bluuebunny/crossref_metadata_2025 huggingface dataset:
Review of Horizontal Drilling
Authors: Ishak I. B. , Steele R. P. , Macaulay R. C. , Stephenson P. M. , Al Mantheri S. M.
Published: December 2007

Petroleum Development Oman (PDO) has drilled 350 horizontal wells in the past 8 years in 33 different oil and gas fields. Since the first wells were drilled the technology and its applications have evolved considerably. The paper describes that rapid evolution using four fields as examples. There has been a diversification of well designs as we have learnt how to tailor horizontal drilling most effectively to different situations. In many cases wells can be drilled faster and Cheaper than 5 years ago, but there are also examples where more elaborate designs have been applied. The geological targeting and evaluation of the wells has also improved. Further evolution is planned with the next step likely to be the wider use of multi-wellbore horizontals.
Application of Carbonate Environmental Concepts to Secondary Recovery Projects
Authors: Dowling Paul L.
Published: December 2007

Carbonate environmental concepts have been applied to a typical Permian dolomite reservoir. The Monohans Clearfork field, Ward and Winkler Counties, Texas, was selected because the initial development was completed and the secondary recovery project was installed prior to the development of the carbonate environmental concept as an operational tool. The problem in the Monohans Clearfork Secondary Recovery Project is twofold. First, oil response to water injection has been less than originally anticipated with twenty million barrels of water that cannot be accounted for. Secondly, as a result of early evaluation techniques, some productive zones were either cased off or not penetrated.

The Clearfork reservoir was divided into five zones. The environmental dolomite types within each of the five zones ranged from supratidal to marine both vertically and laterally. Several marine dolomite types were found to be productive while the intertidal and supratidal were nonproductive in most cases. when leached, however, the supratidal becomes an effective limited reservoir. Net pay isopachs for each zone were constructed and serve to define field limits, quality and continuity. The isopachs indicate the anticipated waterflood performance of each zone, the distribution of suspected thief zones, and wells and/or areas with additional hydrocarbon potential. An exploitation program currently underway potential. An exploitation program currently underway should complete the evaluation of the Monohans Clearfork reservoir. If successful, the program should result in a significant improvement in supplemental recovery performance as well as an increase in field reserves.

Introduction

The purpose of this paper is to discuss the advantages of applying carbonate environmental concepts to the re-evaluation of existing secondary recovery projects. The environmental approach results in a more accurate representation of reservoir distribution and quality. This provides a basis for plans to optimize the secondary recovery project and indicates potential field extensions and recompletions.

The Monohans Clearfork field was selected because the initial development was completed and the secondary recovery project was installed prior to the development of the carbonate prior to the development of the carbonate environmental concept as an operational tool.
Horizontal Well Applications in Complex Carbonate Reservoirs
Authors: Rahman Mahmood , Al-Awami Haider
Published: December 2007

Over the past four years, Saudi Aramco has drilled over eighty horizontal wells, onshore and offshore. It has successfully applied this technology to develop new reservoirs as well as enhance recovery from its mature fields.

This paper presents the reservoir engineering aspects of ‘horizontal’ and ‘high angle’ wells drilled in a major offshore field in Saudi Arabia. It shows how horizontal wells have a) increased the recovery of bypassed oil, b) improved well productivity in tight reservoirs, c) increased production from thin oil zones underlain by water, and d) improved peripheral injection.

The paper discusses the actual performance of the horizontal wells and compares them with offset conventional wells. It presents the results of logging and testing of these wells, and highlights actual field data on a) relationship between productivity gain and horizontal length, b) pressure loss along the horizontal wellbore, and c) effect of heterogeneity on coning and inflow performance.
Relative Productivities and Pressure Transient Modeling of Horizontal Wells with Multiple Fractures
Authors: Horne R. N. , Temeng K. O.
Published: December 2007

An analytical model has been developed to describe the inflow performance and transient pressure behavior of a horizontal well with multiple hydraulic fractures. The model has been used to compare the relative productivities of multiple fractures, the objective being to determine the conditions under which multiple fractures provide significant improvement over a single fracture.

