bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interpretation of Fracture Height From Temperature Logs—The Effect of Wellbore/Fracture Separation
Authors: Davis E. R. , Zhu Ding , Hill A. D. 
Published: December 2007

Summary
Temperature logs commonly have been used to evaluate fracture height by locating cool anomalies that indicate the locations where cool fracture fluids were injected. Instead of cool anomalies, however, warm anomalies (called "warm noses") often occur on temperature logs run after fracture treatments. When interpreting fracture height from a temperature log, warm anomalies make it difficult to identify the top and bottom of the fracture. We believe that a plausible reason for warm anomalies is that the wellbore and the fracture are not coincident over the entire extent of the fracture; instead, away from the perforations, the fracture and the wellbore may be separated a finite distance that varies with depth. This paper investigates the effect of the existence and magnitude of the displacement between the wellbore and the fracture on wellbore temperature behavior after fracturing. The results obtained explain the "warm noses" on shut-in temperature logs run after a fracture treatment and, more generally, illustrate how fracture-wellbore separation can result in a variety of characteristic temperature log responses.
A mathematical model has been developed to simulate the wellbore temperature after fracturing for cases where the wellbore and the fracture are not coincident for the entire extent of the fracture. The study shows that the temperature behavior strongly depends on the pattern and the magnitude of the displacement. When the fracture is perfectly connected with the wellbore, the cool region on the log indicates the top and bottom of the fracture clearly. However, the cool region is much smaller than the fracture height if the wellbore deviates from the fracture at a constant angle away from the perforations—a situation that may occur in a well that is deviated slightly from vertical, for example. Furthermore, "warm noses" appear on the log if the well spirals in a helical trajectory because the spacing between the wellbore and the fracture will vary with depth for this geometry. Therefore, when evaluating a postfracture temperature log, the possibility of a deviated wellbore-fracture system must be considered to avoid misinterpreting the fracture height. Longer shut-in times are shown to improve the fracture-height interpretation.
Virtual Reserves—And Other Measures Designed To Confuse the Investing Public
Authors: Tobin J. C. 
Published: December 2007

Summary
Norman Augustine, CEO of Martin Marietta, in his book Augustine's Laws,1 observed that, "Cost estimating is the first professional activity to make practical use of the mathematics of a complex number. It is easy to see the imaginary component in these estimations. The difficulty is in finding the real part."
Over the years, I believe we have seen this form of math creep into reserve estimation. In that we are once again dealing with numbers that have no resemblance to reality, I think that the appropriate label for such reserves, in keeping with the terminology of modern technology such as virtual imaging and virtual memory, is to call them "virtual reserves."
Fill-Up Pressure Buildup Test: An Effective Method for Wells With Low Initial Production and Deep Drawdown
Authors: Megyery Mihály 
Published: December 2007

Summary
261 oil and 680 gas reservoirs have been explored within the territory of Hungary. Their depths and pressures range from 300 to 4500 m (1,000 to 15,000 ft) and from 3 to 85 MPa (430 to 12,000 psi), respectively. The highest temperature ever measured during our reservoir test operations was 218.3°C (425°F) at 4550 m depth in Well L-II. (1973). Some of the testing methods elaborated during the exploration and development of this large amount of reservoirs can be of international interest; the fill-up procedure, providing pressure buildup (PBU) curves equivalent to those of bottomhole shut-in tests in low-production oil and gas wells, is one of them. The paper presents and analyzes the results of 497 fill-up PBU tests with particular attention to the impacts of reservoir "reworkings" (retesting, acidizing, fracturing, horizontal drilling).
Mud-Induced Formation Damage in Fractured Reservoirs
Authors: Jiao Di , Sharma Mukul M. 
Published: December 2007

Summary
A set of experiments was completed that clearly shows that drilling muds can cause large irreversible damage to fractures and dramatically reduce the productivity of wells producing from a natural fracture network. The use of sized fibers as an additive to drilling muds can significantly reduce both the depth and extent of formation damage. Granular additives (such as CaCO3) are much less effective. The use of acid soluble fibers is, therefore, recommended for reducing formation damage in fractured reservoirs.
Computer Codes for Oilwell-Perforator Design
Authors: Regalbuto J. A. , Gill B. C. 
Published: December 2007

