bluuebunny/crossref_metadata_2025 huggingface dataset:
Safe Perforating Unaffected by Radio and Electric Power
Authors: Huber K. B. , Pease J. M.
Published: December 2007

Radio transmission, radar, electric welding, cathodic protection, and electric generators, motors and their connections can create an unsafe environment for certain operations using explosives. Transporting and arming electrically initiated explosive perforating devices in this environment can be hazardous. A premature detonation can occur if correct procedures are not followed. The procedures required to prevent premature detonation often include the interruption of radio and microwave transmission, welding operations and cathodic protection systems. These shutdowns are costly and cause operational and logistical difficulties and may pose new safety problems. This problem is especially acute when operating offshore or in highly congested urban areas.

The paper briefly reviews perforating equipment and operations and identifies the potential hazards of transporting and arming explosive devices in the previously described environment. The present safety procedures and equipment are discussed, along with a detailed analysis of the problems and the procedures used to allow limited radio silence. A new method of initiating perforating guns is described that is based on the principle of a foil, subjected to a large electric power burst, slapping a secondary explosive and a safe and arm system that totally eliminates the need for radio silence. Electric welding, cathodic protection and other electric equipment can also be operated without interruption.

SECTION 1 - RADIO AND ELECTRIC POWER INSTALLATIONS AFFECTING PERFORATING
The Nonhomogeneous Flow Character of a Delayed Crosslinked Gel
Authors: Cameron J. R. , Joha R. J. , Veatch R. W.
Published: December 2007

Experiments were done using modified Model 50C Fann viscometry and tubular flow tests to study the nonhomogeneous flow character of a delayed cross- linked fracturing fluid. Previous testing showed that a delayed crosslinked fracturing fluid can exhibit two distinct forms of nonhomogeneous flow when tested on the Model 50C Fann viscometer. At low shear stresses, the fluid exhibited apparent slip flow with low viscosities, but when the stress was increased to a critical value, the gel broke up forming a dispersed fluid with a much higher viscosity. However, in the dispersed form, nonhomogeneous flow was still evident. Testing described in this work found that when this fluid is crosslinked at very low shear energies on the Fann viscometer, the resulting gel still exhibits apparent slip flow, but with very high viscosities. In this case, high stresses are required to break up the gel. Flow visualization tests indicate that the stress buildup during gel breakup results from a flocculation process and secondary flows as well as destruction of the low-viscosity slip layer. When tested in a tubular-flow loop, this gel did not exhibit comparable stress buildup behavior. However, retesting of flow-loop generated gels on the Fann viscometer showed that flow-loop data corresponded most closely to the low viscosities observed on the Fann viscome-ter when the gel was in apparent slip-flow. Thus, this gel may slip when tested in tubular flow and perhaps when flowing in fractures.
Remote Gas Measurement for Production Allocation: Douglas Creek Arch Region, Colorado
Authors: McConnell J. D.
Published: December 2007

A Supervisory Control and Data Acquisition system has been installed as a part of natural gas production operations in Northwestern Colorado.

The system was installed in conjunction with a large production acceleration project and assists in monitoring gas production from the individual well, through a gas gathering system and into a company owned processing facility.

Advantages offered by the system include a comprehensive overview of gas production and gathering operations from a central location and improved efficiency by allowing production operators to target their daily activities toward problem areas.
Reducing the Risk of Ductile Fracture on the Canyon Reef Carriers CO2 Pipeline
Authors: Marsili D. L. , Stevick G. R.
Published: December 2007

There exists in the pipeline industry a potentially catastrophic phenomenon known as ductile fracture. This report presents new technology which minimizes the effect of a ductile fracture if preventive measures fail.
Implementation of a Mainframe-Supported Handheld Data Terminal Collection System
Authors: Lopez M. A. , Merritt R. J.
Published: December 2007

In 1989, Oryx Energy Company implemented a handheld data collection system throughout all its U. S. field locations. Its purpose was to replace various paper reporting processes and provide real time data. This system is uniquely characterized by the maintenance of all data describing a particular lease operator job on a mainframe system. The job file is updated and automatically downloaded to the handheld terminal. Data collected daily by the lease operator is uploaded to a main-frame based collection file. The system is multitasking, incorporates electronic mail messages, and provides other features not normally found in handheld terminal systems.
Real-Time 3-D Hydraulic Fracturing Simulation: Theory and Field Case Studies
Authors: Meyer B. R. , Cooper G. D. , Nelson S. G.
Published: December 2007

This paper presents a foundation and methodology for real time three-dimensional hydraulic fracturing simulation and analysis. The equations governing fracture propagation are summarized for both rate and net pressure boundary conditions. A new dimensionless pressure slope parameter is introduced which prevents using chaotic measured or calculated pressures. This parameter also helps identify near wellbore restrictions.

