bluuebunny/crossref_metadata_2025 huggingface dataset:
Field Application of a New Well Testing Concept for Evaluating Damaged and Stimulated Horizontal Wells
Authors: Malekzadeh D. , Azari M. , Day J. J. , Abass H.
Published: December 2007

The potential for severe formation damage around horizontal wells exists due to the increased time of formation exposure to the drilling fluids as compared to the time that a vertical well is exposed to these fluids. This paper explains that the combined effect of the formation damage and the presence of impermeable barriers and low permeability regions in the vicinity of some sections of the horizontal wellbore will manifest itself as skin factor in well test analysis if the total drilled length of the horizontal section is used in the calculations. The purpose of this paper is to present practical new equations, based on a recently introduced concept in well performance analysis, for evaluating the actual length of the horizontal well contributing to production. It is determined that the performance of a horizontal well with mechanical skin and of length Xf1 can be substituted by the performance of a horizontal well of length Xf2 with no skin. Xf2 is smaller than for a damaged well and is greater than for a stimulated well. By combining the concepts of equivalent horizontal well length and equivalent wellbore radius, one will be able to evaluate the performance of a horizontal well in comparison to its expected performance and to subsequently relate it to an equivalent stimulated vertical well. The new equations and guidelines can be used to determine the magnitude of formation damage around horizontal wells and to evaluate the success of a stimulation treatment

The concept of effective horizontal well length developed in this paper was applied to the pressure drawdown analysis of well test data obtained on a horizontal well. A good match was obtained which were used to calculate the parameters of interest.

Furthermore, in the analysis of interference tests with mechanical skin damage at the active horizontal well, the observation well will seem as if it is closer to the active horizontal well than it actually is. The effective horizontal well length is obtained from type curve matching which will then yield the mechanical skin factor.

It is expected that the concept of effective horizontal well length and effective hydraulic fracture length will gradually be adopted and implemented by the petroleum engineers and by groundwater hydrologists in the evironmental engineering discipline.
Coupling Pressure and Rate-Time Data in Performance Analysis of Horizontal Wells: Field Examples
Authors: Vo D. T. , Madden M. V.
Published: December 2007

Horizontal well performance analysis can be difficult. Pressure transient interpretation on horizontal wells is complicated by the possibility of a multiple-flow-regime appearing during testing, and even by the non-appearance of a particular flow regime due to wellbore storage and testing time limitations. As a result, interpretation of horizontal well pressure transient data alone may be ambiguous and unreliable for performance predictions. Rate-time data is frequently available and can be used to improve the analysis, but is often overlooked in horizontal well evaluation.

This paper presents a practical procedure to evaluate and predict performance of horizontal wells. The procedure couples the analysis of pressure transient and rate-time data to enhance the reservoir-well description and accurately predict long-term performance of horizontal wells. The applicability of the procedure is demonstrated by several field examples.

Results from the field tests illustrate that inclusion of the rate-time data in pressure transient testing can be valuable to the design of a successful pressure test. Field examples of the design, planning, and tools used in the pressure tests are discussed. Rate-time data can also help improve the pressure match resulting in a comprehensive set of reservoir and well properties (vertical and horizontal permeabilities, well skin condition, effective well length, reservoir pressure, boundary effect, etc.) which enhances the reservoir-well description. This enhanced description can be used to realistically predict a well's long-term performance. Results indicate analytical solutions available in the literature can be used with care to perform the analysis. The application and limitations of the use of these models are discussed. Good agreement between model prediction and actual long-term well performance is shown.
Selective Tests in Horizontal Wells for a Better Reservoir Characterization
Authors: Lara A. Q. , Renard Gerard
Published: December 2007

Conventional pressure tests in horizontal wells present a lot of practical problems and interpretation difficulties. As a result, they are performed less and less often by oil companies.

In this paper a new procedure — pressure tests on limited lengths of horizontal wells — is proposed. It has some important advantages over conventional tests such as shorter duration and more reliable characterization of the major heterogeneities located near the well.

The need for good reservoir characterization is illustrated by a numerical example of a reservoir with a discontinuous shale lens located between the well and a bottom aquifer. First, we demonstrate that knowing some shale lens parameters such as the relative position of the shale may be very important to maximize well production. Then, we point out how these parameters can be obtained by selective tests conjugated with production logs performed at different times.

Finally, we discuss the advantages of the new procedure on a heterogeneous reservoir generated by stochastic simulation.
Cernent Resistivity and Implications for Measurement of Formation Resistivity Through Casing
Authors: Klein J. D. , Martin P. R. , Miller A. E.
Published: December 2007

Measurement of formation resistivity through casing is an emerging logging technology, with prototype logging tools currently under development. Modeling studies show that the presence of cement could reduce the sensitivity of the TCRT™ (Through Casing Resistivity Tool™). Physically this tool has some similarity to a laterolog. Measurements would be seriously affected if the cement was much more resistive than the formation. We have carried out a laboratory study of cement resistivity with the funding from the Gas Research Institute. Our main objective was to provide hard data to use in assessing the impact of cement resistivity on measurements made with the TCRT™.

