bluuebunny/crossref_metadata_2025 huggingface dataset:
An Improved Method for Computing Directional Surveys
Authors: Wilson G.J.
Published: December 2007

Difficulties experienced in correlating vertical and lateral locations of subsurface features that are encountered in directional wells prompted critical review of the tangential method of computing directional surveys. Inherent discrepancies were indicated to cause small incremental but significantly large cumulative errors in computed vertical depth and horizontal departure. A radius of curvature method, developed for planning and analyzing directional wells, was studied as a means of more accurately calculating survey data. Errors incurred in the tangential method were not present in the radius of curvature method. Conflicting assumptions in calculating dog-leg severity by the tangential method were resolved by a new procedure that was derived from the radius of curvature method. Results of the investigation showed the radius of curvature method to be an improved method for computing directional surveys.

Introduction

Many improvements in directional drilling tools and techniques have been made in the past 10 years, but the method of computing survey data has remained virtually unchanged. While use of computers greatly aids the process of calculation' and eliminates many human errors, manual and computer calculations are still made with the assumption that the wellbore consists of straight-line segments. This paper points out discrepancies in the method and presents an improved method in which the wellbore is assumed to be curved.
Steam Zone Growth in a Preheated Reservoir
Authors: Closmann P.J.
Published: December 2007

Steam zone growth as a function of time bas been calculated for the case of constant rate steam injection into a preheated reservoir. To simplify the calculation a linear temperature profile has been assumed in the cap and base rock at the start of steam injection. The results indicate that at early times augmentation of steam zone growth due to preheating should be greatest. At longer times the steam zone development becomes close to that calculated with no preheating.

Introduction

With the increasing application of thermal recovery processes to recover viscous oil, cyclic steam injection has become important in many large-scale projects. In this process the cycle of steam injection followed by oi1 production is repeated a number of times. At the beginning of the second and later cycles, steam is injected into a reservoir that has already been heated but that has lost part of its heat both in produced fluids and by conductive heat loss away from the injection zone. In such a case, the temperature level of the injection zone and the temperature distribution of the surrounding rock will affect the growth of the steam zone developed during the subsequent steam injection. Knowledge of the size of steam zone developed is important in determining the amount of oil displaced and the extent of heating in the reservoir. It is also useful to be able to compute the size of the steam zone for cases where thief zones take most of the injected steam. This paper presents a fairly straightforward method of estimating the steam zone developed in a preheated formation, based on certain simplifying assumptions. Some cases of steam injection into a reservoir at its original temperature have already been considered elsewhere.

Because it is difficult or impossible to obtain an accurate representation of the temperature distribution in the reservoir some time after initial heating has taken place, in this work, a linear temperature profile in the cap and base rock is assumed (Figs. 1A and 1B).

SPEJ

P. 313ˆ
Perturbation Analysis of Stress-Sensitive Reservoirs
Authors: Kikani Jitendra , Pedrosa Oswaldo A.
Published: December 2007

The assumption of constant rock properties in pressure-transient analysis of stress-sensitive reservoirs can cause significant error in determination of reservoir transmissibility and storativity. On the other hand, inclusion of pressure-dependent rock properties makes the governing equation for the pressure in the reservoir nonlinear. These nonlinearities can be treated only approximately by numerical means. If a permeability modulus is defined, the nonlinearities associated with the governing equation become weaker and an analytical solution in terms of a regular perturbation series can be obtained for a radial infinite-acting reservoir. Three terms in the perturbation series are derived to show the convergence and accuracy of the solution. The equation obtained for each order (zero, first, and second) in the perturbation series is solved exactly, and hence, the solution is exact to the third order.

The effect of wellbore storage on the pressure behavior is also investigated. First-order approximation for bounded systems is presented to show qualitative effects. A field example is analyzed to determine the permeability modulus and reservoir properties.
Solution of the Immiscible Fluid Flow Simulation Equations
Authors: Breitenbach E.A. , Thurnau D.H. , Van Poolen H.K.
Published: December 2007

American Institute of Mining, Metallurgical and Petroleum Engineers, Inc.

This paper presents the methods used to solve the finite difference equations which we developed in a companion paper (1).

Various possible methods of solution are discussed. Experience has narrowed the numb of suitable numerical methods that are practical to three: Gauss elimination, successive practical to three: Gauss elimination, successive overrelaxation, and the iterative alternating direction implicit process.

The final sections of the paper are devoted to a presentation of computational technique which are vital to actual use of each of the above-mentioned methods.

FINITE DIFFERENCE EQUATIONS, THE MATRIX AND DEFINITIONS

The final finite difference equation for pressure developed in Reference (1) is: pressure developed in Reference (1) is: ..........................................(1)

All the terms are defined in the paper. Here, however, we have dropped the subscript denoting the pressure, p, as an oil pressure. Further breakdown requires definition of the numerical solution to be used. This paper describes the breakdown and solution processes most often used in the MUFFS program. Sufficient detail is given so that computer programming can be done.

