bluuebunny/crossref_metadata_2025 huggingface dataset:
The Geological Influence in Offshore Directional Drilling
Authors: Pfau D.J.
Published: December 2007

Offshore Louisiana's early development was in shallow water, with virtually all wells drilled as straight holes. As drilling edged into deeper water, multiple-well jackets with one or more directional wells became an economic necessity to reduce structure and line costs. When larger platforms with more wells evolved, longer platforms with more wells evolved, longer directional kicks resulted which demanded more engineering effort. Today's offshore directional drilling programs are designed on a delicate balance of economics, engineering, and geology, with the latter factor exerting an ever-increasing influence.

Directional drilling has become an indispensable tool to the geologist or engineer planning offshore exploration and development. The problems inherent to this operation are often outweighed to the extent that some wells are directionally drilled when complete freedom of choice in surface locations is available. Testing an entire series of objectives at the optimum structural positions in an exploratory well, or penetrating several pays instead of one in penetrating several pays instead of one in a development well, can often justify the added cost or risk of unusually complex directional programs. Specialized directional drilling can make some development programs profitable that would otherwise be programs profitable that would otherwise be uneconomical, even with straight-hole development.

When drilling from fixed, multi-well platforms, the problems of attempting to platforms, the problems of attempting to adapt the directional programs to the geometry of domal or highly faulted geologic structures become extremely complex. A thorough study of the forces acting between the drill pipe and casing plus the walls of the open hole is necessary to determine what can be accomplished with the equipment available and what improvements are needed. By reducing these adverse forces and/or compensating for them, additional directional drilling capabilities are possible. Continued progress in providing this flexibility is essential if we are to economically discover and develop the smaller reserves in our offshore fields.

Introduction

Shell's effort in the development of Offshore Louisiana oil and gas began 20 years ago at Main Pass Block 69 Field, just east of the Mississippi River Delta.
Design Applications of Genetic Algorithms
Authors: Jefferys E. R.
Published: December 2007

The paper outlines the basis of Genetic Algorithm (GA) optimisation and discusses the areas where these powerful computer based search procedures can best be used. Applications include many kinds of engineering design, financial optimisation, scheduling and finding rules to describe data.

An interface between a GA package and the design engineer’s problem specification has been developed. The system is simple yet powerful, permitting the engineer to use sophisticated software on a PC without becoming an optimisation expert. Real applications to TLP column design optimisation and scheduling are presented to illustrate the power and flexibility of the method and the simplicity of the interface.

Future additional application areas are suggested.
A Cyclic Surfactant-Based Imbibition/Solution Gas Drive Process for Low-Permeability, Fractured Reservoirs
Authors: Flumerfelt R. W. , Li Xiaoyu , Cox J. C. , Hsu Wen-Fu
Published: December 2007

A surfactant based imbibition/solution drive process is described which has significant promise for application as a single well treatment in low permeability, fractured environments. The process utilizes a carbonated surfactant slug in a multi-cycle injection-soak-production sequence to increase production by (1) enhancing imbibition rates and (2) promoting an induced solution gas drive (SGD) mechanism. Imbibition is enhanced through surfactant and CO2 stimulated alternations in wetting and CO2 stimulated decreases in oil viscosity. The solution gas drive arises from the evolution and expansion of dissolved gas during pressure decline with production. The presence of the surfactant promotes the formation of an in situ foam which decreases the mobility of the gas phase and significantly enhances the effectiveness and the solution gas drive mechanism.

Here, laboratory studies are presented to evaluate the process for different oils (kerosene and crude oil) in low permeability dolomite rock samples. To provide baseline comparisons, separate imbibition/production tests were conducted with (1) water only, (2) carbonated water (no surfactant), and (3) carbonated water with surfactant. During the tests, advanced NMR imaging methods were used to track the temporal and spatial variations of oils saturation within the core samples. This provided a basis for evaluating the relative contributions of the imbibition and solution gas drive mechanisms.

The tests with kerosene in water-wet media clearly showed the effectiveness of CO2 in promoting higher imbibition rates and in stimulating the solution gas drive. In these tests, the surfactant improved the solution gas drive production, but the effect was marginal. In the crude oil tests, the surfactant based carbonated water imbibition and production was clearly superior to that observed with the carbonated water alone. The surfactant systems were particularly effective in rock samples with mixed or oil-wet conditions. The surfactant appears to alter the wetting state of the rock and promote imbibition significantly beyond that possible with water alone or water with dissolved CO2. Also, during the production phase, the SGD mechanism is significantly enhanced with the presence of the surfactant. Oil recoveries in excess of 50% were possible with multi-cycle treatments with the carbonated surfactant systems, while only 20% recovery was possible with carbonated water alone.
Determining Total Petroleum Hydrocarbons in Soil
Authors: Holliday G. H. , Deuel L. E.
Published: December 2007

