bluuebunny/crossref_metadata_2025 huggingface dataset:
Drilling Safely Offshore in Shallow Gas Areas
Authors: Sandlin C. W.
Published: December 2007

Procedures for top-hole drilling should emphasize the maintenance of hydrostatic control of the well. Crew and rig safety, together with environmental protection, are the most important factors used both in the design of drilling procedures and in choosing among alternative drilling methods. This paper discusses the detailed engineering design of operating procedures, seismic interpretation, selection and maintenance of equipment, contingency planning, and crew training that are key elements to successfully drilling offshore in areas prone to have shallow gas.
Drilling Environmentally Sensitive Wells in Southern England
Authors: Redman P. J.
Published: December 2007

Recent experience at Humbly Grove and at various Southern England environmentally sensitive locations has demonstrated that wells can be drilled without unacceptable intrusion and at reasonable costs. While Southern England is an area that is particularly sensitive to any industrial encroachment a drilling programme conducted during 1985 and 1986 has helped to prove that exploration, appraisal and development wells can be drilled in an environmentally acceptable manner. Particular attention was paid by the Operator to a close working relationship with the planning and environmental officers, and the use of innovative methods of noise suppression and operational efficiency. It follows that other sensitive areas of outstanding natural beauty onshore Britain can be drilled if sufficient planning is carried out and the oil company takes a responsible and ethical approach, giving due regard to the protection of the environment in the operational methods used.
Exploration for Oil and Gas in the Michigan Basin: A Historical Review
Authors: Aminian K. , Ameri S. , Bomar R. M.
Published: December 2007

The Michigan Basin, which is centered in Michigan's southern pennisula, has been an oil and gas producing province for decades. The first substantial oil production in Michigan was obtained in 1925. Various structural and stratigraphic traps of different geological age have since been discovered and have produced oil and gas.

All Paleozoic systems in Michigan, except the Cambrian, have produced oil and gas. The Mississippian rocks were the major target of explorations during the 1930's and 40's while Devonian rocks became the major producers during the 1950's. The Ordovician reservoirs contributed most of the oil produced in the state during the 1960's. The discovery of the Niagaran reefs in southeastern Michigan during the late 1950's, which was followed by extensive exploration of the northern reef trend during the 1970's, resulted in the development of the Niagaran Reef Belt which has been the most prolific producing formation in Michigan.

The Niagaran Reef Belt still has good potential for future development especially in the southern and western parts of the state. In recent years, however, attention has been focused on a new deep target zone of Early Ordovician age in the central part of the basin termed Prairie du Chien. The first discovery well was drilled in 1980 with additional discoveries during the past two years. The recent discoveries suggest that the wells, which are drilled in the existing Devonian fields, are most favorable to encounter Prairie du Chien structures.

This paper reviews the exploration and developmental activities in Michigan and provides geological background as well as reserves estimates and reservoir characteristics for the selected producing formations. The emphasis is placed on those formations which have the most potential for future exploration and/or development.
Developing Gas Resources in Appalachian Basin Through Recompletion: An Economic Feasibility Study
Authors: Ameri S. , Aminian K. , Kutska H. M. , Waldrop L. A. , Yost A. B. , Komar C. A.
Published: December 2007

The Appalachian Basin is one of the oldest gas producing provinces in the United States. Over the years, many low permeability reservoirs of different geological ages have produced gas in this area. In recent years, the gas produced in this region has encountered difficulties in remaining competitive due to the decline in gas demand and supply surplus. In order for this gas to remain competitive and regain markets, it is necessary to reduce the cost of drilling and/or completion. One economic means of developing gas resources is through deepening/recompleting the existing gas wells to new horizons. This is particularly applicable to the Appalachian Basin where there exists many old and marginal gas producing wells.

This paper provides a general methodology to evaluate the economic feasibility for deepening/recompleting existing shallow gas wells to new horizons through slim-hole drilling. In this study, several geological units in Appalachia have been selected to demonstrate the feasibility of slim-hole drilling/recompletion as well as their relative economic incentive. Various data on these geologic units have been collected and compiled. The collected data were analyzed to delineate the production history as well as the characteristics of the formations under study. The results were later utilized in conjunction with the discounted cash flow model for determination of the rate of return and the payout time for different horizons (which are most suitable for deepening marginal wells through slim-hole drilling). In addition, the areas which are potential candidates for recompletion have been identified. These areas have further been ranked based upon the economic indicators such as the rate of return, payout time, etc. The results clearly indicate that gas can be produced at substantially lower prices in comparison to drilling new wells to the same target intervals. Thus, recompletion through slim-hole drilling provides a significant incentive for development of gas resources in this region.
An Improved Microcomputer Approach to Well Test Interpretation
Authors: Chang J. , Ershaghi I.
Published: December 2007

