bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pressure Buildup for Wells Produced at a Constant Pressure
Authors: Ehlig-Economides C. A. , Ramey H. J. 
Published: December 2007

Abstract
Conventional well test analysis has been developed primarily for production at a constant flow rate. However, there are several common reservoir production conditions which result in flow at a constant pressure instead of a constant rate. In the field, wells are produced at constant pressure when fluids flow into a constant-pressure separator and during the rate decline period of reservoir depletion. In geothermal reservoirs, produced fluids may drive a backpressured turbine. Open wells, including artesian water wells, flow at constant atmospheric pressure.
Most of the existing methods for pressure buildup analysis of wells with a constant-pressure flow history are empirical. Few are based on sound theory. Hence, there is a need for a thorough treatment of pressure buildup behavior following constant-pressure production.
In this work, the method of superposition of continuously changing rates was used to generate an exact solution for pressure buildup following constant-pressure flow. The method is general. Storage and skin effects were incorporated into the theory, and both bounded and unbounded reservoirs were considered. Buildup solutions were graphed using conventional techniques for analysis. Horner's method for plotting buildup data after a variable-rate flow was found to be accurate in a majority of cases. Also, the method by Matthews et al. for determining the average reservoir pressure in a closed system was determined to be correct for buildup following constant-pressure flow.
Enhanced Iterative Formation Evaluation of El Tordillo Field, San Jorge Basin, Argentina: Using Electrofacies and Production Prediction Index Determination
Authors: Stinco L.P. , Elphick R.Y. , Moore W.R. 
Published: December 2007

Summary
Formation evaluation, electrofacies, and production prediction index determination based on inductive and deductive methodologies were completed in El Tordillo field, north flank of the San Jorge basin, Argentina. The applied methodology consisted of a number of steps, including the following: editing and normalization of the log data; modeling of the deep resistivity; electrofacies determination; standard log analysis; computing a production prediction index; and summations. Using cutting and core data, the 15 electrofacies determined were associated with the geological facies encountered within the field and on the rock types. Consequently, porosity/permeability relationships were established between the core data and the productive electrofacies. These relationships permit computing permeability from the computed effective porosity. A production prediction index was derived from the computed results and correlated well with existing production data. Zones of possible bypassed production were identified, and some tested successfully. Finally, summations were used as input for original-oil-in-place estimation, geological modeling, and numerical simulation.
4D Seismic Monitoring of Water Influx at Bay Marchand: The Practical Use of 4D in an Imperfect World
Authors: Behrens Ronald , Condon Patrick , Haworth William , Bergeron Mark , Wang Zhijing , Ecker Christine 
Published: December 2007

SummaryMany waterflooded or aquifer influx reservoirs are old or marginal and thus do not have ideal data conditions, either historic or current, for 4D seismic. We modeled the synthetic seismic response for the 7100 Sand in the Bay Marchand field and found it suitable for 4D. To determine the noise level in modeling, we derived relations for calculating the appropriate level of noise from differences in the field data. We also developed relations between measured noise and the quantitativeness of calculated saturation changes. These methods, as applied to the Bay Marchand, showed that useful saturation predictions could be made from the seismic data shot 30 years after initial production with a recent, nonexclusive survey. From these data, both downdip and updip wells were drilled successfully.Multiple seismic surveys over time that were not intentionally designed for 4D evaluation can be used for imaging fluid and pressure changes and locating bypassed reserves. Bay Marchand is a mature Gulf of Mexico field with a series of stacked reservoirs separated by shale. The first 3D seismic survey was acquired after first production, and the second seismic survey was a nonexclusive survey having very different acquisition parameters. These circumstances make interpreting 4D results difficult but not impossible. We were able to make a reasonable interpretation of the "A" fault block on the original data before cross-equalization (XEQ), although XEQ reduced the acquisition and processing differences between the cubes. We were able to identify areas of water influx and areas not yet invaded by water, even though we were prevented from following the typical steps in 4D. Reliability estimates were derived for estimates of saturation change as a function of signal-to-noise ratio and scatter in the rock physics relationships. This paper discusses these steps in contrasting the ideal case with Bay Marchand and shows where a 4D project can still be successful even with compromises forced by lack of early data or current budget.
Inflow Analysis and Optimization of Slotted Liners
Authors: Kaiser T. M. V. , Wilson S. , Venning L. A. 
Published: December 2007