Many state agencies, using an infrared analysis [IR], establish total petroleum hydrocarbon (TPH) levels above which soils are considered contaminated. As a result, clean closure of contaminated areas are prohibited and, in some cases, Deed Recordation required. In many instances, a fraction of the hydrocarbon observed using the IR technique is co-extracted carbohydrates, fats and proteins associated with the indigenous soil humus. Test results from the field biodegradation studies reveal TPH analysis by gas chromatographic [GC] technique provide an accurate index to treatment efficiencies and treatment methods establishing petroleum residual levels. Significant decrease in TPH-GC with time corresponds to a significant decrease in the dry weight loss on ignition [LOI] quantified at 150°, 200° and 250° C. The authors conclude complete analyses [IR and GC] are required to avoid improperly characterizing the source and level of TPH contamination.
Simulation of Foam Transport in Porous Media
Authors: Kovscek A. R. , Patzek T. W. , Radke C. J.
Published: December 2007

Foam is an excellent fluid for achieving mobility control of gas in porous media. Practical application of foams for EOR processes, however requires a predictive model of foam displacement. Further, quantitative information on foam-flow behavior at reservoir flow rates and pressures is required as input to any field-scale modeling.

An experimental and mechanistic-modeling study is reported for the transient flow of foam through 1.3 μm2 (1.3 D) Boise sandstone at backpressures in excess of 5 MPa (700 psi) over a quality range from 0.80 to 0.99. Total superficial velocities range from as little as 0.42 to 2.20 m/day (1.4 ftVday to 7 ft/day). Sequential pressure taps and gamma-ray densitometry measure flow resistance and in-situ liquid saturations, respectively. We garner experimental pressure and saturation profiles in both the transient and steady states.

Adoption of a mean-size foam-bubble conservation equation along with the traditional reservoir simulation equations allows mechanistic foam simulation. Since foam mobility depends heavily upon its texture, the bubble population balance is both useful and necessary as the role of foam texture must be incorporated into any model which seeks accurate prediction of flow properties. Our model employs capillary-pressure-dependent kinetic expressions for lamellae generation and coalescence and also a term for trapping of lamellae.

Additionally, the effects of surfactant chemical transport aie included.

We find quantitative agreement between experimental and theoretical saturation and pressure profiles in both the transient and steady states.
Team Strategies: Managing Technical Specialties
Authors: Woodyard Alan , Hall Jim , Kendrick Bob
Published: December 2007

Allocating technical and managerial staff based on the requirements of the activity may provide an effective application of skills, but the strategies of the 21st century demand that a more efficient use of staff be made. Conoco’s Production and Project Engineering Division response to this demand has been to "pilot" the organization of a corporate engineering support team around a selected core production area. This arrangement offers the greatest opportunity for profit with the least investment of people. The production increases resulting from this pilot effort have paid for the engineering support seven fold in one year.
A Robust Neural Network Model for Pattern Recognition of Pressure Transient Test Data
Authors: Ershaghi Iraj , Li Xuehai , Hassibi Mahnaz , Shikari Yusuf
Published: December 2007

A modified approach for pattern recognition from derivative plots by using neural network methodology is proposed. Instead of training only one single comprehensive neural net to recognize all possible patterns, multiple neural nets are employed in which each neural net is trained to recognize patterns for a specific conceptual reservoir model. This improves the full representation for each model. At the same time the proposed approach assists in recognition of various models with similar responses. A hybrid approach is suggested where the output from the proposed neural network can be cross correlated with models suggested from other data sources.
Logging of Water Mass Entry in Deviated Well Oil/Water Flows
Authors: Lenn C. P. , Kimminau S. , Young P.
Published: December 2007

A new interpretation has been applied to the WFL* Water Flow Log which determines the mass flow rate of water and gathers both velocity and holdup information from the activation signal. The interpretation enables the WFL log to function as an effective cased hole production logging tool. It has been tested with extensive laboratory experiments. Field trials at the Wytch Farm oilfield have demonstrated the practicality of the method in conditions typical of many offshore oil fields with medium to high production rates.

Downhole measurements of mass water flow rate that are consistent with other production logging and test separator data have been made in field conditions. The measurements have been used as part of an integrated program of waterflood management, and in the particularly complement the TDT* data.

The method is of value in highly deviated or even horizontal wells where conventional production logging (PL) sensors can be ambiguous in resolving oil-water flows. The pulsed neutron tool presents no external obstructions to flow.
Restrictive Diffusion From Uniform Gradient NMR Well Logging
Authors: Coates G. R. , Vinegar H. J. , Tutunjian P. N. , Gardner J. S.
Published: December 2007

ABSTRACT*

Nuclear magnetic resonance (NMR.) has long been recognized for its potential as a well logging method for measuring pore size and permeability. NMR spin–lattice and spin–spin relaxation times, T1 and T2, respectively, are typically used in these applications because they are related to the surface-to-volume ratio of the pore system via the surface relaxivity.