Our results show that cement resistivity is generally low, varying from less than 1 to 8 Ω-m at 120° F. Light-weight cements were generally the least resistive, with Class A, G and H cements more resistive. Resistivity was essentially independent of either confining or pore pressure. It was also independent of either current density or voltage. Cement resistivity appears to vary with temperature according to Arp's equation, as would be expected for nonconductive material saturated with water.

Thin sections and mercury injection capillary pressure data show that porosity in cement is dominantly microporosity, with pore throat diameter less than 0.1 microns. In addition helium porosity is high, ranging from 35 to 40%. The low observed resistivity is due to large amounts of water-filled microporosity.

The results of this study signify that the presence of cement will not seriously degrade measurements of resistivity through casing in many environments. Our work concentrated on cements normally used on the North Slope of Alaska, as well as Class H cement, a common Gulf Coast cement.

Potential applications of the TCRT™ include water flood monitoring at Prudhoe Bay and elsewhere, and detection of "missed pay" behind casing.
Well Test Analysis of Heterogeneous Reservoirs
Authors: Deng Xianfa , Home R. N.
Published: December 2007

The method of Green's functions has been a powerful tool to solve unsteady flow problems in homogeneous reservoirs. This paper extends the application of Green's function method to difFusivity problems in heterogeneous reservoirs. A basic formula is obtained for expressing in terms of Green's functions the general solution to the pressure equation with nonhomo-geneous initial and boundary conditions. Through some practical examples, appropriate methods are suggested to obtain the Green's function, which is more difficult to find in heterogeneous problems than in homogeneous ones. Reciprocity is a basic and useful property which facilitates our understanding of porous media flow problems. With the Green's function method developed, the conditions under which the Principle of Reciprocity holds in heterogeneous formation are studied. The application of the reciprocity principle to interference tests in heterogeneous reservoirs is discussed for practical cases.
Pressure-Transient Behavior of Reservoirs Forming a Pattern of Coupled Linear Segments
Authors: Larsen Leif
Published: December 2007

Solutions and examples are presented for the pressure-transient behavior of wells producing from reservoirs made up of two or more coupled linear segments. The solutions are based on numerical shemes in terms of Laplace transforms of the pressure behavior of linear reservoirs.

The simplest cases considered consist of single self-intersecting linear reservoirs, and reservoirs formed as intersections of two and three linear reservoirs with identical properties. Generalizations to cases where each reservoir has its own properties is straightforward, only with more detailed input parameters.

General rectangular patterns of linear segments are also treated, with symmetric square patterns simplified to stepwise linear system.
Application of Fractal Reservoir Model for Interference Test Analysis in Kamojang Geothermal Field (Indonesia)
Authors: Aprilian Salis , Abdassah Doddy , Mucharam Leksono , Sumantri R.
Published: December 2007

This paper presents the application of a new concept, i.e.; fractal model, to analyze pressure transient test data in complex naturally fractured geothermal reservoir.

Application of conventional type curves has been unsuccesful in analyzing and interpreting the interference test results in Kamojang geothermal reservoir which is considered as a complex naturally fractured system. Using the conventional type curve method, the pressure test data, in this case, can not match to the curve, primarily at early time data. The match, however, can be achieved by using the type curves generated based on "fractal reservoir model" which has been previously developed by Chang and Yortsos in 1990. Using the diffusivity equation of fractal reservoir, the equation for interference test has been derived and the result is then used for generating a new type curve method. In addition, the procedure to use this method has also been developed.

Using the generated type curves, application has been performed on analyzing the interference test data from Kamojang geothermal reservoir. The analyzing results demonstrate the viability of the model in describing characteristics of the reservoir such as transmissibility, storativity and fractal dimension of the medium.
Stochastic Relative Permeabilities Usually Have Neglectable Effect on Reservoir Performance
Authors: Tjølsen C. B. , Damsleth Eivind , Bu Tor
Published: December 2007

During the last couple of years Norsk Hydro has developed a 3D model for simultaneous generation of stochastic absolute and relative permeabilities.

By using core data containing relative permeability curves measured on a large number of core plugs from one single well in the North Sea, we have been able to model relative permeability curves (represented by endpoints and exponents) stochastically for four different depositional environments ranging from highly permeable mouthbar sands to low permeable tidal deposits.

We show that for all the depositional environments, stochastic variation of the relative permeabilities have only marginal, if any, effect on the production characteristic, compared to keeping the relative permeabilities constant at their mean.

