluted into a distribution of relaxation times, which is intimately related to surface-to-volume ratio distribution. The median relaxation time was determined to be the most sensitive statistic to convey flow performance. Residual oil saturation was adequately represented by a power law function of the median relaxation time.
Relaxation time is recognized to be a function of pore size, shape, surface roughness, and mineral composition. It was determined through direct observation by scanning electron microscopy that variation between samples was principally due to pore size distribution. Samples with larger mean pore size were observed to be less efficiently swept. Larger pores within a distribution are envisioned to bias individual fluid flow pathways, causing significant stranding of oil.
Interfacial Tension Measurement of Oil-Water-Steam Systems Using Image Processing Techniques
Authors: Huygens R. J. M. , Boersma D. M. , Ronde H. , Hagoort J. 
Published: June 2014

SUMMARY
To study the assumed correspondence between increasing spreading coefficients and decreasing residual oil saturations during steamflooding, knowledge of the spreading behaviour is essential. In this paper, the emphasis is on the accurate measurement of interfacial tensions (IFTs) that are required for the determination of spreading coefficients. With the pendant drop method in combination with image processing techniques, which considerably improve the quality of the measurements, we examined several calculation methods for determining the IFT from processed drop images. A new direct calculation method is less time-consuming than existing methods, but more sensitive to the quality of the experimental data. We applied the experimental procedures to three oil-water and oil-steam systems. The results show that the interfacial tensions of these systems tend to decrease with increasing temperature. Calculation of the spreading coefficients shows that accurate IFT-measurements are of paramount importance and that n-tetradecane spreads on water in the presence of steam in the temperature range investigated.
Polymer-Enhanced Foams Part 2: Propagation Through High-Permeability Sandpacks
Authors: Sydansk Robert D. 
Published: June 2014

SUMMARY
In this Part 2 paper on the initial laboratory study and development of polymer-enhanced foams (PEFs), the performance (effective viscosity and mobility control), propagation, and stability of relatively small (0.2 PV) PEF banks (slugs) were studied as they were flooded through long (20 ft), slim-tube-type, high-permeability sandpacks.
The objective of this study was to investigate the performance of PEFs under more demanding experimental conditions than the laboratory studies reported in the Part 1 paper of this series. Another explicit goal of this work was to study the performance of PEFs in the presence of crude oil.
Results of constant-differential-pressure flooding experiments, conducted at ambient conditions, showed that small (0.2 PV) PEF banks were propagated, were stable, and promoted relatively large effective viscosities and good mobility control during flow through the entire length of the 20-ft-long sandpacks. The high-permeability sandpacks were intended to be a one-dimensional model of a propped fracture. The standard PEF formulation of this study was shown, during these flooding experiments, to perform much better, to be much more propagatable, and to be much more stable than its counterpart conventional foam. The PEFs were also shown during these experiments to be much more stable and functional in the presence of the studied crude oils than their counterpart conventional foams.
Aging in a sandpack for 20 days after the PEF bank had been initially injected had little impact on the performance, propagation, and stability of the standard PEF. The PEFs were shown during these flooding experiments to be able to effectively mobilize and recover crude oil, especially a viscous (440 cp) crude oil. Relatively good performance, propagation, and stability of PEF banks during these flooding experiments were observed for PEFs formulated with, respectively, carbon dioxide, nitrogen, and methane. Carbon dioxide PEFs were exceptionally effective at promoting large effective viscosities and good mobility control. In addition, they were especially effective at mobilizing and recovering crude oil. For the PEFs of this study, the minimum effective polymer and surfactant concentrations for effective performance in the presence of a crude oil were determined. Minimum polymer and surfactant concentrations required for effective performance were greater in the presence of crude oil, than in the absence of crude oil.
Scleroglucan Gels for Profile Modifications in High-Temperature Reservoirs
Authors: Fjelde Ingebret , Stavland Arne 
Published: June 2014