Another NMR measurement, restrictive diffusion at short interecho spacings, is also proportional to surface-to-volume ratio buthas no dependence on surface relaxivity. Anew pulsed NMR logging tool, the MRIL, is capable of making continuous restrictive diffusion measurements because its permanent magnet generates a uniform magnetic field gradient of 25 gauss/cm.

Restrictive diffusion logs run in Shell’s Johnson City test well clearly show the effect of nearly unrestricted diffusion in the permeable zones. The MRIL logs are confirmed by laboratory NMR measurements of restrictive diffusion on core plugs from the test well. Several NMR relations are then compared for permeability estimation using bound water, T1, T2, and restricted diffusion data.
The Pressure-Transient Behavior of Vertical Wells With Multiple Flow Entries
Authors: Larsen Leif
Published: December 2007

Solutions and examples are presented for the pressure-transient behavior of vertical wells with multiple flow entries in homogeneous formations. Any number and pattern of intervals can be chosen, with skin values allowed to vary along the well. Total effective skin is also obtained as a byproduct of the solutions.

Using standard mathematical techniques, solutions are obtained with both a finite wellbore radius, as opposed to the more common use of a line-source well, and outer boundaries included for circular and unbounded systems. With boundaries that can be induced by image wefls one can also include these directly. However, except for cases with small distances involved, one can just as well add boundary effects from fully penetrating wells.

The pressure-transient solutions are first computed as Laplace transforms and then inverted numerically by standard techniques. With more than one interval, only the total well rate is assumed. The rate distribution along the well must therefore be determined numerically as part of the total solution.
Early Quantification of Uncertainty in the Estimation of Oil-in-Place in a Turbidite Reservoir
Authors: Norris R. J. , Massonnat G. J. , Alabert F. G.
Published: December 2007

A description of an integrated approach to the quantification of uncertainty in the estimation of oil-in-place (OIP) is presented. The approach is unusual in two respects: firstly, the uncertainty is quantified by using traditional stochastic methods combined with an analysis of the representative of wells, secondly, the oil-in-place is calculated within a sedimentological framework, that is, by genetic sedimentary units. The former step is performed by a method known as the "Bootstrap" technique. The geostatistical modelling is constrained by detailed seismic, well and pressure data.

The statistical and geostatistical methods are presented, along with a discussion of the broader implications for the quantification of uncertainty. The second part of the paper details the application of the technique to an appraisal stage field.
Reservoir Facies and Their Distribution in a Heterogeneous Carbonate Reservoir: An Integrated Approach
Authors: Vashist N. , Dennis R. N. , Rajvanshi A. K. , Taneja H. R. , Walia R. K. , Sharma P. K.
Published: December 2007

A new technique for defining reservoir facies has been established which incorporates the geological features of deposition and diagenesis with the dynamic flow capacity (kh) of the reservoir. This technique was designed to overcome the difficulties that a conventional porosity-permeability relationship has in a heterogeneous diagenetic carbonate reservoir. The vertical distribution of these reservoir facies has been established in the studied wells and their lateral variations mapped across the field using the ternary diagram approach. The reservoir description obtained in the study is being directly applied to numerical simulation and ultimately to the field development.
Geographical Distribution and Forecast Models of Infill Drilling Oil Recovery for Permian Basin Carbonate Reservoirs
Authors: Lu G. F. , Brimhall R. M. , Wu C. H.
Published: December 2007

This paper presents the results of a study on the geographical distribution of oil recovery efficiencies of carbonate reservoirs in the Permian Basin of West Texas. The primary oil recovery efficiency of San Andres units was grouped into five geographical regions and that of Clearfork units into six geographical regions. Results indicate that the initial waterflood recovery efficiency appears to be dependent on the primary recovery efficiency; and the infill drilling waterflood recovery efficiency on the initial waterflood recovery efficiency. The geographical location of a unit with reference to a paleo-depositional setting appears to have an important bearing on the waterflood infill drilling oil recovery efficiency.

The forecast models for primary recovery and waterflood infill drilling recovery efficiency were developed for each region. Infill drilling recovery index (IDRI) was introduced to develop the infill drilling oil recovery forecast models. It represents the effectiveness of infill drilling and is correlated with the reservoir, process and operational parameters. Three carbonate reservoirs were used to demonstrate the application of these models for forecasting waterflood infill drilling recovery.
Stress-Induced Permeability Reduction in Fissured Reservoirs
Authors: Buchsteiner Hubert , Warpinski N. R. , Economides M. J.
Published: December 2007

