bluuebunny/crossref_metadata_2025_split huggingface dataset:
Theoretical Development of the Brooks-Corey Capillary Pressure Model from Fractal Modeling of Porous Media
Authors: Li Kewen 
Published: December 2007

Abstract
The capillary pressure model proposed empirically by Brooks and Corey has been used widely for several decades. However it is not clear why the Brooks-Corey capillary pressure model works so well. In this study, it has been found that the empirical Brooks-Corey capillary pressure model can be derived theoretically from fractal modeling of porous media. Also found was the correlation between the pore size distribution index in the Brooks-Corey capillary pressure model and the fractal dimension. The pore size distribution index increases with the decrease in fractal dimension of the porous media. Capillary pressure curves of different types of rock samples were measured using a mercury intrusion technique. The values of pore size distribution index and fractal dimension were calculated. The relationship between the two parameters obtained from the experimental data was consistent with the relationship derived theoretically. This implies that the fractal dimension of porous media may be inferred directly using the Brooks-Corey capillary pressure model instead of the fractal model. The theoretical development in this study demonstrates that the Brooks-Corey capillary pressure model, once considered as empirical, has a solid theoretical base. This may be why the Brooks-Corey capillary pressure model works satisfactorily in many cases.
Pre-Darcy Flow: A Missing Piece of the Improved Oil Recovery Puzzle?
Authors: Longmuir Gavin 
Published: December 2007

Abstract
Does Darcy’s Law apply at the very low fluid velocities typical for petroleum reservoirs? There is a body of experimental evidence, primarily from non-petroleum disciplines, demonstrating departures from Darcy’s Law at low fluid velocities – Pre-Darcy flow. If Pre-Darcy behavior occurs in oil & gas reservoirs, there could be substantial currently-unrecognized opportunities for increasing the economic recovery of hydrocarbons.
The Use of Turbodrills in Coiled Tubing Applications
Authors: Beaton Tim , Seale Rocky 
Published: December 2007

Proposal
Coiled tubing (CT) has evolved in recent years to include more complex applications in drilling and remedial work. As wellbores have extended deeper, the challenges of intervening with CT have increased. For years the limitation in CT work was the coiled tubing itself. However, with advancements in metallurgy and manufacturing processes, the applications where CT can be utilized have expanded to include deeper, hotter, and more complex wellbores. The challenges of performing this work have now been directed at providing reliable equipment.
One of the main challenges in these more hostile environments is temperature. At elevated temperatures, work performed with motors becomes very erratic and unreliable. To perform this work, alternate methods have to be analyzed. One solution is the use of downhole turbines or turbodrills. Turbodrills have been used in the drilling industry for decades. It is only recently, however, that the benefits derived by turbodrills have been applied to CT for drilling and workover operations. With the remedial work CT is now required to perform, turbodrills are a natural fit as they address the issues which limit motor performance. This paper analyzes the applications and developments in turbodrills with analysis of recent runs on CT.
A New Generation Chemical Flooding Simulator
Authors: John A. , Han C. , Delshad M. , Pope G. A. , Sepehrnoori K. 
Published: December 2007

Abstract
Compositional reservoir simulators that are based on equation of state (EOS) formulations typically do not handle the modeling of aqeuous phase behavior and those that are designed for modeling chemical processes typically assume simplified hydrocarbon phase behavior. There is a need to have a single reservoir simulator capable of combining both approaches to benefit from the advantages of both aqueous and hydrocarbons models. Developing and implementing fully implicit procedures for modeling both hydrocarbon and aqueous phase behavior simultaneously is a complex process. An approach to integrate a surfactant phase behavior model into an existing fully implicit, parallel, equation of state compositional simulator is presented in this paper. Physical property models describing the flow and transport of surfactant and polymer species have been implemented. These properties include surfactant phase behavior, interfacial tension, capillary desaturation, viscosity, adsorption, and relative permeability as a function of trapping number. Polymer properties include viscosity, permeability reduction, inaccessible pore volume, and adsorption. The simulation results were validated by comparison with analytical solutions and results from the explicit chemical flooding simulator, UTCHEM. Test runs were performed with high-resolution models in a parallel environment with results indicating a good scalability of the simulator.
Analytical Theory for Three-Phase Partially Miscible Flow in Ternary Systems
Authors: LaForce Tara , Johns Russell T. 
Published: December 2007