SUMMARY
It is found (hat Cr3+ cannot form gel with scleroglucan. Using dichromate, Cr2O72−, it is found that dichromate has to oxidize alcohol groups on the scleroglucan molecule to carboxyl groups, before Cr3+ crosslinking is possible. The thermal stability of these gels is a function of the amount of dichromate added, because less thermal stable carboxyl groups are formed on the scleroglucan molecule.
Melamine-formaldehyde resins crosslink polyols like scleroglucan without any derivatisation of the polymer.
A Note On Pressure-Transient Analysis Of Fractal Reservoirs
Authors: Chang Jincai , Yortsos Yanis C. 
Published: June 2014

Abstract
In a recent paper1 we introduced a novel approach for the identification and description of a fractal reservoir using concepts from fractal geometry. However, the analysis presented in Ref. 1 was unduly restrictive and suffers from two drawbacks: First, it is based on the use of a generalized diffusivity equation, the validity of which has been the subject of recent debate.2 In that formulation, the diffusivity was taken to be position-dependent. This reflects the long memory associated with random walks (diffusion) on fractal objects. Alternative approaches in anamalous diffusion have also been used, e.g. with time-dependent diffusivity, or with the use of an integro-differential equation (see Ref. 3 and references therein). Second, as in all formalisms, the underlying assumption is that of a single source (well) in an unbounded medium. As a result, the equation cannot be directly extended to many wells and variable rates as is the case with normal diffusion. Although generalized diffusivity equations have also been used in other fields involving fractals4 it appears that alternative approaches based on Green's functions are more appropriate. It is the purpose of this note to provide such an alternative and to clarify certain issues related to the description of single-phase, slightly compressible fluid flow in fractal reservoirs.
We emphasize from the outset that as in Ref. 1, finite effects are not considered in this note. This presupposes a reservoir which is fractal over a wide range of scales, such that upper and lower cutoffs are greatly separated. The implication is that effects of boundaries are absent. Our recent numerical results5 have demonstrated that finite size, namely boundary, effects affect significantly the late-time behavior and must be carefully differentiated from the purely fractal response. Nonetheless, developing the proper formalism for an unbounded (theoretical) fractal is still desirable to serve as a guide for the more realistic finite size cases. In fact, it is only outside of boundary effects that a fractal response can be clearly identified.
In theory, fractals obey power-law scaling around an arbitrary point. In particular, properties, such as permeability, are scale-dependent with the same exponent at any location. Consider then the pressure response in such a fractal reservoir at location x due to n wells located at x_i(i =1, 2, …, n), and producing at rate qi(t) (where qi may also be negative). The solution of this problem can be obtained in terms of the free space Green's function g(ξ_−ξ_′,   t−t′), which represents the response at point ξ_ and time t due to an instantaneous point source at point ξ_′ and time t′. Because of the linearity of the process, a simple superposition gives the result
On-Site Real-Time Analysis Allows Optimal Propped Fracture Stimulation of a Complex Gas Reservoir
Authors: Johnson D. E. , Wright C. A. , Stachel Alfred , Schmidt Holger , Cleary M. P. 
Published: June 2014

ABSTRACT
In order to increase gas production in an under-producing formation, the German utility/eneigy company RWE-DEA stimulated the Wardboehmen Z1 well with a propped fracture treatment on December 6, 1991. Two days prior to the main fracture treatment, a step-rate test and mini-fracture were pumped for the purpose of evaluating more accurately the characteristics of the reservoir, including closure stress, leak-off rates, and permeability (and stress) profile. This information was then used to substantially improve the originally proposed design, provided by the service company, in order to create an effective/optimal propped fracture in this reservoir, incidentally also producing major savings in job cost. For the first time in Germany, electronic bottomhole pressure-measuring equipment with surface readout was used, during the minifirac. Availability of the bottommhole pressure data in the minifrac and repeated abrupt flow-rate changes, including shut-ins of about one minute, during both the minifrac and main fracture treatment allowed realistic simulation of fracture development with an on-site real-data 3D simulator. It was possible to determine the continually changing friction losses in the near-wellbore vicinity of the perforations: this tortuosity was very high initially but reached acceptable values after pumping the re-designed pad volume. This finding was important because it minimized the risk of a premature nearwellbore screen-out resulting from the planned proppant concentrations, up to 1,250 g/1 (10 ppg). The fracture treatment led to a consistent four-fold increase in the gas production rate. This success was due, at least partly, to careful planning and use of novel technology in the fracture treatment, which allowed the on-site determination of actual reservoir conditions, with growth influenced by extremely variable permeability as against idealized models used for initial design.
Darcy Flow Dissipation in Petroleum Reservoirs and the Productivity Index
Authors: Inayat-Hussain A. A. , Buckingham M. J. 
Published: June 2014

