bluuebunny/crossref_metadata_2025 huggingface dataset:
Practical Applications of EPT Measurements in Gas, Condensate, and Oil-Bearing Reservoirs in the North Sea
Authors: Harrison Bob , Jeffs Paul , Skelt C. H.
Published: December 2007

The Electromagnetic Propagation Tool (EPT) remains unloved by many in the North Sea oil industry due to concerns over tool performance, log interpretation and value for money. While acknowledging its limitations, this paper sets out to show that, given the right circumstances, the EPT can provide information unavailable from any other electric logging device, especially in wells drilled with OBM. Examples of EPT applications are given for several reservoirs in the North Sea, each bearing different hydrocarbon phases.
The Use of a New Technique To Determine Permeability Anisotropy
Authors: Wannell M. J. , Colley N. M. , Halford F. R.
Published: December 2007

Vertical permeability is an important input to coning and water influx studies and also choice of perforation policy. For British Gas Exploration and Production knowledge of this parameter is important for a number of small gas fields underlain by very large aquifers where water influx could significantly reduce reserves.

Conventional ways of measuring Kh/Kv (anisotropy) at reservoir scales have either proved unsuccessful or can only be undertaken once differential depletion effects become apparent.

A new openhole testing technique is described. It uses a dual inflatable packer run with a wireline formation tester as part of the logging program. The measurement scale is greater than that for core measurements and offers both versatility and precision to measure anisotropy within and between selected reservoir units at in-situ conditions.

The technique and analysis are briefly described, and results compared with other sources of permeability data. The paper concludes that this type of interference test can provide valuable and timely data that reduces the risk involved in a development decision and the cost of using conventional testing equipment.
The Environmental, Reservoir, and Operational Advantages of Cable Tool Drilling Natural Gas Storage Wells
Authors: Hayes J. P. , Fisher Peter
Published: December 2007

The first oil well in North America was drilled in 1858 near Oil Springs, Ontario, Canada. Today, over 135 years later, Union Gas Limited is using cable tool rigs to drill natural gas storage wells within a 30 kilometer radius of that first well.

Union's storage pools are located in Lambton County, Southwestern Ontario, Canada (Figure 1). Lambton County is approximately 5,600 hectares (560,000 acres) of which 88% is actively farmed. There are over 3000 farms located in this area, and it is Union's priority to minimize environmental damage to these agricultural lands during well drilling activities.

This paper discusses cable tool drilling as an alternative to rotary drilling, and examines the environmental, reservoir, and operational advantages of cable tool drilling natural gas storage wells.
New Direct-Control Gas Storage Safety Valve
Authors: Gano J. C. , Revay J. R.
Published: December 2007

Subsurface safety valves for large-completion, gas-cavern storage systems must comply with the economic, safety, and regulatory restraints required by industry standards in addition to satisfying the demanding environmental restraints imposed by gas wells with significantly high flow potentials. In addition, location of the valve and all protected systems must also be given careful consideration in completion design since this type of well is prohibitively expensive to kill if workover is required.

A direct-control subsurface safety valve has now been developed to meet these stringent requirements. The valve, which can be installed in the tailpipe below the packer, can be expended into the cavern, if necessary, and has the capability to provide efficient operation with minimal pressure loss at anticipated high flow rates.

This paper will discuss the history and field testing of the earlier prototypes of this valve and how the unique design criteria of the new design address the problems of valve mechanism damage that are generally attributed to high-flow-rate closures. An actual case history from a storage facility in Germany will demonstrate the advantages that the newly-designed valve can provide.

At present, two valves have been installed, with one being used to conduct long-term evaluations. All closures have been as predicted with no subsequent leakage or damage to the valve or lock. The new valve design has demonstrated excellent reliability in a demanding, high-flow-rate environment and maintains structural integrity during high-energy valve closures. Elimination of a hydraulic control system also allows unrestricted setting depths. Design analyses, surface testing, field testing, and wireline applications all indicate that a poppet-closure mechanism can be combined with "up-to-set" and "down-to-set" lock mandrels to successfully to address the problems previously associated with high-flow-rate closures in applications of this type.
Design Appproach Accounts for Condensate in Gas Pipelines
Authors: Adewumi M. A. , Nor-Azlan N. , Tian Shifeng
Published: December 2007

With more than 1.2 million miles of gas pipelines crisscrossing the entire landmass of the United States, there is little doubt that the capital investment on these pipelines is tremendous. Optimal use of these pipelines is a must, both for operational reasons and cost-effectiveness. One of the prevalent problems in these pipelines is condensation. The existence of the condensate, in addition to reducing deliverability, creates several operational problems. Pigging and drips are two of the methods used to alleviate this problem. Since condensates are not uniformly distributed along the pipeline, either of these two solution strategies will be rendered ineffective unless the distribution of condensate in the pipeline is known. During the past several years, a compositional hydrodynamic model has been developed at Penn State University. This couples a phase behavior model with a fundamental multiphase hydrodynamic model. This model has since been tested and validated. Several design strategies and operational options that may be encountered in the field are defined and modelled. The results of these are reported in this paper. The results clearly demonstrate that in spite of the complex nature of this problem, condensation in pipelines can be modelled by using the approach presented here.
The Effect of Pressure Pulsation and Pilot Setting on the Performance of Pressure Relief Valves
Authors: Foy C. E. , Kiel Darwin , Jungowski Wiktor
Published: December 2007