AbstractThree-phase flow often occurs in reservoirs, particularly during secondary or tertiary oil recovery. There is significant mutual solubility of components in the phases for near miscible gas floods or chemical floods. Unfortunately there is insufficient understanding of how three partially miscible phases can affect flow. Furthermore, there are currently no benchmark analytical solutions available to validate numerical simulations for this complex flow regime.In this research, compositional solution routes are developed by the method of characteristics (MOC) for one-dimensional, dispersion-free flow where up to three partially miscible flowing phases may be present. The method is applied to a water/alcohol/oil system that exhibits a large three-phase region in laboratory experiments. Unique solutions are found based on continuity arguments, shock-jump conditions, entropy constraints, and velocity constraints. The analytical solutions are compared to fine-grid finite-difference simulations to verify that they converge to the same dispersion-free limit.The results show that within the three-phase region one phase is below its residual saturation so that only two phases are flowing. As miscibility is approached, cumulative oil recovery initially declines because of the development of constant states in the solution, which cause the leading shock to speed up. We show that multi-contact miscibility is developed along the boundary of the three-phase region where all shocks and waves flow at a dimensionless velocity of one. Last, we show that injectivity (or inverse flow resistance) changes by a factor of two over the range of injection compositions considered for the specific relative permeabilities used.
Fast History Matching of Finite-Difference Models Using Streamline-Derived Sensitivities
Authors: Cheng Hao , Kharghoria Arun , He Zhong , Datta-Gupta Akhil 
Published: December 2007

Abstract
We propose a novel approach to history matching finite-difference models that combines the advantage of the streamline models with the versatility of finite-difference simulation. Current streamline models are limited in their ability to incorporate complex physical processes and cross-streamline mechanisms in a computationally efficient manner. A unique feature of streamline models is their ability to efficiently compute the sensitivity of the production data with respect to reservoir parameters using a single flow simulation. These sensitivities define the relationship between changes in production response because of small changes in reservoir parameters and thus, form the basis for many history matching algorithms. In our approach, we utilize the streamline-derived sensitivities to facilitate history matching during finite-difference simulation. First, the velocity field from the finite-difference model is used to compute streamline trajectories, time of flight and parameter sensitivities. The sensitivities are then utilized in an inversion algorithm to update the reservoir model during finite-difference simulation.
The use of finite-difference model allows us to account for detailed process physics and compressibility effects. Although the streamline-derived sensitivities are only approximate, they do not seem to noticeably impact the quality of the match or efficiency of the approach. For history matching, we use ‘a generalized travel-time inversion’ that is shown to be extremely robust because of its quasi-linear properties and converges in only a few iterations. The approach is very fast and avoids much of the subjective judgments and time-consuming trial-and-errors associated with manual history matching. We demonstrate the power and utility of our approach using a synthetic example and two field examples. The first one is from a CO2 pilot area in the Goldsmith San Andreas Unit, a dolomite formation in west Texas with over 20 years of waterflood production history. The second example is from a giant middle-eastern reservoir and involves history matching a multimillion cell geologic model with 16 injectors and 70 producers. The final model preserved all of the prior geologic constraints while matching 30 years of production history.
Enhanced Oil Recovery by In-Situ Combustion Process in Santhal Field of Cambay Basin, Mehsana, Gujarat, India – A Case Study
Authors: Chattopadhyay S. K. , Ram Binay , Bhattacharya R. N. , Das T. K. 
Published: December 2007

Proposal
In-Situ Combustion Process has been implemented in Santhal field in commercial scale for the last 6 years for enhancing the recovery of heavy oil. The process monitoring is the key factor for ensuring the effectiveness of the method. This paper describes the field practices of ignition well preparation, sampling and analysis strategy of produced fluids coupled with well head pressure, temperature for effective monitoring. The effectiveness of the process is evident from the enhancement of net oil production from the field.
Preformed Particle Gel for Conformance Control: Transport Mechanism Through Porous Media
Authors: Bai Baojun , Liu Yuzhang , Coste J-P , Li Liangxiong 
Published: December 2007

AbstractPreformed particle gel (PG) has been successfully synthesized and applied to control excess water production in some mature water-flooded oilfields in China. Investigations show that PG is strength- and size-controlled, environment-friendly, stable over long periods of time, and very likely capable of overcoming some drawbacks inherent in gel treatments based on in-situ gelling. Its thermostabilization is not sensitive to reservoirs minerals and formation water salinity. To support its future applications, this paper describes experiments that investigate the mechanisms for PG propagation through porous media.Visual observations in etched-glass micro-models demonstrate that PG propagation exhibits six patterns of behavior: direct pass, adsorption and retention, deform and pass, snap-off and pass, shrink and pass, and trap. Which pattern is dominant is related to the diameter ratio of swollen PG and pore throat, PG strength and the driving force.In macroscopic scale, PG propagation through porous media can be described by three patterns: pass, broken and pass, and plug. Which kind of pattern is dominant can be determined by pressure change with time at different tap, particle size of effluent and residual resistance factor at different segment of a core.Measurements from core-flooding and micro-model experiments show that a swollen PG particle can pass through a pore throat whose diameter is smaller than its diameter due to the elasticity and deformability of swollen PG. PG strength is a principle parameter to determine the diameter ratio of a PG particle and a pore throat that PG can pass through a porous medium.A PG particle can move through a porous medium only if a driving pressure gradient is higher than a threshold pressure gradient. The threshold pressure depends on PG strength, the diameter ratio of particle and average pore size.Further work will investigate the potential for PG to improve oil recovery and the optimization method to design PG treatments.
Simulation of a Sector Model of the Heavy Oil Thermal Recovery
Authors: Eremenko E. , Kochanova S. , Kourenko M. , Perevozchikov S. 
Published: December 2007