SummaryThis paper presents three computer codes used to analyze and design oilwell perforators that are specifically tailored to hydrocarbon-bearing formations. The codes are a Lagrangian, finite-element code; a Eulerian, finite-difference code; and a coupled Lagrangian/analytical code.Applications of the codes involve charge-to-charge interference effects, estimation of penetration and hole size, explanation of charge/gun-system behavior, and perforator-design optimization.Analysis of an existing six-shot/ft system, which showed charge-to-charge interference, is presented. The solution, which eliminated the interference and increased overall performance, involved charge-case modification. Topics discussed include the following.Initial correlations between experimental and calculated penetrations and hole size in steel and cement. The mechanism of producing burr-free holes in casing, explained by modeling the perforation system. An example of perforator-performance improvement by determination of discrete jet properties. Expanding the application of the codes by enlarging the equation-of-state database to include fluid-filled porous media.
Imaging of Sand Production in a Horizontal Sand Pack by X-Ray Computed Tomography
Authors: Tremblay Bernard , Sedgwick George , Forshner Ken 
Published: December 2007

Summary
A laboratory experiment was performed to better understand how sand production can increase heavy oil recovery. A horizontal sand pack with an orifice at one end modeled the production of oil and sand into a perforation in a vertical well. The sand pack was scanned using X-ray computed tomography (CT). The CT images revealed that a high-porosity channel (wormhole) formed in the pack while sand was produced. The wormhole followed regions within the pack where the porosity was higher, and, consequently, the unconfined compressive strength of the sand was lower. This experiment suggests that wormholes will form within the weaker sands of a formation. The development of these high-permeability channels increases the drainage of the reservoir, which leads to higher oil recovery.
Pressure Transient Analysis in Horizontal Wells in Some Sole Pit Area Fields, U.K.
Authors: Gilbert C. J. 
Published: December 2007

Summary
This paper presents a discussion and interpretation of a variety of transient pressure responses observed in nine flow and buildup surveys performed in horizontal wells in the Sole Pit area fields Barque and Clipper. Horizontal well pressure transient flow regimes and signatures associated with heterogeneous reservoirs are observed in the survey log-log pressure derivatives. The signatures show considerable variability and emphasize the strongly heterogeneous nature of the reservoirs. Rapidly declining transmissibilities in the vicinity of the wellbore are observed in two surveys, while other survey log-log derivative responses suggest a dual-porosity characteristic followed by horizontal well intermediate-time linear flow. Pressure transient testing contributes to an understanding of the reservoir behavior by revealing essential characteristics of a flow model that can describe flow in the heterogeneous, fractured sandstone.
Seeking Synergy Between Drawdown and Buildup Analyses
Authors: Kabir C. S. 
Published: December 2007

Summary
Drawdown tests are rarely interpreted unless accompanied by instantaneous surface or downhole rate measurements. Rate variations prevent a constant-rate analysis in most situations. Unsteady wellbore dynamics precipitated by progressive formation cleanup, multiphase fluid flow, and wellbore thermal effects influencing compressible fluids, to name a few, may prevent one from obtaining a stable surface rate. This reality compels an analyst to fall back upon buildup interpretation. Thus, one typically presupposes that the rate was held constant before shut-in. Drillstem tests and long-duration exploratory well tests are cases in point. This conventional practice raises an important question: Can we calculate a variable-rate history such that the drawdown analysis will be consistent with the buildup?
This paper presents a method to interpret drawdown data whenever variable rates are encountered, either inherent in a test or induced by design, such as in a gas-lift well test. The method entails a stepwise procedure. First, buildup data are interpreted assuming a constant rate during drawdown. Second, the estimated parameters are used to compute instantaneous rate corresponding to each pressure data point by superposing constant-pressure solution with an appropriate pD model. The reconstructed rate history is then used to perform the variable-rate (convolution) analysis of drawdown data. Third, the new rate history is used to reinterpret buildup data. Parameters obtained from the two analyses provide the desired consistency.
The proposed procedure is entirely general, in that any appropriate reservoir pD model may be used to compute the instantaneous rate values. However, best results are obtained when the late-time data are free from outer-boundary effects. We present field examples from various scenarios to show the usefulness of this approach. These examples include a short-duration onshore drillstem test (DST), a gas-lift well test involving a gas-vent period, a long-duration production test with suspected pressure-sensitive rock properties, and a slug/closed chamber test. In all cases, we have shown the synergy between the results of the two tests.
Geologically Consistent Resolution Enhancement of Petrophysical Analysis With Image Log Data
Authors: Ramamoorthy Raghu , Flaum Charles , Coll Carolina 
Published: December 2007