The real time fracturing simulator utilizes the same numerical modules and routines as the design program. This will insure design, real time and post-design simulation compatibility. Simulated results for the rate and net pressure driven models can be displayed concurrently during the hydraulic stimulation.

Comparative studies of the rate and net pressure driven numerical results are included. A post-treatment analysis of a real time field case study is presented to illustrate the application of this real time fracturing system. The importance of using a dimensionless pressure slope is also discussed.
Improved Rod String Taper Design
Authors: Gault R. H. , Takacs G.
Published: December 2007

This study presents an improved method for designing sucker rod taper percentages.

The API RP11L is the usual source for sucker rod taper percentages. When it was last revised, in 1976, it was necessary to make several simplifying assumptions because the complete calculations were too laborious for hand calculation.
Correlation of Scale Inhibitor Structure With Adsorption Thermodynamics and Performance in Inhibition of Barium Sulfate in Low-pH Environments
Authors: Breen P. J. , Diel B. N. , Downs H. H.
Published: December 2007

In order to develop improved barium sulfate inhibitors for acidic (pH 4) environments, adsorption thermodynamics have been measured for several homologous series of inhibitors wherein the molecular structures have been varied systematically.

Correlations between thermodynamic, structural and performance data will be discussed.
Application of the Continuous Annular Monitoring Concept To Prevent Groundwater Contamination by Class II Injection Wells
Authors: Janson L. G. , Wilson E. M.
Published: December 2007

This paper will present a continuous annular monitoring concept that allows Class II injection wells that have insignificant leaks in the casing to demonstrate mechanical integrity. Inherent in this concept is the premise that an insignificant leak in the casing is any leak that will not endanger a USDW and that this test will therefore meet the regulatory requirements under 40 CFR 146.8 (a) and (b). A case history will be presented to demonstrate the viability of this concept as an alternative mechanical integrity test. This concept has been approved as an alternate mechanical integrity test by the Regional Administrator of USEPA Region 6 for use in the Osage Mineral Reserve under 40 CFR 147.2912 (a)(1)(V).
Predicting Oxygen Depletion in Reservoir Environments
Authors: Welch V. S. , Dann M. W. , Mehta B.
Published: December 2007

Iron pyrite (FeS2; ferric sulfide; "Fool’s Gold") is one of the most common of all naturally occurring minerals in sedimentary rock. Any reservoir process involving oxygen (air) might be affected by the aqueous oxidation of pyrite in the reservoir. During this reaction, one mole of pyrite can consume 3.75 moles of oxygen, or the equivalent of all the oxygen present in 6,469 SCF (183 m3) of air. Reservoir pH may be reduced significantly by the major reaction product, sulfuric acid. The precipitation of ferrous hydroxide may cause permeability reduction.

This paper discusses the case history of a pilot air storage test, the results of laboratory studies which identified pyrite as the prime suspect for the oxygen loss during the test, the reaction stoichiometry for the reservoir environment studied, laboratory equipment and procedures used to test synthetic sand-pyrite mixtures and core plugs for oxygen consumption, and the empirical relationship which was derived to predict oxygen consumption.
Reservoir Description and Steamflood Development in the Lost Hills Field
Authors: Chiou R. C. S. , Kirst T. L. , Kiven C. W.
Published: December 2007

A steamflood was developed in the Lost Hills field, located in the southwest portion of the San Joaquin Basin in California. The heavy oil reservoirs consist of shallow-marine Upper Etchegoin sands overlain by the fluvio-lacustrine Tulare formation. Steamflood development was complicated by the presence of desaturated zones in both the Tulare and Upper Etchegoin sands. Core analyses, density-neutron logs, and temperature profiles aided in the identification of three genetically different types of desaturation: 1) gravity drainage response to anticlinal growth and/or regional uplift, 2) possible paleo-oil seeps related to an unconformity, and 3) production depletion due to nearby thermal operations. Reservoir mapping indicates that the the first type of desaturation was widespread in the Upper Tulare sand. This type of desaturation not only significantly reduced the oil-in-place, but could also become a major thermal thief zone. Steamflood patterns and well completions were designed to minimize the effect of desaturation and maximize the project efficiency. The design and development of the steamflood may be applied to other partially desaturated, multiple sand reservoirs.
Evaluation of Geostatistical Techniques for Reservoir Characterization
Authors: Chopra A. K. , Severson C. D. , Carhart S. R.
Published: December 2007

One of the most important problems in reservoir management and EOR applications is to describe interwell heterogeneity for optimum well spacing and process design. The conventional approaches to build reservoir descriptions use interpolation schemes based on the geometric distance of the samples. In geostatistics, on the other hand, the interpolated values depend on geometric orientation and correlation. Geostatistics has been used in the mining industry for the past forty years and in hydrogeology for the past twenty years. However, its application has been limited in reservoir engineering because of skepticism due to a lack of needed data and the absence of comparisons with the conventional techniques.