A direct search method called "DFS", Derivative Free Search is proposed for estimation of an initial guess of parameters in non-linear regression technique used in well test interpretations. The procedure consists of locating the neighborhood of a point where the objective function is minimum among qq points which are most uniformly distributed in a kk dimensional space. For certain cases, repetition of the procedure alone may result in a convergence of the solution. In general, however, the coordinates of the neighborhood minimum can be used as a starting point for any gradient type algorithm.
Production Data Analysis Type Curves for the Devonian Shales
Authors: Hazlett W. G. , Lee W. J. , Narahara G. M. , Gatens J. M.
Published: December 2007

Analysis of production data from the Eastern Devonian Gas Shales has shown that certain reservoir characteristics correlate with observed well performance. This result led to an investigation to determine whether some combination of these characteristics in dimensionless form could be used to construct a general set of Devonian Shale production data analysis type curves. This paper presents the results of this Investigation.

A set of dimensionless production performance graphs, or type curves, has been constructed using an analytical dual-porosity reservoir model. Although developed specifically for Devonian Shale gas wells, these curves apply generally to longterm production data from dual-porosity reservoirs. These type curves can be used to analyze long-term production data. From results of this analysis, it is possible to determine certain reservoir characteristics and to predict future performance. Example applications of the type curves to typical Devonian Shale wells are presented in this paper.
Analysis of Air Drilling Circulating Systems with Application to Air Volume Requirement Estimation
Authors: Wolcott D. S. , Sharma M. P.
Published: December 2007

Air drilling uses air or gas as the circulating medium. Because there are so many variables involved in air or gas drilling no one general method has been developed to predict the appropriate volumetric requirements for field use. In an attempt to alleviate this problem a computational model has been designed and developed which can analyze the pressure drop contributions for the complete air drilling system. This will facilitate the optimization of the air or gas pressure and volume requirements. The model is capable of analyzing the effects of variations in flow rate, sandpipe pressure, cutting size distribution, and loading.

Studies conducted using the computational model includes an analysis of several methods for determining pressure drop due to the solids phase. The results from these studies were compared with Industry Field Experience Data. Two of the methods indicated good agreement with the data.
Continuous Mixture Computational Algorithm of Reservoir Fluid Phase Behavior Applicable for Compositional Reservoir Simulation
Authors: Du P. C. , Mansoori G. A.
Published: December 2007

Development of compositional reservoir simulators is presently hampered due to the complexity of the existing computational algorithms of reservoir fluid phase behavior calculations. Through the application of the theory of polydisperse fluid mixtures we have been able to develop a number of algorithms for phase behavior calculations. In the present report we introduce one of such algorithms. In this algorithm reservoir fluid is considered to consist of a continuous mixture with a defined molecular weight/composition distribution function. Computational computer time required for the new algorithm is shown to be one order of magnitude smaller than the existing algorithms. As an example, the new algorithm is used to perform retrograde condensation calculations for two different gas-condensate reservoir fluids. Comparisons of experimental data with the calculated results indicate good agreement between the two.
Development and Application of a Limited-Compositional, Miscible Flood Reservoir Simulator
Authors: Bolling J. D.
Published: December 2007

A simulator to model immiscible and miscible displacements was developed. The simulator uses a multi-component, limited-compositional PVT model with pressure dependent K-values. A mixing parameter formulation is included to account for displacement instabilities in miscible studies. The simulator can be used for studies involving a variety of important reservoir fluids. A finite-difference numerical formulation uses each cell's pressure and component masses as primary variables. This choice offers flexibility in coupling PVT models of varying complexity to the reservoir flow equations. The formulation solves the PVT relationships, component mass balances, and a volume constraint simultaneously using a Newton-Raphson method. Of the three nonlinear terms of the component balance equations, the accumulation and well terms are treated implicitly in all variables. In the IMPES method the flux terms are treated implicitly in pressure only. If required, a fully-implicit method evaluates the flux terms implicitly in all variables. The simulator code has been written in an efficient, structured, and modular manner with vectorization of the majority of the cell and matrix calculations. Benchmark problems and examples comparing results from this model to a fully-compositional simulator are presented.
A New Simulator for Naturally Fractured Reservoirs
Authors: Sonier F. , Eymard R.
Published: December 2007

This paper describes a three-dimensional, three-phase, simulator designed for modelling fluid flow in a naturally fractured reservoir. A dual permeability system and/or a dual porosity system, is used to describe complex porous media including highly-fractured, micro-fractured and non-fractured regions. In addition to the viscous and capillary pressure forces, the matrix-fracture exchange terms can handle gravity effects with differing results depending on matrix block sizes or matrix block connections.