Summary
Slotted liners have been used for many years to provide sand control in many oil industry applications. They are commonly applied in western Canadian reservoirs that produce high-viscosity oil from horizontal wells with unconsolidated, high-permeability sands. Both primary and thermal applications are common, and the steam-assisted gravity drainage (SAGD) process1 is beginning to see widespread application in this area of the world. They are relatively inexpensive to manufacture and tolerant of installation loads, but historically they have not been able to offer the very small opening sizes of wire-wrap screens for controlling production of fine sands. However, recent advances in slot manufacturing methods provide slot openings that match and surpass the size and tolerance of wire-wrap screens. Furthermore, slotted liners offer an advantage in providing a variable slot density that can be used to optimize inflow or outflow distributions.
In the development of its south Bolney reservoir, Marathon Oil Canada and Noetic Engineering Inc. performed an analytical evaluation of inflow characteristics for a new generation of commercially available slots. Several interesting conclusions were reached, the most significant of which was that inflow resistance depends much more strongly on slot density than on open area. The inflow characterization was also used to optimize the slot-density distribution and to promote more uniform production throughout the well. The slotting was incorporated with a deformation-management system that controlled thermally induced loads, preventing compromise of sand-control characteristics.
Multiple Controls on Petroleum Biodegradation and Impact on Oil Quality
Authors: Wenger Lloyd M. , Davis Cara L. , Isaksen Gary H. 
Published: December 2007

Summary
Biodegradation of oils in nature is important in reservoirs cooler than approximately 80°C. Oils from shallower, cooler reservoirs tend to be progressively more biodegraded than those in deeper, hotter reservoirs. Increasing levels of biodegradation generally cause a decline in oil quality, diminishing the producibility and value of the oil as API gravity and distillate yields decrease; in addition, viscosity, sulfur, asphaltene, metals, vacuum residua, and total acid numbers increase. For a specific hydrocarbon system (similar source type and level of maturity), general trends exist for oil-quality parameters vs. present-day reservoir temperatures of &lt;80°C. However, other controls on biodegradation may also have significant effects, making predrill prediction of oil quality difficult in some areas.
It has long been observed that fresh, oxygenated waters in contact with reservoir oil can cause extensive aerobic biodegradation. More recently, it has been recognized that anaerobic sulfate-reducing and fermenting bacteria also can degrade petroleum. Highly saline formation waters may inhibit bacterial degradation and effectively shield oils from oil-quality deterioration. The timing of hydrocarbon charge(s) and the post-charge temperature history of the reservoir can have major effects on oil quality. Reservoirs undergoing current charging with hydrocarbons may overwhelm the ability of bacteria to degrade the oil, resulting in better-than-anticipated oil quality. Fresh charge to reservoirs containing previously degraded oil will upgrade oil quality. Calibrated methods of oil-quality risking, based on a detailed evaluation of reservoir charge and temperature history and local controls on biodegradation, need to be developed on a play and prospect basis.
A New Concept in Continuous-Flow Gas-Lift Design
Authors: Mach J. M. , Proano E. A. , Mukherjee H. , Brown K. E. 
Published: December 2007

Abstract
The importance of the differential pressure at the point of injection in continuous-flow gas-lift design is discussed. The role played by differential pressure in the selection of optimal flow in gas lift is also explained. It is shown that good wells with high productivity have continued increase in production as the differential pressure decreases. Weaker wells with low productivity, however, are less sensitive to the change in differential pressure. Also, a concept of error envelope surrounding the point of gas injection is presented. Suitable valve spacing in this error envelope is shown to offset any errors in locating the depth of injection caused by errors in the multiphase flow correlations or in the well productivity. The maximum valve spacing within the error envelope is shown to be directly proportional to the differential pressure. The smaller this differential pressure, the smaller the valve spacing.
Added Value of a Multiphase Flowmeter in Exploration Well Testing
Authors: Mus E. A. , Toskey E. D. , Bascoul S. J. F. , Norris R. J. 
Published: December 2007

Summary
A multiphase flowmeter was used in addition to conventional surface well-test equipment during five deep offshore exploration drillstem tests. Several immediate benefits were derived. The cleanup phase was monitored, which improved control of the formation drawdown as well as the prediction of well eruption. The flow history was better quantified, which improved the pressure-transient analysis. The instantaneous flow-rate measurements shortened flow periods and accelerated the decision process, reducing the overall test duration. In general, the multiphase flow-meter enhanced operation flexibility, confidence in the information acquired, and accuracy of the results.
Considerations For Conducting Coiled-Tubing Well-Control Operations To Minimize Formation Impairment
Authors: Sas-Jaworsky Alexander , Ghalambor Ali 
Published: December 2007

