bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of Fracture Permeability by Using a Fractal Model
Authors: Murata S. , Mitsuishi H. , Saito T. 
Published: December 2007

Abstract
Correct estimation of fracture permeability is a key factor for the successful development of fractured reservoir. Based on the Kozeny-Carman equation, we have described the deviation from the conventional cubic law of the fracture permeability by using a fractal model of fracture surfaces. In order to confirm the validity of the description, we carried out several laboratory experiments and numerical simulations to the artificially prepared fracture specimens whose geometric surface properties were controlled by the fractal model. Consequently, the validity was confirmed and it was cleared that the two-dimensional tortuosity and the shape factor affect on the deviation from the cubic law more remarkably than the fractal dimension and the steepness, and therefore, these parameters are very important to estimate the deviation from the cubic law of fracture permeability correctly. Furthermore, it was cleared that fluids flow through a fracture with selecting the large aperture regions and the tortuosity increases with increase in the contact area of the fracture.
Variable Saturation Exponent Effect on the Determination of Hydrocarbon Saturation
Authors: Hamada G. M. , AL-Awad M. N. , Alsughayer Alsughayer 
Published: December 2007

Abstract
An accurate determination of initial oil in place in the early life of reservoirs or an evaluation of a developed reservoir is required to well estimate the hydrocarbon volumes. Modified Archie formula (Sw = (a Rw / ϕm Rt)1/n) is the basic equation to compute water saturation in clean formation or suitable shaly water saturation model in shaly formation. The accuracy of water saturation value for given reservoir conditions depends on the accuracy of Archie parameters a, m and n. The terms of Archie relationship have been subjected to many laboratory investigations and even more speculations. There are many factors affecting porosity exponent, m, saturation exponent, n and tortousity factor, a. Therefore, it is very difficult to fix Archie parameters and neglecting reservoir characteristics; rock wettability, formation water salinity, permeability, porosity and fluids distribution. This paper presents a new technique to determine Archie parameters a, m and n. The developed technique is based on the concept of three dimensional- regression (3-D) plot of water saturation, formation resistivity and porosity. This 3D technique provides simultaneous values of Archie parameters. Also, the 3D technique overcomes the uncertainty problems due to the separate use of formation resistivity factor- porosity and water saturation equations to get a, m and n parameters.
Two field examples are given to show the applicability of the 3-D technique in comparison with three other techniques: 1) common values of Archie parameters, 2) conventional technique and 3) core Archie parameter estimation (CAPE) technique. The comparison among the four techniques has shown that 3-D technique provides an accurate and physically meaningful way to get Archie parameters a, m and n for given core samples. Water saturation profiles, using Archie parameters obtained from the four techniques, have been obtained for the studied section in the wells. These profiles have shown a significant difference in water saturation values. This difference could be mainly attributed to the uncertainty level for Archie parameters from each technique. The effect of saturation exponent on the accuracy of water saturation computation was tested using Archie's parameters derived from conventional technique and 3-D technique in the two wells.
Reservoir Monitoring with Carbon-Oxygen Logging Through non Characterized Dual Concentric Casings: A Case Study
Authors: Wilson Michael 
Published: December 2007

Abstract
Many reservoirs in the North West Shelf of Australia have low salinity formation water (in the order of 20ppk), which makes detection of water contact movements difficult with traditional pulsed-neutron capture logging techniques (sigma logging). Carbon-Oxygen logging has proven very successful in reservoir monitoring in such cases. The characterization of the response of these measurements relies on a database of thousands of physical models of lithology, formation fluids, borehole fluids and wellbore completion characteristics. However, not all completions and scenarios have been modeled physically, and built, due to the infinite number of possibilities. Monte Carlo modeling is used to interpolate between common situations, but there are variations, such as in this case, dual concentric casings, that fall outside the present database.
The well on the North West Shelf of Australia involved in this case study, was originally completed as a monitoring well, with only the top of the reservoir sand perforated and producing dry oil. The completion has a 4 ½" tubing cemented inside a 7" liner, i.e., a dual concentric casing. Nearby wells in the same field are also perforated in the lower sands, from which they are producing. The objective of the carbon/oxygen logging was to ascertain fluid movement (oil water contact) in the lower zones and utilize this information to optimize the subsequent perforation intervals thus accelerating the production of the well without increasing water flow.
This paper describes a methodology and case study to plan, acquire and extract qualitative answers from carbon-oxygen logging in the dual-concentric casing scenario, in order to make a near real time decisions on the perforations to follow. The methodology utilized in this well can be used for job planning, execution and interpretation of similar, non-characterized wells.
Applying MAK Gas-Water Relative Permeability Correlations to Predict a Gas-Condensate Relative Permeability and Production Performance (Case Study)
Authors: Mulyadi Henny , Mason Tom , Steer David 
Published: December 2007