Contrary to popular opinion, economic simulation has been found to require the development of several solution methods, rather than relying on a single one. This requires that the computer subprogram for generating coefficients (A's and O's) be written as a distinct, separate entity to supply the coefficients in Equation (1). Furthermore, it is necessary to be able to obtain these coefficients automatically in column-by-column, row-by-raw, or point-by-point form, in any order required by a point-by-point form, in any order required by a numerical solution. Columns, rows, and points refer to the columns, rows, and points of the finite difference grid. A program that can generate coefficients in several forms is a simple but important concept, for it allows the easy insertion and modification of experimental methods. The computing inefficiencies that may be incurred within a general coefficient generator are small in comparison to the computing time saved by using the fastest of several solution techniques.
Reservoir Simulation on Low-Cost, High-Performance Workstations
Authors: Young L. C. , Hemanth-Kumar K. , Bratvold R. B.
Published: December 2007

Reservoir simulation with two different computer systems is investigated. A reservoir simulator with demonstrated high performance is used to test these machines. Both systems can perform reservoir simulations at more than 10 times the speed of an Intel 80486 and at a significant fraction of the speed of a supercomputer. With an efficient simulator and enough memory, both processors can solve compositional problems with 40, 000 gridpoints and blackoil problems with 200, 000 gridpoints. With starting prices of less than $15, 000 for a complete machine, these systems provide an attractive alternative to mainframes and supercomputers.
Mud/Gas Separator Sizing and Evaluation
Authors: MacDougall G. R.
Published: December 2007

Recent wellsite disasters have led to an increased emphasis on properly sized mud/gas separators. This paper reviews and analyzes existing mud/gas separator technology and recommends separator configuration, components, design considerations, and a sizing procedure. A simple method of evaluating mud/gas separation within the separator vessel has been developed as a basis for the sizing procedure. A mud/gas separator sizing worksheet will assist drilling personnel with the sizing calculations. The worksheet provides a quick and easy evaluation of most mud/gas separators for a specific well application. A brief discussion of other mud/gas separator considerations is provided, including separator components, testing, materials, and oil-based-mud considerations.
Determination of Effective or Relative Permeabilities From Well Tests
Authors: Hatzignatiou Dimitrios G. , Reynolds Albert C.
Published: December 2007

This work presents a procedure for estimating effective or relative permeability curves directly from well-test pressure data obtained from a well producing a solution-gas-drive reservoir. The method requires accurate drawdown data. The basic procedure developed and discussed in this study combines computed effective permeability versus pressure values with nonlinear regression analysis techniques to determine the parameters involved in Standing's and Corey's relative permeability correlations. Once these parameters are determined, effective or relative permeability curves as a function of saturation can be generated.
A Comparison of Mixed-Gas Foams with N2 and CO2 Foam Fracturing Fluids on a Flow-Loop Viscometer
Authors: Harris P. C.
Published: December 2007

A study of the rheological properties of mixed-gas foams was conducted on a flow-loop viscometer. The variables studied included different ratios of N2 and CO2 in 70%-quality foams, base gel concentration, crosslinking agent, and temperature.

The rheological properties of mixed-gas foams are very similar to the rheologies of N2 and CO2 foams. This finding was anticipated, because the rheologies of N2 and CO2 foams are similar. The exact static stability behavior of these foams was not anticipated. Pure CO2 70%-quality foams have four to five times the static half-life as pure N2 70%-quality foams. Replacement of CO2 by N2 in a 70%-quality foam decreases the half-life of the foam. The inclusion of only 20%-quality N2 in a 70%-quality mixed-gas foam decreases the foam stability to equal a pure N2 70%-quality foam. We saw no evidence that addition of N2 to a CO2 foam improved its stability.

Previously published foam-rheology equations for N2 and CO2 foams were found to be valid, and only minor adjustment to a few coefficients were needed to include the effects of mixed gases. A BASIC program is included which allows foam viscosity to be calculated as a function of quality, gas type and concentration, external liquid-phase power-law parameters n′ and K′, shear rate, and temperature.

Fluid loss characteristics of mixed-gas foams were found to be the same as for N2 or CO2 foams.
Groundwater Issues Relating to an Alaskan Methanol Spill
Authors: Robertson S.B.
Published: December 2007

A Dec. 1989 methanol spill resulted from sabotage to three railroad tank cars. Samples taken from nearby drinking-water wells and groundwater-monitoring wells were below the analytical detection limit. Monitoring well data demonstrated that groundwater flow was not toward local residential wells. Dilution by snow and subsequent freezing in the soil limited the downward spread of the methanol, an advantage not found in milder, more temperate conditions. Contaminated material was removed and processed to reclaim the methanol. Volatilization and biodegradation should remove any remaining methanol. Cleanup options were limited by the possible hazardous waste classification of the contaminated soil. The regulatory status of spilled methanol waste should be re-evaluated, especially if use of methanol as a motor fuel increases.