SummaryCoiled-tubing (CT) services are frequently used to conduct kill operations concentric to existing production tubulars. Kill operations are typically performed to effect a temporary hydrostatic balance of formation pressure at the exposed completion. Because CT well-control operations are conducted concentric to existing production tubulars, special attention to job design and implementation is critical to ensure proper placement of kill fluids within the wellbore to achieve the desired pressure balance and to minimize the potential of formation damage.In those cases in which wellbore operations subsequent to the kill program are not intended to return the existing completion to active status, formation damage induced by the kill practice is typically of little consequence. However, when return of the existing completion to active status is desired, the well-control operation must be conducted with a complete understanding of the pressure balance and effect of kill fluid circulation on the completion. Many practices used in performing concentric-tubing well-control services lead to varying degrees of formation damage and impair completion flow performance.This paper discusses typical damage mechanisms resulting from completed wellbore kill programs, along with the related formation damage consequences for these types of operations, alternative well-control kill processes with CT, and the potential for reducing formation damage with CT well-control processes. In addition, recommendations for planning and implementing CT-conveyed well-control programs within existing production tubulars are provided to guide the user in conducting well-control operations with minimal induced formation damage.
Semianalytical Modeling of Complex-Geometry Reservoirs
Authors: Zhao Gang , Thompson Leslie G. 
Published: December 2007

SummaryComplex geometry reservoirs can be encountered in the field for a variety of depositional and tectonic processes. For example, fluvial depositional environments may produce interbranching channel reservoirs or reservoirs consisting of relatively high-permeability channels in communication with low-permeability splays.This paper presents a general methodology for computing pressure responses and flow characteristics in complex geometry reservoirs. The proposed method consists of decomposing the original complex-geometry reservoir into a set of simple-geometry reservoirs, which interact with each other by transfer of fluid and equality of pressure over the regions where they are in hydraulic contact. Analytical solutions are written for each of the simple reservoir components in terms of the unknown pressures and fluxes at their boundaries, and the coupled systems are solved for the desired wellbore pressure responses.The method of sources and sinks is used to compute the pressure response in the Laplace domain, and the results are inverted numerically with the Stehfest Inversion algorithm.1 We present fast, accurate methods of taking numerical Laplace transforms of the source/sink solutions that make the computations reasonably fast and efficient.The proposed methodology can be extended to any system (infinite or bounded) in which the Laplace-space solution can be written easily in terms of integrals of real-space source/sink functions, including production at constant bottomhole pressure, wellbore storage effects, or naturally fractured systems. We demonstrate the applicability of the method by modeling branching channels and channel/splay systems.
Non-Darcy Flow Near Hydraulically Fractured Wells
Authors: Hagoort Jacques 
Published: December 2007

Summary
In this work, we analyze the effect of non-Darcy flow near hydraulically fractured wells on well inflow performance. It is based on a dedicated numerical model of plane, steady-state flow of an incompressible fluid toward a vertically fractured well in the center of a circular reservoir. The results show that non-Darcy flow manifests itself as a positive skin factor, which is the product of a non-Darcy flow factor and the production rate, as is the case with nonfractured wells. An empirical relationship is presented that enables the estimation of the non-Darcy flow factor of fractured wells as a function of fracture length. Compared with nonfractured wells, hydraulic fractures will reduce the effect of non-Darcy flow in all practical situations. An intuitive approach to incorporate non-Darcy flow in the inflow performance relationship of fractured wells on the basis of total inflow area is a good first-order approximation.
Use of Permanent Resistivity and Transient-Pressure Measurement for Time-Lapse Saturation Mapping
Authors: Charara M. , Manin Y. , Bacquet C. , Delhomme J. P. 
Published: December 2007

Summary
Optimization of hydrocarbon recovery requires information on the space and time behavior of the saturation of various fluids present in the reservoir. This is particularly true for oil fields under secondary recovery such as waterflooding, where an even reservoir sweep or zones of bypassed oil can be assessed by a proper description of the waterfront advance. Recently, permanent downhole electrodes have been deployed successfully in oil wells.
This technology allows the time variation of the electrode potentials to be interpreted in terms of changes in saturation within the formation. However, the depth of investigation of such measurements is limited. Time-lapse pressure transient is an independent source of information with a greater depth of investigation and, therefore, it provides an adequate complement to the permanent resistivity array measurement.
In this paper, we propose to use pressure buildup from repeated shut-in in association with the electrical measurements. After recalling analytical analogies in both types of measurements, we propose a quick-look method for interpreting the time-lapse pressure transients. We then compare the physical and practical advantages of each type of measurement and the domain of application of the two measurements with respect to fluid and reservoir properties. Finally, we propose an example showing the benefit obtained by coupling the two techniques.
Planning and Preparing for the First Subsea Field Test of a Full-Scale Dual-Gradient Drilling System
Authors: Schumacher J. P. , Dowell J. D. , Ribbeck L. R. , Eggemeyer J. C. 
Published: December 2007

Summary
Dual-gradient drilling (DGD) is an emerging technology that will enable operators to drill in environments where mud weights are quite high and formation fracture pressures are quite low. This step-change technology will allow access to deepwater reserves and will fundamentally change the way deepwater wells are drilled.
This paper describes the planning and preparation for the world's first dual-gradient well in Green Canyon 136. Our objective was to deliver a functioning and proven DGD system for commercial application in deepwater environments. The dual-gradient system worked as designed, and 100% of all critical objectives were successfully met.
Today's Petroleum Engineering Graduate - Will He Meet Tomorrow's Challenge?
Authors: Sherborne John E. 
Published: December 2007