The conservation equations are expressed in compositional form and equilibrium K-values are used. The fully implicit equations are linearized by a Newton-Raphson iteration scheme. The method of checking the changes of phase allows a complete compatibility with the conservation equations. Because of the multi-purpose nature of the model, several different choices of discretized time-solution techniques are available. Various sequential solutions and the IMPES solution are obtained as simplified versions of the fully implicit technique.

This multi-purpose simulator is designed for solving full-field reservoir problems as well as laboratory experiments. Standard one porous medium black-oil problems can be solved with this simulator without any computer-time penality.

Examples are presented to illustrate the stability of the model, the differences in performance depending on the time-solution schemes used and the essential differences between the new approach and those used in earlier naturally fractured reservoir models.
Local Grid Refinement for Three-Dimensional Simulators
Authors: Wasserman M. L.
Published: December 2007

A static local grid refinement technique has been developed and implemented in a three dimensional, three phase reservoir simulator. The technique increases simulator accuracy without a major increase in computing cost. The method performs a "domain decomposition" whereby rectangular regions (called windows) are chosen from a coarse grid and refined in all three dimensions. Areal grid lines terminate when they hit the boundary of the refined domain. They need not be extended to the boundary of the model, as is the case in our current simulators. An efficient linear equation method is used which takes full advantage of the domain decomposition. Using this technique, the time required to solve a multi-window model increases linearly with the number of windows – not exponentially, as would be the case when no advantage is taken of the matrix structure. Results for several idealized test cases are given.
A New Innovation in Directional Only MWD Systems
Authors: Wesenberg D. L. , Polito J.
Published: December 2007

As the petroleum industry continues to feel the impact of a depressed economy and the erosion of world oil prices, some of the world's leading service and manufacturing companies have made great technical advances toward improving the drilling industry's ability to drill for oil and gas in these difficult economic times.

An example of one of the latest technical advances is a new directional only MWD system. Simplicity and flexibility provides real cost savings over many existing systems. Design simplicity has led to a helicopter supportable system which is easily delivered to both on and offshore drilling locations.

The results of a series of directional only MWD field tests and commercial jobs, run worldwide under a wide variety of drilling conditions, are presented in this paper. The results substantiate the viability of the low cost, high reliability approach to the directional-only MWD market.
Automated Pipe Handling: A Fresh Approach
Authors: Brugman J. D.
Published: December 2007

A new generation pipe racking system has been developed which combines the functions of traditional power pipe racking systems with the functions of remote controlled floor mounted iron roughnecks into one machine for automated pipe handling. The machine enables a single operator to execute all the pipe tripping functions from the floor to the monkey board. It incorporates stand makeup and breakout within itself, which eliminates the need for other equipment and people to perform those functions. The one operator can individually control each function manually, using observed position, or he can let automatic sequences take over. Improvements over previous racking systems and iron roughnecks include:

– One-man operation versus up to five-man operation, and no derrickman; – Total pipe handling – drill pipe and drill collars without jaw changes; – Improved safety through elimination of manual floor operations.

This paper describes this system, which represents a major step toward a practical automated drilling rig, and documents its performance during actual field operations.
An Evaluation of the API Oil/Water Retort Apparatus and Procedure for Monitoring Oil in Offshore Discharges
Authors: Jones M. , Bagnall R. A.
Published: December 2007

The API Oil/Water Retort Apparatus was evaluated for use in monitoring oil content of offshore drilling discharges. A total of 526 samples of various drilling muds were retorted with 5 different models of two basic types (heating element and heating jacket) and 3 sample sizes (10, 20, and 50 mL). The 20 mL heating element retort was determined to be the best unit for this purpose in terms of accuracy, speed, convenience, and cost. The minimum amount of oil in a mud that could accurately be measured was 1% (v/v), although <1% could be detected. To achieve precision and accuracy of retort measurement required modifications of the API procedure. Retort extraction was compared to shaker and soxhlet extraction and to the proposed EPA cup sheen test.
Improving BHA Tool Reliability with Drillstring Vibration Models: Field Experience and Limitations
Authors: Burgess T. M. , McDaniel G. L. , Das P. K.
Published: December 2007

Statistics on BHA tool components revealed significantly more failures in vertical holes than in deviated holes. The difference was attributed to damping of vibrations at stabilizers in deviated holes. Modelling of drillstring vibrations showed that high shocks associated with transverse vibrations of the BHA were the probable cause of failure.