Pressure relief valves are essential components of natural gas pipelines. To ensure safe operation of the pipeline it is imperative that these valves function properly and reliably. Improper installation or setup can lead to potentially catastrophic problems in the field. In this study the performance of a commonly used pilot operated safety relief valve was examined under both normal and abnormal circumstances. The fundamental operating principles of the valve are reviewed, followed by presentation of experimental data illustrating the blowdown performance of the valve. The experimental techniques employed in the laboratory to simulate pipeline conditions are also described. While the performance of the relief valve was consistent with the manufacturer's specifications under normal setup and operation, significant problems were found to exist when the pilot was incorrectly adjusted, or when pressure pulsations were present. Examples of both cyclic venting and premature relief are shown in the paper. To assist in determining when a pulsation suppressor is required a semi-emperical relationship between pulsation strength, and premature opening pressure, is proposed.
Complexities in the Analysis of Pressure-Transient Response for Non-Newtonian Power-Law Fluid Flow in Fractal Reservoirs
Authors: Chakrabarty Chayan , Tortike W. S. , Farouq Ali S. M.
Published: December 2007

This study presentient model for transient flow of a non-Newtonian power-law fluid in a fractal reservoir. The pressure, pressure derivative, pressure-derivative-to-pressure-ratio and rate behaviour of such a flow system are examined. The model is shown to be useful in the identification and modeling of power-law fluid flow in a fractal reservoir. The model also demonstrates the importance of analyzing both transient pressure and rate data for a single-well situation in such flow systems.
A Comparison of Two Devonian Shale Wells: Why Is One Well Better Than the Other?
Authors: Hopkins C. W. , Jochen J. E. , Fink K. J.
Published: December 2007

This paper summarizes the detailed analysis of geological, geophysical, geochemical, and well test data from three Devonian Shale and Berea sand wells located in Pike County, Kentucky. These three wells were part of a Gas Research Institute (GRI) project designed to gain a better understanding of the producing mechanisms of the Shales and Berea and the impact of stimulation on well performance.1 All three wells were completed in both the Shales and Berea, which is typical for the area. Detailed data were collected in both the Shales and the Berea on two of the three wells which were used to develop layered, naturally fractured reservoir descriptions for each producing horizon. Each formation was stimulated with nitrogen foam and sand fracture treatments, and in general, the pre- and post-stimulation well performance was similar to predictions made using the layered, naturally-fractured reservoir descriptions. This paper compares these reservoir descriptions and provides a technical basis for the widely varying production often observed with Shale and Berea wells in this region.
The Evaluation of Proppant Transport and Cleanup of Foamed Fluids Used in Hydraulic Fracturing of Shallow, Water-Sensitive Reservoirs
Authors: Penny G. S. , Conway M. W. , Schraufnagel R. A.
Published: December 2007

The use of foamed fluids has become popular in coal and shale reservoirs due to their inherent non-damaging properties. Foam is generally considered to be a perfect transport fluid. However, the proppant transport properties have not been fully measured in the laboratory. This paper discusses the design and construction of equipment to generate stabile foams in the laboratory and in the field, as well as the measurement of proppant transport and cleanup of foams commonly pumped into shallow, water sensitive reservoirs.

The equipment assembled for measuring proppant transport of foamed fluids includes a high pressure slurry pumping system, a choke system to generate field quality foams, a pipe rheometer to obtain in-line pipe rheology, a high pressure, see-through slot with remote video to observe proppant transport and a pressure control and exhaust system. Other equipment used includes a conventional sand column generator and core flow equipment to look at the impact of foam on coal permeability.

Several tests have been completed including the optimization of mixing tube diameter and velocity to achieve a stabile foam in the laboratory and in the field.

The impact of gel concentration and surfactant concentration on foam stability is measured to achieve minimum stability and maximum cleanup. Various surfactants are evaluated for cleanup. Their ability to avoid foam regeneration or blockage during flowback is also evaluated. Finally, the rheology, transport properties and half-lives of foams with and without sand are examined.
Improving Hydraulic Fracturing Results in the Clinton Sandstone of Ohio: A Case History
Authors: Jacot R. H. , Hopkins C. W. , Gonzalez D. W. , Meyer B. R.
Published: December 2007

This paper describes a hydraulic fracturing study undertaken on the Clinton Sandstone in southern Ohio. The purpose of this study was to improve the effectiveness of the fracturing treatments being pumped to increase well production. The methodology employed in this study used a hydraulic fracturing simulator and production data analysis to evaluate the effectiveness of the treatments.