Abstract
In Russia, development of fields with difficult-to-recover oil reserves, especially heavy-oil fields, becomes a high-priority task. Heavy-oil fields requiring thermal stimulation are of that class. Many of such fields have deep reservoirs (occurring deeper then 1000 m). This paper describes the study of a sector of one of such fields. It is one of the biggest heavy-oil fields in Russia and is being developed during last 20 years. About 900 wells are running. The in-situ oil viscosity is 150 cP. In the oilfield’s life, many thermal technologies have been used in different sectors of the field (including combinations of huff-and-puff, cycling process, continuous injection of hot water or steam). The field sector with 71 wells was chosen to resolve the problem of current OIP distribution and to evaluate the efficiency of the applied technology. The development uses cycling thermal injection(hot water or steam injection followed up by cold water injection) in the sector. Dynamic simulation was performed., the model was matched to the production history of the last 20 years. An appropriate technology for further development of the sector was selected.
Formation Damage in Gas Sandstone Formations by High-temperature Borate Gels Due to Long Term Shut-in Periods
Authors: Siddiqui M. A. , Nasr-El-Din H. A. , Al-Anazi M. S. , Bartko K. M. 
Published: December 2007

Abstract
Description of the Paper: The U-A reservoir unit is an eolian deposition where the primary facies are dune deposits. These sands are composed of quartz grains with feldspars. These grains are large in diameters and coated with illite clays, which made the formation sand friable. These sands require sand control and one of the techniques applied is to frac-pack the wells. The usual practice is to clean up the well as soon as possible to minimize formation damage. This process can take up to seven days, which results in frac fluid being le ft in the formation. This paper examines the effect of shut-in times following hydraulic fracturing treatments on the return permeability of the reservoir core.
Lab studies included conducting coreflood experiments using reservoir cores and typical treatment fluids. The study was performed at bottomhole conditions (300°F) using cores with air permeabilities ranging from 25 mD to 28D. Polymer and breaker concentrations in the fracturing fluid were identical to those used in the field. Core plugs were tested by both methods: injecting and circulating the fracturing gel, and soaking it under pressure for up to seven days. Tests were performed in the absence and presence of a breaker, unencapsulated sodium bromate.
Application: Guar gum and its derivatives are commonly used to prepare hydraulic fracturing fluids. During fracturing treatments, the polymer invades the formation and leaves a gel residue in the fracture and formation, which impairs well deliverability. Several factors like polymer loading, formation temperature, shut-in time and clean-up process contribute to the treatment outcome. A common belief (misconception) has been that long shut-in periods after fracturing a gas well will further reduce the permeability, and the impairment of delivery becomes severe. To avoid the resulting damage of the well, the treatment fluids are recovered while the rig on location, which costs rig time. This concept has led us to study the impact of shut-in time on the retained permeability of reservoir cores.
Results, Observations, Conclusions: Experimental results reveal that 25% reduction in the permeability of reservoir cores occurs at a polymer loading of 45 lb/1,000 gals. A lower polymer loading of 35 lb/1000 gals caused less damage to the permeability. Most of the damage occurred during the first few hours of interaction of the gel with the core plug. Longer shut-in times did not cause additional damage. This study resulted in a significant cost savings by avoiding the need to flowback the well with the rig on location.
Technical Contributions: Guar gum polymer used in hydraulic fracturing treatment can cause damage up to 25%. The damage occurred once the fracturing gel invades the formation. Longer shut-in times don’t cause additional damage up to seven days. The degree of damage depends on the breaker concentration.
The Perfect Permeability Transform Using Logs and Cores
Authors: Haro Carlos F. 
Published: December 2007