Abstract
An analytical correlation to describe relative permeability is extremely useful in the absence of laboratory measured data, or when a general representative fluid flow is required. Previously, experimental work has been done to develop new correlations to predict gas-water relative permeability (RP) data for various permeability and porosity media. The newly developed technique consists of quick laboratory measurements to measure end-point saturations and newcorrelations to predict gas-water relative permeability behaviour.
These differ from previous work because they honour the reservoir's rock and fluid properties – such as reservoir permeability, porosity, interfacial tension and gas density. The effectiveness and practicality of applying these new correlations to simulate laboratory measured gas-water relative permeability data (for various permeability and porosity cores) has been demonstrated in SPE 71523.
To conclude, as part of a doctoral dissertation, the correlations were tested on simulation models. The aims of this work segment were twofold: To investigate the applicability of the newly developed analytical correlations to reservoir simulation and their impact on history matching and forecasting of reservoir production. No attempts were to be made to re-match the production history.To investigate the effect of applying the correlations pre and post-upscaling of static reservoir model. This part of the investigation demonstrates that in situations where the upscaling of the static model has resulted in significant distortion of the K and ϕ relationship, application of Mulyadi-Amin-Kennaird (will be refered to as MAK through out this paper) correlations, or similar, would be erroneous.
The new correlations were used to generate several sets of gas-water relative permeability data to replace the corresponding history-matched relative permeability data in the pre-upscaled and a post-upscaled producing gas-condensate reservoir models. The implications of the new correlations were assessed from the model's historical and forecasted reservoir production performance.
The results of the specific cases investigated demonstrated that while the new correlations did not significantly affect the history-matched period, it did havesignificant impact on the forecasted production profiles and ultimate recovery. Although these are not unexpected, the differences were significant enough to warrant attention; in particular the manner in which such correlations are used to populate dynamic models.
Smart Well Solutions for Thin Oil Rims: Inflow Switching and the Smart Stinger Completion
Authors: Jansen J. D. , Wagenvoort A. M. , Droppert V. S. , Daling R. , Glandt C. A. 
Published: December 2007

Abstract
The production of oil from horizontal wells in thin rims sandwiched between gas and water is notorious for coning problems. There is a strong tendency for early gas or water breakthrough at the heel, especially if the pressure drop over the length of the well is in the same range as the drawdown. We present two conceptual solutions to counteract the negative effect of well bore pressure drop through the application of downhole measurement and control. One solution concerns inflow switching in a segmented well bore and allows for coning control after breakthrough has occurred. The other solution aims at preventing breakthrough as long as possible. This is achieved by flattening the drawdown profile along the well through controlling inflow at one or more points in an extended stinger. The feasibility of the solutions was demonstrated through numerical simulations over a range of reservoir and well bore parameters. Implementation would require further development of downhole water and gas detection capabilities.
New Friction Factor Correlations for Non-Newtonian Fluid Flow in Coiled Tubing
Authors: Zhou Y. , Shah S. N. 
Published: December 2007

Abstract
This paper presents a complete set of friction factor correlations for both Newtonian and non-Newtonian fluids in laminar and turbulent flow in coiled tubing. The friction factor correlation for non-Newtonian fluids in laminar flow is obtained based on theoretical analysis and numerical solutions of the flow equations of a power-law model fluid in curved pipes. The empirical correlation for non-Newtonian fluids in turbulent flow is developed based on full-scale experiments of polymeric fluid systems in various 1", 1–1/2", and 2–3/8" coiled tubing reels. To consider the effect of pipe roughness in coiled tubing, a modified correlation is proposed by combining the Srinivasan et al. correlation for smooth curved pipe and the Chen correlation for rough straight pipe. Examples are given to illustrate the applications and accuracies of the newly developed correlations.
Quantifying the Fracture Mechanics Properties of Rock for Fractured Reservoir Characterization
Authors: Olson Jon E. , Holder Jon , Rijken Peggy 
Published: December 2007

Abstract
Natural fractures are important conduits for fluid-flow and can control the deformational behavior of rock. The accurate evaluation of natural fracture geometry in the subsurface is difficult because of the sampling problems inherent to wellbores and indirect investigation methods such as seismic. Because of these limitations in observational capability, predictive models are needed to provide more constraint on natural fracture characteristics. One approach is to look at the mechanics of fracture propagation in sedimentary rock as controlled by subcritical crack growth (also known as stress-corrosion cracking). We have measured the subcritical fracture properties of numerous sedimentary rocks, including core samples from petroleum reservoirs, in conjunction with detailed petrographic analysis. Our preliminary results suggest that carbonates and sandstones tend to have very different subcritical fracture properties, and the variation in sandstone properties can be linked to grain and cement mineralogy and volume fractions.
Estimation of In-Situ Rock Parameters From Pressure Time Series
Authors: Schulze K. C. , Brudy M. , Kjørholt H. 
Published: December 2007