The approach used was to approximate the series of fractures as fully penetrating, uniform flux, vertical fractures in a box-shaped reservoir of closed boundaries. Interference between the multiple fractures was accounted for by the superposition of influence functions. The effect of wellbore storage and skin was incorporated by numerically converting the solution into the Laplace space.
Numerical Simulation of Alkali/Surfactant/Polymer Flooding
Authors: Shiyi Yuan , Puhua Yang , Zhongqiu Dai , Kuiyou Shen
Published: December 2007

This paper presents a 3-D compositional numerical simulator of alkali/surfactant/polymer (ASP) flooding. It takes into consideration 5 major mass-transfer processes (convection, diffusion-dispersion, liquid-liquid transfer, liquid-solid transfer and chemical reactions) and all important phenomena such as decrease of interfacial tension with synergism, variation of each phase residual saturation and relative permeability, polymer solution behavior (viscosity, rheology, residual resistance factor, in-situ gelation, etc.) and mobility control, fast and long-term alkali losses by different factors (ion exchanges, acid oil, CO2, polymer and rock), chemical adsorptions in presence of alkali, fluid and rock compressibihties, capillary pressure, gravity, etc. All phenomenological parameters in this simulator have definite physical senses and are obtainable from experimental data without extra assumption so that it is more capable to simulate real problems. This simulator can be applied to simulate different chemical flooding processes using polymer, alkali and/or surfactant agents with any combination. It has been verified by comparing the results of calculation with experimental data and it is a reliable tool for simulating and forecasting ASP flooding processes. A complete series of runs presented in this paper make understanding various mechanisms and parameter effects such as ASP synergistic actions, dynamic and equilibrium interfacial tensions, fluid viscosities, alkali consumption and other chemical losses, injection strategy, etc. The studies are very useful to guide ASP field application. The forecasting results of a real AP flooding pilot by using this simulator are presented in the paper.
Pitfalls in Interpreting Pilot Steamflood Performance
Authors: Hong K. C.
Published: December 2007

Because of the unconfined nature of a steamflood pilot, its results cannot be extrapolated directly to a fieldwide project. Careful analyses of the pilot performance with consideration for fluid migration across the pilot boundary are needed for design and implementation of a successful fieldwide project. Large-scale simulation models that include both the pilot and surrounding patterns should be used for history matching the pilot performance, and the history-matched models used for design and implementation of a fieldwide project. As an approximation, a weighted average of confined and unconfined patterns in a project area as predicted from simulation or observed in the field can be used for designing a fieldwide project.
Husky's Long-Range Planning Model
Authors: Ensign M. Dale , Wasmuth J.F.
Published: December 2007

This paper describes the long range planning process in Husky and its use of planning process in Husky and its use of computers and especially a computer simulation model which compiles forecast data from multiple departments/subsidiaries into a finished long range plan. The model performs all the arithmetic calculations involved performs all the arithmetic calculations involved in consolidating basic input data to furnish consolidated cash flow, earnings, earnings per share, capital requirements, debt and per share, capital requirements, debt and interest schedules as well as certain operating data for a six year period. It permits easy insertion of new variables, which may represent a proposed acquisition or simply an alternate method of operating, and quickly determines the net effect of the variables.

Introduction

As one Husky executive put it, "Planning is making things happen." And, around Husky this concept of planning has been taken very seriously since 1961 when the first formal written plan was prepared. It consisted of a dozen pages of charts and other data in summarized form. Today's plan contains over 60 tables, covering all major financial and operating aspects of each department as well as consolidated totals. The Planning and Economics Department, who is Planning and Economics Department, who is responsible for developing plans, is made up of a Manager, who has direct access to the President, one Planning Coordinator, who President, one Planning Coordinator, who assembles and formulates various data into the Long Range Plan model, and a Coordinator of Operations Research, who applies computer techniques to solve complex planning and economic problems. Because of planning and economic problems. Because of computer usage, the equivalent of one-half manpower unit is devoted to the mechanics of plan preparation at the corporate level. plan preparation at the corporate level. Planning in Husky consists of a budget year plus five years of the long range plan. This process consists of three major activities:

Top management defines the overallgoals and objectives of the company, including earnings and earnings pershare growth.
Recent Advances and Emerging Technologies for Extended Reach Drilling
Authors: Payne M. L. , Wilton B. S. , Ramos G. G.
Published: December 2007

Extended-Reach Drilling (ERD) is being successfully pursued by various major operators in locations world-wide. Specialized ERD equipment and operational procedures are advancing rapidly from a number of different sources. Case histories of ERD achievements and detailed analyses of specific ERD technologies are proliferating in industry literature. This paper summarizes recent advances and emerging technologies to document available systems for ERD projects and to accelerate technology transfer and development within the industry. This paper highlights recent industry ERD projects and provides specific advances in the areas of wellbore stability, drilling fluids, drilling equipment, drilling systems, and tubular design and running.
Small Diameter Packers Can Solve Big Well Control Problems
Authors: Girola G. , Cerrito E.
Published: December 2007

Hazardous situations due to well control problems are not uncommon in exploration and production activity. Timely actions are of relevance when well conditions are time sensitive and in the presence of deteriorating situations.

In addition, precarious well conditions prevent you from taking wrong steps.

Small diameter packers and bridge plugs are often considered too weak to withstand particular environments, where pressure, temperature and mechanical stresses are present.