SUMMARY
The conventional definition of the productivity index is ambiguous under some conditions. Similar difficulties have long been resolved, for the case of electrical conduction in continuous media, in terms of a dissipation function. Consideration of the energy dissipation in steady Darcy flow in a reservoir yields a new and more general definition of the productivity index (PI) as the ratio of the square of the petroleum production rate to the total energy dissipation in the reservoir. This definition leads to an unambiguous interpretation of the flowing pressure which appears in the conventional definition of the PI. The dissipation approach also yields the conditions which maximize the PI for production from a single well and from multiple wells in a reservoir.
Novel Approaches to the Determination of Archie Parameters I: Simplex Method
Authors: Chen D. S. , Fang J. H. , Kortright M. E. , Chen H. C. 
Published: June 2014

SUMMARY
The Nelder-and-Mead simplex method is employed to obtain optimal sets of parameters (m, n, a) used in the commonly used form of Archie's equation. This derivative-free optimization method avoids trapping by local optima. We have found that the method is very effective, highly efficaceous, and easily implemented on a PC. The agreement between the results obtained from this method and those from the nonlinear least-squares approach is remarkable. A comparison paper addresses the same problem via fuzzy regression.
Application of Human Health Risk Assessments in Oil and Gas Production
Authors: Ulrich G. A. , Agnew W. W. , Proctor D. M. 
Published: June 2014

SUMMARY
This paper illustrates the use of a health-based risk assessment in the investigation and closure of surface impoundments at an oil and gas production site. The risk assessment demonstrated that removal of contaminated soils would not be required to protect human health under future use conditions. As a result, the regulating state agency agreed that soil removal was not required, which resulted in significant cost savings over previously proposed remedial action plans.
A Laboratory Study of New, Surfactant-Containing Polymers for High Salinity Reservoirs
Authors: Uhl J. T. , Ching T. Y. , Bae J. H. 
Published: June 2014

ABSTRACT
To overcome the deficiencies of partially hydrolyzed Polyacrylamides, viscosity loss at high salinity and poor injectivity at high injection rates, terpolymers having ionic surfactant side chains were synthesized. It was conceptualized that brine tolerance can be obtained by a salt-induced, surfactant side-chain aggregation mechanism. Experimental results show that these new polymers develop higher solution viscosities and screen factors than conventional Polyacrylamides in 0.5 to 30 wt% NaCI brines. These polymers have better injectivity due to their shear-thinning properties and lack of the viscoelastic effect at high injection rates.
Asphaltene Precipitation and Crude Oil Wetting
Authors: Buckley Jill S. 
Published: June 2014

ABSTRACT
Precipitates that form as the result of interactions between an asphaltic crude oil and low molecular weight paraffin solvents can remain suspended in the oil phase, rather than being adsorbed onto solid surfaces. Adsorption may be restricted to surfaces made oil-wet by oil/brine/rock interactions prior to precipitation. Visual observations show that the wateirflood displacement mechanisms after asphaltene precipitation are similar to the mechanisms of displacement of the unprecipitated crude oil. Trends of wettability alteration in a Berea sandstone core, as measured by the Amott method, are shown to be similar, whether the test is performed with the crude oil or with a low-molecular weight paraffin oil with which the crude oil may be incompatible.
Transient Analysis of Variable Rate Tests for Solution Gas-Drive Reservoirs
Authors: Camacho R. , Vésquez M. , Roldan J. , Padilla R. , Macías L. 
Published: June 2014