Conventional and geostatistical reservoir characterization techniques are compared in this paper. Field data from about 50 wells are used in this evaluation. Interwell properties are computed using conventional and geostatistical techniques, cross-validated, and compared. Histograms show there are no geographically distinct populations requiring separate modeling. Experimental variograms identify the scales of variability of the reservoir properties and the existence of preferential directions of maximum and minimum variability. Variogram models are fitted to the experimental correlations.

The results of this work indicate that the success of any technique is a function of the geological environment, selection of proper reservoir parameters for that environment, an adequate number of samples, an appropriate sample spacing, and most importantly, the correct application of the technique. Geostatistical techniques have more potential to incorporate the underlying correlation present in the data in the final analysis.
General Coning Correlations Based on Mechanistic Studies
Authors: Lee S. H. , Tung W. B.
Published: December 2007

The coning of water can impact well productivity and increase water treatment requirements. Coning correlations are often used to model water-breakthrough time and water cut due to coning. Most existing coning correlations are based on a steady state approximation so that the prediction of water-breakthrough time and initial water cut development are generally unreliable. By first determining the key reservoir, production, and well completion parameters through a theoretical analysis, improved correlations were developed. They have been extensively compared with numerical simulation results to validate their general applicability. The correlations simplify the procedure in the study of the effects of production rate, vertical and horizontal permeabilities, well completion location, physical properties of fluids, relative permeabilities, aquifer thickness, completion interval size, and drainage radius on coning dynamics.

The new correlations can be used in a stand-alone program or in reservoir simulation. In field-scale reservoir simulation, correlations are often employed to model sub-scale flow behavior near a well. Hence, technical issues in implementing correlations into a finite difference simulator are also discussed. In addition, the new correlations are extended to multi-layered, nonhomogeneous reservoir models.
A New Adaptive Orthogonal Grid Generation Procedure for Reservoir Simulation
Authors: Sharpe H. N. , Anderson D. A.
Published: December 2007

The generation of boundary conforming, orthogonal, smooth curvilinear grid systems for regions containing internal boundaries, which can also cluster dynamically to physical solution gradients, is of major importance to reservoir simulation. This paper develops a practical methodology for achieving these objectives for two-dimensional problems. The procedure is based on elliptic mapping methods and equidistribution schemes. The extension to 3–D is simple for thin reservoirs.
Implementation of a Reservoir Management Program
Authors: Thakur G. C.
Published: December 2007

Reservoir management can be defined as the judicious use of various means available to maximize benefits or economic recovery from a reservoir. Although there are numerous reasons why reservoir management programs sometimes do not succeed, perhaps the most important reason is the lack of team effort in developing and implementing such programs. A step-by-step procedure to improve success in this effort is outlined.

Two distinct approaches have been utilized: one is a comprehensive approach for large reservoirs and the other is a problem solving approach for small (and/or less profitable) reservoirs. Although the approaches are philosophically quite different, each has produced useful results. It is not necessary for all reservoirs to have the most comprehensive management program; rather, it should be dictated based upon need, keeping the cost-benefit analysis in mind.
Geostatistics for Reservoir Characterization
Authors: Journel A. G.
Published: December 2007

Geostatistics and, more specifically, stochastic modeling of reservoir heterogeneities are being increasingly considered by reservoir analysts and engineers for their potential in generating more accurate reservoir models together with usable measures of spatial uncertainty. Geostatistics provides a probabilistic framework and a toolbox for data analysis with early integration of information. The uncertainty about the spatial distribution of critical reservoir parameters is modeled and transferred all the way to a risk-conscious reservoir management. The stochastic imaging (modeling) algorithms allow the generation of multiple, equiprobable, unsmoothed reservoir models yet all honoring the data available.
Remobilization of Natural Gas Trapped by Encroaching Water
Authors: Ancell K. L. , Trousil P. M.
Published: December 2007

Water drive gas reservoirs are frequently abandoned at high pressures which results in low recovery of the initial gas in place. The gas remaining in these reservoirs is trapped as residual gas saturation. The techniques to remobilize a portion of this gas that has been trapped by encroaching water are presented along with a method to evaluate the incremental reserve potential of such reservoirs. The remobilization of the trapped gas requires the production of large volumes of water to lower the reservoir pressure which in turn allows the gas to expand and flow.

A new use of the p/z vs cumulative production chart is presented which gives the engineer a quick method to evaluate the feasibility of recovering a portion of the gas that has been trapped by water influx.