This paper discusses details of some utilization of inflatable bridge plugs and solid body bridge plugs, run with different techniques under limit conditions to overcome severe emergency well situations.
The Upscaling of Miscible and Immiscible Displacement Processes in Porous Media
Authors: Zhang H. R. , Sorbie K. S.
Published: December 2007

The concept of pseudo-functions has been developed as a practical technique for representing the behaviour of small-scale multi-phase fluid mechanics and heterogeneity in coarse grid simulation models. Most of the existing methods for deriving pseudo-relative permeabilities make some specific assumptions and, for this reason, they do not apply under all conditions.

This paper explores a more general upscaling technique that may be applicable to both miscible and immiscible displacements and may be applied in arbitrary geometries and for all mobility ratios. In the new method, which is based on the approach of Stone,1 the dynamic pseudo-functions are produced from a fine grid simulation using a weighted fractional flow formulation with unit-mobility-ratio flow information. It avoids calculating the potential differences and has no limitation to flow rates. The flow rates out of the coarse grid block boundaries need to be calculated only once in producing the pseudo-relative permeabilities for "miscible" flow.

The method has been validated numerically by simulating certain immiscible and experimental miscible displacements for adverse mobility ratios within an areal quarter-five-spot porous medium on both fine and coarser two-dimensional grid meshes. Good agreement in effluent/recovery performance for the fine grid model, coarse grid model and the experiment has been obtained with a substantial saving in computing cost for the upscaled model. The new method is successful in capturing both the effects of interaction of the fluid displacement process with the small scale heterogeneity and also the numerical dispersion effects and the influence of the local boundary conditions.
Technical Challenges of the Yacheng 13–1 Pipelines Design and Construction
Authors: Wilburn J. S. , Fei Miao Yuan , Roberts P. M.
Published: December 2007

The Yacheng 13–1 Gas Project is under development by ARCO China Inc. acting as Operator, with its partners CNOOC and KUFPEC. The field lies to the south of Hainan Island in the People's Republic of China (PRC). Gas, containing some CO2 and H2S, is due to be produced and processed through two offshore platforms in approximately 90 meters water depth.
Research on Helical Flow of Non-Newtonian Fluids in Eccentric Annuli
Authors: Cui Hai-qing , Liu Xi-Sheng
Published: December 2007

The governing equations, the boundary and connective conditions of the helical flow of non-newtonian fluids in eccentric annuli, which are the 4th order nonlinear nonhomogeneous partial differential equations with varible coefficients expressed by the stream function and axial velocity in the bipolar coordinate system, are established theoretically and calculated numerically by using the finite difference method.

The calculation steps of the above mentioned equations are given and, being as the examples of the experimental data of the aqueous solution of CMC in the laboratory, the helical flow of the non-newtonian fluid in eccenric annuli are calculated and analysed practically. The results are as follows: There is a secondary flow, which is very important for analysing cuttings carrying capacity of drilling muds in the annuli and for preventing drill pipe from being suck, in the helical flow of the non-newtonian fluid in eccentric annuli.The flow rate of the helical flow is enhanced by the rotation of the inner cylinder of eccentric annulus.The results of comparison between the numerically calculated flow rates and the flow rates meassured in the experiments show that the governing equations and the method of the numerical calculation of the helical flow of the non-newtonian fluids in eccentric annuli in the paper are correct.
Biodegradable Invert Oil Emulsion Drilling Fluids For Offshore Operations: A Comprehensive Laboratory Evaluation and Comparison
Authors: Xiao Lihua , Piatti Cesare
Published: December 2007

Synthetic-based mud ( SBMs ) proposed to substitute the toxic mineral oil based muds need to be fully investigated and compared on the basis of both performance and environmental acceptability. Esters, polyalphaolefins, ethers and alkyl-benzenes are the biodegradable fluids candidates to replace mineral oil and solve the critical problem of disposal of the drilled oily cuttings into the marine environment without the need of costly washing processes or transport to onshore disposal sites.

This paper describes the experimental procedures and the results of the tests and analyses performed on different pseudo-oil based mud systems: stability to contaminants, HTHP rheology, lubricity, effect on cement slurry and ecotoxicity characteristics are evaluated and compared. The study includes the investigation of the quantity of pseudo-oil retained on cuttings by the tested mud formulations.
Improved Inhibition and Rheological Properties are Observed in Amphoteric Polymer Mud System
Authors: Pinya Luo , Jian Li , Yabin Niu , Darning Zhang , Tongtai Xui
Published: December 2007