Abstract
Most of the work on variable rate-variable pressure tests that is available today is related to single-phase systems. The purpose of this study is to examine variable rate-variable pressure tests (VRT), during the transient period, considering multiphase flow effects in the reservoir for solution gas-drive systems.
The only procedures present today to evaluate VRT run under multiphase flow conditions use either pressure drop, pressure squared, or pseudopressure function. The first two approaches are empirical in nature and their use is restricted. The direct use of pseudopressure approach is more general but it requires the availability of representative relative permeability data.
This paper presents methods that permit the determination of the mechanical skin and sandface effective permeabilities. These methods are derived from the pseudopressure function but they require only traditional information, i.e. rate and wellbore pressure versus time. The expressions developed in this study are useful for both single-phase and solution gas-drive systems. Synthetic and field data are analyzed to illustrate the use of the techniques developed in this work.
Rate normalization, using pressure and pressure squared drop, and the use of superposition principle are analyzed, and their advantages and limitations under multiphase flow conditions are compared to the methodology presented in this study.
New Approaches for Robust Nonlinear Parameter Estimation in Automated Well Test Analysis Using the Least Absolute Value Criterion
Authors: Rosa Adalberto J. , Horne Roland N. 
Published: June 2014

Abstract
In this study new robust algorithms for automated well test interpretation are proposed. The robustness of the new procedures lies in the fact that the techniques can handle well cases in which the errors do not follow the usually assumed Gaussian distribution or cases in which outliers are present, as opposed to least-squares minimizations. Also, the proposed methods are robust due to the fact that they can converge faster and from initial estimates for which previously reported methods would diverge.
The first method presented in this study is referred to as the MLAV (Modified Least Absolute Value) method. It consists of an iteratively reweighted nonlinear least-squares, where in each iteration the weighting factors are the inverses of the absolute values of the residuals obtained in the previous iteration. This procedure was found to be resistant to outliers and also to converge from poor initial estimates for the unknown parameters. One defect of this technique, although not a major concern in well test applications because usually the computational time is small, is that it tends to behave like a steepest-descent type of method, producing large decreases in the objective function during the first iterations but requiring many iterations before converging to the minimum of the objective function.
Because of the relatively large number of iterations required by the MLAV method, a second approach is suggested in this work. This second technique uses the reweighted nonlinear least-squares (MLAV method) during the first few iterations, and the LAV (Least Absolute Value) criterion thereafter. This combined approach is referred to as the MLAV-LAV method.
Examples of application indicated that the second proposed method (MLAV-LAV) combines the robustness of the least- squares type of methods, in terms of convergence from poor initial estimates, with the robustness of the least absolute value criterion, in terms of low number of required iterations and resistance to outliers in the data.
Enhanced Oil Recovery Pilot Project, Catriel Oeste Field
Authors: Gagliano A. J. , Lasalle D. D. , Olivo J. A. , Sabas R. A. , Ali S. M. Farouq 
Published: June 2014

Abstract
In terms of improving oil recovery in Catriel Oeste Field, a project was undertaken to determine the feasibility of applying an Enhanced Oil Recovery process by Polymerflood. A pilot was selected in two productive reservoirs projecting to start with polymer injection on August 1993.
This paper describes the studies made for the pilot design and the conditions in which it will set, taking into account aspects as reservoir characteristics, present conditions, laboratory testings and a brief description of the facilities.
An Integrated Approach To Interpret and Quantify Cusiana Hydrocarbon System
Authors: Lee S. T. , Gomez P. A. , Toczylkin L. 
Published: June 2014

AbstractThis paper presents PVT properties and phase behaviour of Cusiana hydrocarbon system. The interpretation and quantification of the hydrocarbon system was made possible through an integrated program involving fluid sampling, laboratory fluid analyses as well as equation-of-state (EOS) prediction. In the light of the complex fluid system encountered, it was found important to have a developed EOS to guide welltesting, perforation selection and laboratory programs.The Cusiana hydrocarbon system contains favourable thermodynamic factors (composition, pressure and temperature) for a gas injection process to improve hydrocarbon recovery. Laboratory fluid work, including swelling, multiple-contact and gasflooding in reservoir cores, demonstrated that efficient recovery can be achieved through a vaporization mechanism. EOS compositional simulations were also conducted to validate the EOS model and to further investigate the recovery mechanisms.