Historical fracture treatments were analyzed with a 2dimensional fracture design model1 to estimate propped fracture half-lengths. These treatments, typical of Clinton fracture treatments in Ohio, consisted of a gel pad followed by gel and slick water carrying 20/40 Ottawa sand at low concentrations. Results showed that most of the fracturing sand was falling out of the pay zone due to the low fluid viscosity. Over a period of one year, the treatments were modified using the fracture simulator as a design tool. Some of these changes included increasing sand concentration and pumping the sand with a higher viscosity fluid.

This simple methodology presented in this paper is applicable to Clinton wells in Ohio and other tight gas formations throughout the Appalachian Basin to improve production by modifying fracturing practices without increasing fracturing costs substantially. The methodology does not require large data collection and thus is cost effective to apply.
CO2/Sand Fracturing in Devonian Shales
Authors: Yost A. B. , Mazza R. L. , Gehr J. B.
Published: December 2007

A total of five carbon dioxide (CO2) /sand well stimulations were successfully executed with two Devonian shale operators in Perry and Pike Counties, Kentucky. This new stimulation method offers a minimum formation damage proppant stimulation approach for natural gas producers in the United States.

Some operators have been concerned about the frac fluid formation damage associated with the water and chemicals used in conventional foam stimulations, whereas other operators have been concerned about the lack of proppant in straight nitrogen fracs used by service companies today. Two carefully screened geological areas of established Devonian shale production were selected based on active ongoing drilling and completion operations. One selected control area contained an existing set of wells with established production histories.

More specifically, one operator furnished three offset wells which were stimulated with the carbon dioxide/sand frac method. The quantity of proppant and fluids pumped during each well stimulation ranged from 23,000 to 43,000 pounds of proppant and from 120 to 160 tons of liquid carbon dioxide. Another operator furnished two offset wells which were each stimulated with approximately 47,000 pounds of proppant and 120 tons of carbon dioxide.

The logistics and field layout of a typical carbon dioxide/sand frac treatment has been described and highlighted. The importance and unique aspects of the closed system blender that is required for job execution is discussed. Five stimulation treatments have been reviewed, and stimulation and preliminary production data compared to offset wells stimulated with nitrogen, and explosives. Initial production results indicate more than a 50 percent increase in production rate compared to nitrogen fraced wells in the Pike County area. In addition, production is also 4.8 times better than conventional shot wells in the same area. These results are encouraging enough to formally combine existing pumping equipment, a closed system blender, and liquid carbon dioxide supplies to develop a new fracturing service in the eastern U.S. A total of 22 additional jobs are planned in the eastern U.S. in low permeability gas formations over the next year.
Using a Three-Dimensional Concept in a Two-Dimensional Model To Predict Accurate Hydraulic Fracture Dimensions
Authors: Rahim Zillur , Holditch S. A.
Published: December 2007

Hydraulic fracture treatments can be used to increase oil and gas flow rates, and ultimate recovery. A fracture treatment should be designed to optimize profit from the well. To design and optimize the fracture treatment, the engineer must use 1) a fracture propagation model, 2) a reservoir fluid flow model, and 3) an economics model.

To properly simulate the fracture and the reservoir, the engineer should use three-dimensional (3D) models.13 Hydraulic fractures grow up, out, and down from the perforated interval. Oil and gas reservoirs are layered and the flow of reservoir fluids occurs both horizontally and vertically within the reservoir and the fracture. Even though 3D models should be used for most reservoirs, a majority of the fracture treatments are designed using two-dimensional (2D) fracture propagation models. The most common models used by industry are the Perkins-Kern-Nordgren (PKN)4 and the Geertsma-deKlerk-Daneshy (GDK)4 models.

Two-dimensional fracture propagation models are used most often because they are easy to program and run fast on a personal computer. Fortran code for both the PKN and GDK models can be found in Appendix G of SPE Monograph 12.5 We have found that 2D models can be successfully used to design a hydraulic fracture treatment when (1) there are barriers that eventually suppress or restrict vertical growth, and (2) the engineer chooses the correct input value for created fracture height. When these two criteria are met (and all other data are reasonable), a 2D model will provide reasonable estimates of created fracture length and created fracture width.
Comparison of Fracture Stimulation of the Berea Sandstone in the Haysi Field
Authors: Norton Jerry , Hyde P. V. , Rothman E. M.
Published: December 2007

The Berea Sandstone has long been and continues to be a favorite drilling target in many producing areas of the Appalachian Basin. However, its low permeability makes it necessary to fracture stimulate the Berea to obtain economic production rates. The Haysi Field located in western Virginia has responded well to various hydraulic fracture stimulations using a wide range of frac fluids and proppant densities. The initial fracture systems pumped utilized fresh water with linear gels as the fracturing fluid, these were followed by foams, and several massive fracture treatments.