This paper presents the design and the field application of amphoteric polymer mud system to solve the problems conventional polymer caused, when drilling high reactive shale formation. It has been studied relationship of the structural features and mechanisms of polymer molecules with the performance of polymer mud. Amphoteric polymers have been developed with cationic and anionic groups in the one polymer molecule chain to be the dual function to improve the inhibition and to maintain excellent rheology of mud. This new kind of polymer mud system has been utilized in most oilfields of China, in diverse geographic locations, formation lithologies and hostile environments such as high density, high salinity and high temperature. It has been observed in the fields that this new drilling fluid has the desired optimum shale and borehole stabilization, improved rheological properties, high rates of penetration and benefit for oil formation protection.
Very Long Reach Drilling Technology Application in North Sea
Authors: Lal Manohar , Guild G. John
Published: December 2007

This paper discusses the design and application of the drilling and wellbore stability technology for an extended reach well drilled in the UK sector of the North Sea Central Graben Basin. The use of this technology can provide reservoir and development planners with an alternative means to economically and efficiently develop accumulations which are situated beyond conventional reach of drilling platforms. Very long reach drilling can enable developers to either defer or eliminate the capital spending associated with additional platforms and facilities or subsea development of satellite accumulations.

The paper addresses several areas that include mud weight and mud system, rock mechanics aspects impacting well-bore stability, well path design, drill string, casing and cementing considerations. It gives a detailed discussion of how the safe operating window for the mud weight was predicted from stability analysis and used to successfully drill the South Everest Extended Reach well (SEER T12) to TD. The paper also describes the rock mechanics data, in situ stress and pore pressure analysis, and operational practices trying to maintain the desired equivalent mud weight within the safe operating range.
Development Adjustment of Heterogeneous Sandstone Reservoir at Late Period of High Water Cut Stage
Authors: Heng Liu , Xinde Wan
Published: December 2007

Severe heterogeneity of continental sandstone reservoir has set great difficulty for understanding and smoothly developing oil field. But can we make effective adjustment at late period of high water cut stage making use of this characteristics? Daqing oil field has made useful attempt, including developing new technologies to deepenly tap the two sides potential of thin, poor and thick reservoirs through fine reservoir description; conducting development adjustment in old area by taking advantage of various differences in oil field development caused by heterogeneity to realize oil production replacement and maintain oil production stabilization at the level of relatively high annual oil production; fluid production and water cut increase rate are also effectively controlled, opening up a new way of niaintaining oil production at late period of high water cut stage, and obtaining considerable economic benefits. Practice proves that this set of methods are novel in thought and feasible economically, and can promote the development of reservoir description and developing technology. So systematic introduction is presented here just for reference for the same type of oil fields.
Modeling Transient Wellbore Behavior in Horizontal Wells
Authors: Su H- J. , Lee S. H.
Published: December 2007

For long horizontal wells, the pressure drop along the well can exceed the drawndown between the wellbore and the reservoir. Therefore, it is very important to calculate the wellbore pressure profile with accuracy when determining the productivities of horizontal wells.

A comprehensive wellbore model, based on a transient, two-fluid approach, has been implemented in a general purpose reservoir simulator. The model can handle black oil, miscible, thermal, and compositional cases. The wellbore is represented by one dimensional finite-difference grid-blocks which are simultaneously solved with reservoir grid-blocks. A mechanistic model of multiple-phase fluid flow is employed to calculate flow regime identification, interfacial drag, and friction losses between the tubing wall and fluids. Phase changes and heat transfer inside the wellbore are also rigorously modeled.

Several horizontal well examples including the seventh SPE comparative project are studied. It is found that the production profile along the well can be very different between the cases with and without wellbore hydraulics. However, for most cases, the wellbore hydraulics impact on the ultimate oil recovery is minor unless the reservoir is poorly communicated within itself. In addition, we use the transient wellbore model to study the performance of a horizontal steam injector and the transient wellbore behavior of a shut-in well.

The use of the comprehensive wellbore model can be very time-consuming from the CPU standpoint, especially for extremely transient cases. For CPU time efficiency, we also have implemented a simplified approach to model the wellbore hydraulics, based on a steady state correlation. The phase changes and heat transfer inside the wellbore are neglected in the simplified approach. The results from this simplified approach are compared with those from the more rigorous comprehensive wellbore model.
Enhanced Geostatistical Mapping of Reservoir Fluids
Authors: Pérez G. , Chopra A. K. , Severson C. D.
Published: December 2007

Monitoring fluid movement is important for selecting infill locations and completion intervals and optimizing production operations in reservoirs producing under waterflood and gravity drainage mechanisms. Estimation of the fluid contacts in the interwell regions can be difficult due to complex interactions between fluid movement and reservoir heterogeneities. Previously, we developed a systematic geostatistical fluid mapping methodology that integrates multiple sources of data and accounts for the spatial correlation and uncertainty due to the sparcity of the data.1 We found that this methodology is more efficient and accurate than the conventional mapping approach. This paper describes several enhancements incorporated into the geostatistical methodology and evaluates their advantages.