A model of the transverse vibration response of the BHA was developed to improve the design and the location of the tools in the drillstring. The model was able to associate the failure of many MWD and other components with resonance in the drillstring. Application of the model at the BHA planning stage reduced the number of tool failure attributed to BHA design and operating conditions by about one half. As a consequence a rig site program was developed.

This paper gives examples of field case studies, describes the rig site model, and discusses the sometimes real limitations of BHA vibration models.
BHA Lateral Vibrations: Case Studies and Evaluation of Important Parameters
Authors: Allen M. B.
Published: December 2007

Recent efforts to compute and measure drillstring and bottom hole assembly vibrations have shown that vibrations occur in the BHA which do not coincide with computed natural frequencies for axial and torsional vibrations. Analysis of BHA failures has indicated that lateral vibrations in the BHA was the probable cause of some failures.

This paper presents a collection of bottom hole assembly failures. The possibility of lateral vibrations being the cause of a failure has been evaluated by considering circumstances surrounding the failure and making comparisons to a lateral vibration computer model. Similarities between lateral vibration failures are analyzed to determine what parameters are important in identifying the susceptibility of a bottom hole assembly to large lateral vibrations. The parameters include depth, hole size, ratio of hole size to drill collar diameter, and stabilizer placement.

The results of this paper allow the drilling engineer to avoid BHA designs which have been shown to be susceptible to lateral vibration failures and identify designs which should be evaluated in more detail such as with a lateral vibration analysis.
Preliminary Field Test Results of Diamond-Enhanced Inserts for Three-Cone Rock Bits
Authors: Salesky W. J. , Payne B. R.
Published: December 2007

Increased penetration rate accompanied with longer life have always been primary objectives of both rock bit manufacturers and drilling contractors. Tungsten carbide inserts have been used in rock bits for over 30 years and are a mature technology. Synthetic diamond insert technology may prove to be the next step in three-cone rock bit performance.

For the past 24 months a development program has been conducted focusing on the application of high pressure diamond technology to three-cone rotary rock bit drilling. A diamond coated insert has been developed that shows little wear even when run in the gage row, after drilling over 200 hours and 6000 feet of formation.

This paper reviews the design and laboratory testing of diamond enhanced gage Inserts with an emphasis on field performance. The impact of this technology on bit life, penetration rate, and drilling costs will also be discussed.
Dynamic Drilling Strategy for PDC Bits
Authors: Wojtanowicz A. K. , Kuru E.
Published: December 2007

A new mechanistic drilling model for PDC bits was presented. The model was fully explicit with physical meanings given for all constants and functions. The response of the drilling model to weight-on-bit and cutters removal and the stability of constants were tested using some field and laboratory data. The preliminary results were encouraging.

The concept of maximum bit performance (MBP) curve was introduced. The curves represented the maximum values of the average drilling rates for various pre-assumed footage values. In contrast to elaborate drilling models, the MBP curves are a single, comprehensive correlation representing drilling bit behavior in a formation. For calculating purposes the curves were normalized and thus they became insensitive to drillability change vs. depth as well as formation abrasiveness. The curves were plotted and analyzed for both rockbits and PDC bits. The simple method for using the MBP curves for drilling optimization was presented.

A new method for preparing a multi-bit drilling program, the dynamic drilling strategy, was developed. The dynamic drilling strategy provided the best combination of PDC bit runs to achieve the minimum drilling cost for a long borehole interval. The method was numerically compared to the conventional drilling optimization and to field practices. Considerable savings of 30% and 300% respectively were estimated.
A Comparative Analysis of PDC Bit Performance in Colorado's D-J Basin
Authors: Spradlin W. N. , Sheshtawy A. , Lohmann E.
Published: December 2007

The following is a study of polycrystalline, or PDC, bit performance in Colorado's D-J Basin, Weld County, Colorado. Data utilized in the study incorporates over 200 bit records in the area of study, from wells drilled within the last three years. Analysis of data in the area of study is based on examination of the cost per foot drilled for each well, as well as each bit run.

Results indicate that rig efficiency has generally increased over the last three years when using either conventional or PDC bits, with the lowest cost per foot being achieved by proper application of PDC bits. A statistical difference between performance of differing types of PDC bits is noted in the data, which indicates optimum PDC selection should be based on available performance and geologic data.
Can Fluorohydrocarbon Elastomers Used in Oilfield Service Be Improved by Varying Carbon Black Type?
Authors: Cain D. E. , Peters L. A. , Pugh T. L.
Published: December 2007

Elastomers for oilfield seals are often specified by hardness and generic type. Experienced compounders recognize that hardness of a seal can be achieved by many different formulations. The filler type and amount plus the cure system in these formulations have the most profound influence on the hardness. Carbon black and finely divided minerals are the most common fillers used in elastomer compounding.