Stresses near any wellbore are different and likely to be higher than the far-field stresses. In addition, fluid production and the corresponding pressure drawdown lead to an increase of the effective stress. This increase results in a substantial reduction in the corresponding permeability, especially if the latter is primarily due to natural fractures. The phenomenon may result in unequal reduction in the components of the permeability tensor, thus inducing permeability anisotropy and, in certain naturally anisotropic cases, may alter the direction of the maximum and minimum permeabilities. A model, relating effective stress and permeability / permeability anisotropy has been employed to study the expected well performance and implications on hydraulic fracturing. The effect of the permeability alteration ranges from moderate to severe and appropriate reservoir exploitation must consider these phenomena.
High-Pressure Packing with Water: An Alternative Approach to Conventional Gravel Packing
Authors: Ledlow L. B. , Johnson M. H. , Richard B. M. , Huval T. J.
Published: December 2007

Many methods of gravel packing have been applied to control sand problems in injection or producing wells.1 Successful application of a sand control technique to obtain a productive well completion requires an understanding of the process limitations of the selected method. Some of the limitations imposed on a gravel packing process are operational. These constraints are more often dictated by operating company philosophy than by technical limitations. In some cases operational goals are in conflict with well productivity goals. A lack of understanding the relationship between the various components and disciplines in gravel packing can magnify productivity problems encountered in gravel packed well completions.

This paper presents an alternative approach that challenges the conventional wisdom of gravel packing below fracture pressure. High rate/pressure water packing breaks down damaged perforations with small amounts of gravel at low pump rates and with a limited volume of fluid. This meets the completion objectives of lower cost, higher productivity and simpler field operations. In a previous paper2 examples of HEC "gel" gravel pack completions were presented that demonstrated the beneficial effects of exceeding fracture pressure to enhance the slurry dehydration and increase the packing efficiency.

Laboratory research as well as field experience has demonstrated that gravel packing with water is an effective method of placing sand in the perforation tunnels and the annulus.3-4
Influence of Light Ends on the Onset Crystallization Temperature of Waxy Crudes within the Frame of Multiphase Transport
Authors: Meray Véronique Ruffier , Volle Jean-Luc , Schranz C. J. P. , Le Marechal Pierre , Behar Emmanuel
Published: December 2007

For some offshore fields, multiphase production and transport can be an economic solution. In the case of waxy crude reservoirs, keeping the light ends in contact with the stock tank oil can reduce the onset crystallization temperature.

The influence of light components and ends on the wax appearance temperature (WAT) of two oils has been studied by differential scanning calorimetry.

In order to determine the role of the pressure, an equipment based on the use of an ultrasonic pulse has been designed. The main features of this device are presented.

It has been found that light components induce a decrease of the onset crystallization temperature of waxy crudes. This decrease is proportional to the amount of light ends, inversely proportional to their carbon atoms number, and dependent on the chemical nature of the components added.

Furthermore, it has been possible to correlate these experimental data, in order to calculate the variation of the wax appearance temperature of two stock tank oils, due to the addition of a light end.
Hilly Terrain Effects on Slug Flow Characteristics
Authors: Zheng Guohua , Brill J. P. , Shoham Ovadia
Published: December 2007

A mathematical model is developed to include the hilly terrain effects on slug flow characteristics. The model is based on a new sink/source concept applied at each pipeline connection, termed an elbow. An elbow accumulates liquid as a sink, releases liquid as a source, and has a characteristic capacity which can be either positive or negative. This concept allows the flow interaction between two pipeline sections to be studied with relative ease, including the generation of additional slugs at a positive-capacity elbow and dissipation of slugs at a negative-capacity elbow. The model shows the persistent existence of slug flow in the downhill section, as observed in the experiments. It also predicts slug length variation with pipeline orientation, which agrees well with the acquired experimental data. This work is applicable to the design and analysis of field pipelines and separation facilities.
Three-Phase Flow-Rate Measurement by Pressure Transducers
Authors: Qiu Jianhang , Toral Haluk
Published: December 2007

A multiphase flowmetering technique based on characterisation, classification and identification of pressure signals has been developed and tested in oil-water-air slug flow. The technique extracts a set of stochastic features from pressure signals and relates these to water-cut and liquid and gas flowrate by training back-propagation neural networks with calibration samples. Laboratory tests in 3 inch and 4 inch horizontal three-phase flow over a wide range of flow conditions have shown a measurement accuracy of +/- 10% for liquid-gas flowrates and +/- 5% for water-cuts.
The Use of Vapor Recovery Units in the Austin Chalk Field
Authors: Liu Dianbin , Meachen J. V.
Published: December 2007

This paper deals with the practical problems and considerations associated with the installation and operation of Vapor Recovery Units (VRUs) in the Austin Chalk field. Other aspects will also be discussed such as oxygen sensing and working together with gas gatherers and oil haulers.

VRUs have been used successfully in Austin Chalk field to recover the gas otherwise vented to the atmosphere. The Austin Chalk horizontal wells usually give high production initially. For high GOR (Gas Oil Ratio) wells, they tend to cause separation problems which result in significant volumes of gas in the stock tanks. PVT analysis, mainly flash calculations, can be used to optimize liquid recovery at separation point and predict the gas volume at the stock tanks.