Based on fractional flow theory, this paper summarizes the results from a theoretical and empirical statistical analysis of the correlation between the water shock front velocity and the absolute permeability for the different depositional environments, and we show that in specific cases this correlation can serve as an indication of the potential effects of stochastically varying relative permeability curves.

The main conclusion, which must be very comforting to practicing engineers, is that in some situations stochastic modeling of the relative permeability curves is of minor importance. However, the choice of mean relative permeabilities may be crucial.
Reservoir Description by Inverse Modeling: Application to EVGSAU Field
Authors: Sultan A. J. , Ouenes Ahmed , Weiss W. W.
Published: December 2007

The major problem of conventional geostatistical reservoir characterization by conditional simulation is that none of the equiprobable realizations (permeability and porosity) generated may fit the field data when used in a reservoir simulation. A recently developed inverse modeling procedure was tested on the CO2-foam pilot area of the East Vacuum Grayburg/San Andres Unit (EVGSAU). The modeling procedure estimated reservoir properties through an automatic and multi-well history matching algorithm. The reservoir parameters, which were estimated by solving an inverse problem, were permeability distribution, average relative permeability and capillary pressure curves, reservoir engineering parameters such as the productivity or injectivity index at the wells, and effective injection rates. All parameters were estimated at reservoir scale in this approach.

A least-square error objective function was minimized by using the simulated annealing method (SAM). The field data matched were the oil, gas, and water productions at each well. The convergence of this new algorithm is guaranteed by the use of SAM, and the permeability distribution generated is conditioned to the dynamic field data. Additionally, for the first time, reservoir engineering parameters were estimated at reservoir scale.

At each iteration, a limited number of reservoir parameters were adjusted. Then, a black oil reservoir simulator was used to evaluate the impact of these new parameters on the field production data. Finally, after comparing the simulated production curves to the field data, a decision was made to keep or reject the altered parameters tested.

A reliable, efficient computer code was developed to estimate reservoir properties by automatic history matching. The algorithm was tested on the EVGSAU for the waterflood period (1980–1985). After optimization, a good match was obtained for all the dynamic field data (production of oil, gas, and water) at all the wells located in the pilot area of the EVGSAU. The resulting large-scale reservoir description was then used to simulate CO2 injection after 1985. The pilot region production history from 1986–1991 was suitably matched using the waterflood reservoir description.
Vertical Interference Testing With a Wireline-Conveyed St raddle-Packer Tool
Authors: Pop J. J. , Badry R. A. , Morris C. W. , Wilkinson D. J. , Tottrup Peter , Jonas J. K.
Published: December 2007

A new approach to the in-situ determination of permeability, permeability anisotropy and lateral continuity of barriers to vertical fluid flow is introduced. The procedure employs a wireline-conveyed inflatable straddle-packer in conjunction with a vertically displaced pressure monitor probe to conduct vertical interference tests in openhole. The relatively large spacing between the packer interval and monitor probe (approximately 5 ft) results in a larger depth of investigation than is currently available with other wireline-conveyed tools. Multiple interference tests may be conducted during a single trip in the well.

The method of analysis is illustrated with data acquired in an oil well located in a complex, low-permeability, carbonate reservoir that has been under production for almost 40 years and under waterflood for approximately 30 years. As part of a field management program the operator wished to assess the status of pressure maintenance by means of a pressure survey and to measure the permeability anisotropy for use in subsequent numerical simulation work. Analysis of core data indicated that the permeability anisotropy should be low.

Feasibility of the testing procedure was established bearing in mind the restriction that flowrates would have to be limited during the pumping and sampling sequences to keep the test pressure above the bubble point pressure. Computer modelling and automatic parameter estimation techniques were employed to estimate the permeability and permeability anisotropy from the interference test data. Electrical and nuclear logs in conjunction with core photographs provided the means to establish the boundaries of the zones tested and to locate the major lithologic units. For comparison the pressure transients measured in the packer interval were analysed by established well testing methods.
A Mechanistic Approach to Understanding Wellbore Phase Redistribution
Authors: Hasan A. R. , Kabir C. S.
Published: December 2007

Wellbore phase redistribution (WPR) frequently occurs during a shut-in test in wellbores having very compressible fluids, such as low-pressure, single-phase gas and high gas/liquid ratio multiphase fluid mixture, including steam. The consequence of WPR is a pressure buildup signature that deviates greatly from the commonly used constant-storage model, thereby precipitating test interpretation problems. A lack of physical understanding of the underlying process has led us to rely solely on empirical approaches — exponential and error function models — for analyzing field data. The existing methods have some drawbacks. For example, one may obtain nonunique results. Further, we cannot predict whether a particular well will exhibit WPR a priori. Thus, the available methods are restricted to the test analysis mode only.