The foam treatments afforded quicker cleanup due to the nitrogen present. However, higher initial production rates with lower decline rates are the direct result of increased proppant densities in the fracture. This concept is supported by the production histories of the individual wells.

Twenty-five (25) years of production data from twenty (20) wells has been analyzed and used as a basis for comparing the different types of fluids pumped and the various proppant densities achieved. Propped fracture lengths were also calculated to compare production results (Figure 5).
A Simple Method for Evaluating Pore Surface Mineralogy
Authors: Mohaghegh Shahab , Ameri Samuel , Aminian Khashayar
Published: December 2007

Majority of mineralogical studies directed at hydrocarbon producing formations are conventional studies that treat the formation as a bulk entity. Focusing on pore surface mineralogy, which is the identification of the elemental composition of the pore surface, seems to be a more realistic approach, since fluids in the formation come into direct contact with these elements on the surface. Rock-fluid properties such as relative permeability, wettability, capillary pressure and certain rock properties, are influenced by pore surface mineralogy. Hence, characterization of pore surface mineralogy will enhance understanding of the interaction between fluid and the porous medium.

This paper discusses Multiple Voltage Scanning Electron Microscopy as a novel method for characterization of pore surface mineralogy. Multiple Voltage Scanning Electron Microscopy, a new method that has successfully been used to study the surface of particles, has been implemented to identify the elemental composition of pore surface.

Results of the investigations of pore surface mineralogy for a reservoir in West Virginia is presented. This reservoir has experienced high injection pressures during a waterflooding project. The concentration of clays on the pore surface can be a possible explanation for high injection pressure.

This paper will try to direct the attention of scientists and researchers to this issue and emphasize the importance of pore surface mineralogy and its effects on rock-fluid properties.
Effects of Rock-Pore Characteristics on Oil Recovery at Breakthrough and Ultimate Oil Recovery in Water-Wet Sandstones
Authors: Owolabi O. O. , Watson R. W.
Published: December 2007

The effects of rock/pore characteristics such as porosity, permeability, tortuosity, formation factor, wettability index, irreducible water saturation, and mercury porosimetry properties, on oil recovery (at breakthrough and floodout) have been investigated in linearcores. Berea sandstone cores were placed in horizontal position with their flood planes parallel to their bedding planes and oil displaced from them by brine at injection rate ranging from 1.20 cc/min to 7.90 cc/min. A scaling-coefficient (product of core length in cm, water velocity in cm/min and water viscosity in cp) of about 5.0 was maintained in each of the waterfloods.

A 10 cp (at 35°C) binary mixture of refined oils, and twenty-one sandstone linear-cores ranging in length from 7.3 to 52.1 cm and diameter ranging from 3.79 to 3.88 cm were used for the study. For the waterfloods, the investigation was conducted at a temperature of 35°C and confining pressure of 500 psi. Six to fifty-four core plugs were extracted from each of the waterflooded cores for a total of 580 core plugs. The core plugs were further analyzed by conducting wettability and mercury porosimetry tests.

The results of the tests show that the core samples investigated were all water-wet and they all exhibited steep-concave unimodal pore-size distribution. Furthermore, the results show good correlations between waterflood sandstone oil recovery (at breakthrough and floodout) and porosity, permeability, formation factor, irreducible water saturation, pore intrusion volume, pore surface area, pore specific surface area, apparent (skeletal) density and mercury recovery efficiency. The accuracy of the oil recovery predictions by these newly proposed empirical models show encouraging results.
Performance Evaluation of Waterflood Project in Southern West Virginia
Authors: Mohaghegh Shahab , Samuel Ameri , Aminian Khashayar , Chatterjee Ujjal
Published: December 2007

Granny Creek oil field is located in Southern West Virginia in the Appalachian Basin. It has been producing from the Big Injun formation. Primary production was initiated in the 1920's and continued until early 1970's. Around the mid 70's, new wells were drilled and a waterflood project was started which is still in progress. During the course of the waterflood project, some problems were encountered. These problems included, inconsistency in sweep efficiency in adjacent patterns, and high injection pressure.

In this field often two adjacent five spot patterns with similar injection to pore volume ratios exhibit totally different oil and water production rates. While water does not breakthrough in some patterns for months, other patterns experience instantaneous water breakthrough. Unusually high injection pressure is observed almost throughout the field, and yet some injection wells exhibit normal injection pressures.

Presented in this paper is a summary of approaches, methodologies, results and conclusions that have been reached during the performance evaluation of this waterflood project. With the aid of reservoir simulation studies, some major heterogeneities were characterized and modeled for this field. Interpretations of seismic studies were used to confirm the orientation of such heterogeneities in the field.
Characterization of a Complex Reservoir in West Virginia
Authors: Aminian Khashayar
Published: December 2007

Reservoir characterization plays a significant role in economic success of the reservoir management. Nearly all reservoirs show some degree of heterogeneity which invariably impacts production. As a result, the production performance of a complex reservoir cannot be realistically predicted without accurate reservoir characterization. Reservoir characterization is a complex problem which requires integration and interpretation of various geological and engineering information.