Introduction

Methanol is used in the oil fields of the North Slope of Alaska for freeze protection. Air temperature, ground temperature (wells are drilled through 2,000 ft [610 m] of permafrost), and gas expansion are sources of cooling that may result in its use. For example, methanol is used to protect pipelines and shut-in water injection wells, to reduce the freezing point of water vapor and hydrates in natural gas handling, and as a component in water-based hydraulic fracturing for well stimulation. Before 1990, Arco Alaska Inc.'s standard practice was to transport the material by railroad tank car to its North Star Pipeyard, a material storage and transfer facility in Fairbanks, AK. There it was transferred to tank trucks and driven up the Dalton Highway (the Trans Alaska Pipeline Haul Road) to Prudhoe Bay.

On Dec. 4, 1989, at approximately 2:30 a.m., while moving tank cars on a siding in the pipeyard, the railroad switching crew noticed methanol leaking from three 30,000-gal [114-m3] -capacity cars. The crew closed the valves on the bottom of the tank cars, which had been opened by saboteurs. Special tools are required to open the valves and seals had to be broken. Graffiti written on all three cars, also indicated that sabotage was involved. The Fire Dept. and other emergency personnel were quickly called to the scene. Because of the potential fire and health risks, nearby residents inhabiting homes southwest of the pipeyard were evacuated. After organic vapor analysis demonstrated little or no atmospheric contamination and no danger of explosion, the residents were allowed to return home. Because vents on top of the cars had not been opened, a partial vacuum developed upon drainage. This prevented release of the entire contents of the cars. Subsequent measurement of the remaining contents revealed that only about 9,300 gal [35 m3] of methanol had spilled, rather than the 67,000 gal [254 m3] originally feared.
Time Series Analysis for Reservoir Zonation
Authors: Bennion D.W.
Published: December 2007

A time series is a set of data of which each element is associated with a moment of time. In this report the elements of the set are denoted by x(t). If two time series are used, the second will be denoted by y(t). Well logs can be considered to be time series and can be analyzed using time series techniques. Methods for analyzing time series have been discussed by Weiner and Bendat and Piersol, and have been employed in geophysical studies. The cross-correlation function is used for two time series whose elements are x(t) and y(t). It is used to determine the dependence of the two series on each other. The cross-correlation function is given by the following equation:

(1)

(2)

where

Rsy = cross-correlation function for time series x(t) lagging y(t) by lag number r Ryx = cross-correlation function for times series y(t) lagging x(t) by lag number r N = number of data points in each time series r = lag number r = 0, 1, 2, . . . . m m = maximum lag number, usually 10 to 15 percent of N.

If each time series is normalized so that it has a mean of zero and a variance of one, the cross-correlation function will range from minus one to plus one. A perfect correlation between two time series yields the value plus one. Filtering is used to remove noise from time series and thus helps to increase the cross-correlation function. Many techniques to filter out noise have been proposed. For this report a simple smoothing method proposed by Healy and Bogert was used.

(3)

where

Si = smoothing data, i = I to F Xk = unsmoothed time series Wj = weighting series G = a given selection interger; for example, G=3 applies weight to every third item of the time series N = number of sample points in time series M = number of weights, must be odd k = j . G - G + r r = i - I + 1

I =

F = N - .

P. 913
Extended-Reach Drilling From Platform Irene
Authors: Mueller M. D. , Quintana J. M. , Bunyak M. J.
Published: December 2007

Two wells extending more than 2 miles were drilled from Platform Irene in the Pt. Pedernales field, offshore California. These wells are the two longest extended-reach wells on the U.S. west coast. Although several wells around the world have been drilled beyond two miles, none extend at such shallow true vertical depths (TVD's) as the two from Platform Irene. The average angles from rotary table to total depth (TD) for Platform Irene Wells A-16 and A-17 are 70.9° and 68.2°, respectively. This paper presents the concepts of a "negative-weight well" and "drag-risk analysis, " focusing on the innovative technology used to drill and complete a high-drag well. The successful drilling and completion of these wells will allow recovery of millions of barrels of oil originally expected to be produced from a second platform.
Gravel-Pack Field Examples of a New Pulsed-Neutron-Activatlon Logging Technique
Authors: Watson J. T. , Carpenter W. W. , Carroll James F. , Smith B. C.
Published: December 2007

Gravel packs traditionally have been evaluated with gamma/gamma density and neutron logging tools, but some environments adversely affect the measurement resolution of these tools. These environments include high-density completion fluids, matched-density gravel-pack systems, and changes in fluid density and hardware. This paper presents an alternative measurement of gravel-pack quality.
A Coupled Analysis Approach to the Assessment of Marine Drilling Systems
Authors: King G. W. , Burton Kevin , Hodgson Trevor
Published: December 2007