In this work, we present a mechanistic approach to understanding the principal causes for WPR. A simple physical model, consisting of a liquid column and a small pocket of segregated gas at the top, is assumed to mimic a wellbore. The model well cannot receive any fluid from the reservoir upon shut-in; however, backflow from the wellbore into the reservoir is permitted to relieve excess pressure, generated by a rising bubble.

A mathematical model is developed for the idealized well by studying the rise velocity of a single bubble in the liquid column. Interestingly enough, a simplified analytical solution leads to an exponential form to describe the excess pressure behavior, caused by a single-bubble rise, as hypothesized by Fair. Thus, this work provides a basis for Fair’s intuitive exponential model.

The results show that both the wellhead and bottomhole pressures increase with elapsed time as a single gas bubble ascends up the liquid column. The magnitude of pressure rise is a strong function of flow impediment or skin in the wellbore vicinity, well diameter and its orientation, and wellhead pressure. A comparison of the simplified (exponential) and the rigorous solutions shows good agreement between the two at early times.

The proposed model provides a framework for understanding the physical mechanisms that underlie an anomalous pressure rise during a shut-in test. The model, although simplistic in nature, provides some justification for the use of existing empirical methods for interpreting field data.
Characterization of Low-Permeability Media Using Outcrop Measurements
Authors: Knutson C. F. , Cox D. O. , Dooley K. J. , Sisson J. B.
Published: December 2007

A complex fracture system in a formation with low matrix permeability was evaluated to provide data that could be used in fluid flow and contamination migration modeling. Outcrop and well measurements and observations were used as the basis for this study. To determine fracture permeability, fractures were chosen and their apertures measured with a feeler gauge. A flange and nipple were cemented in the middle of the fracture. Cement was injected at least 25 mm (1 in.) into the outcrop edge of the fracture, for a distance of about 0.5 m (18 in.) on both sides of the flange. A fiberglass seal was epoxied over the area to provide additional support for the equipment and cement seal. Fracture permeability was calculated from the pressure needed to inject air into the fracture at a known rate. Flow capacities ranged from 13 to 6717 md-ft on five tests and averaged 1646 md-ft. Outcrop face fracture apertures varied from 0.5 to 2.5 mm (0.02 to 0.1 in.).

Matrix permeability was determined by cementing 6 mm (0.25 in.) washers to a flat outcrop surface area and drilling a shallow hole through the center of the washer to provide a clean injection surface. Matrix permeability was determined by injecting air into the center of the washers while monitoring rate and pressure. Matrix permeabilities ranged from 0.08 to 2.2 md with an average of 0.28 md.

A well was drilled 4.5 m (15 ft) back from the outcrop through an overlying basalt flow into the measured basalt flow. A borehole TV log of the well indicated only one fracture in the measured flow and a continuation of the two foot flow top rubble zone noted in the outcrop. Water was injected into this well at a rate of 23 m^/h (100 gpm) with a 6 m (20 ft) head. This water formed a pancake in the rubble zone and flowed downward into the measured flow’s fractures system and ultimately out of fractures in the outcrop face. The heterogeneity of the system was indicated by the effectiveness of less than 10% of the fractures in distributing the flow to the outcrop.

A thermal image of the outcrop during hot air injection into the well displayed a major anomaly at the rubble zone contact.
Quantitative Description of Muddy Sandstone: Geostatistical Parameters, Automated Facies Generations, and Measurement Methodologies
Authors: Kara Bayram , Kasap Ekrem , Tillman R. W.
Published: December 2007

Our objectives are to study analogous outcrops and subsurface cores to test the aptness of outcrop characteristics to subsurface reservoirs and to determine whether sedimentologically defined geologic units are useful in modeling flow units. The approach involves characterization of the Muddy Sandstone of Wyoming by using geostatistical analysis methods. Incised valley-fill muddy sandstone outcrops and reservoirs near Newcastle and Casper, Wyoming are used.

First, a mechanistic model to calculate statistical error as a function of the number of measurements is derived. The proposed error model indicate a linear relationship between statistical error and the square root of the number of measurements. The slope in the linear relationship is related to a constant and the coefficient of variation. However, the model indicates a quadratic relationship for possible maximum error.

A field permeameter is used to measure permeability on both outcrop and subsurface formations (core slabs). An algorithm and a computer program were developed to generate flow units of measured sections based on permeability derivatives. Sedimentologic descriptions of those measured sections are also produced. Comparison of computer generated and geologically described facies (units) boundaries show an excellent agreement..