A systematic and synergistic approach has been employed in this study for characterization of an oil reservoir in West Virginia. Stratigraphy, structural, and seismic data have been utilized to develop a model of the reservoir. Significant amount of reservoir data were collected, compiled and analyzed. Innovative approaches were employed to integrated and reconcile thin-section and scanning-electron microscopy results, petrographic data, initial production data, core analysis, pressure transient tests, and well log interpretation results to quantify model parameters. Primary and secondary production data have been utilized to evaluate and modify the model and its attributes. The results indicated the existence of major heterogeneities in the reservoir which have had profound impact on the performance of the reservoir.
Viscous and Degradation Properties of Crosslinked HPG Gels: Some Laboratory Observations
Authors: Fan Yong , Holditch S. A.
Published: December 2007

Measuring the viscosity of fracturing fluids is important to designing and supervising a fracture treatment. Viscosity is a critical parameter used to compute fracture dimensions and estimate proppant transport. Accurate knowledge of the viscous properties of crosslinked gels is also indispensable for laboratory evaluation of potential fracturing fluid systems. However, attempts to reliably measure the viscous properties of crosslinked gels have proven difficult because of the complex nature of the fluids. Studies by Prud'homme el al.1,2 have demonstrated that viscous properties of crosslinked HPG polymers are controlled by the gel network structure that is formed during crosslinking. The gel network structure is determined by chemical reaction kinetics and process conditions in which the reaction proceeds. The crosslinking reaction causes the gel to be a viscoelastic fluid. As such, temperature and shear histories, crosslinker type, solution pH, degree of hydration of the HPG solution as well as test duration can have a profound effect on the viscous properties of crosslinked HPG gels. Detailed rheological characterization of a crosslinked fracturing fluid remains a difficult and elusive challenge.3,4

Generally, both steady shear and dynamic oscillatory measurements are required to describe the viscoelastic behavior of a crosslinked gel. In a dynamic test, a sinusoidal movement is imposed on the system that results in measurements of storage modulus, G′, and the loss modulus, G″. These parameters provide information about fluid elasticity and energy dissipation and can be used to determine the gel structure and evolution of structure.5,6

In steady shear, shear stress as a function of shear rate is measured, then the viscosity is calculated. Viscosity is important to the design of a fracturing treatment. To generate meaningful viscosity data, the experiment should be conducted at conditions that represent the actual fracturing treatment. Proposed test techniques require dynamic crosslinker injection, continuous shear during gelation, plus controlled temperature and shear rate histories during the measurements.7

The rheology research laboratory at Texas A&M University is equipped with a standard industry Fann 50 viscometer, in addition to the GRI/TAMU rheology flow loop. Both are capable of measuring the steady-shear viscous behavior of complex gel under simulated fracture conditions. The unique aspect of the laboratory is that different types of viscometers have been linked together in a continuous flow loop. As such, it is possible to run simultaneous tests using identical gel formulations, mixing procedures and shear rates with different geometry viscometers. The following text will briefly discuss the equipment; detailed information can be found in the literature.8-10
Crude Oil Fingerprinting by the Total Scanning Fluorescence Technique
Authors: Reyes M. V.
Published: December 2007

EXTENDED ABSTRACT

Texaco's Exploration and Production Technology (EPTD) Division has been developing a crude oil identification method to improve surface logging techniques (formerly known as mud logging). Mudlogging is a commercial service designed to locate with respect to depth the occurrences of hydrocarbons in a well while drilling.
Order No. 636: The Evolution of an Industry
Authors: Mullen Mary , Rich R. S.
Published: December 2007

The implementation of Federal Energy Regulatory Commission ("FERC") Order No. 636 will result in major changes in the operations of interstate natural gas pipelines and the way natural gas is bought, sold, and transported. Instead of a "bundled" service for which the customer pays one price for gas, transportation, storage and related services, interstate pipelines will offer a menu of services from which customers can choose.

This paper discusses the major changes brought about by Order No. 636 and focuses on the "unbundling" of interstate pipeline services and the resulting operational changes, the development of market centers, and the role of storage in this new environment.
Drilling Optimization of an Oil or Gas Field
Authors: Rampersad Paul , Hareland Geir , Pairintra Thamarat
Published: December 2007

This paper demonstrates how information obtained while drilling an oil or gas well, is utilized to optimize drilling costs for upcoming wells in the same field by creating a Geological Drilling Log (GDL). The GDL is created by using drilling models specific to the bits used for individual intervals to generate a formation profile of properties for the entire section drilled on a foot by foot basis. The simulation and optimization is used in the field with the GDL to properly select bits (Tricone or Natural Diamond) and operating conditions for the lowest cost per foot.