This paper describes the development of a new approach to marine-drilling-system analysis. From studies with traditional analysis techniques where components were treated independently, a decision was made to develop a new model. This new model was based on a requirement to analyze the system as a complete entity by "coupling" the system components. This new approach was used to analyze the behavior of a drilling riser and conductor. It has demonstrated the influence of conductor parameters on riser response and the factors that influence conductor design.
Varied Applications of Invert Emulsion Muds
Authors: Gray George R. , Grioni Sergio
Published: December 2007

Invert emulsion muds, compounded so as to have specific properties, can solve such divergent problems as are encountered in producing from water-sensitive pay zones; in drilling formations that dissolve, disperse and disintegrate in water; and in alleviating pipe corrosion.

Introduction

Within the last 7 years there has been a significant increase in the use of drilling and completion fluids having oil as the continuous phase. This extension in applications for oil-base muds has been due in large measure to the development of products designed to provide specific properties. Users are no longer provide specific properties. Users are no longer restricted to certain proprietary mixtures but can devise a suitable composition to satisfy the immediate requirements in much the same way as is done with water muds.

"Oil mud" has oil as the continuous phase. AH oil muds after use contain some water. The term "invert emulsion" often is applied to oil muds having water as a component that has been added to produce a desired property. In this discussion, the term "oil mud" is applied without regard to specific water content, with the limitation that the filtrate is all oil under the conditions of use.

Our purpose is to review briefly some of the varied applications for oil muds and thereby to demonstrate the wide adaptability of these compositions.

Oil muds are not to be regarded as cure-alls for every type of drilling and completion problem. On the contrary, before the decision is made to use an oil mud, attention should be given to specific local conditions. Factors such as potential loss of circulation and rapid accumulation of drilled solids or inclusion of excessive amounts of water in the oil mud affect the economic practicability. Nor should oil muds be used without due regard to the importance of the rig equipment - specifically, facilities for mud mixing, removal of drill cuttings, storage, and the like. Qualified supervision is a necessity, of course.

Oil Mud Additives for Specific Functions

With the objective of affording oil mud compositions as versatile as water muds, products have been developed to control various properties. These products are:Gelling and suspending agents organophilic clays.Emulsifiers: anionic mixed calcium and sodium soaps of fatty acids; cationic amine derivative stable to salts and high temperature.Oil-wetting agent: organic phosphate.Filtration control agent: nonasphaltic oil- dispersible organic colloid.

The development and characteristic properties of these materials have been dealt with in detail in several publications and will not be reviewed here.

The selection of an oil mud for drilling or completion usually involves the recognition of a problem with water muds and the conclusion that savings will result from using the product of higher unit cost. Frequently, the use of oil mud to solve the basic problem brings equal or greater associated benefits.

JPT

P. 261
Correlation of PVT Properties for UAE Crudes
Authors: Dokla Mahmoud E. , Osman Mohammad E.
Published: December 2007

Available PVT data from UAE reservoirs was used to obtain correlation equations for bubblepoint pressure and oil FVF as functions of oil specific gravity, gas gravity, solution GOR, and reservoir temperature. Error bounds of the obtained correlations are calculated and compared with other available correlations. The correlations of this study result in lower errors and should work better for UAE crudes.
Impact of Gelation pH, Rock Permeability, and Lithology on the Performance of a Monomer-Based Gel
Authors: Seright R. S. , Martin F. D.
Published: December 2007

Resorcinol/formaldehyde gels are used to show that gel performance in porous rocks depends critically on the pH at which gelation occurs. The gels generally reduced the permeability of low-permeability sandstone more than in high-permeability sandstone. However, residual resistance factors can be greater in sandstones than in less permeable carbonate cores. A simple mathematical model is used to assess whether pH effects can be exploited to optimize gel placement in injection wells.
Surfactant-Enhanced Alkaline Flooding: Buffering at Intermediate Alkaline pH
Authors: Rudin Jeff , Wasan Darsh T.
Published: December 2007

An experimental investigation of buffered alkaline flooding system chemistry was undertaken to determine the influence of various species present on interfacial tension (IFT) as a function of pH and ionic strength. IFT was found to go through an ultralow minimum in certain pH ranges. This synergism results from simultaneous adsorption of un-ionized and ionized acid species on the interface.
Adsorption of Asphaltenes and Its Effect on Oil Production
Authors: González Gaspar , Travalloni-Louvisse Ana Maria
Published: December 2007

Asphaltenes show moderate capacity to reduce oil/water interfacial tension (IFT) and/or to stabilize emulsions. However, in the presence of other surfactants and fine particles presenting intermediate wettability, these compounds enhance emulsion formation and stability. At the solid/solution interface, asphaltenes adsorb up to a saturation value of 2 to 3 mg/g and modify the mineral wettability. At the oil/gas interface, the asphaltic fractions adsorb as single molecules or as liquid crystalline phases, causing foaming problems.
CT-Scan-Monitored Electrical-Resistivity Measurements Show Problems Achieving Homogeneous Saturation
Authors: Sprunt E. S. , Desai K. P. , Coles M. E. , Davis R. M. , Muegge E. L.
Published: December 2007