A field example is presented which illustrates the concepts and techniques. Presented is field data that demonstrates the remobilization of gas that had been trapped by encroaching water. Significant increases in recovery have been experienced at the demonstration field, and ultimate recovery is estimated to be about 8% of initial gas in place greater than was recovered using conventional practices. Also given are actual operating costs and revenue calculations that show the process to be economic at 1990 market prices.
Using Depletion Ratios To Select and Evaluate Drilling Locations in Naturally Fractured Gas Reservoirs
Authors: Hower T. L.
Published: December 2007

A reservoir characterization technique is presented which can significantly lower the risk involved in developing naturally fractured gas reservoirs. It is shown that depletion ratios can be used to delineate the limits of a field, highlight the prolific trends often associated with naturally fractured reservoirs, and provide a simple, yet accurate, means of assigning reserves to undrilled locations.

A field case history is described and the results of a successful twenty well drilling program are presented. Pre-drill reserve estimates for the entire program were within seven percent of the actual post-drill reserve estimates from production decline analysis.
A Comparison of Mass Rate and Steam Quality Reductions To Optimize Steamflood Performance
Authors: Messner G. L.
Published: December 2007

Most mature steamflood projects have the heat injection rates reduced to minimize fuel costs and extend the economic life of the project. However, there is little industry consensus on whether the heat cuts should take the form of 1) mass rate reductions while maintaining the same high steam quality, or 2) steam quality decreases while keeping the same mass rate. Using a commercial three-phase, three-dimensional simulator, oil recovery schedules were generated for several steam mass rate and quality reduction cases under a variety of reservoir and operating conditions. The results indicated that for equivalent heat injection rates, decreasing the steam injection mass rate at a constant high quality will yield more economic oil than reducing the steam quality at a constant mass rate. A sensitivity analysis confirmed this conclusion and demonstrated the importance of the gravity drainage/steam zone expansion mechanism in a low-pressure, heavy oil steamflood with gravity segregation. Furthermore, the impact of discontinuous silts and non-uniform initial temperatures within the steamflood zone was studied, again indicating that a decreasing mass rate injection strategy is a superior operating practice.
Optimal Reduction of the Analytical Data Necessary for the Thermodynamic Characterization of Natural Gases
Authors: Ruffier-Meray V. , Barreau A. , Behar E.
Published: December 2007

Analytical procedures presently available lead to a large amount of compositional data when applied to reservoir fluids. Even though it can be considered to use all these informations as input for thermodynamic models when research is carried on how to improve their predictions, this use is no more possible in big reservoir simulators because the computation cost would become prohibitive, as these call thermodynamic subroutines a great number of times. It is thus necessary to reduce analytical data in order to get an optimal ratio (accuracy/computing time) while calculating the thermodynamic properties of natural gases.

In the work described here, we have compared different lumping procedures as well as thermodynamic characterization methods of the obtained fractions, and propose a way to quantify the loss of accuracy resulting from the reduction of the analytical data.

In order to avoid any bias due to modelling (analytically and thermodynamically) real natural gases, the comparison has been performed with synthetic fluids. After having selected the best lumping method amongst those tested, the whole procedure has been applied and checked in the case of a condensate gas produced from a North Sea reservoir.
The Gavilan Field: Inverse Rate Sensitivity in Dual-Porosity Reservoirs
Authors: Hueni G. B. , Jones R. E. , Fitzgerald K. M. , Kohlhaas C. A.
Published: December 2007

The Gavilan Mancos Pool, located in the San Juan Basin of New Mexico, produces from the Niobrara siltstone interval within the Mancos Shale. This type of reservoir in this area has previously been described as a fractured shale in which the matrix has been assumed not to contribute to low porosity and low permeability. This paper discusses the dual porosity character of the formation and shows the method in which the dual porosity nature of the reservoir was identified. The identification process reflects an integration of all available information including geologic description, core analysis results, pressure buildup analysis and a review of performance history. The presence of capillary pressure effects give rise to inverse rate sensitivity behavior in which the gas-oil ratio declines at higher withdrawal rates. Maintaining maximum withdrawal rates in this reservoir increases ultimate recovery by one-half percent of oil in place, which is an increase of approximately 4 percent of recoverable oil.
Development and Operational Planning for a Fractured, Gas-Condensate Reservoir With a Thin Oil Column, Szeghalom Field, Hungary
Authors: Lumsden G. H. , Black P. J. , Troemboeczky S. , Mobarak S. A. , Falucskai L. , Carnes A. C.
Published: December 2007

The Szeghalom field contains gas condensate and oil in two faulted, anticlinal structures separated by a saddle. The larger structure has a gas column in excess of 200 m [656 ft] thick which is underlain by a 23-m [75-ft] oil column. The reservoir interval consists of metamorphosed and fractured Precambrian basement rocks which are intermixed and overlain in most areas of the field by basement breccias, which in turn are overlain by sedimentary Miocene sandstones, conglomerates, and carbonates.