This investigation evaluated the influence of the effect of carbon black particle size in fluorohydrocarbon formulations. Several fluorohydrocarbon compounds were formulated with carbon black types ranging from N330 to N990. These compounds were aged by exposure to aqueous hydrocarbon and gaseous fluids, which were intended to simulate oilfield environments. Changes in the physical properties of these compounds were determined and tabulated for comparison.

CONCLUSIONS
Improvement of BOP Sealing Systems Is an Urgent Requirement for HP-HT Deep Wild Well Control
Authors: Alliquander O. , Hingl J. , Szabo G.
Published: December 2007

A recent high pressure and temperature wildcat well control operation of the Hungarian National Oil and Gas Co. on a 4 239 m/13,907 ft/deep well required 46 days up to capturing in closed cooperation with numerous major and service companies. The operating shaft damage of a BOP caused the blowout. Up-to-date technologies and materials, among others sophisticated elastomers were introduced because of the extremely severe conditions.

The wellhead temperature exceeded 130°C /300°F/, the flowing pressure varied between 36 and 48 MPa /from 3100 to 6900 psi/, and the produced fluids were aggressive-gas contaminated, superheated brine water, i.e. steam.

The sealing elements of the recommended BOP failed to work after 48 hours service, thus jeopardizing the specially designed snubbing operation.

On the basis of the case history, the conclusion of the paper calls for improvement of /1/ the wellhead equipment and blowout preventer systems, /2/ the achievement of harmony in the field of sealing elastomers and the employment of metal-to-metal seals and /3/ proper selection of elastomer formulations on the basis of environmental agents. The above three are the preconditions of successful wild well control operations.
Cementing High-Angle Wells Using Cement-Expanded Formation Packers and/or Casing Rotation
Authors: Webster M. B. , Otott G. E. , Rice D. L.
Published: December 2007

This paper describes an ongoing program to improve primary cementing results for casing in high angle or deviated wells. Thums Long Beach Company, acting as Contractor for the City of Long Beach, Operator of the Long Beach Unit, has drilled and completed over 1100 wells from four man-made islands and four land filled pier locations. The average well exceeds 55° hole angle with some wells exceeding 80° from vertical.

Two techniques have been recently utilized to provide a competent shut-off between the completion interval and the surface. The first technique employs the installation of a twenty foot (20′) Cement Expanded Formation Packer usually set in a competent shale immediately above the completion interval. The CEFP is expanded with cement at the completion of the primary cement job. This method employing specifically approved equipment has proven so successful that the State of California will accept a successful installation as a substitute for the normally required water shut-off test.

The second technique involves the rotation of a selected length of casing at the bottom of the casing string. A specially designed casing swivel is integral to the casing string and is rotated by a spline drive installed on drill pipe. The casing segment is rotated during a conditioning period and while the cement is being placed. Up to 600′ of centralized casing has been rotated with excellent results in high angle wells.
Drilling Time Predictions from Statistical Analysis
Authors: Noerager J. A. , White J. P. , Floetra A. , Dawson R.
Published: December 2007

Drilling, completion and trouble times have been collected for 489 platform wells and 51 subsea wells drilled in the North Sea. Equations have been fit to these data bases; these equations can be used to estimate times for wells to be drilled in the future.

Measured depth is the most important factor in predicting well times. Spud date and learning effects are also important. Hole angle has only a minor influence outside of its effect on measured depth.
The Application of Limited-Entry Techniques in Massive Hydraulic Fracturing Treatments
Authors: Cramer D. D.
Published: December 2007

Application of the limited entry-technique has been extended to massive hydraulic fracturing (MHF) of low permeability formations, such as the Niobrara and Codell intervals of the DJ Basin.

Analysis of the bottomhole pressure data of these treatments indicates that proppant alters the mechanical configuration of the perforations, as evidenced by a change in the magnitude of perforation friction in opposition to the Bernoulli constant energy equation. The practical significance of changing pressure drop across perforations in limited entry stimulation treatments is that it alters treatment fluid distribution and injection rate profiles among the multiple intervals. This can result in zonal shut-off due to insufficient pressure drop (i.e., zone fracture pressure> wellbore pressure) or zonal sand-out due to inadequate pad volumes and/or treating rate.