Variograms of both subsurface and outcrop show the same degree of oscillatory behavior (hole effect) indicating strong similarity. Various geostatistical parameters for all measured sections of both outcrop and subsurface were calculated. In all cases, Dykstra-Parsons coefficients are in the neighborhood of 0.35 for the single-unit and of 0.65 for the multi-unit data. This is true for both the outcrop and subsurface formations. We concluded that the geostatistical characteristics of valley-fill outcrops are very similar to valley-fill subsurface reservoirs for the Muddy Sandstone studied.
Lithology Determination Using Downhole Bit Mechanics Data
Authors: Wolcott D. S. , Bordelon D. R.
Published: December 2007

A technique has been developed which uses downhole weight on bit (DWOB) and downhole torque (DTOR) measurements to determine the occurrence and thickness of cemented zones in the pay sands of the Kuparuk River oil field. The DWOB/DTOR measurements are made by the MWD tool which is located above the bit and is normally not affected by frictional losses along the drill string. The cemented zones, containing siderite in the upper sand and ankerite in the lower, are high density streaks that reduce production or in the case of Ankerite are non productive.

Using these measurements the cemented zones can be detected, in real time, when the bit first contacts the zone. Because the downhole sensors respond immediately to the changes in lithology the vertical resolution is one ft. which is better than the open hole logs commonly obtained in the field.

From comparisons with density-neutron log data it was demonstrated that the new technique reliably discriminated between cemented and non cemented zones while drilling. Because of the reliability and the high vertical resolution of the technique, the mapping of the cemented zones and the resulting oil in place estimates have improved.

The lithology information obtained from the DWOB/DTOR measurements compliment the triple combo data. By comparing the drilling mechanics data with the density and neutron logs suspect data can be highlighted. In areas where washouts have occurred the wireline data may be adversely affected but the drilling mechanics arc not. The acquisition of downhole bit mechanics data is a useful addition to the logging program and can be effectively utilized in combination with a full log suite or as a replacement for the density-neutron tools as an ankerite or siderite locator.
A Combined Phase and Amplitude Technique for Controlling the Investigation Depth of Propagating Electromagnetic Wave Resistivity Sensors
Authors: Rodney P. F. , Bittar M. S.
Published: December 2007

The general question of combining electromagnetic wave phase differences and amplitude ratios to produce apparent resistivities is explored in this paper. When dealing with a step invasion model, it is possible to combine these measurements in different ways to produce readings which cover a range of investigation depths. Most significantly, the investigation depths corresponding to some of these combinations exceed those obtained using either the amplitude ratio or the phase difference alone. Tradeoffs in terms of bed resolution, effects due to instrument accuracy and uncertainties in the dielectric constant also are discussed. The paper concludes with some field examples showing the benefits and limitations of the method.
The Miniporopermeameter for Simultaneous Measurement of Permeability and Porosity
Authors: Chen Zhongming , McLemore Jim , Heller J. P.
Published: December 2007

Porosity, as well as permeability, of small regions at and just below the surface of a larger, slabbed sample of porous rock can be measured by using the device discussed in this paper. Measurement of permeability is accomplished as in the well-known "Minipermeameter" by forcing a steady flow of air or other gas into the face of the rock through the central passageway of a deformable rubber probe or tip that could consist of the end of a soft rubber tube. The permeability of a region of the rock directly under the probe tip is computed from the ratio of flow rate into the rock to the pressure drop between the air in the probe-tip and the atmosphere. As shown in this paper, the capability of the minipermeameter can be expanded, so that it can be used to measure porosity as well. Immediately after calculation of the permeability, and under defined conditions, a precise value of the porosity (of the same portion of the rock) may be computed from the transient pressure change that is observed at the probe-tip after cutting off air flow into the rock from the probe. This paper describes both the mathematical/numerical analysis that stands behind the measurement and computation, and the experimental apparatus and procedures required for operation of the instrument. The key device needed is a pressure transducer with very fast response, high mechanical impedance and low dead volume.
Intelligent Diagnosis of Rod Pumping Problems
Authors: Alegre Lideniro , Morooka C. K. , da Rocha A. F.
Published: December 2007

Rod-pumping is the most common artificial lift method used to move oil to the surface in low pressure resevoirs. A variety of mechanical problems can occur with this system. The adjustment of the pumping capacity to the reservoir production rate is another source of error compromising pumping efficiency. The need to identify these problems quickly and accurately is essential in attempts to minimize operating costs and maximize production. A dynamometer is attached in general to the polished rod of the pumping unit, and a plot of load vs. position, known as (downhole) dynamometer card (DC), is obtained for the purpose of rod load monitoring. Altough DC is a very important piece of information, other data may be required to support complex decision making about the actual rod-pumping condition. For this purpose, the engineer uses also information about the characteristics of the well, the type of oil being pumped, etc., besides taking into consideration the DC shape, maximum and minimum load values, etc. A new type of neuron is used to built neural nets having powerful numeric and symbolic processing capabilities, besides permiting knowledge to be encoded not only on the wiring of the net, but also on the selection of the types of neurons and synapsis composing the net. This new type of neural nets was used to develop SICAD, a hierarchical neural system whose purpose is the intelligent control of rod-pumping. SICAD is composed by two famillies of neural nets specialized, respectively, in pattern recognition (PRN) and expert reasoning (ERN). Different modes of interactions between ERN and PRN define different pumping control strategies.
Quantitative Three-Phase Profiling and Flow Regime Characterization in a Horizontal Well
Authors: Chauvel Yves , Clayton Francis
Published: December 2007