The major sources of data used in the geostatistical methodology are the surveillance and shale databases. The surveillance data provide the locations of fluids (oil, gas and water) intervals at the wells based on logs. The shale data provide the locations of shales intervals at the wells based on cores and logs. The first step in the methodology is to transform the surveillance and shale data into indicators. Then, the methodology uses indicator variograms to evaluate the spatial correlation of the data. The last step generates multiple equi-probable three-dimensional fluid and shale descriptions using a conditional simulation technique that honors the well data and variograms.

The enhancements introduced into the geostatistical methodology account for more information about the data and quantify the quality of the surveillance data. The stratigraphic coordinates and vertical proportion curves account for variations in the reservoir structure and major trends in the data, respectively. The indicator variables for fluid movement at different times and shales in different zones account for the different correlations. The quality variables account for the degree of confidence engineers assign to the log interpretations. Cross-validation of the enhanced methodology consisted of the.estimation of fluid column thicknesses at infill locations and visualization of three-dimensional distributions of oil and gas in a gravity drainage area of Prudhoe Bay. The results of the methodology are in excellent agreement with actual data.
The First Experimental Hydraulic Energy-Storing Workover Rig XXJ 300/600
Authors: Xin-yi Gu , Yun-an Wan , Wei Pan
Published: December 2007

The hydraulic energy-storing workover rig is a new type of rig invented by the authors of this paper. The first experimental rig has passed through field test (see Fig. 1). This rig differs from other types of workover rigs not only in appearance but also in working principle.

There is an energy-storing system, so some energy issued from motors or from running down pipestring can be stored and used later when needed. This new invention has obtained a lot of advantages such as energy saving, safety, less noisy, possibility of using hydraulic tubing tongs without another hydraulic system, etc.
Analysis and Design of Articulated Downhole Motor Assembly for Short Radius Horizontal Drilling
Authors: Yinao Su , Yundun Chen , Junping Zhao , Hai Zhang
Published: December 2007

This paper offers a study of a new model of articulated downhole motor assembly for short radius horizontal drilling. Theoretical analysis of this model and relationships among acting forces, deformations, structure, borehole geometry and operating parameters are given. Design principles of the assembly configuration and main conclusions are also presented.
The Application of Acoustic Full Waveform Logging in Petroleum Engineering
Authors: Yan Shuwen , Chang Guizhao , Zhang Yongmin , Qiao Wenxiao , Du Guangsheng
Published: December 2007

This article briefly introduces the application and processing of acoustic full waveform data and dipole shear imager (DSI) data. The emphasis is on the applications of compressional waves, shear waves and Stoneley waves in the calculation of mechanical parameters of rock. The actual results is given through the analysis of in-situ applications.
Fracturing Fluid Leakoff and Net Pressure Behavior in Frac&pack Stimulation
Authors: Fan Yong , Economides Michael J.
Published: December 2007

A rigorous model that describes the transient flow of a polymer solution displacing a reservoir fluid was developed as a means to account for leakoff phenomena and net pressure during frαc&pαck treatments. An exact solution with a moving interface problem was derived in terms of the pressure profiles from the fracture face into the reservoir, in turn determining the fluid leakoff rate. The results show that the leakoff rate is dependent on the fracture net pressure, fluid and rock properties and injection conditions. The concept of a constant bulk property such as the leakoff coefficient is no longer necessary (or physically meaningful) in high-permeability reservoir stimulation. The developed leakoff model has been incorporated into a fracture propagation model to predict fracture dimensions, net pressure and the interactions between leakoff and created fracture during the propagation, packing stage and fracture closing. The variation of the slope behavior of the net pressure with time at a constant injection rate suggests a new method to diagnose fracture tip screenout.
Reservoir Description From Static and Well-Test Data Using Efficient Gradient Methods
Authors: Chu L. , Reynolds A. C. , Oliver D. S.
Published: December 2007

Recently, we have shown that inverse problem theory can be applied to generate realizations of a two-dimensional permeability field conditioned to the variogram and pressure data. In this work, we extend the approach to the generation of well skin factors and two-dimensional porosity and permeability fields that are conditioned to porosity and permeability variograms and multi well pressure data. Multiwell production data as well as multiwell interference test data are considered. We show that in certain instances the incorporation of "hard" porosity and permeability data reduces the uncertainy in our estimates of rock properties and well skin factors.
X-Ray Imaging of Waterflood Fluid Saturations in Heterogeneous Rock Slabs
Authors: Huang Y. , Ringrose P. S. , Sorbie K. S.
Published: December 2007

X-ray computerised tomography (CT) has been increasingly applied in the study of rock properties and the in-situ monitoring of fluid displacements. A series of oil-water drainage-imbibition floods in laminated rock slabs have been performed in this laboratory. X-ray CT imaging techniques were used to evaluate the rock characterisation and to monitor the fluid saturation processes.