This paper investigates the mechanisms involved in fluid and slurry flow through perforations. Fluid mechanics research and experimental laboratory and field testing are referenced. The effect of proppant on perforation friction is calibrated. Limited entry design and procedural guidelines for large scale fracturing treatments are presented to assist in achieving the desired placement of fluid and proppant into individual zones. Fundamental limitations of the limited entry technique in MHF applications are also discussed.
The Effect of Excess Propped Fracture Height on Well Productivity
Authors: Cipolla C. L. , Lee S. J.
Published: December 2007

A three-dimensional reservoir simulation study indicates that propped fracture height in excess of the productive thickness of the reservoir can add to well productivity. The effect of excess propped fracture height is more evident when fracture conductivity is relatively low compared to formation conductivity. The simulations indicated that in cases where dimensionless fracture conductivity (Cr), as defined by Cinco et al,1 is less than ten, any excess fracture height will increase well productivity. The magnitude of the productivity increase is a function of the dimensionless fracture conductivity and excess height.

A series of type curves is presented that compares the transient pressure behavior of hydraulically fractured wells where the propped fracture extends uniformly above and below the reservoir to the same wells where there is no excess fracture height. In addition, a comparison of the pseudo steady-state productivity increase that would be expected for a hydraulically fractured well is presented for wells with and without excess propped fracture height.

Selected cases are presented to illustrate the economic impact of excess propped fracture height and how it may affect proppant selection.
Modified Fracture Stimulation Techniques for Shallow Oil Sands in Carter County, Oklahoma
Authors: Marple G. T. , Ruley G. E. , Worley H. W. , Freeman E. R.
Published: December 2007

Carter County in south central Oklahoma has 1000's of shallow oil wells producing from various formations less than 2000' in depth. These zones, although shallow, still require some stimulation to facilitate economic development. When a hydraulic fracturing procedure is dictated, the treatment typically utilizes lease crude or brine water as the carrying medium to transport a maximum sand concentration of 3 to 5 pounds per gallon. Preliminary studies have shown that by modifying this conventional fracture design, increases in well productivity may be achieved. These modifications include a more efficient carrying medium and an improved permeability contrast.
Ultra-High Conductivity Fracture Stimulations: A Case History
Authors: Barby B. G. , Barbee W. C.
Published: December 2007

Ultra-high sand concentration fracturing is taken one step further by achieving tremendous fracture conductivity with extra large proppants. The results of these fracture stimulations demonstrate that the Morrow Formation can be impregnated with very large proppants in high concentrations to achieve production improvements.
Recent Advances in Fracture Evaluation
Authors: Noblett B. R. , Fertl W. H. , Guy J. O.
Published: December 2007

Conventional acoustic logging devices have long been used for locating natural fracture systems which intersect the wellbore in a horizontal or near-horizontal plane. Such devices typically employ shear wave detection techniques applied to full-wave acoustic signatures. Loss of shear wave amplitude, coupled with increasing transit times in the presence of a fluid-filled fracture system, is used to determine fracture location. As the direction of fractures shifts toward the vertical plane with respect to the intersecting wellbore, conventional acoustic devices become unreliable for fracture detection purposes.

An acoustic logging system which uses circumferentially propagated waves can be used to identify and evaluate the presence of vertical and/or near-vertically oriented fractures in fluid-filled boreholes. When run with an orientation section, this new circumferential logging instrumentation is also capable of determining the major lateral direction of fracture systems and regional stress patterns.

Field examples and recently developed interpretive software developments are presented.
Study on the Effect of Pore Blocking Mechanisms on Formation Damage
Authors: Wojtanowicz A. K. , Krilov Z. , Langlinais J. P.
Published: December 2007

The process of formation permeability damage due to solids movement and capture was quantitatively modeled by using principles of deep bed filtration and chemical reactions kinetics. The developed theory describes the pore blocking mechanism caused by particles from completion fluids (foreign particles invasion) as well as the mechanism of release and capture of rock fines (in-situ mobilization).

For practical applications, this theory was used in the context of pattern recognition, ie, to examine the experimental data on rock permeability change vs time from the laboratory flow experiments. Thus, a straight line section of data plotted in a certain system of coordinates indicates the type of formation damage occurring.

The verification study was performed in two series of laboratory experiments. In the first, a drilling mud, consisting of a contaminated completion fluid, was pumped through the simulated synthetic rock. In the second, four typical, solids-free completion brines were pumped through actual samples of water sensitive, unconsolidated sandstones taken from Adriatic Sea gas fields.