Production logs have been used for flow profiling in horizontal wells for a number of years, thanks mainly to the advent of the CTL* Coiled Tubing Logging, a technique which allows strings of electrical tools to be lowered into the well and pushed along the horizontal section. Production logs are typically run for reservoir monitoring purposes or for diagnosis of problem wells. However, flow profiling in horizontal wells is usually restricted to single phase analysis owing to lack of enough applicable measurements and due to inadequate understanding of the physics of three-phase horizontal flow.

In this example a complete data set was acquired, including measurements such as the Nuclear Fluid Densimeter and the WFL* Water Flow Log. These additional, independent measurements provide data of outstanding quality and allow individual and independent quantification of the flow rates of oil, water and gas at any location in the well. Moreover, the acquired data set allows the validity and consistency of the measurements to be crosschecked. Finally, strong anomalies in the sensor readings, caused by the in-situ conditions of the flow, allow the identification and description of two highly contrasted, alternating flow regimes, and the correlation of their occurrence with changes in elevation of the well path.

Thus, besides solving a complex production identification problem, this unique data set and its interpretation shed additional light on the dynamics of multiphase flow in horizontal wells.
Friction Factor of Perforation Roughness in Pipes
Authors: Su Ze , Gudmundsson J. S.
Published: December 2007

The friction factor of perforation roughness was measured in pipes geometrically similar to casing used in horizontal wells. There was no fluid flow through the perforations in the work reported. The experimental data were analyzed using the universal velocity distribution law and the concept of roughness function. It was found that the roughness function increased linearly with the perforation/casing diameter ratio. An empirical relationship was obtained to estimate the friction factor in pipes with perforation roughness.
Formation and Fracture Characterization by Inversion of Fracture Treatment Records
Authors: Bhalla Kenneth , Brady B. H.
Published: December 2007

The design of hydraulic fracture treatments requires reliable determination of in-situ parameters. The algorithm presented in this paper is a method of formation and fracture characterization based on the application of a formal inversion procedure to fracture treatment data records, collected during calibration treatments before the main treatment or in the full scale treatment of offset wells.

During a fracture treatment, the bottomhole pressures are related to a set of treatment and formation parameters. The treatment parameters may be determined explicitly through measurement but the formation parameters contain considerable uncertainty.

The inversion algorithm implements pseudo-three dimensional and multi-layer fracture simulators. Results are presented for the inversion of synthetic data records generated by the fracture simulators and for field data, where independent formation characterization has been performed.

In the case studies, it is observed that the parameters which are determined by inversion, e.g., leakoff coefficient, formation Young's modulus and fracture closure pressure, are in excellent agreement together with the corresponding pressure history match.

This work suggests that useful formation characterization parameters can be extracted from a pressure history record. Furthermore, the geometry of the fracture can be determined from the defined formation parameters and the pump schedule.
"Pipelining": Viscous Fingering Prop Fracture Technique Finds Wide Success in Permian and Delaware Basins
Authors: Ely J. W. , Hargrove J. S. , Wolters B. C. , Kromer J. C.
Published: December 2007

During the past two and a half years, a new fracturing technique has been developed to selectively place proppant across a well's producing interval. The new technique, termed "pipelining," has been employed in hundreds of wells in the Permian and Delaware basins. This technique utilizes high differential viscosity to selectively place high concentrations of proppant across the well's producing zone. This technique involves specialized design and iterative modeling procedures.

In the paper, we will discuss the ongoing improvement of the "pipeline" fracture design and present numerous case histories of various sand members of the Delaware formation throughout Southeastern New Mexico as well as other producing horizons in the Permian Basin.

