bluuebunny/crossref_metadata_2025_split huggingface dataset:
Production Decline Curves for Low-Pressure Gas Reservoirs Undergoing Simultaneous Water Production
Authors: Mohaghegh Shahab , Bilgesu H. I. , Ertekin Turgay 
Published: December 2007

SummaryA family of production decline curves for low-pressure gas reservoirs are presented for radial flow geometry with closed outer boundary and with a centrally located well. The proposed production decline curves are applicable to conventional gas reservoirs that produce gas and water simultaneously. The proposed decline curves exhibit unique characteristics for a variety of reservoir and fluid properties and pressure, specifications at the well. The performance of the proposed decline curves were investigated against two different numerical simulators, and they were found to be capable of predicting the production of conventional gas reservoirs under two-phase flow conditions with good accuracy.The decline curves presented in this paper have the potential of providing a practical tool by which production performance of gas reservoirs under two-phase flow conditions can be predicted for pragmatic purposes without using sophisticated numerical models.
A Convective-Heat Transfer Model for Underground Combustion
Authors: Kuo C.H. 
Published: December 2007

In the underground combustion process, part of the heat generated at the combustion front is carried downstream by convection. Temperature distribution in the combustion process can be obtained by including a delta function for heat generation at the combustion surface. This is similar to the hot-fluid injection model of Lauwerier. The dimensionless temperature in the reservoir, phi T1(x, t), and the overburden, phi T2(x, y, t), are as follows:
..........................................(1)
..........................................(2)
The ratio R of the heat-front velocity, u, h, to the combustion front velocity, uc, is one of the most important factors governing the temperature distribution in the pay zone. For cases of ub less than uc, no heat is carried ahead of the combustion front and the temperature at the combustion front remains constant for all times. The fraction of the heat stored between the heat front and the combustion front decreases as the time increases. This is because more of the heat is consumed in heating the formation behind the heat front and in heating the cap and bass rock.
A more advantageous condition obtains for uh is greater than uc. For this case, the formation ahead of the combustion front is preheated and the amount of heat in this region increases with time. Therefore, due to heat generation and preheating, the total temperature rise at the combustion front also increases with time. Eq. 1 also shows that the temperature at the combustion front is higher at a given time for a thinner reservoir. This seemingly paradoxical result takes place because the amount paradoxical result takes place because the amount of heat recovered from the overburden and subrock upstream of the combustion front is almost independent of the pay zone thickness. On the other hand, this heat is distributed in the pay zone, which has a heat content directly proportional to the formation thickness b. For thin reservoirs, therefore, the temperature rise in the pay zone due to heat recuperation is higher than that in thick reservoirs. For very thick pay zones (h-oo) there would be no heat recuperation, and consequently the combustion- front temperatures would be lowest.
For many cases encountered, uh is smaller than uc. Convective-heat transport. ahead of the combustion front can be achieved by increasing uh to obtain the condition uh, &gt;uc. The wet and partially quenched combustion processes have a similar objective. The temperature at the combustion front, however, decreases as the uh/uc ratio increases. If this temperature should fall below the ignition point, the fire would die out. Consequently, at any point, the fire would die out. Consequently, at any time there exists a maximum ratio of uh/uc for which the formation ahead of the combustion front can be heated to increase oil mobility while combustion is maintained.
For the case where the heat front moves faster than the combustion front (uh is greater than uc), the downstream heat efficiency E can be derived by applying the integration method given in Ref. 3.
P. 323
Evaluation of Residual Oil Saturation After Waterflood in a Carbonate Reservoir
Authors: Verma Mahendra K. , Boucherit Michel , Bouvier Lucienne 
Published: December 2007

Summary
Four different approaches, including special core analysis (SCAL), log-inject-log, thermal-decay-time (TDT) logs, and material balance, were used to narrow the range of residual oil saturation (ROS) after waterflood, Sorw, in a carbonate reservoir in Qatar to between 23% and 27%. An equation was developed that relates Sorw with connate-water saturation, Swi, and porosity.
An Investigation of the Flow Regime for Hele-Shaw Flow
Authors: Smith R.C. , Greenkorn R.A. 
Published: December 2007

Abstract
Hele-Shaw cells are used to model creeping flow through porous media (where Darcy's law is valid). The effects of inertia on flow about obstructions in a Hele-Shaw cell can be calculated by a perturbation method if one can determine a solution to Laplace's equation.
Results of a computer solution for flow about circular, square and elliptical obstructions are presented These results show that for a modified presented These results show that for a modified Reynolds number of less than 1, the inertia terms are small; and for values of less than 3, the average streamline predicts the ideal flow. Therefore, the analogy might be used for studying flow in porous media up to a modified Reynolds number of at least 3.