Historically, engineers have been men whose function has been to analyze what is needed for solution of practical problems, to design or plan the needed systems. circuits, structures, or processes for this purpose and to predict their performance and cost. A hundred years ago as our national expansion began to accelerate, man was forced by lack of transportation and communication to work in much greater isolation than is now the case. The engineer was sought for the experience and judgment he could bring to a particular project - for the art he had developed - rather than for his scientific nowledge.
In discussing "Objectives of an Engineering Education," W. V. Houston illustrates the importance attached at that time to engineering experience, as well as the growing realization of the value of science to the engineer. In doing this he tells of the important part played by William Thomson in the laying of the Atlantic telegraph. Although the chief electrical engineer on the project was a man of considerable experience and of good reputation, he had no experience with cables as long as the one across the Atlantic. Thomson, who had virtually no practical experience, had, however, given considerable thought to electrical transmission and had pointed out the importance of capacitance and resistance in long conductors. Unfortunately, Thomson's findings were ignored, the engineer believing an extrapolation of his own experience preferable. The first cable thus laid at a cost approximating one million dollars was a failure and not until the advanced scientific findings of Thomson were employed was success achieved. This is not to discredit practical experience and the valuable wisdom it produced. Far from it! Rather, it is to indicate the importance placed upon such experience in the middle of the 19th Century.
It is not surprising, therefore, that as engineering education developed in the United States, the first educators were drawn from practice; nor that early curricula dealt with the art of engineering and consideration of existing engineering works and systems. As our fund of scientific knowledge expanded, its value in the solution of engineering problems became increasingly evident.
Coupled Geomechanical and Reservoir Modeling Investigating Poroelastic Effects of Cyclic Steam Stimulation in the Cold Lake Reservoir
Authors: Walters D. A. , Settari A. , Kry P. R. 
Published: December 2007

Summary
The heating of bitumen reservoirs by cyclic steam stimulation (CSS) requires high pressures and temperatures that disturb the soil matrix. This disturbance results in a dilation of the soil matrix, creating regions of enhanced permeability and porosity, which impact both the injection and production cycles of steam stimulation and the porous zones not hydraulically connected to the reservoir. The volumetric strain changes reach far beyond the region of injection and include areas of both expansion and compression. The magnitude of the volumetric strains may result in significant displacements and strains being transferred to porous zones outside the reservoir. This can result in observable pressure changes in an otherwise hydraulically static system.
Pressure data at an observation well drilled to monitor aquifer pressures showed a significant response to the CSS process occurring in the reservoir approximately 300 m below the aquifer. Coupled geomechanical and reservoir modeling and an analytical calculation both show that this pressure behavior is attributed to the poroelastic response of the aquifer caused by the CSS process occurring in the reservoir. This paper describes the field data, the methodology of the coupled reservoir and geomechanical modeling, and the result of the analysis of the field data with the coupled model. The analysis shows clearly that the aquifer response is not caused by a hydraulic communication with the reservoir. It also shows the capabilities of coupled modeling, as this type of a problem could not be analyzed with conventional reservoir simulation tools.
Field-Scale Characterization of Permeability and Saturation Distribution Using Partitioning Tracer Tests: The Ranger Field, Texas
Authors: Illiassov Pavel A. , Datta-Gupta Akhil 
Published: December 2007

Summary
This paper discusses the application of an efficient streamline-based inversion method to a large multiwell multitracer Partitioning Interwell Tracer Test (PITT) in the McClesky sandstone, the Ranger field, Texas, to characterize both permeability and oil saturation distribution. During a typical PITT, a conservative and a partitioning tracer are injected into the reservoir. The partitioning tracer gets partially absorbed into the oil phase, leading to a separation in the tracer responses that can be used to infer oil saturation distribution in the tracer-swept area. Our approach is extremely efficient because it relies on analytic computation of the sensitivity of the tracer response to reservoir parameters such as permeability and saturation using a single streamline simulation. We follow a two-step procedure whereby we first match the conservative tracer response to determine the permeability distribution, and then match the partitioning tracer response to obtain oil saturation distribution in the reservoir. The entire history matching took less than 6 hours on a PC as opposed to several months typically required for a manual history matching.
We compared our results to a manual history match obtained using a finite-difference simulator. Both the manual history matching and the streamline-based inversion identified similar large-scale trends in permeability and saturation distribution. However, well-specific matches were significantly improved over those obtained through the manual history matching. Our approach is much more efficient in terms of computation time and effort, and the results are less sensitive to personal bias compared to manual history matching. Finally, we discuss a procedure to assess the results in terms of resolution of the estimates of permeability and saturation distribution.