Summary
Very thin, laminated sand-shale sequences pose a challenge to petrophysical evaluation. The poor vertical resolution of the log measurements results in pessimistic estimates of hydrocarbon volumes and producibility. An earlier proposal by Flaum1 to enhance the resolution of the analysis using a high-resolution clay indicator did not account for variations in clay mineralogy and porosity with clay content. We present a technique to incorporate results of core mineralogy measurements to ensure a geologically consistent resolution enhancement of the petrophysical analysis, and we compare the results in an actual field example.
Development and Testing of a Compact Liquid-Gas Auger Partial Separator for Downhole or Surface Applications
Authors: Weingarten J. S. , Kolpak M. M. , Mattison S. A. , Williamson M. J. 
Published: December 2007

Summary
In some applications, complete separation of liquid and gas is not required and removing only a portion of the gas is sufficient. One application that was developed fully is separation of gas from one well for raw gas lift of other wells. This can be done either on the surface or downhole. The auger separator is a new, patented device that was initially developed to fit inside production tubing and, thus, is an ultra-compact separator design. It differs from other separators in that it requires no complex controls or power to operate and, for most applications, has a diameter of only a few inches. The multiphase fluid enters an auger section where the pitch of the stationary auger blade causes the flow to rotate. Centrifugal forces created by this rotation cause the liquid to flow along the outer wall with the gas flowing in the center. A portion of the gas is ported through a crossover to the annulus in downhole applications or to a gas line in surface applications. The downhole separator can be placed by wireline in the tubing. The surface version is placed as a spool piece in the production line.
Equations were developed to predict performance and were incorporated into a spreadsheet for ease of design. Laboratory tests were performed to validate the predictions and to explore various design details. Following successful lab testing, the prototype separator, which was 3½ in. in diameter, was placed downhole inside 4½-in. tubing. The separated gas was ported to the annulus through a gas-lift mandrel. This test showed that the equipment could be placed in the well with wireline, that downhole separation was feasible, and that the theoretical pressure-drop calculations were accurate.
Following this test, an 8-in.-diameter auger separator was designed for separation of gas on the surface as a full-scale pilot test. This was placed in the production line from a well, and the separated gas was used to provide raw lift gas for other wells on the drillsite. These two field tests showed that partial separation was feasible with this device, and that the equations used for design were reasonable. The surface auger separator was left in place after the test and continues to provide lift gas.
This paper presents the concept, design equations, laboratory test results, and field-test results of both a downhole and a surface application. Although raw gas lift is an application that has been fully developed, other potential uses also are discussed.
Field Installation of an Acoustic Slug-Detection System
Authors: Dhulesia Hasmukh , Bernicot Michel , Romanet Thierry 
Published: December 2007