The experiments revealed the applicability of the theory and the method of diagnostic plots to describe and analyze formation permeability damage.
Surfactants Can Affect Corrosion Inhibition of Oil-Field Steel
Authors: Growcock F. B.
Published: December 2007

Surfactants greatly improve the performance of t-cinnamaldehyde (TCA) as a corrosion inhibitor for J55 steel in hydrochloric acid. They function in this capacity by enhancing adsorption at the surface; increased solubility or dispersibility of the inhibitor is an incidental effect. The cationic surfactant n-dodecylpyridinium bromide (DDPB) is effective in this regard far below its critical micelle concentration, probably as a result of electrostatic adsorption of the monomeric form of DDPB; this leads to formation of a hydrophobic monolayer, which attracts the inhibitor. On the other hand, an ethoxylated nonylphenol (nonionic surfactant) acts by incorporating the inhibitor into micelles, which themselves adsorb on the steel surface and facilitate the adsorption of TCA.
Free World Total Primary Energy Demand: An Econometric Approach
Authors: Dougherty E. L. , Al-Blehed M. S.
Published: December 2007

This paper presents results of a modeling study undertaken to quantify the effects of recent changes in energy prices on future total energy consumption and oil's market share. To predict these two quantities vs time, five pairs of regional models, which together span the Free World, were developed. The explanatory variables in the models are income, population, total energy price, crude oil price, and non-oil energy price. The most recently published data were used to estimate coefficients in these models. Projections of total energy demand and oil share through 2000 for different scenarios are given. The sensitivity of future demand for crude oil to changes in income and prices is examined. Both multiple regression and linear programming were used to estimate coefficients. These two methods gave essentially identical results under identical conditions. Because the LP approach allows greater flexibility in imposing judgemental bounds on coefficients and selectively weighting historical data, it was used to obtain the coefficients presented.

We find that considerable judgement must be applied to obtain coefficients that cause the models to yield reasonable results. The tailored computer system developed to use the models allows hindcasting as well as forecasting. Hindcasting experiments reveal that a perfect history match does not always mean that the model will provide reasonable projections.
Exploration Strategy Development Under Volatile Pricing Conditions
Authors: Caldwell R. H.
Published: December 2007

This paper discusses techniques which may be used to evaluate the risk/reward relationship of exploration drilling under conditions of volatile pricing. The theme is developed through case studies where historical drilling statistics and discovered reserves are analyzed to develop probability functions which characterize each play. This information is further analyzed to develop ranking criteria as a function of oil price to characterize each play.
Thermal Model for Establishing Guidelines for Drilling in the Arctic in the Presence of Hydrates
Authors: Roadifer R. D. , Godbole S. P. , Kamath V. A.
Published: December 2007

Natural gas hydrates exist in the North Slope of Alaska, the Northwest Territory of Canada, the U.S.S.R. and offshore waters deeper than 5,000 ft. Actual hydrate cores have been obtained from the Gulf of Mexico and the western coast of Guatemala. In addition, ARC0/EXX0N have recovered a gas hydrate core sample at a depth of 666 m in 1972 from N-W-Eileen Number 2 well in Prudhoe Bay, Alaska.

Drilling through hydrate deposits causes mud gassification and an increase in the drilling rate. Chilled drilling fluid with higher mud weight at high circulation rates are routinely used to avoid any possible problems due to severe gassification. This study involves a development of a thermal simulator to determine the position of the hydrate dissociation front and gas influx rate as a function of drilling conditions.

The solution of this problem involves the tracking of a moving boundary between thawed and unthawed hydrate regions. This is a r-z simulator for unsteady state heat conduction in the presence of a moving boundary. The heat losses to overburden as well as underburden are accounted for in the formulation of the model. A finite difference numerical scheme is used to generate temperature profiles in thawed and unthawed zones, and the hydrate dissociation rate during drilling.

Results are presented in graphical form for reservoirs with a range of porosity, geothermal gradients, mean annual surface temperatures, and pressures relevant for in-situ hydrate deposits in the arctic. Furthermore, these results provide quick guidelines for the selection of drilling variables, such as mud temperature, mud weight and circulation rate.
Pump-Off Control Application in Thermal Recovery Operations
Authors: Yoch R. J. , Williams R. L. , Jones J. A.
Published: December 2007

Santa Fe Energy Company (SFEC) has planned to install pump-off controllers (POC's) on all new wells in the Midway-Sunset Field and is in the process of retrofitting the majority of its existing wells. This effort is the result of a year long, 88 well study begun in 1984 on pump-off control effectiveness on a predominately steam stimulated, Potter sand property. After a total capital investment of $345,000 ($4,100 per well), the 1985 gross revenue attributed to the POC installation was $472,500, and the trial achieved a ten month simple payout. This revenue does not include the one time cash rebate of $72,300 offered by the local utility for power consumption reduction. The revenue increase came from a 31% reduction in power consumption ($81,700 savings), a 23% reduction in well work expenditures ($66,800 savings), and a 47 BOPD increase in lease oil production ($343,100 revenue at $20/bbl oil, 1985 prices). The increase in production was due to reduced downtime, reduced problem frequency, and an accelerated recovery in the first month of post steam stimulation response. Details of the cost savings from the field study are provided in the discussion. A cursory evaluation of a 519 well expansion to three other Santa Fe properties will be conducted.
Observations and Recommendations in the Evaluation of Tests of Hydraulically Fractured Wells
Authors: Economides M. J.
Published: December 2007

The pressure transient behavior of hydraulically fractured wells has been the subject of considerable study over the past few years. Several investigators have presented solutions of the fundamental equations, identified qualitative diagnostic trends and suggested interpretation techniques. This paper presents a systematic approach to the problem along with substantial observations on the potential of unique interpretations.