So far over two dozen VRUs have been installed recovering about $10M daily. More will be installed in the near future. The installation of VRUs is an attractive idea because it is both environmentally conscious and profitable.

The ideas and discussions presented here can also be applied to other oil fields with high GOR and high production.

The results presented in this paper will further one’s understanding of the oil field operations and also help the environment.
Scale Prediction and Control in the Denver Unit CO2 Flood
Authors: Morgenthaler L. N. , Lawson J. B. , Faircloth R. J. , Berkshire D. C.
Published: December 2007

Mineral scale deposition, a costly problem in many oil recovery operations, becomes more severe as producing wells respond to CO2 injection. Carbon dioxide reduces brine pH and enhances mineral dissolution at reservoir conditions, increasing brine scaling tendency in the wellbore. In this work, we report on scaling tendency trends in the Denver Unit (Permian Basin, San Andres) CO2 flood based on both thermodynamic calculations and field water analyses. Results of taking the effect of CO2/brine interactions into account are presented. The impact of reduced pH and temperature on scale inhibitor performance is also described.
The Effect of pH, Calcium, and Temperature on the Adsorption of Phosphonate Inhibitor Onto Consolidated and Crushed Sandstone
Authors: Sorbie K. S. , Jiang Ping , Yuan M. D. , Chen Ping , Jordan M. M. , Todd A. C.
Published: December 2007

In this paper, results are presented from an extensive series of phosphonate inhibitor adsorption experiments using both consolidated and crushed clean (clay free) sandstone core material. A near complete account of phosphonate adsorption in highly quartzitic systems is developed from the results presented. Although some details are known in the literature, we believe that this is the most complete analysis of these effects on phosphonate adsorption that has been assembled to date. The effects on inhibitor adsorption of pH, calcium ion concentration, temperature and inhibitor concentration are investigated in some detail. The appropriate adsorption mechanisms which operate under the various conditions are elucidated from the inhibitor adsorption experiments and from the additional work on the ζ-potential measurement for quartz. In particular, the respective roles of hydrogen bonding at low pH (~2) and calcium binding at higher pH (~6) are clearly demonstrated and explained. At intermediate pH values (~4) at room temperature, the adsorption of inhibitor is found to be lower than at both pH 2 and pH 6 due to a relative weakening of both the hydrogen bonding and calcium binding mechanisms. Mechanistic results from the crushed rock and core adsorption experiments are consistent although the level of adsorption is rather different for each medium. At elevated temperatures, inhibitor adsorption is higher under all conditions and, when Ca2+ is present, the effect of calcium enhanced surface condensation (or surface precipitation) is clearly shown. The importance of this enhanced adsorption mechanism is discussed in the context of field scale inhibitor adsorption/desorption and "precipitation" type squeeze treatments.

This work should be viewed in the context of: (a)previous work on the effect of pH on phosphonate adsorption1 and;(b)forthcoming work on adsorption onto pure clay mineral substrates and in clay-containing reservoir cores.2
Update Case History: Performance of the Twofreds Tertiary CO2 Project
Authors: Flanders W. A. , DePauw R. M.
Published: December 2007

The performance of the first Texas field-scale tertiary CO2 injection project in a sandstone formation is updated. The Twofreds tertiary CO2 injection project was developed in two phases. The east side of the reservoir was initiated in February 1974 and is now essentially completed. Expansion to the west side started in the early 80’s. Detailed evaluation of the actual performance of the east side CO2 flood will be presented along with operations, design, and monitoring considerations.
Integrated Methods for Coal Gas Reservoir Completion Zone Selection
Authors: Pratt T. J. , Close J. C.
Published: December 2007

Successful selection of single and multiple completion zones in heterogeneous, layered coal natural gas reservoir systems is predicated upon vertically partitioning the stratigraphic interval into zones with discrete ranges of geologic and reservoir characteristics. In gassy zones, the estimation and determination of true net pay depths with respect to permeability-thickness product values is accomplished through integrated interpretation of field operation, well test, geophysical log, and core/fluid property data (in order of increasing vertical resolution). Such partitioning of reservoirs enables more accurate and comprehensive estimates of reservoir simulation input parameters required for quantitative reserve assessments to be obtained. Cost effective completion decisions for exploration, development and workover well candidates can consequently be formulated and implemented. The principles and implications of completion zone selection methods are also applicable to most non-coal petroleum reservoir systems, which are inherently heterogeneous and layered.
Application of Extended Equation of State Work To Optimize the Pegasus Devonian Field Unit No. 3 Gas Cycling Operation
Authors: Whitaker C. A. , Kim J. S.
Published: December 2007