X-ray computerized tomography (CT) scans obtained during measurement of the electrical resistivity of core samples revealed some problems in obtaining uniform saturation along the lengths of the samples. The electrical resistivity of core samples is measured as a function of water saturation to determine the saturation exponent used in electric-log interpretation. An assumption in such tests is that the water saturation is uniformly distributed. Failure of this assumption can result in errors in the determination of the saturation exponent. Three problems were identified in obtaining homogeneous water saturation in two samples of a Middle Eastern carbonate grainstone: a stationary front formed in one sample at 1-psi oil/brine capillary pressure, a moving front formed at oil/brine capillary pressure ≤4 psi in samples tested in fresh mixed-wettability and cleaned water-wet states, and the heterogeneous fluid distribution caused by a rapidly moving front did not dissipate when the capillary pressure was eliminated in the samples.
Optimization of Fracture Length and Well Spacing in Heterogeneous Reservoirs
Authors: Meehan D. N.
Published: December 2007

Well spacing and hydraulic fracture treatment designs are the two most important operator-controlled factors in the development of low permeability gas reservoirs. Prior studies of optimization of fracture length and well spacing assumed homogeneous permeability, porosity, thickness, etc. This analysis illustrates the importance of understanding spatial variability of permeability and permeability anisotropy. Geostatistical techniques are incorporated with economic and reservoir modelling to show the quantitative value of reservoir description in tight gas reservoirs.
Design of the HCl Preflush in Sandstone Acidizing
Authors: Hill A. D. , Sepehrnoori Kamy , Wu P. Y.
Published: December 2007

HCl usually precedes an HF/HCl mixture in the sandstone acidizing process to reduce HF consumption by carbonates and to avoid the precipitation of HF reaction products. Assuming equilibrium reactions between injected HCl and calcium carbonate in a sandstone formation, we developed a numerical model of HCl frontal movement in the radial direction from the wellbore and added it to an existing sandstone acidizing simulator. In general, only small preflush volumes (as little as 25 gal/ft can be adequate) are needed to prevent live HF from coming in contact with high-pH regions. In almost all treatments, however, spent HF will penetrate beyond the live HCl front; larger HCl preflushes displace the region where spent HF comes in contact with undissolved carbonates in the formation farther from the wellbore. The new simulator predicts the distribution of HCl and HF in a multilayered formation with damage around the wellbore. Using this model, we investigated the required size of the HCl preflush for a range of initial concentrations of HCl and carbonate. We also studied the influence of fluid diversion on the HCl frontal locations in multilayered reservoirs for multiple sequence treatments. In particular, we simulated treatments where HCl was injected without diversion, followed by an HF/HCl sequence including diverting agent to determine whether the HF would be diverted to regions that had not been reached by HCl.
Leak Before Break of CRA Tubing in Sour Environments
Authors: Chen W-C. , Sisak W. J. , Petersen C. W.
Published: December 2007

This paper demonstrates that net-section yielding controls the fracture of corrosion-resistant-alloy (CRA) tubulars. Fracture modes observed in actual tests of CRA tubes in sour environments agree with net-section yielding predictions. The paper also shows that leak before break of production tubing in certain sour environments can be achieved with commercially available CRA tubulars.
Esperson Dome Oxygen Combustion Pilot Test: Postburn Coring Results
Authors: Choquette S. P. , Krishnaswamy Sampath , Northrop P. S. , Edwards J. T. , Hooman Laall , Bret Rowland , Morrow D.
Published: December 2007

Postburn corehole data from an O2 combustion pilot test in Esperson Dome field, Liberty County, TX, show that the combustion temperature was 930 to 1, 020°F. Final oil saturation was 0% in the burned zone and 11% to 34% in the sand adjacent to the burned zone. Roughly 49, 000 bbl of incremental oil was produced at an injected O2/produced-oil ratio of 4.1 Mscf/bbl.
3D PDC Bit Model Predicts Higher Cutter Loads
Authors: Behr S. M. , Warren T. M. , Sinor L. A. , Brett J. F.
Published: December 2007

Historically, PDC bit modeling has incorporated the assumption that cutter forces are constant for a full revolution of the bit. This assumption places considerable limits on the model's ability to simulate drilling in nonhomogeneous rock and in cases where the bit whirls. Recent studies have shown that cutter damage caused by impact loading is a primary cause of PDC bit failure. These impacts may be caused by both bit whirl and drilling through nonhomogeneous rock. The 3D model presented provides the capability to evaluate cutter loading for both conditions. It shows that the cutter loads for common drilling situations may be as much as 10 times greater than those calculated with previously available 2D models.
Field Studies of Circulating Temperatures Under Cementing Conditions
Authors: Davies S. N. , Gunningham M. M. , Bittleston S. H. , Guillot Frederic , Swanson B. W.
Published: December 2007