The authors feel that the "pipeline" fracture technique, combined with intense quality control and aggressive forced closure, greatly enhances the ability to selectively place proppant in the pay zone and allows for highly conductive propped fractures for much greater lengths than were heretofore felt possible.
Development of a Standard Coiled-Tubing Fatigue Test
Authors: Newman K. R. , Brown P. A.
Published: December 2007

The understanding and modelling of coiled tubing (CT) fatigue life has continued to be a major area of concern as CT diameters have increased, usage and variety of applications continue to grow, and tubing is subjected to higher pressures. This paper presents a method and testing apparatus which has been developed in an attempt to simplify and standardize CT fatigue testing. Preliminary results from this testing method are compared with full-scale tests and a fatigue life prediction model to demonstrate that this method is valid.
Measurement and Prediction of the Kinetics of Paraffin Deposition
Authors: Brown T. S. , Niesen V. G. , Erickson D. D.
Published: December 2007

Economically and technically viable methods for controlling paraffin buildup in pipelines and wellbores are critical to the production of crude oil in deep water and cold environments. Laboratory test methods and a computational model have been developed to predict rates of paraffin deposition in pipelines and the effect of long-term deposition on the pipeline pressure drop and temperature profile. The model has been incorporated into a fully menu-driven program that runs on a personal computer. The two major portions of the program are the thermodynamic model which is used to calculate solid-liquid-vapor phase equilibria and the kinetic model which is used to predict the deposition and paraffin buildup rates. The thermodynamic portion is described in a companion paper7. The kinetic model is based on information present in the literature and on several hundred measurements of paraffin deposition rates in a laboratory-scale test loop.
Development of a Film-Persistent Water-Dispersible Corrosion Inhibitor
Authors: Cain J. J. , Rosenthal L. M.
Published: December 2007

We have developed a new film-persistent, water-dispersible corrosion inhibitor, a quaternary ammonium salt, that was optimized for brine dispersibility and corrosion inhibition. The inhibitor was tested at several concentrations under many accepted industry methods, including kettle tests and continuous and film persistence wheel tests. Our inhibitor performance in those tests was equivalent or superior to the performance of common quaternary intermediates at only one quarter of their concentrations.

Most importantly, the inhibitor displays excellent film persistence. This can be a major advantage as most existing water soluble corrosion inhibitors have very poor film persistence, and must be administered continuously rather than batch-wise. They do not strongly adhere to metal surfaces, and are ineffective unless continually present in the surrounding fluid. The new film persistent inhibitor will allow batch treatment to be an option, which in some cases could reduce chemical cost significantly.
Optimization of Heavy Oil and Gas Pumping in Horizontal Wells
Authors: Rondy Philippe , Cholet H. J. , Federer Imre
Published: December 2007

Horizontal and highly deviated wells have become very attractive for the production of reservoirs with gas coning problems.

The presence of free gas has been recognized as having, in general, detrimental effects on the performance of downhole pumps: production is drastically decreased, equipment is damaged, etc. This document put forward the experimental tests that have been carried out in a laboratory- scale flow loop to investigate the efficiency of gas-anchor systems under various conditions (inclined position, different GLR, …).

Using the important contrast of density and velocity of the two different phases, the tested apparatus prevents free gas from entering the pump intake, and provides a simple and reliable mean for optimizing production from inclined drainhole, capable of handling two-phases viscous mixtures with gas fractions as high as 80% without excessive downtime/production losses. The tests data show that performances measured on the lab bench could potentially reach 75-100%. The role of GOR, as well as the influence of viscosity (up to 1000cP) are specially identified and discussed.
Fluid Selection for Fracturing High-Permeability Formations
Authors: McGowen J. M. , Vitthal Sanjay , Parker M. A. , Rahimi Al , Martch W. E.
Published: December 2007

Hydraulic fracturing is a well established technique for stimulating low permeability formations and for bypassing damage in moderate permeability formations. It is now being applied to high permeability formations (k > 10 md) to increase production and control formation fines. Fluid selections for these treatments range from typical gravel pack fluids to typical hydraulic fracturing fluids. To determine guidelines for fluid selection, detailed measurements, of fluid loss, core damage, and fracture conductivity were performed under realistic fracturing conditions on cores with liquid permeabilities ranging from 10 md to 1000 md. The bulk of the data presented is on Berea Sandstone ranging from 200 md to 400 md. Results of these tests indicate the relative effectiveness of these treatment fluids for fracturing high permeability formations based on fluid loss, formation permeability damage, and fracture conductivity. Treatment and production simulations are provided stressing the difference in performance between systems.
Elastomeric Composites for Use in Well Cementing Operations
Authors: Onan D. D. , Goodwin K. J. , McPherson T. W.
Published: December 2007