Due to the retrograde condensate characteristics of the reservoir fluid, gas cycling operations were initiated in the Pegasus Devonian Field Unit No. 3 during 1963 to maximize condensate recovery. At the initial reservoir conditions of 5,400 PSIA and 203° F, the condensate yield of the reservoir fluid was 189 BBL/MMSCF. Since production began in 1952, the condensate yield has declined steadily to 25 BBL/MMSCF due to changes in fluid composition resulting from pressure depletion and injected lean gas breakthrough. In order to describe the complex mass transfer and composition changes of the mix between reservoir fluid and injected gas, a twelve component fluid characterization model was developed for the Devonian hydrocarbon fluid system using a Peng-Robinson equation of state program. This paper details how this model has been used to determine the degree of gas cycling, monitor the effectiveness of surface production facilities, and establish an efficient field development plan which will maximize the value of this property.
Capillary Effects in Heterogeneous Porous Media: Experiments, Pore Network Simulations, and Continuum Modeling
Authors: Chaouche Mohamed , Rakotomalala Nicole , Salin Dominique , Xu Baomin , Yortsos Y. C.
Published: December 2007

We investigate effects of capillary heterogeneity induced by variations in permeability in the direction of displacement in heterogeneous porous media. The investigation is three-pronged and uses macroscopic simulation, based on the standard continuum equations, experiments with the use of an acoustic technique and pore network numerical models. It is found that heterogeneity affects significantly the saturation profiles, the effect being stronger at lower rates. For drainage, a good agreement is found between continuum model predictions, experimental results and the pore network numerical models based on which it can be concluded that capillary heterogeneity effects in the direction of displacement act much like a body force (e.g. gravity). The results are interpreted with the use of invasion percolation concepts. For secondary imbibition, a poorer agreement exists between continuum model and experimental results at low capillary numbers, which requires the use of a pore network simulator involving film flow. Numerical simulation results are discussed for 2-D geometries.
An Investigation Into the Processes Governing Flow and Recovery in Different Flow Regimes Present in Gas Condensate Reservoirs
Authors: Henderson G. D. , Danesh Ali , Tehrani D. H. , Peden J. M.
Published: December 2007

A series of long core experiments have been conducted at reservoir pressures, where a synthetic gas condensate fluid was used in order to study the flow of gas and condensate in the area of the reservoir close to the wellbore, and the region of the reservoir away from the producing wells. A horizontally orientated core was used in order to investigate flow of gas and condensate in the region around the producing wells, with the flow rates of gas and condensate being increased from capillary dominated to viscous dominated in order to observe the effect of flow rate on flow and recovery. The final flow velocities were comparable to field conditions around the wellbore region. A vertical core was used at similar pressures in order to simulate flow of condensate in a gravity and capillary dominated regime away from the producing wells, where viscous forces are negligible.

The results of the horizontal core tests have highlighted that the mobility of condensate in the area around the wellbore may be greater than previously assumed. In the vertical core tests, the rate of free-fall gravity drainage of condensate at conditions where the interfacial tension between the gas and condensate was low has been measured. It has been shown that the reduction of the condensate saturation by drainage is in this gravity/capillary dominated regime can be considerable.

Experimental methods such as those described in the paper are required in order to obtain suitable relative permeability curves for simulation purposes.
Modeling Commingled Reservoirs With Pressure-Dependent Properties and Unequal Initial Pressure in Different Layers
Authors: Gao Chao , Lee W. J.
Published: December 2007

This paper introduces a new approach to model the performance of commingled reservoirs with pressure dependent fluid properties in each layer. With this approach, reservoir engineers can readily modify an analytical model for slightly compressible liquids to model commingled gas systems. We used a numerical simulator to verify this approach. Based on the analytical model and this approach, we developed an analytical computer simulator which reservoir engineers can use to model the performance of commingled reservoirs with unequal initial pressures in different layers and which allows each layer to be homogeneous or dual porosity, hydraulically fractured or have radial flow (with skin), and to be finite or infinite in extent. This analytical simulator can be used to predict future performance, match past performance, and to assist in the analysis of pressure transient tests. A major advantage of this simulator is that it requires far less computer time than conventional finite-difference simulators to solve the same problem.

Using the new analytical simulator, we can model several important reservoir situations with different inner and outer boundary conditions and reservoir rock types. Most importantly, in this paper we present a new technique to model pressure buildup performance of a commingled reservoir following constant pressure production.
Drilling Close to Salt Diapirs in the North Sea
Authors: Seymour K. P. , Rae Graeme , Peden J. M. , Ormston Keith
Published: December 2007

In the period May 1991 to April 1992 Ranger Oil (U.K.) Ltd., drilled five separate wells close to salt diapir structures in the Central Graben area of the North Sea. Two different salt diapirs were appraised, one in block 23/27 and the other straddling blocks 29/2a and 22/27a.