This paper describes significant technical advances in X-ray measurement of fluid saturations in very heterogeneous rock slabs. Approaches to minimising the beam hardening effect and suppressing high-frequency artefacts are also described. A number of typical experimental results indicate that our improved CT techniques can be used to accurately evaluate the rock heterogeneity and its effects on fluid displacements. These include the distribution of porosity and permeability in a laminated aeolian sandstone, the distributions of irreducible water and remaining oil saturation, as well as oil recovery. CT measurements were checked and calibrated against probe permeameter and fluid mass balance measurements and excellent agreements has been obtained.

At capillary-dominated conditions (low flow rate and unit ratio of water to oil viscosity), the average remaining oil saturation is around 35–40 % of OOIP. For flow across lamina, about 30–55% of the original oil was trapped in the upstream regions of low permeability layers due to the interaction of capillary forces with the lamination. For flow along lamina, the capillary trapping is reduced but flow bypassing results in similar levels of oil retention. The distributions of remaining oil saturation and oil recovery across lamination shows clear variations related to the local permeability and the initial oil saturation. By incorporating the detailed petrophysical analyses into a simulation model, an excellent match of experiments with numerical simulation was obtained both for cross-lamina and along-lamina flows.

These findings have important implications for the determination of field-wide residual oil saturation from core plug measurements.
Completions and Stimulations for Coalbed Methane Wells
Authors: Palmer Ian , Vaziri Hans , Khodaverdian Mohamad , McLennan John , Prasad K. V. K. , Edwards Paul , Brackin Courtney , Kutas Mike , Fincher Rhon
Published: December 2007

Amoco is producing coalbed methane from several hundred wells in both San Juan and Warrior basins. These wells were completed/stimulated in one of two ways: (1) openhole cavity completions, (2) hydraulic fracture stimulations through perforations in casing. Cavity operations are described, and new data from several cavity completions is presented and analyzed. The latest geomechanics modeling of the formation of cavities in coalbeds is presented. The model allows the growth of a cavity as tensile failure occurs, and computes increases in permeability in a stress-relief zone that extends tens of feet from the well. Critical parameters are given for the success of cavity completions. A pulse interference analysis is discussed: as well as interwell permeability, this can provide information on stress-dependent permeability. Finally, some wells which were originally cavitated did not perform up to expectation, and have been recavitated with remarkable success – these are also examined.

Amoco has tried several different kinds of hydraulic fracturing treatments. Results of comparisons between foam fracture, slick water fracture, and gel fracture treatments are presented. Statistical comparisons are given for regions outside of the fairway zone in the San Juan Basin. In the Warrior Basin, water fracture treatments with and without sand have been compared. Lastly, foamed water cleanouts, without sand, have been deployed, and their success is reviewed.
Two-Dimensional Polymer Flood Simulation
Authors: Slater George E. , Ali S.M. Farouq
Published: December 2007

The present experimental and theoretical investigation was concerned with the oil recovery and sweep efficiency obtained in a two-dimensional polymer flood. Both single phase (brine displaced polymer flood. Both single phase (brine displaced by polymer solution) and two-phase (oil and brine displaced by polymer) displacement studies were conducted. The mathematical models developed utilize the concept of the polymer resistance factor, and its variation with throughput past any given point in the flow pattern. The models were validated on the basis of good agreement observed between the predicted and the experimental results.

Experimental displacement studies were carried out in both homogeneous and heterogeneous two-dimensional transparent models, representing the quadrant of a five-spot pattern. The models were packed with glass beads of different sizes in a predetermined manner. Prior to a polymer flood, the porous medium was saturated with brine, or with brine and a refined oil, depending on the type of run. Next a polymer solution, containing a dye, was injected into the model. Effluent samples were collected, and the flood fronts were photographed at regular intervals.

For the purpose of simulation, resistance factors under two-phase flow conditions were determined, and it was shown that the average mobility of the displacing phase across a linear element of the porous medium used can be calculated-as a function of throughput across this element. This technique was generalized for areal elements, and was incorporated into the mathematical models.

The single phase, two-dimensional model considered a flow system in which the mobility of the displacing liquid was changing with time behind the flood front. The pressure distribution in the flow system at each time step was obtained, and was used to compute the sweep patterns for comparison with the experimentally patterns for comparison with the experimentally determined patterns.

The two-phase, two-dimensional model involved the simultaneous solution of the two-phase flow differential equations, incorporating the resistance factor concept in the solution scheme. An implicit-explicit technique was employed for solving the finite difference equations obtained.