Considerable work has been conducted in the study of cement sheath stress failure. Laboratory and field tests indicate that conventional cementing compositions are susceptible to the effects of excessive casing test pressure or temperature changes experienced during production or workover operations. More specifically, those studies show that the typical range of compressive strengths used in most cementing operations, as well as the limited tensile properties afforded by pore-filling latex cements, are not adequate to prevent failure under conditions of excessive differential temperature and pressure. A crosslinked synthetic polymer containing a quick-setting cement has been developed that provides unique resilient properties better suited for those conditions where Portland cements will not suffice. These elastomeric formulations enhance tensile and shear strength, as well as increase resistance to chemicals and heat. Thus, both pipe support and sufficient ductility to complement pipe expansion are achieved with little or no permeability. These properties can be further enhanced by the addition of reinforcing agents such a silica, ground rubber, hard hydrocarbon, natural and synthetic fiber, barite, clays, carbon black and microspheres. Data from field case histories and laboratory studies are discussed. This investigation was limited to the evaluation of a synthetic rubber, styrene-butadiene. The use of the elastomeric system in other applications is also discussed.
A Study of the Effects of Mixing Energy Imparted on Cement Slurries by Field Equipment and Coiled Tubing
Authors: Heathman J. F. , Sands F. L. , Sas-Jaworsky Alexander , Badalamenti A. M.
Published: December 2007

More widespread application of coiled tubing workover operations involving cement slurry placement has developed in recent years because of associated advances in coiled tubing technology.1–3 Consequently, one of the parameters of job design which has come under scrutiny for cement slurries associated with coiled tubing operations is the effect of various levels of mixing energy during batch mixing, as well as the effect of shear through a coiled tubing spool.4-7 The measurable effect on a cement slurry batch mixed for extended periods of time can be seen as being very much a factor of the slurry design (admixtures, water ratio, etc.) as well as the energy applied at the point of cement-water contact.8 The work presented in this paper examines the effects of various levels of energy (mixing power) imparted by batch-mixing equipment on various types of cement slurries. Likewise, the effects, on a slurry, of pumping it through a length of coiled tubing are also examined.
Propellant Gas Fracture Stimulation of a Horizontal Austin Chalk Wellbore
Authors: Hollabaugh G. S. , Dees J. M.
Published: December 2007

Oryx Energy has been drilling horizontal wells in the Pearsall Field of South Texas since 1985 and stimulating a number of these wells since 1989. Until 1992, stimulation techniques included acid washes, acid fracs and high rate water fracs. In 1992, Oryx Energy stimulated wells with high injection rate water fracs with varied success and high costs. A new stimulation method for these horizontal wells was desired to improve the degree of stimulation and reduce costs.

In 1992, a horizontal well was stimulated with a propellant gas fracture tool in an attempt stimulate the well in a method that would be cost competitive and have better results than the water fracs. The process permits simultaneous initiation of numerous multi-oriented fractures. The gas fracture propellant tool was designed to create fractures into the formation down the axis of the wellbore that are more or less perpendicular to the existing natural fractures. This treatment, while not economically successful, did result in sustained increases of oil, water and gas. This showed that the stimulation was successful in connecting some lesser depleted fracture intervals with ones that were producing before the treatment.

This paper reviews the results of Oryx Energy’s propellant gas fracture stimulation treatment of a horizontal well with 1028’ of 4 1/2" O.D. propellant in a 5 1/2" carrier run in an openhole wellbore. The job design, problems encountered, and results are reviewed in this paper.
Evaluation of the Performance of a New Upflow Design
Authors: Aretz H. J. , Stell J. D.
Published: December 2007

The design and performance of a new patented upflow vane developed by Burgess-Manning, Inc. is discussed in this paper. The BM 627 vane operates similarly to high performing Burgess-Manning horizontal flow vanes. The concept of shielding the separated liquid from the gas stream, used extensively for horizontal vanes, has been integrated into an upflow configuration.

In this paper a comparison of the performance of the new BM 627 vane to more traditional separation methods such as meshpads is presented. The test data will show that the new vane design outperforms other upflow configurations in separation efficiency, turndown ranges, and pressure drop.

The BM 627 vane incorporates the combination of hollow vanes which are interconnected with a drain channel. This design allows the separated liquid to be shielded and removed from the gas stream. The advantages of this new vane design include; higher velocities through the vanes, lower pressure drops across the vane bundles, higher separation efficiencies over an extended turndown range, and smaller vessel sizes. The BM 627 is also well suited for easy retrofits into existing vessels with meshpads. The supporting structure for the current meshpad can be utilized for the new upflow vane bundle, thereby eliminating the need for welding.
Analysis of Residual Corrosion Inhibitors in Oilfield Brines
Authors: Fortenberry C. L. , Grahmann N. J. , Miller C. D. , Son A. J.
Published: December 2007

Ultraviolet (UV) spectroscopy can be used to detect low levels of organic corrosion inhibitors in produced water. An analytical method has been developed using a diode array UV spectrophotometer. The specifics of sample handling and preparation, and methods to stabilize samples for later analysis have been developed. The method is routinely used in the field as part of a comprehensive corrosion monitoring program. The partitioning behavior of corrosion inhibitors, between oil and water, can also be observed using this technique.