AbstractA systematic method is proposed to better understand the relation between permeability, porosity, saturation, and clay content, to get representative permeability distributions as part of reservoir characterization.This method utilizes the combination of a well-recognized permeability-porosity relationship and the Archie equation, as a predictive link between cores and well logs. This approach mathematically bonds the hydraulic (dynamic) and geometric (static) properties of the rocks. Permeability and rock types from well logs are obtained by careful theoretical and practical selection of parameters. The methodology converts a multidimensional correlation problem into sets of smaller correlations.The procedure leads to a system of simultaneous equations, where the slope of one of the linear equations constitutes an exact calibration parameter between permeability and saturation. The equations allow a sequential transformation process from permeability-saturation, to permeability-porosity, and rock type-depth coordinates. The equations are solved for rock types, using reference grids constructed in all three coordinate systems. A calibration/diagnostic crossplot (slope-rock type) enables to find permeability, assess the integrity of the model, identify outliers, and perform consistency checks at different depths.The practical implementation consists of transform tables, and correlations. Results can be extended to shaly sections, transition zones, and swept intervals. Some examples are presented using data from diverse reservoir classes.Advantages:Calculates permeability honoring and integrating conventional core analysis, capillary pressure, and logs Requires log curves generally available in every well Quantitative in uncored sections Follows a deterministic method, so results can be easily extrapolated to uncored wells. No black box approach Based on well-documented engineering and geological theory (flow zones, rock fabric, pore geometry). Formulation permits a connection to the geology through rock fabrics, for interwell extrapolation.Previous models lack a good nexus between cores and well logs. Neural networks, fuzzy logic, multiple regression, or a combination of statistical methods establish this connection, usually with difficulty and not very effectively. The creation of an effective direct link and accuracy are some of the strengths of the proposed procedure.
An Improved Prediction of Coiled-Tubing Lockup Length
Authors: Adnan Sarmad , Chen Y. C. 
Published: December 2007

Abstract
In both deviated and vertical wells, coiled tubing takes a helical shape. The conventional approach to describing coiled tubing constrained inside a wellbore relies upon the relationship between the axial force and the helical pitch. However, in the field and in experiments, it is hard to measure accurately the helical pitch for very long tubing. Instead, the tubing operators collect data on the force and shortening of coiled tubing in the axial direction of wells. This paper transforms the classical expression for coiled-tubing deformation into an alternative form that relates the axial force to the axial shortening of the tubing. The new model is consistent with experimental data from several previous studies. Moreover, through this new model, a simple technique is developed to predict the lockup length of the coiled tubing resulting from friction. This leads to an improved prediction of lockup length for coiled tubing, allowing more accurate modeling of downhole depth.
Coiled Tubing in Sour Environments - Theory and Practice
Authors: Crabtree A. R. , Gavin W. 
Published: December 2007

Abstract
Carbon steel Coiled Tubing strings have been used in sour wellbore environments for many years. The use of Coiled Tubing in sour service has increased by job number, job complexity, pipe size and the stresses to which the pipe is subjected. A number of papers have been written on the steel chemistry and low cycle fatigue behaviour. These have been based on both theoretical and laboratory work. Great progress has been made in understanding the chemical and physical interaction of Coiled Tubing and hydrogen sulfide but little information is available from "real world" situations where the pipe has been worked in a variety of job types (acidising, gas lifting, drilling, etc) and where a large number of other factors may come into play (injector damage, well stimulation chemicals, sour inhibitor application techniques, erosion of inhibitors, CO2, high chloride water production, etc).
This paper will discuss the application of a Coiled Tubing technical specification (based on theoretical and laboratory work) in the operational world. Comparisons will be made between theoretical expectation and practical observation for 70 and 80 grade Coiled Tubing with regard to low cycle fatigue, pipe life and damage in sour environments.
Utilizing Innovative Flexible Sealant Technology in Rigless Plug and Abandonment
Authors: Barclay Ian S. , Johnson Carl R. , Staal Timo W. , Choudhary Suresh , Al-Hamandani Abdulhameed 
Published: December 2007

Abstract
This paper presents Petroleum Development of Oman's (PDO's) rigless plug and abandonment (P&A) technologies and practices resulting from a corporate goal to find a costeffective means to abandon its oil wells. PDO is abandoning aging wells and must balance environmental and financial objectives. Technically sound abandonment practices are essential for long-term environmental protection. Many operators are revising procedures to ensure that depleted reservoirs remain permanently sealed. During a 60-well pilot project in Oman, PDO optimized its practices by employing new cementing and plugging technologies to minimize the cost of abandonment while ensuring long-term environmental protection from once-prolific oil wells.
PDO used a new expanding, flexible sealant system on the P&A project, conveying the flexible sealant with a coiled tubing (CT) unit. The new sealant has improved elastic and expansion properties to meet PDO's requirement for a longterm mechanical durability and zonal isolation. The presence of expanding material leads to an optimum configuration to prevent loss of zonal isolation resulting from changes in downhole conditions over time. The presence of flexible and expanding materials increases the elasticity and decreases compressibility and permeability of the set cement while retaining good compressive strength.
Use of a CT unit eliminated the need for a rig, which reduced the time and cost of operations. The novel flexible sealant system provided the long-term isolation necessary to meet environmental standards. This paper presents case histories on the use of this new flexible, expanding sealant and its influence on the P&A project.