One of the most important but least well-known parameters in cementing operations is the circulating temperature. Many authors have presented theoretical analyses of the wellbore conditions, formulated mathematical models, and presented actual field measurements. However, very little temperature data have been reported for conditions of greatest concern (i.e., with casing in hole). To gather such data in detail, circulating temperature and pressure measurements were made with downhole tools lowered on wireline. In one case, temperature measurements were made during circulation immediately before cementing to record the circulating temperature in the well. In another case, measurements were made after the slurry was been placed to record the thermal recovery of the well. Data collected during these field trials (with casing in hole) are presented and demonstrate the different thermal response of a well with casing instead of drillpipe in the hole. Measured circulating temperatures are lower than those derived from the API schedules and highlight the necessity to account for well geometry properly when determining downhole temperatures.
Troll Horizontal Well Tests Demoristrate Large Production Potential From Thin Oil Zones
Authors: Seines Knut , Lien S. C. , Haug B. T.
Published: December 2007

This paper presents the results of two long-term horizontal well tests in the Troll field. Planning and evaluation of the tests and simulation of and consequences on field development are summarized. The two tests demonstrated significant production potential from 12- to 22-m oil columns and verified the pretest assumption that one horizontal well could replace four vertical wells.
Extended Production Tests in the Liuhua 11-1 Reservoir
Authors: Peng C. P. , Bateman C. F. , Kaffenes J. M. , Yanosik J. L. , Huan-Min Liu
Published: December 2007

Amoco Production Co. and Chinese Offshore Nanhai East Corp. have conducted three extended production tests (EPT's) on the Liuhua 11-1 reservoir offshore China in the South China Sea. The wells selected for these EPT's included a vertical well, a high-angle deviated well, and a long horizontal well. This paper presents results and analyses of these EPT's.
What Price Quality—The Implementation of the API Quality Program for Drilling-Fluid Materials
Authors: Davis Neal , Perricone A. C. , Warnack M. F. , Grantham C. K. , Hale A. H.
Published: December 2007

In 1985, the American Petroleum Inst. (API) issued the first edition of API Spec. Q1, which dealt with new certification procedures for equipment and materials. This paper discusses API's Spec. Q1 program as it relates to drilling-fluid products and reveals the problems encountered when API Spec. 13A was modified.
Performance of Electric Submersible Pumps in Gassy Wells
Authors: Sachdeva Rajesh , Doty D. R. , Schmidt Zellmir
Published: December 2007

A comprehensive investigation was undertaken to study two-phase flow in a radial electric submersible pump (ESP) using diesel/CO2 mixture data from an earlier study. Currently, no dynamic model is available for multistage pumps. A dynamic five-equation model was developed and verified. The model incorporates pump geometry, stage inlet pressure, inlet void fraction, fluid properties, and number of stages. The two-phase flow physics for the pump is found to be vastly different from that in pipe flow. Insights into a pump's surging tendency were obtained.
Rheological Characterization of Hydraulic Fracturing Slurries
Authors: Shah S. N.
Published: December 2007

Few studies have dealt with the flow behavior of concentrated suspensions or slurries prepared with non-Newtonian carrier fluids. Therefore, the purpose of this investigation is to present experimental results obtained by pumping various hydraulic fracturing slurries into a fracture model and gathering data on differential pressure vs. flow rate. Several concentrations of hydroxypropyl guar (HPG), a wide range of proppant concentrations, and three test temperatures were studied. The effects of such variables as polymer gelling-agent concentration, proppant concentration, test temperature, and fracture-flow shear rate on the rheological properties of slurries were investigated. The correlations for predicting the relative slurry viscosity for these HPG fluids are presented. Substantial increases in viscosity of fracturing gels were observed, and results are discussed in light of several affecting variables. Results also are compared with those available for Newtonian and non-Newtonian concentrated suspensions. Application of these correlations to estimate the hindered particle-settling velocity in the fracture caused by the presence of surrounding particles also is discussed. The correlations presented can easily be included in any currently available 2D or 3D fracture-design simulators; thus, the information can be applied directly to predict fracture geometry and extension.
Effects of Nonstandard Operating Conditions on the Accuracy of Orifice Meters
Authors: Ting V. C.
Published: December 2007

This paper presents the effects of four nonstandard operating conditions on orifice-meter gas-flow measurement accuracy: reversed orifice plates, bent orifice plates, surface roughness on the orifice-meter tubes, and liquid entrainment in the orifice-meter tubes. These are common problems in fields not operating in accordance with the ANSI/API 2530 [American Gas Assn. (AGA) Report 3] orifice-metering standard. This paper provides information to stress prudent operating practices that will reduce measurement errors.
Offshore Oilfield Development Planning
Authors: Behrenbruch Peter
Published: December 2007

This paper presents general guidelines to determine the feasibility of offshore petroleum projects in terms of field appraisal, subsurface development planning, and facilities options. It also illustrates the multidisciplinary nature of various tasks and includes examples for illustration. The emphasis is on oil fields, particularly marginal fields.