Abstract
For a borehole of the Gullfaks field in the northern North Sea 60 days borehole pressure data of two successive registrations (hereafter parts I, II) were analyzed. From correlation with theoretical ocean tides a loading efficiency γ of 0.35-0.40 and of 0.16-0.19 were obtained for parts I and II, respectively. No influence of air pressure or earth tides could be resolved. Assuming an undrained Poisson ratio vuranging between 0.30 and 0.36 and assuming that the vertical loading results in an areal strain εa of the same magnitude as the vertical strain εV a Skempton ratio B of about 0.45 for part I and of about 0.20 for part II were derived. B values are somewhat higher assuming smaller εa. The notably different values for γ and thus, B can be explained by a significant change in reservoir properties, which was induced by several injections in the borehole in the time between the two registrations.
Controlled Acid Jet (CAJ) Technique for Effective Single Operation Stimulation of 14,000+ ft Long Reservoir Sections
Authors: Hansen J. H. , Nederveen N. 
Published: December 2007

Abstract
Horizontal wells with continuous reservoir sections between 10,000 and 20,000 ft are being used for the development of the laterally extensive low permeability chalk in the Dan/Halfdan oil accumulation, offshore Denmark.
The concept, design and practical experiences from an efficient and effective completion and stimulation method, Controlled Acid Jet1 (CAJ), which has been developed to stimulate very long horizontal well sections in a single operation, is described. It is a non-cemented liner, with a limited number of unevenly spaced holes (perforations) which ensures efficient acid stimulation of the complete reservoir section, provided the acid is pumped at sufficiently high rates.
The CAJ liner has in several ways set new standards for the completion and stimulation of long horizontal wells. The most significant achievement with the CAJ liners is the remarkably effective acid coverage with efficient stimulation of reservoir sections up to 14,400 ft in a single operation. This is more than 20 times the interval length covered during matrix acid stimulation in a traditional cemented and perforated liner.
The CAJ liner completion and stimulation concept has proven to be efficient, uncomplicated to install and very cost effective. Currently, 35 CAJ liners are producing from more than 220,000 ft of reservoir sections in the Dan West Flank/Halfdan field.
The production performance of the wells completed with the CAJ system is concluded to be superior to the performance of wells completed with conventional systems.
Performance of Cased-Hole Sand-Control Completions in High-Rate Wells — A Case Study from the Girassol Field, Angola
Authors: Delattre Eric , Mus Emmanuel , Van Domelen Mark , Azer Alfred , Payer Nicolas 
Published: December 2007

AbstractWells in the Girassol field, offshore Angola, are in the deepest water and contain some of the highest transmissibility reservoirs completed in west Africa. These conditions have presented significant challenges for well completions in this field. While the completion strategies employed to date have included both openhole and cased-hole (OH and CH) wells, concerns existed before the development phase regarding whether the cased-hole completions were a viable option. These concerns were primarily a result of (1) the potential loss of flow efficiency in the perforations and near-wellbore region caused by turbulence effects in these high-rate wells and (2) the ability to successfully place the frac packs in these high-mobility reservoirs.This paper provides an overview of the Girassol field, along with the factors and desired benefits that led to the decision to employ CH completion techniques. The paper also describes the methods used to help mitigate the non-Darcy flow effects in the completions, details the design and implementation of the completions, and presents the well test and production results.
Selection of EOR/IOR Opportunities Based on Machine Learning
Authors: Alvarado Vladimir , Ranson Aaron , Hernández Karen , Manrique Eduardo , Matheus Justo , Liscano Tamara , Prosperi Natasha 
Published: December 2007

AbstractThe Venezuelan National Oil Company, PDVSA, has dedicated a sustained effort to adapt EOR/IOR technologies to rejuvenate a large number of its mature fields. The first step towards achieving this objective was to select cost-effective technologies suited for conditions of Venezuelan reservoirs. The current strategy for screening EOR/IOR applications is based on the Integrated Field Laboratory philosophy, where a representative pilot area of a number of reservoirs is selected to intensively test EOR/IOR methods, such as WAG injection (water alternating gas) and ASP (alkali polymer surfactant), currently underway. Two problems with this approach are the lack of objective rules to define a reservoir type and the project completion time. In general, the trouble with using expert opinion is that it tends to be too biased by operational experience. It is known that the success of a given EOR/IOR method depends on a large number of variables that characterize a given reservoir. Therefore, the main difficulty for selecting an adequate method is to determine a relationship between reservoir characteristics and the potential of an EOR/IOR method. In this work, data from worldwide field cases have been gathered and data mining was used to extract the experience on those fields. Here, a space reduction method has been used to facilitate the visualization of the needed relationship. Machine learning algorithms have been utilized to draw rules for screening. To illustrate the procedure, several Venezuelan reservoirs have been mapped onto the extracted representation of the international database.
Uses and Abuses of Equations of State
Authors: Kawahara Hiroshi , Hiraiwa Takeshi , Yoshida Koichi , Watanabe Makoto 
Published: December 2007