The concept of a learning curve is utilized by conducting a number of simulations using the GDL, so that the optimum drilling parameters and conditions are eventually obtained. The approach to drilling optimization using a simulator and a GDL in this study showed a substantial reduction in drilling cost. The drilling models used in this study are capable of accurately simulating the drilling of a well and reproducing realistic Rates of Penetration (ROP).
Comparison and Verification of Two Models which Predict Minimum Principal In-Situ Stress from Triaxiai Data
Authors: Hareland G. , Harikrishnan R. , Warpinski N. R.
Published: December 2007

This paper evaluates the correlation between values of minimum principal in situ stress derived from two different models which use data obtained from triaxiai core tests and coefficient for earth at rest correlations. Both models use triaxiai laboratory tests with different confining pressures. The first method uses a verified fit to the Moor failure envelope as a function of average rock grain size, which was obtained from detailed microscopic analyses. The second method uses the Mohr-Couiomb failure criterion. Both approaches give an angle of internal friction which is used to calculate the coefficient for earth at rest which gives the minimum principal in situ stress. The minimum principal in situ stress is then compared to actual field mini-frac test data which accurately determine the minimum principal in situ stress and are used to verify the accuracy of the correlations. The cores and the mini-frac stress test were obtained from two wells, the Gas Research Institute's (GRI's) Staged Field Experiment (SFE) #1 well through the Travis Peak Formation in the East Texas Basin, and the Department of Energy's (DOE's) Multiwell Experiment (MWX) wells located west-southwest of the town of Rifle, Colorado, near the Rulison gas field. Results from this study indicate that the calculated minimum principal in situ stress values obtained by utilizing the rock failure envelope as a function of average rock grain size correlation are in better agreement with the measured stress values ( from mini-frac tests) than those obtained by utilizing the Mohr-Couiomb failure criterion.
The Effect of Rotational Speed and Eccentricity on Annular Flows with Application to Slim Hole Drilling Hydraulics
Authors: Ribeiro P. R. , Podio A. L. , Sepehmoori K.
Published: December 2007

One of the major issues in slim-hole drilling and coring operations is the accurate prediction of pressure losses in the annulus, in order to guarantee optimum operating conditions. As has been pointed out in the literature, the small annular clearance and the high rotational speeds of the drillstring are factors which preclude the common assumption of unidimensional axial flow in the annulus, which has commonly been applied for conventional pressure drop computations.

In order to address the effect of rotational speed and eccentricity of the inner core in the laminar flow of power law fluids in the annulus, a finite element scheme was applied. The numerical model showed good agreement with available laboratory data for axial-rotary flows in concentric annuli and axial flows in an eccentric annulus. The analysis revealed the significant effect that the rotational speed and eccentricity of the inner cylinder have on the pressure loss of flows through the annulus.
Flow in Porous Media
Authors: Baigorria R. , Pousa J. L. , Di Leo F. , Marañon J.
Published: December 2007

The aim of this paper is to review the numerical simulation methods now being used for dealing with fluid displacement in porous media. One of them is the invasion percolation method, IP, which applies where capillary forces are dominant with respect to viscous forces at the fluid interface. The diffusion-limited agregation method, DLA, consists in the construction of an aggregate of particles from a single particle, the seed, with the restrictions imposed by a probability field gradient satisfying the Laplace equation. Finally, the method of stochastic capillary networks takes advantage of the analogy between the displacement of a fluid in a porous medium and the circulation of the electric current in a purely resistive circuit. A flow problem in a porous medium is said to be solved when analytical expressions relating the pressure and the velocity fields are obtained. From this viewpoint the IP method and the DLA method do not provide this kind of information, although the latter describes the behaviour of the fluids at the interface correctly. The method of stochastic networks, on the other hand, do provide both pressure and velocity fields through the simulation process itself. These fields enable one to calculate flow rates at the inlet and oulet faces of the network as well as inside it, so making it possible to match numerical and experimental results. These methods are mainly applied to assisted and secondary oil recovery as well as in the contamination of aquifers. In particular, the method of stochastic networks is a valuable tool that constitutes a suitable complement to petrophysical and fluid mechanical laboratory measurements, which are of the utmost importance for the reservoir engineer.
Sweep Efficiency Estimates for Reservoirs with Nonuniform Layers
Authors: Araque-Martinez A. N. , Lake L. W.
Published: December 2007

We study a new vertical sweep efficiency correlation for reservoirs with non-uniform layers and compare the effect of permeability autocorrelation on these estimates. Vertical sweep efficiency correlations are important because, in spite of sophisticated numerical simulators now available, there still remains a need for rapid estimates of oil recovery. The vertical sweep efficiencies are calculated using the chemical flooding simulator UTCHEM for a two-dimensional vertical cross-section with one injector and one producer, both also vertical.