Reservoir performance was simulated using a three-dimensional, three-phase, compositional, dual-porosity, dual-permeability reservoir simulator. After matching history, the model was used to predict performance under four different operating plans: (1) Natural depletion; (2) Cycling of produced gas; (3) Pressure maintenance by CO2 rich gas injection; and (4) Partial gas storage followed by full gas storage.

Conceptual facilities design and cash flow projections were prepared for all prediction cases. All methods of operation were shown to have profit potential, but natural depletion is the clear choice from an economic viewpoint.
Determining Downhole Flow Rates of Oil and Gas in Oil Wells Using Pressure Drop and Spinner Response Measurements
Authors: Gang X. Z. , Golan M. , Sveen J.
Published: December 2007

This paper presents a method that improves the current practice of interpreting downhole pressure drop and spinner response measurements. Two mathematical models have been developed, one relating the flow rate of each phase to the spinner response and the other relating the rates to the measured pressure drop. Simultaneous solution of the two models with measured data determines the in-situ flow rate of gas and liquid phase with minimum interpretation assumptions. Laboratory experiment performed in a large scale flow loop using commercial logging tools validated the method and substantiated the theoretical considerations involved.
Hydraulic Optimization of PDC Bits
Authors: King I. , Bratu C. , Delbast B. , Besson A. , Chabard J. P.
Published: December 2007

The aim of our work is to improve the understanding of flow distribution and determine the optimum set of hydraulic design parameters that favour the drilling fluid circulation, with both computations and experiments. Once a new bit design has been defined according to these criteria, field tests will be done for a final validation.

This paper deals with a modelling of the turbulent flow occurring around a PDC bit. Numerical simulations have been done to study and quantify the influence of parameters such as flow rates, nozzles sizes, locations and inclinations, on the fluid behaviour. Comparisons with theory and experiments done on the same bit, including laser velocimetry data allowed us to check the accuracy of the computer code.

All these studies have revealed complex flows with various main structures such as eddies, counter currents, low circulation zones and impact points. To improve the fluid distribution along the bit and especially along the cutting edges, we have searched the most fitted design parameters which could avoid negative hydraulic structures. In that way, we are now able to design a more efficient bit.
Walk Rate Prediction on Alwyn North Field by Means of Data Analysis and 3D Computer Model
Authors: Bannerman J. S.
Published: December 2007

This paper describes a study which was performed in order to improve the understanding of Rotary Drilling Assembly walk rates. It was based on data collected during 23 wells which were drilled from the ALWYN NORTH platform in North Sea. This platform is operated by Total Oil Marine, the British subsidiary of Total Compagnie Française des Pétroles. The ALWYN NORTH FIELD is a partnership between TOTAL (33 1/3% operator) and ELF (66 2/3%). The field location is shown in Fig 1. The study was performed within the scope of an ARTEP (Association de recherche sur les techniques d'exploitation du pétrole) research project "Maitraj".

By analyzing data from both the 17½″ and 12¼″ phases an attempt is made to explain the variation of walk rates from well to well.

A calibration of a 3 dimensional bottom hole assembly computer model (ORPHEE 3D) has been attempted and the results are presented.

Following the study the lead angle on two subsequent ALWYN NORTH wells was chosen taking into account the conclusions reached and the outcome of this is contained within the paper.
Improving Lateral and Vertical Resolution in Geotomography
Authors: Quint E. N. M.
Published: December 2007

Well-to-well acoustics can be used to image the formation between two boreholes. In this paper we make some proposals for improving the accuracy by modification of the data acquisition and of the reconstruction. So far the resolution of the cross-well image has been limited by critically refracted signals overtaking the direct signals. We propose using three-component detection not only to separate P and S waves, but also to classify the P waves from the arriving angle. A successful classification – into direct and critically refracted rays – enables one to improve the vertical resolution of the tomographic reconstruction considerably.

Since ray-bending effects cannot be ignored, one needs a (guessed) starting model of the formation before any reconstruction can be performed. Usually a layered velocity model is chosen, which is deduced either from the travel times of horizontal rays between the two wells or from the sonic logs measured in the wells. We propose combining the sonic and horizontal ray information to come up with the optimum starting model. This model already gives a good description of the formation without any tomographic reconstruction, if the major structural variations are intersected by either one of the boreholes. The subsequent (iterative) reconstruction will average out travel-time errors and can reveal interwell structures not intersected by a borehole.
Quantitive Evaluation of Thin Bedded Reservoirs Through a "Cluster Analysis" Using High Resolution Tools
Authors: Descalzi C. , Rognoni A. , Spotti G.
Published: December 2007

The evaluation of reservoirs in thin beds has a fundamental role in the Italian oil industry since they potentially represent one of the main gas resources. The problem is the correct evaluation, not only from the qualitative point of view, of the reservoir potential and the production horizons as well as the definition of the petrophysical characteristics as concerns volumes, mineralization and connectivity.