Summary
A pipeline operating in the slug flow regime creates high fluctuations in gas and liquid flow rates at the outlet. The detection of slugs and the estimation of their length and velocity are necessary to minimize the upsets in the operation of downstream process facilities. A new method based on the acoustic principle has been developed by Total and Syminex with two variants—passive and active. The passive method gives the slug length and velocity, whereas the active method also gives the fluid density. The prototype of this system has been installed permanently on a 20-in. multiphase pipeline in Argentina. As this system detects the slugs and determines their characteristics approximately 2 minutes before they arrive at the first-stage separator, the operators take appropriate action in the case of arrival of an excessively long slug and, thus, avoid possible shutdowns. At a later stage, an automatic adjustment of the process control valves will be realized.
Wetting Alteration by Brine and Crude Oil: From Contact Angles to Cores
Authors: Buckley Jill S. , Bousseau Christophe , Liu Yu 
Published: December 2007

Abstract
Factors that affect wetting alteration of a rock upon contact with crude oil include composition of the oil and brine, temperature and duration of aging in oil, and initial water saturation. Similar factors affect contact angle measurements, but the relationship between the surface and core wetting conditions remains to be clearly demonstrated for crude oil/brine/rock systems.
An asphaltic crude oil and two sodium chloride solutions of varying pH have been used to alter wetting of flat glass surfaces, two-dimensional etched glass micro-models, and two core materials:
synthetic core composed of silica and alumina (Aerolith-10), and Clashach–a relatively clay-free sandstone.
Wetting changes on flat glass surfaces are consistent with the wetting conditions established in synthetic silicate cores; the effect on oil recovery by waterflooding is shown. In Clashach sandstone cores, wetting is less directly influenced by the brine pH; both high and low pH cores are distinctly mixed-wet.
Slug-Sizing/Slug-Volume Prediction: State of the Art Review and Simulation
Authors: Burke N. E. , Kashou S. F. 
Published: December 2007

Summary
Slug flow is a flow pattern commonly encountered in offshore multiphase flowlines. It is characterized by an alternate flow of liquid slugs and gas pockets, resulting in an unsteady hydrodynamic behavior. All important design variables, such as slug length and slug frequency, liquid holdup, and pressure drop, vary with time and this makes the prediction of slug flow characteristics both difficult and challenging. This paper reviews the state of the art methods in slug-catcher sizing and slug-volume predictions. In addition, history matching of measured slug flow data is performed using the OLGA transient simulator.
This paper reviews the design factors that impact slug-catcher sizing during steady state, during transient, during pigging, and during operations under a process-control system. The slug-tracking option of the simulator is applied to predict the slug length and the slug volume during a field operation. This paper will also comment on the performance of common empirical slug-prediction correlations.
Alba Field Cased-Hole Horizontal Gravel Pack: A Team Approach to Design
Authors: Alexander Karen , Winton Suzanne , Price-Smith Colin 
Published: December 2007

Summary
A 700-ft cased-hole horizontal well was gravel packed and completed in the Alba Field, central North Sea. The completion incorporated a number of new technologies adopted for a horizontal casedhole completion, including both equipment and fluids. The zone was completed in two stages using a horizontal stack-pack approach. Perforation packing was optimized by performing a staged acid prepack with the guns in the hole using a low-density synthetic gravel substitute in a shear thinning carrier fluid. This was a world-first achievement at a cased-hole gravel pack using the stack-pack approach in a horizontal well. A solids-free fluid-loss control material was evaluated and chosen for the high-permeability Alba sands (3 darcies). Extensive lab testing was performed to ensure minimal damage from various fluids. A 30-ft physical model was used to optimize annular pack efficiency. A gravel placement computer simulation was used to design pump rate, sand concentration, and gel loading to optimize annular and perforation-pack efficiency.
Permeability Determination From Well Log Data
Authors: Mohaghegh Shahab , Balan Bogdan , Ameri Samuel 
Published: December 2007

Summary
We discuss and compare three different approaches for permeability determination from logs from a practical point of view. The three methods, empirical, statistical, and the recently introduced "virtual measurement," make use of empirically determined models, multiple variable regression, and artificial neural networks, respectively. We apply all three methods to well log data from a heterogeneous formation and compare the results with core permeability, which is considered to be the standard. Our comparison focuses on the predictive power of each method.
Simulation of Transients in Natural Gas Pipelines
Authors: Zhou Junyang , Adewumi M. A. 
Published: December 2007