As measures of heterogeneity we use the Dykstra-Parsons coefficient (VDP) in the case of a strictly layered reservoir and the Gelhar-Axness coefficient (HI) in the case of a nonlayered reservoir. We validate a strictly layered case and predict the vertical sweep efficiency in cases with nonuniform layers. We show that for mobility ratios greater than one, the effluent concentration of the injected fluid (in this case, polymer) oscillates because of viscous instability.

For unlayered cross sections, we show that the Gelhar-Axness coefficient is a better vertical sweep efficiency estimator than the Dykstra-Parsons coefficient, because it accounts for spatial correlation (autocorrelation) as well as for heterogeneity. The vertical sweep efficiency decreases as we increase HI for the same VDP.
Mud Cake Compressibility and Mobility of Fluid Loss Evaluation
Authors: Tovar J. G. , Martinez A. , Bockh A. , Ford M.
Published: December 2007

Presently, the mud cake and the filtration of the mud are evaluated under qualitative criteria, using API rules. In this paper, a novel method is introduced to determine the consistency and the mobility of the fluids through the cake. A study was conducted both statically and dynamically in the lab to determine the effect of the mud components and contaminants. Some field applications are presented.
The Effect of Wettability on Two-Phase Flow
Authors: Calvo A. L. , Chertcoff R. H. , Cachile M. A. , Rosen M. , Cena N. H.
Published: December 2007

Wettability variations during the exchange of wetting and non-wetting fluids flowing in a solid porous medium are essential effects in enhanced oil recovery. However it is difficult to analyze wettability effects in real porous media due to the difficulty of controlling surface states as well as to their complex internal geometries. A first important step then is to study the basic interplay between viscous and capillary effects occurring during the motion of an interface meniscus in a single pore.

We present here an experimental study of diphasic flows in capillary tubes with millimeter size diameters in which we have determined dynamically the capillary pressure variations during the motion of an interface in a such a restricted geometry. We have chosen to analyze the variations of the capillary pressure rather than those of the contact angle θ. As for classical ndiphasic flow measurements in porous rocks, we have studied imbibition and drainage flows. Finally, the thickness of the wetting film remaining on the tube wall during the drainage flow is studied experimentally. An original radiotracers technique was developed and the film thickness is measured as a function of the capillary number.

At the same time, using a visualization technique, the stability of the wetting-water film is studied. Original results have been found showing that final instability configuration (drops, rings and bridges) depends on capillary number.

Wettability and its effects on the distribution of water and oil in a reservoir are highly complex phenomena which often are not properly understood. This work is intended to describe some of the physics of the capillary effects on that distribution.
Prediction of CO2 Minimum Miscibility Pressures
Authors: Ahmed T. H.
Published: December 2007

This paper presents a practical approach for predicting the Minimum Miscibiiity Pressure (MMP) required for the multi-contact miscible displacement of crude oil systems by CO2. The technique is based on applying the modified Peng and Robinson Equation of State (PREOS) in conjunction with a newly introduced "Miscibiiity Function." The miscibiiity function is designed to provide accurate predictions of the MMP. It is the objective of this paper to demonstrate how this miscibiiity function can be used to determine the necessary conditions required for miscible displacement of hydrocarbon system by CO2. The validity and the use of the proposed approach is illustrated by matching several minimum miscibiiity pressure values as determined from experimental slim-tube displacement data.
Applying Expert Systems in Heavy/Extra Heavy Oil Production Operations
Authors: Reina M.
Published: December 2007

Expert Systems (ES) have been widely used in the oil industry. They are capable of giving opportune responses for the decision making, even for the inexperienced in any given field. In Corpoven S.A. (an affiliate of PDVSA), ES have been developed for drilling operations, production, refining, human resources, field maintenance, etc. In this paper, the results of the implementation of an ES in the production of heavy/extra heavy oil fields by cyclic steam injection are discussed. This is a modular system, that can be installed in a PC, which has been in use since 1990 with excellent results.

This ES, called SEIAV (Sistema Experto en Inyecciôn Alterna de Vapor), covers all the activities related to the exploitation of any heavy/extra heavy oil field. The system works from selecting the candidate well for steaming up until the well is put on production. It monitors the whole operation, detecting and suggesting solutions to any anomaly.

The SEIAV have been used with excellent results in the automatic selection of candidate wells for steaming, as well as in detecting anomalies during the steam injection and hot production operations.
3D Seismic and Horizontal Drilling - A Case History, Bodo, Alberta
Authors: Howell E. C. , Stacey E. C.
Published: December 2007

The McLaren sandstone is a Lower Cretaceous fluvial channel complex located in southeastern part of the province of Alberta, Canada. The South Bodo Field produces heavy gravity oil from this formation, but volumes are increased by the use of horizontal drilling. The McLaren sandstone ranges in thickness to a maximum of 36 m. The reservoir contains a gas cap, a heavy oil and a water leg with porosities of approximately 30% and permeabilities of 2-3d. Due to the large velocity contrast between the channel and the surrounding rock, the McLaren channel complex is well defined seismically. In 1992, a 3D seismic program was shot over the field comprising an area of 33.8 square kilometres. The 3D program gave the additional resolution necessary to accurately locate the horizontal wells.