When evaluating very stratified lithologies (for example distal turbidites), the crux is the availability of significant log and cores, able to recognize and discretize production intervals of the order of few centimetres.

The integration of all the information available (logs, cores and well tests) and their homogenization through a "cluster analysis" algorithm, developed in order to utilize logs with a high sampling density (SHDT*), allows obtaining more realistic values concerning the petrophysical parameters.

These results lead to the re-evaluation of reserves and to an accurate estimate of the profitability of reservoirs in thin beds.

The case of an Italian reservoir composed of Pleistocenic turbidites characterized by frequent sand-shale intercalations is given as an example. The methodology was tested in this field and allowed the identification of new levels and a re-evaluation of reserves of the order of 20%.
Relating Sedimentology to Production Behaviour in Deltaic Rocks
Authors: Mijnssen F. C. J. , Weber K. J. , Floris F. J. T. , Kaasschieter E. F.
Published: December 2007

Averaging rock properties over grid block volumes represents a major problem in reservoir simulation studies. Often most small scale heterogeneities are ignored. To better account for common heterogeneity patterns an analogue approach is proposed using realistic models of genetic sand body types.

Because of the extensive available data, deltaic reservoirs have been selected to demonstrate this approach. A total of seven delta types is recognized containing a limited number of different genetic sand body types. These can in turn be described with only eight flow unit configurations. A study has been carried out of the fluid flow characteristics of these units with the aid of 2D simulation models. The results give a qualitative overview of the impact of various common heterogeneity patterns.

Models of this nature are thought to be very suitable for evaluating the sensitivity of simulation results to the presence of observed heterogeneities.
Influence of Production on Chalk Failure in the Valhall Field
Authors: Hermansson L. , Gudmundsson J. S.
Published: December 2007

Chalk failure in six production wells without gravel pack in the Valhall field are observed to occur in two main periods, the early and the late. Early-period failures are related to pre-existing natural damage of the formation and wellbore operations such as drilling and well completion/perforation. Late-period failures are related to depletion in reservoir pressure. As pore pressure falls the effective stress on the formation chalk increases until its yield stress is reached. Early and late-period failures are both triggered by stresses related to pressure gradients in the formation near a wellbore. Shut-in and re-opening of production wells, for example, give rise to high pressure gradients that cause chalk failure. Fluid production below the bubble point also triggers chalk failure. The analyses of 19 chalk failure incidents are expressed in a conceptual damage-release model.
Hydrates: Towards The Complete Solution
Authors: Kalli C. J. , Cowie D.
Published: December 2007

The economic development of many multiphase flow production systems requires a full understanding of hydrates and their control. BP Exploration has recognised this and has set itself the goal of developing the necessary understanding and ability to deal with hydrates and hydrate forming systems.

Three key areas have been targeted for investigation to develop the tools necessary to optimise the economics of hydrate forming systems. An important advance by BP in the first of these key areas is presented. The new BP phase equilibrium hydrate formulation is used to rigorously examine options for using a range of pure and mixed inhibitors.
Simulation Studies of Gas-Injection into Gas-Condensate Reservoirs
Authors: Diamond Luis , Rondon Cesar R.
Published: December 2007

The effects of gas injection into two gas condensate reservoirs in eastern Venezuela were analyzed in order to establish optimum exploitation schemes. One of the reservoirs, the M3U sand, MVR-52, in the Zapatos field, is actually subjected to a pressure maintenance process. The other reservoir, the S3M sand, SG-44, in the Mapiri field, is a dual gas condensate, black oil reservoir, currently at a primary depletion stage.

Sensibility studies were made for both accelerated natural depletion and pressure maintenance through the injection of lean gas. These simulation studies were made utilizing a phase behavior simulator and a compositional simulator (COMPSIM). The first was used to calculate equilibrium constants at different pressure. In order to achieve this, it was necessary to characterize the fluids in function of six (6) pseudocomponents, which represent the mixture of the pure components as given by PVT analysis.

COMPSIM is a three-dimensional, three-phase, compositional simulator, which allows to compute pressure and saturation distributions, as well as the distribution of the fluid components in the oil gas-condensate phases. Mass exchange of each component between oil and gas phases is ruled by the equilibrium constants under conditions of thermodynamic equilibrium.

In the case of the M3U/MVR-52, after introducing pseudocomponents for the characterization of initial fluid compositions, the dew point pressure, liquids deposition and relative volumes were matched using the compositional phase simulator. Production and pressure history matching were attained through the COMPSIM.

The S3M sand, SG-44 reservoir also belongs to the lower section of the Oficina formation of lower Miocene age. The depositional environment consists of a north to south oriented deltaic channel at the center of the reservoirs, and splays with poor sand development toward the borders.

The S3M is a well defined, homogeneous sand body, thinning out to the east and to the west. Due to its depositional environment the sand shows little variations in thicknesses.