Introduction

The life of every oil and gas field begins with its discovery. Almost immediately, we want to know what its potential is (in terms of reserves and monetary value) and what the development options are in terms of subsurface plan and facilities.

To answer these questions, a systematic approach is required to evaluate the discovery, to forecast the reservoir behavior under expected producing conditions, and to design the optimum facilities to meet forecasted production. This paper outlines the required process for studying the feasibility of developing offshore petroleum fields.

A petroleum development project typically is divided into a number of major phases: exploration (including permit acquisition), field appraisal (primary and possibly secondary), feasibility study, project implementation (construction), and field production (operation and maintenance, management, and facilities upgrades, including secondary development phases). Different technical departments, each with specific aims, usually manage these phases (Fig. 1).

While the development sequence is similar for all fields, there are notable differences between onshore and offshore projects. Most significantly, the engineering requirements and capital expenditure tend to be one or two orders of magnitude greater for offshore projects than onshore developments. Furthermore, offshore developments tend to have a much longer development schedule before they come on stream. Reserves and well productivity need to be substantially greater for offshore projects to cover the greater capital expenditure and operating cost, respectively.
Development of Hydrodynamic-Model-Based Air-Drilling Design Procedures
Authors: Shifeng Tian , Adewumi M. A.
Published: December 2007

The lack of systematic analysis of the hydraulics involved in air drilling has inihibited the development and utilization of air-drilling technology because the optimal design of any drilling program requires thorough knowledge of the wellbore hydraulics. A comprehensive study of air-drilling hydraulics yielded the system model used as the basis for a viable systematic set of design procedures. The system model was developed by coupling the models for air flow in the drillstring, air flow through the bit nozzles, and pneumatic transport of cuttings in the annulus. The resulting system model was used to design an air-drilling program. A set of design procedures is outlined to predict the standpipe pressure, to estimate maximum well depth, and to determine the optimal air flow rate required in air drilling. Practical examples are presented to test these design procedures.
Static Reservoir Temperature Determination From Transient Data After Mud Circulation
Authors: Hasan A. R. , Kabir C. S.
Published: December 2007

The current method for estimating the static reservoir temperature from transient data gathered downhole after the cessation of mud circulation is a Horner-type approach. The reservoir temperature estimate so established generally turns out to be lower than the true temperature. This work shows that the temperature analog of the Horner method is limited to large circulation-time situations and is not applicable to cases where the mud circulation time is generally short (less than 30 hours). This study provides a general solution of the thermal diffusivity equation obtained with an appropriate inner-boundary condition to solve the early-time, transient heat-transfer problem. An analytical solution was developed to handle problems requiring a variable-rate heat transfer or the superposition effects. A simple graphical technique is used to interpret data with the superposition function. Three approximate solutions, reflecting different time domains, are also presented. These solutions are reliable as long as they are applied within the specified time bounds. Synthetic examples are used to validate the proposed method, and field examples from both oil and geothermal wells demonstrate application of the method.
Reducing Surfactant Adsorption in Carbonate Reservoirs
Authors: Ahmadali Tabatabai , Gonzalez Maria V. , Harwell Jeffrey H. , Scamehorn John F.
Published: December 2007

This paper compares the adsorption of anionic and cationic surfactants on carbonate minerals. It shows that, in general, cationic surfactants may exhibit significantly less adsorption on carbonate minerals than that exhibited by anionic surfactants. It is also shown that cationic surfactant adsorption on carbonates may be reduced dramatically by the presence of divalent cations, an environment in which the precipitation of anionic surfactants might make their use impractical. It is recommended that cationic surfactants be considered for use in miscible flooding with CO2.
Chemistry and Rheology of Borate-Crosslinked Fluids at Temperatures to 300F
Authors: Harris Phillip C.
Published: December 2007

This paper explains the variables involved in borate chemistry as they affect crosslink formation, stability, and breaking properties. The borate-ion concentration in solution is a function of pH and temperature. A method for calculating borate-ion equilibria is used to help establish the required final pH value for application of a borate-crosslinked gel at a specific temperature.

Introduction

Many of the properties of borate-crosslinked fluids can be explained in terms of the shift in borate-ion equilibria with pH and temperature. Syneresis, the process of forming a dense polymer mass and excluding liquid from the structure, is easily understood as a product of increased borate-ion concentration when a fluid is cooled. Proppant-settling behavior that is pH-dependent also can be explained. As the equilibrium concentration of borate ion increases with increasing pH, the number of network crosslinks increases and hence the proppant-settling rate decreases.