Good agreement was observed between the predicted and the experimental polymer floods. predicted and the experimental polymer floods. Under the experimental conditions involved the improvement due to the use of polymer was approximately 10% for oil recovery, and 5 to 15% for sweep efficiency.
Assessing Political Risk for Foreign Investments
Authors: Downey Marian W.
Published: December 2007

Political risk assessment provides a prediction of the likelihood that future foreign government actions will deteriorate the return on a planned foreign investment. Such political risk predictions are commonly provided with great assurance by political experts. Political risk assessments are frequently quantified to two or three significant figures, so that comparisons can be made between various countries, at various times in the future. It is the contention of this paper that most of such quantifications and predictions are nonsense; that the political future is not being accurately predicted.

It is useful to describe some general axioms on predicting the future: (1) Future events can be predicted in a rigorous manner only if they represent expected outcomes of physical laws; (2) Future events can be predicted with some statistical confidence if they represent a modest extrapolation of consistent history into the future; (3) The farther into the future one predicts, the less reliable history-based predictions should be; (4) Predictions become less certain as more parameters influence the event; (5) Predictions must be less certain as more precision is required; and (6) Predictions of singular future complex political events are merely guesses, no matter how they may be swaddled in statistical mumbo-jumbo.

For proper analysis of political risk it is important to create multiple scenarios of the future, to be well acquainted with foreign politics, and to understand the economic fundamentals of the country where you are considering investments.

Such approaches allow management to look for possible flexibilities in investments, to consider insurance, hedging, and other risk abatement techniques against some of the most likely negative political/economic outcomes. The proper investor question is … "what can I do to mitigate possible future country risk?" … not, "what is the proper discount factor to allow for future country risk?" Wise investors need to take positive actions early in the investment cycle so that they may alter, rather than hope to measure, political risk in foreign investments.
Geophysical Reserve Classification Proved, Probable, and Possible
Authors: Schlagenhauf Mark , Jaynes Earl
Published: December 2007

The development of 3-D seismic is the single most important technological breakthrough in many years1. Some guidelines to separate reserves into the traditional classification of proved, probable, and possible using seismic methods have been developed and refinements to the current definitions proposed. These guidelines supplement the SPE reserve definitions and the SPEE (Society of Petroleum Evaluation Engineers) guidelines, which were published in the 80's and do not detail the use of seismic data in classification of reserves. Since the oil and gas industry is increasing the use of 3-D seismic, it is lime for the SPE to recognize the usefulness of 3-D seismic data in classifying reserves. Use of 3-D seismic data is especially important in classifying reserves in complex structural and stratigraphic traps with limited well and production data. The seismic methodology and thought process and typical interpretation steps are illustrated in two simulated case studies. Smarter, faster, cheaper, more profitable oil and gas development and reserve evaluation result from the use of 3-D seismic.
Financial Incentives for Marginal Oil and Gas Production
Authors: Terzian G. A. , Enright J. M. , Brashear J. P.
Published: December 2007

Congress and the Administration are considering Federal tax incentives to improve the economics of marginal oil and gas wells. The effectiveness of these incentives will depend on the specific provisions of the incentive, primarily whether they can be used by the large percentage of marginal well operators in AMT or without taxable income. Comprehensive assessment of Federal marginal well incentives requires a methodology that accounts for the diversity of marginal production operations. This paper presents a marginal well database, model, and methodology designed specifically to assess the costs and benefits of Federal tax incentives for marginal wells. Selected results are presented, along with general conclusions about Federal marginal well tax incentives based on numerous analyses.
An Alternative Concept of Investment for Improved Profitability Measures
Authors: Clapp Robert V.
Published: December 2007

Discounted cash flow methods for evaluating investment opportunities enjoy wide use in the petroleum industry. The two most popular measures are net present value and internal rate of return. While these two measures are generally suitable as accept/reject criteria, they are not so useful in capital rationing situations, where a ranking of projects is required. Decades ago authorities suggested that the net present value divided by the initial outlay is a better measure for ranking projects.

This kind of measure becomes more difficult to apply correctly when ail the capital costs in a project are not incurred up front, but are spread over a number of years. It is common practice to discount these future capital outlays back to the present and include them in investment (the divisor in the index). Simple examples demonstrate, however, that some obviously erroneous rankings can result from this procedure. By using an alternative definition of project investment, based only on the project net cash flows and the discount rate, we can avoid these pitfalls and obtain a better profitability measure for ranking projects.
Modeling Lease Operating Expenses
Authors: Boomer Robert J.
Published: December 2007

Neural Network modeling of lease operating expenses is more accurate than conventional modeling plus has the added advantage of being able to handle the complicated operating decisions we face today. Three examples are presented that show the accuracy of historical lease operating expense models versus Neural Network models. In addition this presentation looks at these Neural Network models in detail and covers their construction, performance, and use.
An Assessment of Perforating Performance for High Compressive Strength Non-Homogeneous Sandstones
Authors: Blosser W. R.
Published: December 2007

This paper presents the basis, approach, results, and conclusions from a study undertaken to evaluate perforation skin within an environment of high compressive strength non-homogeneous sandstone. It incorporates and integrates both field and laboratory data in an effort to better understand what component completion perforating skin contributes to total mechanical skin in the presence of drilling damage.
A Laboratory Evaluation of Acid Propagation in Relation to Acid Fracturing: Results and Interpretation
Authors: Bazin B. , Roque C. , Bouteca M.
Published: December 2007

To design acid fracturing treatments, acid fracturing models require acid leakoff values including experimental coefficients such as acid propagation rate and acid penetration distance into the formation.