Without exception all of the wells exceeded their planned dry hole drilling time estimates. In addition to two planned geological sidetracks, there were three further unplanned mechanical sidetracks, all caused by unstable hole conditions. A breakdown of non-productive time associated with the wells is outlined.

This paper emphasises the prerequisite of good seismic and geological data in planning salt diapir wells. The use of high angle and horizontal drilling techniques are outlined for appraisal and development, as a means to satisfy both drilling and reservoir engineering requiements in these often marginal prospects.

The history of the salt diapir drilling in other parts of the world is also reviewed. It is concluded that drilling close to salt diapirs is usually complex and that wells must be designed and managed with a high degree of flexibility.
Hydrate Inhibition Effect of Produced Water: Part 1—Ethane and Propane Simple Gas Hydrates
Authors: Tohidi Bahman , Burgass R. W. , Danesh Ali , Todd A. C.
Published: December 2007

Produced waters, due to the presence of salts, have a hydrate inhibiting effect. However, the data on hydrate formation in the presence of electrolytes is scarce. This paper presents experimental and modelling results on the effect of salts on hydrate equilibria for ethane and propane simple gas hydrates. This is a part of an ongoing research project on the hydrate inhibition effect of electrolytes in relation to subsea transmission lines where the proportion of water could be significant.

The conventional graphical method, backed up with visual observation has been used in hydrate dissociation point determinations. For ethane hydrates, dissociation conditions have been determined in the presence of 20 Wt% NaCl solution, while for propane, aqueous electrolyte solutions of NaCl, KC1, and CaCl2, with concentrations ranging from 3 to 20 Wt% have been used.

Both Valderrama (VPT) EoS with Non Density Dependent (NDD) mixing rules and Peng-Robinson (PR) EoS have been used for the fluid phases. The effect of salts in the water phase has been modelled by adding an electrostatic contribution to each EoS, with parameters from vapour pressure depression in electrolyte solutions. For the hydrate phases the model is coupled with the ideal solid solution theory.

The predictions of the model are compared with experimental and literature data and good agreement is demonstrated.
Slim-Hole and Coiled-Tubing Window Cutting Systems
Authors: Faure Alban , van Elst Herman , Jürgens Rainer , Krehl Dietmar
Published: December 2007

Slimhole re-entry horizontal drilling offers operators an opportunity to improve field recovery by infill drilling, and revitalize wells suffering from gas or water coning. Re-entry drilling systems are available for hole sizes down to 3-7/8". The potential for coiled tubing drilling has created significant industry interest over the last 18 months. In offshore applications where there is no derrick in place, use of a coiled tubing drilling system makes it possible to redrill old wells and perform horizontal re-entries.

Coiled tubing re-entry wells completed so far have used a conventional rig to cut the window. This adds unnecessary costs and time to the program. A coiled tubing conveyed window cutting system will dramatically reduce the overall wells costs, and thereby expand the market for coiled tubing re-entries.

The problems of slimhole window cutting include controlling weight on bit while starting the window, and reducing torque while milling to prevent drillpipe failure.

In the coiled tubing application, rotation is supplied by a downhole motor which presents additional problems with respect to controlling weight on bit.

A milling system using downhole motors with hydraulic thrusters to supply constant weight on bit has been bench-tested and field proven. The prototype system required three milling runs after setting and orienting the packer. Subsequent systems will be tested to reduce the number of milling runs to one.

A description of the applications and requirements of the window cutting system is provided, along with bench test and field test results.
Results of Feasibility Study of Running Coiled Tubing to Depths of 30,000 ft in Deviated Wells
Authors: van Adrichem W. P. , Spruill R. L.
Published: December 2007

When planning a workover, Coiled Tubing has become more indispensable due to its ability to accomplish a wide range of tasks yet remain economical affordable.

As wells are drilled deeper and the radial displacement of deviated wells increases, the question arises whether CT can still be utilized. Coiled Tubing is commonly run to 18000 ft in several places around the world. However, wells are now planned with measured depths of 30000 ft, and radial displacements of up to 25000 ft.

There are multiple reasons for drilling wells to such depths: *By drilling wells offshore with a larger radial displacement, more wells can be completed from a single platform, and less platforms may be required. In deep water, this provides a substantial cost saving.*Similarly, onshore applications include minimizing environmental liabilities by directional drilling multiple wells from one location.
The Optimal Design of Thermosiphon Reboilers
Authors: Kerr Clayton P.
Published: December 2007

This paper was prepared for the 44th Annual Fall Meeting of the of the Society of Petroleum Engineers of AIME, to be held in Denver, Colo., Sept. 28-Oct. 1, 1969. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal, provided agreement to give proper credit is made.

Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Introduction

Vertical thermosiphon reboilers are widely used because of their high heat transfer rates and because they do not foul easily. However, in spite of their widespread use they are not easily designed because of the complex nature of two-phase fluid flow and heat transfer. Current design procedures rely heavily on empirical correlations. Obtaining an optimal design of a vertical thermosiphon reboiler in general consists of varying the tube number, length, diameter, tube material, tube wall thickness, and heating medium pressure, then selecting the design that gives the lowest cost or other desired criteria.

This article develops a procedure for obtaining the optimal design of a particular class of vertical thermosiphon reboilers. This procedure will be limited to situations where procedure will be limited to situations where the tube side pressure is high enough so that the sensible heating zone in the tubes may be ignored and isothermal boiling occurs in the tubes. The effect of acceleration losses on the liquid circulation rate will be ignored and is reasonable for isothermal boiling in short tubes. The reboiler liquid will be treated as a one-component material. The heating medium cost will be taken as being directly proportional to its temperature and the tubing cost proportional to its temperature and the tubing cost directly proportional to area. All other costs will be assumed constant. The design problem then is to select the heat transfer area and heating medium temperature to minimize the total annual cost.

DESIGN PROCEDURE

The vapor to be supplied by the reboiler and the tube side isothermal boiling temperature are specified. The heating medium enters as a saturated vapor and leaves as a saturated liquid. With this information, the total cost may be written as

[1]

The total variable cost may be written as

[2] where c1 = c1 (1)Q.

The inside tube area Ai may be written as

[3]

where

[4]
The New Business Challenge for Major Contractors in the Offshore Oil and Gas Industry
Authors: Mourn I. O. , Laskemoen Inge
Published: December 2007

We are expecting that in future developments the smaller and marginal oil and gas fields will dominate the offshore oil and gas business.

Engineering contractors will be more heavily involved at the early stages of such development, and in particular conctractors will be expected to provide innovative technical and commercial solutions that can make more of the fields commercial.

We believe that those contractors that have a wide technological foundation, and a significant engagement in providing new technical concepts, are best prepared for the future challenges.

We also see new contract and cooperation models emerging between client and contractor, and the development of incentive schemes that secures the commitment of the main contractors to the overall economy of each project.
Building a Full-Scale Live Well Simulator
Authors: Hytten Nicolai , Thorsrud A. K.
Published: December 2007

A land rig used for training purposes was upgraded into what may best be described as a full-scale drilling simulator. On-line computer simulation in combination with a fully operational drilling rig open up for staging of various realistic operational situations, to provide practical, hands-on training of drilling personnel in the controlled, safe environment of the live well school.

The rig/software combination has e.g. provided the live well school with a feature which was previously missing: the possibility to drill. By defining a simulated "false" bottom depth, the driller is presented with software-generated indications of weight on bit and penetration rate which realistically respond to the driller's actions on the rig controls.

The final goal should be to use the combination of live well and computer facilities to create a full-scale well control and drilling simulator, for training in well control, stuck pipe avoidance, and handling of similar drilling related problems. This may be done to the point where a student will be presented with conditions similar to those prevailing on one existing drilling location, and through hands-on manipulation of the training rig, acquires drilling experience applicable to that particular area.
Downhole Emulsification for Improving Paraffinic Crude Production
Authors: Beyer A.H. , Osborn D.E.
Published: December 2007

This paper was prepared for the 44th Annual Fall Meeting of the of the Society of Petroleum Engineers of AIME, to be held in Denver, Colo., Sept. 28-Oct. 1, 1969. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal, provided agreement to give proper credit is made.

Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussion may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

The downhole emulsification process has been used to improve the process has been used to improve the producibility and reduce the producibility and reduce the operating cost of oil wells that produce waxy, paraffinic crude. To apply the process, a surface-active chemical process, a surface-active chemical (surfactant) is injected into the well bore to form an oil-in-water emulsion downhole. Produced water in this emulsion wets the steel surfaces with a water film that reduces the adherence of oil and wax. This improves well operation and reduces the need to periodically remove wax deposits by hot-oiling or other means.

Benefits from the process have been demonstrated in a four-month field test involving six pumping wells that produce a paraffinic crude with a 105 degrees F pour point. Wax deposition in wells and flowlines was significantly reduced during treatment with surfactant, permitting 44% fewer hot-oil jobs. Average net gain from reduced operating cost and increased production from the test wells was about $1870 per well per year.

Introduction

The cost of paraffin control in the domestic petroleum industry is estimated by Bilderback and McDougall to be in excess of $5 million annually. This includes only the direct costs of periodic removal of paraffin deposits from oil wells and paraffin deposits from oil wells and surface facilities. Not included are the costs of lost production, increased power requirement, reduced equipment life, and additional labor resulting from wax buildup.

Various methods, such as heat, solvents, plastic-coated pipe and chemical additives, have been used by the petroleum industry in the past to reduce paraffin deposition. past to reduce paraffin deposition. However, to the authors' knowledge these techniques lose much of their effectiveness and economic advantage in wells producing paraffinic crude that has a high wax content.