Introduction
The nature of fluid flow in porous media is of interest in the fields of soil mechanics, ground water flow, petroleum production, filtration and flow, in packed beds. Because it is very difficult to study the phenomenological behavior of flow in porous media, homologs and analogs are used to study flow characteristics. A Hele-Shaw model, made of two closely spaced plates - usually glass - is often used as an analogy to two-dimensional flow in porous media. Hele-Shaw showed experimentally that the streamline configuration for creeping flow around an obstacle located between two closely spaced parallel plates is the same as for two-dimensional parallel plates is the same as for two-dimensional ideal flow about the same obstacle. Stokes verified these observations mathematically. The usual equation of motion for flow in porous media is Darcy's law. The form of the mathematical statement of Darcy's law is identical, within a multiplicative constant, to the expression for the average velocity over the place gap in the plane of a Hele-Shaw model. These models may be used to describe flow in both homogeneous and heterogeneous porous media.
Inflow Performance of Horizontal Wells
Authors: Goode P. A. , Kuchuk F. J. 
Published: December 2007

SummaryThis paper presents formulas for evaluating the inflow performance of a horizontal well in a rectangular drainage region bounded above and below. The upper boundary may be either sealed to flow (no flow) or at constant pressure (e.g., gas cap). The well can be placed anywhere within the drainage volume and be of any length. The inflow-performance formulas for horizontal wells presented in the literature make certain limiting assumptions about the well relative to the size of the drainage region, the formation thickness, and the well location. In addition, simplified formulas are derived that are applicable over a wide range of practical interest for a variety of reservoir geometries.
Long-Term Gas Deliverability of a Dewatered Coalbed
Authors: Seidle J.P. 
Published: December 2007

Summary
Gas and water production from a coal deposit can be divided into three distinct stages. In the first, gas and water production rates are almost constant. The second stage, beginning production rates are almost constant. The second stage, beginning once pseudosteady state is reached, is characterized by a "negative decline" in gas production rate and a declining water rate. The third stage begins when the peak gas rate is reached. This final stage spans most of the economic life of a coal well and is characterized by a gentle decline in gas rate and negligible water production. Gas production in this stage is described by two production. Gas production in this stage is described by two equations. The first is a gas-deliverability equation using the real-gas pseudo pressure developed by Al-Hussainy et al. This equation is applied to published data from a well in the Deerlick Creek field in the Warrior basin of Alabama. The second is a mass-balance equation combining elements from conventional and shale gas reservoirs. The two equations can be coupled to predict gas rates and recoveries of dewatered coal wells. Published simulation results from the Warrior basin Brookwood field and a San Juan basin coal well are compared. The deliverability equation also is used to construct gas-deliverability curves for a typical Brookwood coal well. The method presented here is applicable to coal wells completed in dry coalbeds.

Introduction
An important characteristic of a gas well is its deliverability over the course of reservoir depletion. A considerable body of literature describes conventional gas-well behavior mathematically. Theoretical aspects of wells completed in conventional dry gas reservoirs have been discussed thoroughly. Gas flow in porous media can be described by three methods: pressure, pressure-squared, and the real-gas pseudo pressure of Al-Hussainy et al. and Al-Hussainy and Ramey. While the last method is more cumbersome to use than the first two, it is more rigorous and is the only reliable method when large drawdowns exist. This paper shows that the traditional real-gas pseudo pressure can be extended to describe gas deliverability of a dewatered coal well.
Coal deposits are naturally fractured gas reservoirs. Initially, the natural fractures, or cleats, of the coal typically are water saturated and the coal matrix adsorbs most, if not all, of the gas. Coal gas is mostly methane with minor amounts of CO2, nitrogen, and heavier hydrocarbons, similar to dry natural gas from conventional reservoirs.
Wells completed in coal deposits progress through three distinct stages, as Fig. 1 illustrates. In the first stage, gas and water production rates are almost constant. The second stage is characterized by a negative decline in gas production rate and a declining water rate. Once the peak gas rate is attained, the third stage of production begins where the gas production rate shows a gentle decline and water production is often negligible. This final stage spans most of the economic life of a coal well.
New Single-Well Test for Determining Vertical Permeability
Authors: Burns William A. 
Published: December 2007

A short-term vertical interference test between isolated sets of perforations in the same well can be used to determine the vertical perforations in the same well can be used to determine the vertical and horizontal permeabilities of each tested interval as well as to determine the effectiveness of tight streaks as barriers to vertical flow.