This paper presents an experimental study aiming at defining a methodology for the acquisition of these parameters. The pressure variation curve obtained during a conventional acid injection experiment in a Hassler cell is analysed in relation with the dissolution mechanism. X Ray Computerized Tomography is applied to characterize the dissolution patterns. Influence of core length, acid concentration and acid flow rate are considered. Critical values are found above which the filtration process is dominated by the wormholing mechanism.

Critical lengths and rates are interpreted in terms of the Damkohler Number, i.e. the ratio of the acid brought by transport to the acid consummed by the chemical reaction. In addition, from the interpretation of the experimental results, a new methodology is proposed for the measurement of acid propagation rates and distances.
Visualisation of Drilling-Induced Formation Damage Mechanisms using Reservoir Conditions Core Flood Testing
Authors: Francis P. A. , Eigner M. R. P. , Patey I. T. M.
Published: December 2007

Reservoir conditions core flood tests have been carried out to examine the damage arising from overbalanced drilling-in operations. Gannet field cores were exposed to a number of water- and oil-based field muds currently in use by Shell Expro. Results showed that the initial permeabilities to crude oil were dramatically reduced after exposure to overbalanced mud and subsequent back production of crude oil. Thin section petrography and SEM/XRD analysis of the cores clearly showed the source of impairment in all cases to be a thin layer of mud solids plugging pores and throats exposed to the wellbore face, forming an effective permeability barrier that was not dislodged by crude drawdown under realistic drawdown. The results were confirmed by trimming of 1 cm from the wellbore face of the core that led to a restoration of initial permeability.
An Integrated Experimental Approach for Evaluating Formation Damage Due to Drilling and Completion Fluids
Authors: Longeron D. , Argillier J. -F. , Audibert A.
Published: December 2007

The paper describes an experimental approach to study the formation damage induced by drilling muds in oil bearing formations. This approach includes i) static and dynamic invasion tests on long core samples performed either under CT Scanning or with specific equipment allowing pressure measurements along the core sample, and ii) characterization of both external and internal mud cakes by means of Cryo-SEM examinations.

A series of seven water-based mud invasion experiments has been conducted on high permeability clayey sandstones. The amount and the extent of formation damage have been quantified. The results show that global oil return permeabilities vary from 44% to 90% of initial permeability depending on oil viscosity and overbalance pressure.

Hysteresis of saturations due to retention of invaded aqueous filtrate was always observed, up to 17 saturation units. This induced an adverse relative permeability effect which may significantly contribute to oil permeability impairment.
Stress Sensitivity in the Dulang Field - How it is Related to Productivity
Authors: Bin Tajul Amar Zarool Hassan , Altunbay Mehmet , Barr Duncan
Published: December 2007

All rocks are sensitive to changes in stress. In the Dulang Field sandstones, stress sensitivity is affected by differences in texture, mineralogy and clay type. In this study, we present the results of a study that shows how stress sensitivity is related to the make up of a rock and how it affects the productivity. The sensitivity of permeability - and therefore transmissivity - to stress in the Dulang Field strongly correlates with the general classification of reservoir quality with better quality rocks showing lesser sensitivity to stress. However, there are some anomalies in the stress sensitivity of porosity. While the sensitivity of permeability to stress increases with decreasing rock quality, the same does not hold for the sensitivity of porosity to stress. These deviations are explained by changes in cementation, clay type, clay morphology and clay locations in the pore structure.

Understanding why stress sensitivity changes in the Dulang Field is essential for its future development. Knowing the reasons behind reservoir behaviour allows better prediction and control of future production. Some zones will compact differently from others as the field produces. Differences in compaction are due to the different make up of the reservoir rocks. Heterogeneity in compaction affects the productivity irregularly, and therefore, the economics of the field. By knowing which zones are likely to compact first, production rates and scheduling can be adjusted to reduce the stress-induced damage. The findings of this study can be used to make more realistic prediction of future production rates via numerical simulators, thus providing a tool for improving field management and company profits. This is important not only for the Dulang Field, but also for any field where changes in stress are likely to affect production due to heterogeneous compaction of the reservoir.