Abstract
Equations of state (EOS) are perhaps the most abused and mis-used concept in compositional reservoir simulation. It is believed that the EOS are often need adjusting or tuning and the well-tuned EOS can capture all phase behavior in the reservoir simulation. However, the well-tuned EOS can not calculate appropriately in the reservoir simulation because the matching objectives, the existing PVT experiments, are not enough to cover all necessary pressure, temperature, and components.
An EOS for CO2, hydrocarbon gas and sour gas injection is tuned for a reservoir fluid offshore Abu Dhabi. The universal EOS for gas injection, EOS-U8, was originally developed as EOS-H18 for hydrocarbon gas injection (both sour and sweet). After the EOS-H18 was developed, additional PVT experiments, swelling tests with CO2 and other two hydrocarbon gases, were conducted and the EOS-U8 was tuned in order to capture the phase behavior of the reservoir fluid and all candidate injection gases. The new, tuned EOS is available for evaluating gas injection, including direct comparison between injection gases. Our tuning procedure for an EOS, including laboratory data selection, is applicable to other reservoir fluids.
The Flash calculation is compared utilizing the tuned EOS using all or selected laboratory data. Limited laboratory data may mislead the tuning process of the EOS parameters for extensive application of the EOS. The methods that gave the best match are also discussed.
Three commercial software for generating EOS parameters were compared for performance, accuracy, and ease of use.
The advantages and disadvantages of three commercial EOS PVT programs are compared. The interface and function of the programs are also evaluated. Three EOS based PVT programs show different results with high concentration of CO2 or H2S using the tuned EOS parameters. Therefore, special cares are required for importing EOS parameters form other EOS programs. The most appropriate ways to use the EOS developed by current software products are discussed. The results from this comparison study of EOS based PVT programs are useful for selecting PVT programs.
Finally three EOS (EOS-H8, C8, U8) were compared in the compositional reservoir simulation. The tuned EOS with the selected laboratory data shows different results in the reservoir simulation using the EOS-U8. It is recommended that EOS should be tuned utilizing as much as PVT experiments.
Rock Type Constrained 3D Reservoir Characterization and Modeling
Authors: Silva Fernando P. T. , Ghani Ahmed A. , Al Mansoori Abdulla , Bahar Asnul 
Published: December 2007

Abstract
This paper presents the results of a reservoir characterization and modelling study based on reservoir rock typing (RRT) of Lower Cretaceous carbonate reservoirs in one of Abu Dhabi Onshore oil fields. The final goal is to obtain multiple realizations of 3D descriptions of the petrophysical properties, namely porosity and permeability, which match and are consistent with the underlying RRT scheme, at the grid block level. The RRT were described in all sections of the reservoir for all cored-wells.
The established reservoir rock types were based on depositional facies sequences, diagenetic overprints and petrophysical properties, including pore throat size distribution, porosity and permeability. The model reveals that the vertical changes in the rock types are a function of depositional facies, while the lateral variation down structure across the same lithofacies unit are controlled mainly by diagenesis.
Considering the limited number of cored wells compared to the total number of loged-wells, the characterization started by predicting both permeability and rock type at the non-cored wells. Permeability was predicted using a combination of regression analysis and geostatistics. The use of geostatistics not only has been usefull in capturing the high variability of permeability but also has ensured that the core data is fully honored at plug locations. Rock type was estimated at the non-cored well using discriminant analysis. Consistency checks were been applied to the results of both prediction to ensure consistency between properties and rock types. Non-consistent results were assigned as unestimated-points. A geological conceptual model, in the form of iso-rock type maps, was used to QC the results of the prediction at the non-cored well and as a tool in deriving soft information about the spatial relationship of the different rock types.
The 3D descriptions of the properties were generated using a geostatistical technique. The technique not only honors the conditioning data and spatial relationship of each property, but also honors the local relationship between each property and the rock type. Additionally, some constraints derived from the diagenetic model were implemented in the modeling process to ensure that the model follows the geological conceptual model as much as possible. In transforming the well-log data into the model grid, appropriate scale-up methods and grid-block thickness were selected to ensure that reservoir heterogeneities are maintained. Multiple realizations of the properties were generated in order to capture and to quantify the intrinsic variability of the model. The results of this characterization study will be used for flow performance evaluation.