Rheological measurements from flow-loop and Fann Model 50 viscometers are used to help identify the chemical variables that control such fluid properties as crosslinking time, viscosity development, and the rehearing character of borate fluids. A new theological procedure using steady-state shear rate is presented for obtaining viscosity data for fluids used in fracture design programs.

Background

Borate-crosslinked fluids have been gaining popularity in the fracturing industry. Even though such fluids have been used for more than 20 years, new developments in borate-fluid technology are occurring rapidly, particularly with respect to high-temperature capability. For years, borate-crosslinked fluids were considered inexpensive, high-viscosity fluids limited to low temperature. More recently, wells up to 300F have been treated with borates. To understand the extension to high temperature, we should reconsider the chemistry of borate-crosslinked fluids.

Borate Crosslinking

Borate-crosslinked fluids used for fracturing consist of polysaccharide polymers crosslinked with borate salts. These gels are difficult to investigate with analytical instruments, so model diol chemical systems and model sugars have been used to study the formation of borate esters and crosslinking reactions. Borate crosslinks are viewed as rapid exchange equilibria of monoborate ion on the cis-diols of galactomannan polymers (guar).
Integrated Engineering Decision Making Through the Use of a Data Extract System
Authors: Alameda G. K. , Brink J. L. , Jarzombek L. S. , Maslanka P. M
Published: December 2007

This paper describes Chevron U.S.A. Production Co.'s data extract system, CDX. CDX integrates our corporate mainframe databases with a set of ad hoc data analysis tools. Tools include statistical analysis software, database packages, and a widely used spreadsheet. CDX allows the user, through a single user interface, to access and retrieve data from a variety of databases written in industry-standard languages. CDX also allows access of large indexed data sets, such as Chevron's digital well-log archives. Data are delivered to the user's work environment—mainframe, workstation, or PC—ready to be loaded into ad hoc analysis programs or technical applications. This approach to system integration gives users the ability to mix, match, and reanalyze both technical and financial data in ways only experts could previously.

Examples of how CDX has increased our ability to manage business more effectively include analyzing individual wells and patterns for profitability and optimizing flood operations by generating maps of individual well plots. The benefits of CDX are numerous, considering the business pressures now in effect that drive companies harder than ever to reduce operating costs, increase production, and optimize property portfolios. CDX offers a way to realize the benefits of data integration without having to rewrite multimillion-dollar data systems immediately. CDX also provides an organized way to shift information systems, data, and work processes to the newer relational technologies. Lastly, information derived from operating CDX is allowing Chevron to plan and optimize new relational data models and information systems.
The Ability of Rate-Time Decline Curves to Predict Production Rates
Authors: Ramsay H.J. , Guerrero E.T.
Published: December 2007

Although decline curves have wide use in petroleum engineering problems and have been used for many years, the available literature contains little statistical information comparing the ability of various types of decline curve equations to predict producing rates. Cutler and Nomoto both compared producing rates. Cutler and Nomoto both compared the exponential and hyperbolic equations and arrived at different conclusions. Cutler expressed a preference for the hyperbolic equation while Nomoto preference for the hyperbolic equation while Nomoto preferred the exponential equation. Shea, Higgins, preferred the exponential equation. Shea, Higgins, and Lechtenberg reviewed 347 California reservoirs and tested four decline curve equations. They reported that a coordinate relationship provided the best lit to production data in terms of a deviation factor from a least-squares fit. However, in taking a 5-year production history, extrapolating this over the next production history, extrapolating this over the next 5 years, and then comparing the results with the actual production for the second 5 years, the exponential curve gave the best fit. They did not test the hyperbolic equation. A study was made to test these and other equations against a statistical sample of broad geographic distribution. The equations tested were:

(1) Coordinate (2) Exponential (3) Hyperbolic (4) Reciprocal rate

(also harmonic)

(5) Reciprocal time (6) Reciprocal rate-time

The first three equations are decline curves commonly used. The last three equations were suggested by Pirson. Note that with the proper definition of the constants of integration. Eq. 4 is identical with the so-called harmonic curve:

.....................(7)

defined by Arps as a special case of Eq. 3 when b = 1. To obtain production data for the statistical sample, about 1,150 leases in 250 pools were reviewed. The sample consisted of production data from 202 leases having a geographical distribution as follows:

Number of State Leases Pools Formations Colorado 5 1 1Kansas 3 3 3Wyoming 5 2 2New Mexico 38 18 12North Dakota 33 7 1Oklahoma 46 25 18Texas 72 20 13202 76 50

When combining a group of equations, the lowest percent error for each lease was selected from results percent error for each lease was selected from results of applying each equation in the group. For example, if a lease had percent errors at 10.34, 5.17 and 15.45 for Eqs. 2, 3 and 4, respectively, the error of 5.17 corresponding to Eq. 3 was selected.

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