The reservoir is bounded to the north by a water-oil contact, to the east and west by changes of facies and to the south by a fault, Fig. 3.
Interpretation of Pressure Behavior of Fractured, Deviated, and Horizontal Wells
Authors: Soliman M. Y.
Published: December 2007

This paper discusses the determination and interpretation of fracturing pressure data when the well is deviated or horizontal. The first part of the paper deals with microfrac and minifrac tests on deviated wells while the second part deals with initiation pressure of a transverse fracture intercepting a horizontal well.

Microfractures are usually performed on vertical wells to determine the minimum horizontal stress while minifractures are performed to determine leakoff coefficient. Because a vertical well is in the plane of a vertical fracture, determination of horizontal stress is fairly straightforward. If the well under investigation is deviated, it may not be in the plane of the vertical fracture. Consequently, a fracture may start along the axis of the well as a deviated fracture. At a distance from wellbore it may be realigned in the vertical direction. Because this realignment may affect the observed fracture closure pressure, a larger than conventional microfracturing treatment may be necessary.

This paper reports on tests in which both microfracture and minifracture treatments were performed on a deviated well. The observed closure pressure microfracturing and minifracturing supports the above hypothesis. All pertinent information and analysis for this deviated well are presented.

If the well is horizontal and the fracture intersects the well (transverse fracture), the Hubbert and Willis criterion for fracture initiation may not apply. In this paper, Hoek and Brown failure criterion is used for transverse fractures. The criterion better models and explains the high initiation pressure observed in both field and laboratory.

This paper gives the stress analysis for a horizontal well prior to fracturing. The failure criterion is then discussed and applied to explain laboratory observations.
Fractured Reservoir Evaluation Using Production Testing
Authors: da Prat Giovanni , Jorquera Ricardo , Puthigai Suresh
Published: December 2007

In this work the production testing techniques used for fractured reservoir identification and characterization are presented. For the sake of technical synergy a brief summary is given in open hole logs techniques used for fractured reservoir detection.

The evaluation of different types of production tests conducted in these reservoirs is explained using field data examples. It is also presented as a special case the solution for the pressure behaviour of a well completed in a reservoir where in natural fractures occur over a limited area around the wellbore. A new set of types curves are presented that are quite resolutive for fractured reservoir identification specially for the diagnostic of the flow regime associated to the interporosity transient behavior that is so important for reserves estimation. Also included are the regression methods applied to these systems. As a main conclusion derived from this work is that a combined approach between geology and reservoir engineering is needed for a proper evaluation of these systems.
Large Amplitude Displacements of a Deepwater Moored Floating Offshore Platform
Authors: Morooka Celso K.
Published: December 2007

Large amplitude displacements of deepwater moored floating offshore platform are here discussed. A brief description of typical moored floating systems is made.

Environmental forces which cause the platform motions are described. A motion simulation procedure in time domain is evaluated and results are presented for two different floating systems. Computer simulation results are compared with experiments.

From the present study, it is concluded that the prediction of large, amplitude displacements of floating off shore platforms could be estimated by time domain simulations. These results are very important for mooring designs and for safe offshore drilling and production operations.
Wave Attenuation in Acoustic Logs and Formation Permeability: Case Studies and Experiences
Authors: Perarnau Adrian , Flores Decio , Martinez Oscar
Published: December 2007

Full waveform acoustic logs can be used to study the attenuation of body (compressional and shear) and surface (Pseudo-Rayleigh and Stoneley) waves in rock formations around the wellbore. Neglecting fractures, and for a given geometry, it is widely accepted that body waves are attenuated mainly because of viscous flow in the pores. At the same time, Stoneley wave attenuation seems to be related to flow of mud-derived fluids in and out of the rock frame during wave passage. Apart from the factors previously mentioned, there is a strong dependence of wave attenuation with lithology, especially clay content. This is shown here by simple calculations of wave energy in field logs. Clay volume, therefore, must be taken into account if wavetrains are to be used in the identification of highly permeable strata. To detect zones with significant hidraulic conductivity (rocks with high permeability, in relative terms, saturated with low-viscositv fluids), a simple index is proposed. The index I measures the amount of low frequency energy 'corrected' by clay volume using the traditional GR log. The correlation between I and oil production, in recently-drilled wells in northeastern Venezuela, is strong, even when traditional log analysis shows no differences between the perforated pay zones. The simple type of calculations proposed here are suitable for the quick look kind of presentations used during perforation design. They are, however, of local significance and its relation to true permeability is obscure due to variability in fluid type and saturation. Other methods, more meaningful although time consuming, are in study.
X-Ray Shadowgraph Studies of Areal Sweepout Efficiencies
Authors: Slobod R.L. , Caudle B.H.
Published: December 2007

Published in Petroleum Transactions, AIME, Volume 195, 1952, pages 265–270.