Introduction
Vertical flow is an important mechanism in many petroleum reservoirs. Yet no adequate method has petroleum reservoirs. Yet no adequate method has heretofore been proposed for determining the in-situ vertical permeability in a reasonable length of time. Core measurements of vertical permeability do not necessarily represent effective in-situ values. Cores may be representative of only localized pockets of high or low permeability, and total reliance on cores night cause one to overlook the presence of vertical fractures altogether. Conventional single-well tests, interference tests, and pulse tests commonly are used to determine horizontal transmissibility, k(h)h/mu, but generally are not designed to measure vertical transmissibility or other groups containing vertical permeability, k(v). permeability, k(v). A new well test described here provides a measure of in-situ vertical permeability as well as the previously measurable horizontal permeability. This previously measurable horizontal permeability. This "vertical test" determines the vertical diffusivity, k(v)/phi c mu, and horizontal transmissibility, k(h)d(1)/mu (where d(1) is the length of injection or production perforations). The test is basically a production perforations). The test is basically a short-term interference or pulse test normally lasting less than a day. Conventional down-hole equipment is used between two isolated sets of perforations in the same well, as shown in Fig. 1. A "layer-cake" description of a reservoir can be obtained by running two or more vertical tests in the same well, each over different vertical intervals. Each test can be analyzed for the effective vertical and horizontal properties of the interval tested. In addition, a vertical well test can determine the effectiveness of a shale barrier or tight zone by testing across it. Field use to date of vertical testing has confirmed its utility in reservoir description.

Mathematical Basis
Interpretation of vertical tests for k(v) and k(h) is based on comparison of measured pressure response with computer-generated response. Pressure behavior during a vertical test in a homogeneous, anisotropic, infinite-acting reservoir (infinite in radial extent and bounded in both directions vertically) is given by the diffusion equation for slightly compressible fluids with negligible gravity effects.,.........(1)
with the boundary and initial conditions
= 0, ..........(2)
lim,.....(3)
lim,
,....(4)
,........................(5)
,........................(6)
JPT
P. 743
Review of Phase A Steam-Assisted Gravity-Drainage Test
Authors: Edmunds N. R. , Kovalsky J. A. , Gittins S. D. , Pennacchioli E. D. 
Published: December 2007

Summary
This paper presents a case history of the Phase A steam-assisted gravity-drainage (SAGD) test conducted by the Alberta Oil Sands Technology & Research Authority (AOSTRA) at its underground test facility (UTF). Reservoir description, the recovery process, design of wells and other critical hardware, production operations history, and performance analysis are discussed. Phase A demonstrated a commercially viable combination of recovery, production rate, and steam/oil ratio (SOR). Completions design and production engineering progressed significantly. Phase B scaleup considerations and commercial economic projections also are discussed.
Influence of Wettability on Two- and Four-Electrode Resistivity Measurements on Berea Sandstone Plugs
Authors: Wei Jun-Zhl , Llle Ole B. 
Published: December 2007

Summary
Two- and four-electrode resistivity measurements were conducted on water- and oil-wet Berea sandstone plugs for different saturation directions with a steady-state flooding procedure. The data from nine plugs indicated that reliable resistance values can be obtained on water-wet cores with both two- and four-electrode methods. On oil-wet cores, however, two-electrode measurements yielded higher resistance values than those from the four-electrode method because of end effects and contact resistance, especially for low water saturations. In addition, the saturation history substantially influenced the resistivity measurements of oil-wet cores. The four-electrode technique is better for oil-wet core resistivity measurements because it ensures that correct Archie saturation exponents are derived.
Steamflooding Cold Lake Oil Reservoirs Through a Bottomwater Zone: A Scaled Physical Model Study
Authors: Nasr T. N. , Pierce G. E. 
Published: December 2007

Summary
A series of experiments was conducted in one-eighth of a five-spot-pattern, high-pressure, scaled physical model to evaluate the potential of steamflooding oil-sand reservoirs through a bottomwater zone in Cold Lake, Alta. During the experiments, steam was injected into the bottomwater zone at a constant rate until steam breakthrough occurred at the production well. The steam injection rate then was reduced to limit steam production. Results demonstrate that the process is influenced by the steam injection flow rate because of the important role played by gravity override. Increasing the steam injection rate beyond an optimum value results in decreased oil/steam ratios (OSR's) and reduced final oil recovery because steam channels to the production well. A delay in oil production was noticed in all experiments. A moving-heat-source, gravity-override, analytical model was used to investigate the mechanisms of reservoir heating in the presence of steam-gravity override. In addition, the thermal efficiency of the process, determined from the experiments and extrapolated to field conditions, was compared with predictions from Prats' thermal efficiency model. Prats' model predicted the measured thermal efficiency reasonably well at lower injection rates. As the injection rate increased, however, larger differences between Prats' model and the experiments were noticed.
Steam-Foam Mechanistic Field Trial in the Midway-Sunset Field
Authors: Friedmann Francois , Smith M. E. , Guice W. R. , Gump J. M. , Nelson D. G. 
Published: December 2007