Pre-treatment tests are considered here as necessary. Well tests in tight formations are often of very short duration, to allow the use of established methodologies. Hence, a technique to calculate the maximum reservoir permeability from a short well test is offered.

In the case of post-treatment tests the data are treated using the convolution/deconvolution techniques and influence functions. The term "influence function" defines a relationship between pressure response and time at a constant unit surface flow rate. Although drawdown well tests have advantages over buildup tests because they are used while the well is producing, their interpretation has been hampered by varying flow rates. Conventional interpretation techniques assume either constant well flow rate or controlled variation of it. Pressure buildup tests are conducted with the well flow rate equal to zero and are, as a result, predominant.

In the case of post-treatment well tests of hydraulic fractures a lengthy buildup test and the ensuing shut-in may result in severe damage to the generated fracture. Thus buildup tests are not always desirable for post-treatment evaluation. The convolution/deconvolution techniques and influence "functions," by normalizing the pressure response to a unit flow rate, permit the use of standard techniques for the analysis of drawdown tests.

The interpretations presented here utilize new versions of pressure and pressure derivative type curves including the dimensionless fracture storage coefficient, and the dimensionless fracture conductivity. Based on observations of the sensitivity of the response to these parameters, three type curves have been developed, one for low, one for intermediate, and one for high conductivity fractures. The choice can be made on the basis of pre-treatment analysis and the fracture design. The storage and the half-length of the generated fracture can then be calculated with reasonable confidence.
Mechanical Interactions in Branched or Subparallel Hydraulic Fractures
Authors: Jeffrey R. G. , Vandamme L. , Roegiers J. -C.
Published: December 2007

A numerical simulator has been used in the study of a hydraulic fracture with two nearly parallel branches. The pressure required to propagate a branched fracture is found to be significantly higher than the pressure needed to extend a single planar fracture. Interactions with natural fractures have also been studied. The results show that hydraulic fractures may develop offsets at crosscutting natural fractures. Slip occurring on weakness planes after the hydraulic fracture crosses them has been modeled, demonstrating a reduction in fracture width at the site of the offset. This reduction in width may lead to proppant bridging at that location. An elastic calculation for the size of zones within which sliding may occur on preexisting weakness planes around a pressurized fracture indicates that the extent of these zones is proportional to the length of the pressurized fracture. Slip in such zones is controlled by the far-field stress, the pressure in the fracture, and the orientation and frictional properties of the weakness planes.
Application of Machine Computation of Well Logs in California
Authors: Strozier C.A. , Marquis G.L.
Published: December 2007

This paper was prepared for the California Regional Meeting of the Society of Petroleum Engineers of AIME, to be held in Santa Barbara, Calif., Nov. 17–18, 1966. 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 requested 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 discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Machine computation from well bore measurements can provide more data for analysis than is practical inn many cases, from manual computation. Machine computation minimizes arithmetic time for the individual studying well logs. His time is freed for analyzing the computed data, and he can usually command more data to use in his evaluation. The result is a more comprehensive well evaluation than is normally obtained.

Machine computation lend itself to high density information evaluation and precision calculations While this is not a normal requirement of routine well logs, there are applications for this capability.

In most areas in the State of California, the Engineer, Geologist, or Log Analyst is faced with the problem on each well of evaluating hundreds of feet of sand. From the standpoint of time alone, this makes a detailed evaluation very difficult and at times impractical. This paper discusses applications of machine computation to process well log measurements and tabulate the resulting data.

On standard open hole suite of fresh mud logs emphasis is placed on several values of porosity determined independently and in combination from measured values of formation acoustic travel time and bulk density. Water saturation evaluation is approached from computed formation resistivity factor ratios (F ratios) and apparent formation water resistivities (R .) or water saturations (S ,.). Examples of the application of this program are presented.

A second important application of machine computation is the analysis of Neutron Lifetime Logs. The connate waters encountered in California are relatively fresh (30,000 ppm NaCl) with formation porosities from 20–30%. In using this log in California or any other area of difficult interpretation, machine computation greatly reduces the analyst's work and improves his evaluation.

A third area of application discussed is high-precision wireline measurements.