Summary
Transient flow of natural gas in pipelines is simulated without neglecting the inertia term. The governing equations constitute a non-homogeneous hyperbolic set of first-order quasilinear partial differential equations. The first-order, three-point, explicit Godunov scheme and the second-order, five-point, total variation diminishing (TVD) scheme are used to solve this set of equations. Two examples are simulated. The first is the propagation of a slow transient, with 24-hour cycle, in a 45-mile long, 8-in. inside diameter (ID) transmission pipeline, while the second is propagation of a fast transient in a 24-in., 300-ft long pipe. Comparisons between the predicted results and the measured data are fairly good and appear to be better than the predictions reported in the literature. This suggests that the mathematical model presented in the present study, which includes the inertia term in the momentum equation, is more realistic and the numerical schemes used are more robust.
Kinetics of Tertiary Reactions of Hydrofluoric Acid on Aluminosilicates
Authors: Gdanski Rick 
Published: December 2007

Summary
The standard description of hydrofluoric acid (HF) acidizing chemistry clearly demonstrates a primary and secondary reaction of HF with aluminosilicates.1 Field experience has taught our industry that possible precipitation during the secondary reaction can adversely affect treatment success.2 This statement has been particularly true in formations with high K-feldspar content or formations having temperatures above 300°F. Recent work has also reported the existence of a third, or tertiary, reaction of HF with aluminosilicates.3
This paper reports how the rate law and kinetics for this tertiary reaction are determined on kaolinite and feldspar over a broad temperature range. This document also discusses the discovery of how most clays were thermally unstable to HCl at temperatures above 250°F. These findings were made possible by recently applied experimental techniques including 19F nuclear magnetic resonance (NMR) spectroscopy,3 fractional pore-volume (PV) flow experiments,4 and an accurate knowledge of the HF stoichiometry.5
The tertiary reaction of aluminum fluorides, AlFx (where x is the average F/Al ratio), with clay was slow below 200°F and was dominated by HCl decomposition of the clay above 250°F. The tertiary reaction required the presence and consumption of acid to proceed. Feldspars were very stable in HCl at all temperatures, whereas every clay tested had a temperature above which it was easily decomposed by HCl. Ion-exchanging clays tended to be the least stable of the clays, whereas kaolinite was the most stable clay.
Clay Swelling Diagrams: Their Applications in Formation Damage Control
Authors: Zhou Zhihong (John) , Cameron Shauna , Kadatz Bernice , Gunter William D. 
Published: December 2007

Abstract
A novel method has been developed to quantify clay swelling in aqueous solutions. In this method, a swelling clay is dispersed into an aqueous solution of desired composition, and then mounted in a special cell for X-ray diffraction (XRD) analysis. Using this method, the effects of solution pH, salinity, cation composition, temperature, fluid pressure, and overburden pressure on clay swelling can all be determined efficiently. This method uses only a small amount of sample and offers some advantages over the conventional coreflood method. It can also be used to evaluate the performance of clay stabilizers. We have determined the critical salt concentration (CSC) and critical cation ratio (e.g., Na/Ca, Na/K) for macroscopic osmotic swelling of the most common swelling clays. The information can be represented by a set of swelling diagrams in which the solution composition responsible for osmotic swelling and formation damage is delineated. The swelling diagrams can be used to determine the compatibility between shales and drilling fluids, between swelling clays and drilling filtrate or completion fluids, and between swelling clays and flooding fluids used in EOR. The effects of temperature and pressure on clay swelling have also been quantified using this method. Temperature has a small effect on clay swelling between 20-100°C; but the differential pressure between the overburden and fluid pressures (Po - Pf) has a significant effect on clay swelling. The greater the differential pressure, the less the clay swells. The important implications of these results on petroleum drilling and production will be discussed. It should be cautioned that the swelling diagrams can not be applied to fines migration problems associated with non-swelling clays such as kaolinite and illite.