Summary
A one-pattern, steam-foam mechanistic field trial was conducted in Section 26C of the Midway-Sunset field (upper Monarch sand). The test objectives were (1) to understand the mechanisms of steam diversion caused by foam under reservoir conditions, (2) to establish whether foam can exist in-depth away from the injection well, and (3) to measure incremental oil that can be attributed to foam. Surfactant was injected with steam and nitrogen continuously, and bottom-hole injection pressure (BIHP) increased from 100 to 300 psig, indicating good foam generation. Better steam distribution across the injector's perforations occurred when foam was generated. Improvements in both vertical and areal sweep efficiency of steam were observed. Substantial temperature and gas saturation increases coincided with surfactant breakthrough and local reservoir pressure increases at observation wells. Complementary laboratory core-floods showed that foam generation could occur at low-pressure gradients, which are typical of in-depth conditions. Both laboratory and field data were interpreted as evidence that the in-depth presence of foam was the result of local generation wherever surfactant, steam, and nitrogen were present, rather than propagation of a foam bank generated near the injector. Some oil-production increase was also observed during the test; however, an accurate quantitative estimate of incremental oil owing to foam was difficult to establish.
A Performance Evaluation of Canada's Snipe Lake/Beaverhill Lake A Pool
Authors: Springate G. L. V. , Muir I. D. , Caldwell T. R. 
Published: December 2007

Summary
This paper describes the evaluation of the production performance of the Snipe Lake/Beaverhill Lake A (BHL-A) pool. The purpose of this investigation was to determine the reasons behind the pool's low projected recovery (32%) relative to similar pools (40%) and to recommend steps to remove the causes. This work was initiated because the pool's production is declining under the existing depletion scheme (essentially a downdip waterflood). The evaluation involved simultaneous geological and engineering investigations that improved the quality of data interpretation and the timeliness of the effort and reduced the overlap of work that otherwise might have occurred. The detailed reservoir model developed indicated that the production performance is controlled by the pool's geology. Fluid movement is restricted vertically between reservoir cycles and horizontally within the major reservoir cycle. An analysis of previous infill drilling and producer-to-water-injector conversions demonstrated that incremental recovery of oil was achieved; 4.5% (422× 103 m3) from infill wells on 32-ha well spacing and 6.0% (740× 103 m3) from increased water injection. Converting the entire pool to a 65-ha pattern waterflood will increase the recovery by 1.9% (900× 103 m3). A 32-ha pattern waterflood has the potential of 5.6% (1740×103 m3) additional recovery.
An Analysis of Uncertainty in Directional Surveying
Authors: Walstrom J.E. , Brown A.A. , Harvey R.P. 
Published: December 2007

Knowledge concerning the position of the bottom of a directionally drilled hole is uncertain. This uncertainty can be measured quantitatively either by analysis based on principles of probability and statistics, or by Monte Carlo simulation using a computer that yields a pattern of possible bottomhole locations.

Introduction and Model Description
In view of the large number of wells directionally drilled from offshore platforms and urban drillsites, greater interest is being focused on the directional survey and on the uncertainty inherent in calculating the position of the bottom of the hole, or other benchmarks in the wellbore. Of the two methods presented here for evaluating this uncertainty, the first is analytical and uses the principles of probability and statistics. The second method uses Monte Carlo simulation to generate a pattern of the scatter of possible bottom-hole locations. possible bottom-hole locations. Both methods are based on a model for which the usual assumption is made that the curvilinear axis of the wellbore is adequately represented by a large number, M, of linear segments joined end to end from the top to the bottom of the hole and closely following the course of the hole. The errors due to this approximation are assumed to be negligible and are not studied here. One form of the model is to consider that for a given hole there exists a perfect set of data describing it, of the above form. Each linear segment has an angle of inclination with the vertical Ii in radians, an azimuthal angle from true north Ai in radians, and a length Si, in feet. The subscript variable, i, extends from 1 to M.
Each of the M linear segments representing the axis of the wellbore has three components in the X, Y, and Z directions. These components are calculated from the equations:....................(1)
The bottom-hole coordinates as determined from the reference set of data for the wellbore are given by the following for i = 1 to M:..........(2)
A directional survey instrument, lowered into the wellbore to the M segments, or stations, measures the values of the Ii and the Ti.
In general, because of errors from various sources, the resulting angular measurements will not be precisely equal to the I, and Ai. Random variables Ii precisely equal to the I, and Ai. Random variables Ii and Ai are therefore considered with associated probability density functions fi(Ii) and gi(Ai), probability density functions fi(Ii) and gi(Ai), respectively, which represent the distributions of potential survey measurements for this hole. Since it is assumed that the values Si are accurately measured they are treated deterministically.
The random variables corresponding to the surveyed bottom-hole coordinates are given, for i = 1 to M, by:............(3)
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