In the past, the main emphasis in attacking the problem of the recovery of oil has been on the determination of fluid flow characteristics and residual oil saturation in the part of the reservoir which is contacted by a displacing phase. It is recognized that the determination of the fraction of the reservoir contacted in secondary recovery operations is also of great importance in predicting the ultimate recovery to be expected. A method is described in which radiographic techniques are used to determine these areal sweepout factors for any type of well spacing. Data showing the relationship of viscosity ratio and relative permeability to areal sweepout efficiency are presented for the five spot and the direct line drive well spacing patterns. Further applications of the method to studies of the displacement efficiency in the area contacted are mentioned.

Introduction

The problem of increasing oil recovery from typical reservoirs is generally attacked by trying to devise some means for reducing the residual oil in that part of the reservoir which is contacted. The fraction of the reservoir contacted in the displacement process, however, is also of major importance but has been given less consideration in the past.
Relative Permeability from Centrifuge and Unsteady State Experiments
Authors: Munkvold Fridtjov Ravn , Torsaeter Ole
Published: December 2007

Relative permeability measurements have been conducted using the unsteady state and the centrifuge methods. The drainage of oil with gas was performed on water-wet cores containing irreducible water. An automated measurement system has been developed for the centrifuge experiments. The automated system is of vital importance for the measurement of rapid fluid production, and exhibits excellent performance in data collection compared to manual reading. The oil relative permeability curves calculated from the two methods are comparable only if flow potential is kept equal in the two flow processes during the experiments.
Gel Strength as Related to Carrying Capacity of Drilling Fluids
Authors: Machado José Carlos Vieira , Aragão Átila Fernando Lima
Published: December 2007

It is known that the plastic Bingham model is inadequate to represent some types of drilling fluids1,2, such as low solids and emulsions, especially at medium and low shear rates. Previous experiments on carrying capacity concluded that the average annular velocity and rheological properties affect the fluid transport more significantly than other parameters. Many of these experiments3,4,8,9 refer to the yield point of the Bingham model, calculated at high shear rate, as the most important parameter.

This experiment studies how the initial gel strength and plastic yield point affect the carrying capacity of the drilling fluids, employing the transport ratio concept. For this purpose the terminal settling velocity of the drilled solids through quiescent fluids was experimentally determined. The results showed a better correlation with the initial gel strength than with the yield point. Also, the analysis of the results demonstrated that a gel strength of about 1.92 Pa (4.0 lbf/100 ft2) is necessary and substantial to obtain a transport ratio higher than 0.50 when the annular velocity is in the range of 0.41 m/s (80 ft/min) to 0.66 m/s (130 ft/min), using low solids and polymer drilling fluids.

For any type of water based drilling fluids, a gel strength in the range of 3.35 Pa (7 lbf/100 ft2) to 4.79 Pa (9.0 lbf/100 ft2) is sufficient to remove the cuttings at more than 0.50 of transport ratio, even when the annular velocity is about 0.25 m/s (50 ft/min).
Temperature Profile of a Fluid Flowing within a Well
Authors: Boas Mario Barbosa Villas
Published: December 2007

This work makes a review in the literature about thermal transference fenomena within a well. It proposes an improvement of a model proposed before which allows it to be applyed to complex well geometrics. Some simulations are made and the results are discussed and compared with the ones obtained by API method. The influence of some parameters not considered by API methods are also discussed.
Computerized Well Analysis
Authors: Podio A. L. , McCoy J. N.
Published: December 2007

A system has been developed based on a powerful portable microcomputer and an integrated data acquisition package which allows real-time visualization of pumping well performance.

The system combines all the necessary elements to obtain a complete analysis of the performance of the pumping system which includes the pumping unit, the wellbore, and the reservoir.

The data acquisition package is connected to the expansion slot of the computer and consists of the necessary analog and digital channels to process data from standard transducers such as acoustic, pressure, temperature, rod load, displacement etc. Detailed surface unit performance curves such as dynamometer, speed, acceleration, power etc. can be obtained and analyzed. When the instrument is used in conjunction with an acoustic pulse generator and receiver, it digitizes and stores the reflected acoustic signals which are digitally filtered and automatically processed to determine the liquid level. This is undertaken under program control so that a continuous recording of fluid level vs. time is obtained along with the pumping unit performance parameters. Fluid level data is processed by the software to calculate bottomhole pressure as well as flow into and out of the well bore. Changing the well from flowing to shut in conditions allows recording of pressure of reservoir parameters.

The Well Visualization display can be used as a diagnostic tool to optimize pumping well performance on a periodic basis. The present performance of the well is compared to its recorded past performance and in the case where significant differences are noted, a more detailed analysis is undertaken to recommend changes in operation or remedial actions. In critical well applications, the system can function as a stand-alone dedicated controller.