Several interpreted maps showing the structure on the reservoir and seismic amplitude on the McLaren were used to locate the 15 horizontal wells drilled into the channel. The 3D data set has been inverted using the Generalized Linear Inversion techniques to obtain a velocity log over the zone of interest. Also, an AVO (Amplitude Versus Offset) study will predict the presence of gas in the reservoir from the bin gathers. These techniques may further define the reservoir limits in addition to conventional methods of mapping the structure.

A summary of the drilling results along with the logging and drilling technologies used in this project are reviewed. Reservoir simulation studies will be conducted for future drilling to investigate the gas and water coning properties of the channel sands. Minimum distances above the oil/water and below the gas/oil contacts will be determined from these studies to avoid coning of the gas and water. The MWD tool (Measure While Drilling) and hot wire gas detectors were used to help guide along the correct trajectory

In conclusion, the South Bodo Field represents an integration of technologies to optimize the production from a previously depleted field.
Environmental Issues in Oil and Gas Development in Malaysia
Authors: Evans D. B. , Yong E. F.
Published: December 2007

This paper presents an overall view of the environmental issues associated with oil and gas developments in Malaysia with particular emphasis on offshore platform developments, their associated pipelines and onshore processing facilities. The issues discussed include Malaysian Legislation and requirements for Environmental Impact Assessments, atmospheric emissions, aqueous emissions, waste disposal, wastewater and produced water treatment and discharge, noise, and chemicals usage.
Environmental Management of Offshore Oil Production in Indonesia
Authors: Dahuri Rokhmin , Smith J. P. , Rondonuwu W. A.
Published: December 2007

Increasing public awareness on the limited nature of the environment to absorb wastes generated by various human activities has led to the need to implement sustainable development techniques in real world exploitation practices. Maxus Southeast Sumatra, Inc. has a corporate mandate to practice sustainable development principles for all its operations.

One important manifestation of sustainable development practices within the oil and gas industries is through environmental management aimed at minimizing negative impact of the operations on the receiving environment. Establishing a valid and integrated information base concerning biophysical, socio-economic and cultural entities of coastal and marine ecosystems within the Maxus production area is a vital step in achieving the corporate policy objective.

This paper presents Maxus’ research program, ESACOC (Environmental Sensitivity Analysis and Crude Oil Characteristics), as a means of establishing such an information base. ESACOC consists of four interrelated research packages: (1) risk analysis, (2) shoreline sensitivity analysis, (3) laboratory studies and (4) an interactive computer system. The primary objective of this research program is to provide Maxus and the government of Indonesia the capability of managing environmental problems and issues that may arise in an efficient and optimal manner. This is achieved by integration of data collected from these projects by novel application of a. simulation database and GIS (Geographical Information System).
Quality Criteria in Selecting Glycols as Alternatives to Oil-Based Drilling Fluid Systems
Authors: Bland R. G.
Published: December 2007

High performance polyglycol and polyglycerol based drilling fluids are growing in use to replace less environmentally acceptable oil-based, and the newer "synthetic", invert emulsion drilling fluids. The characteristics and properties of these polyglycols and polyglycerols are presented, discussed and recommendations made with respect to shale stabilization, bit balling, torque reduction, differential sticking and gas hydrates formation.
Indian West Coast Oil Spills: A Remedial Preparedness
Authors: Kapoor Surinder , Rawat H. S.
Published: December 2007

The western offshore oil activities contribute significantly to nation's hydrocarbon requirement. The increased activities of exploration, exploitation processing, handling, transportation, accentuate the risk of oil spillage by accident, human error, equipment failure in operation or natural calamity. Thus the spill of oil into the sea is an inevitable phenomenon that causes serious problem both to marine ecology & oil installations by increasing the risk of fire hazards. The present communique analyses the plausible causes of oil spill & highlights the development of an environmental protection technique that may be applicable to Indian waters. It also exposes all the scientific facts concerning the combatment of oil slick, especially the data base development & analysis system.

Experimental part of the problem has been systematically studied through synergistic bench scale models. The weathering behaviour so studied, was conformed on test slicks in Arabian open sea. The test oil behaved typically having high wax content with low natural combatment features viz.low dispersion & evaporation both below 10% under controlled simulated environment. Further studies indicated that the use of chemical enhanced methodology has limited application as toxicity of test crude may increase many folds.

Efforts have also been made to develop; two predictive models for the area which can be used as a tool for planning an oil spill clean-up strategy. These comprehensive models when integrated can predict the probable contamination, identify low & high sensitive areas and periods in a year and quantum of oil left at any moment for a large oil slick etc.

An emerging technology, net boom with woven socks collection system has been attempted in open sea. Initial field trial is encouraging & speaks about the complete solution to the existing problem with minimal secondary effects.