bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Storage Conditions and Time of Storage on Performance of Perforating Charges
Authors: King G. E. , Buckley P. D.
Published: December 2007

An extensive study of the weather conditions affecting the performance of a tightly controlled set of perforating charges has shown that a large amount of the variance of performance of charges is caused by the storage conditions of both the charges and the detonating cord. The tests were run on a single lot of commercially available perforating charges that were made under extremely rigid quality control methods especially for the test. After initial testing of 15 of the charges to establish a level of variance, the charges were separated into lots and stored at conditions simulating desert, sea coast, mountains, and arctic environments. Charges were stored in both unsealed and moisture resistant, packaging. Charges were removed and fired at regular intervals to establish performance.

Sections of detonating cord were also stored at the weather conditions in unsealed and moisture resistant packaging. The detonating cord was tested after one year in storage. X-ray inspection was evaluated to determine if it could be used to Bpot potential problems in perforator performance.

Long-term exposure to humidity and high temperature storage were proven to be detrimental to charge performance. Cyclic temperature storage was a factor in the degradation of detonating cord.
An Improved Perforating Technique for Rod-Pumped Wells
Authors: Gohar A. , Huber K. B. , Miszewski A.
Published: December 2007

It is now widely recognized that to maximize productivity from certain formations, the well should be perforated underbalanced and control fluids should not be allowed to enter the reservoir during subsequent production operations. During the last few years, tubing-conveyed perforating techniques have been developed for rod pumped wells which allow them to be perforated in an underbalanced condition and then be immediately produced. Thus, completion fluids cannot interact with the formation. The technique described in this paper is an improvement over existing technology. It takes advantage of the fact that insert type sucker rod pumps are easier to run than the tubing string.

This new technique combines the firing head and a bypass assembly with the pump, rather than the tubing and gun string, which allows them to be run and retrieved independently. This improves the safety and operational flexibility of the system since the firing head is not connected to the gun until the moment of firing and the tubing string does not have to be significantly modified for the operation. A light pulling unit or crane is all that is required to retrieve the firing head or to run a subsequent Through Tubing operation.

This paper describes the new equipment and its operation and shows how the unique features of the design have been used to enhance the effectiveness of this type of rod pumped completion. Safety, reliability and cost-effectiveness are discussed. A review of the operational results for a group of wells in the Meleiha Field in Egypt which were completed using this technique is included and mention is made of other potential completion strategies.
A Mechanistic Model for Predicting Annulus Bottomhole Pressures in Pumping Wells
Authors: Papadimitriou D. A. , Shoham O.
Published: December 2007

A mechanistic model has been developed for the prediction of pressure gradients in pumping wells. The proposed model takes into consideration recent developments in two-phase flow through an annulus configuration, is based on the concept of zero net liquid flow, and rigorously incorporates the important flow and system parameters.

A detailed sensitivity analysis was carried out for a typical pumping well case. The effect of the system and flow parameters on the bottomhole pressure is demonstrated. More accurate results can be obtained by this model, as compared to previously published methods, due to the rigorous analysis used in the model development.
Transient Considerations for Flow Measurement at Gas Production Facilities
Authors: McKee R. J.
Published: December 2007

Flow conditions at gas production facilities are usually not the steady and undisturbed conditions which have been used during research to derive orifice coefficients or during meter calibrations. Wellhead pressures and flows are often transient in nature and can vary over a wide range in relatively short periods of time. Flow measurements at typical production installations are subject to more difficult transient conditions than in many other measurement situations. If these dynamic conditions are not taken into account and controlled in the meter installation design and instrumentation implementation, then the transients can lead to significant errors in measured flows.

A research program for transient effects on electronic flow measurement (EFM) has been planned as a part of the Gas Research Institute's (GRI) metering research effort at SwRI. The objectives of the research program include the development of design and installation guidelines for minimizing EFM susceptibility to transient-induced errors. The successful metering system will result from specific recommendations for piping arrangements, gage lines, transducers, and signal processing specified for given transient conditions. This paper describes the transient-induced errors affecting both the primary and secondary orifice metering elements, and discusses the requirements to account for and minimize these errors. Past research work has defined the errors caused by pulsations and some transients, and has addressed the question of what is required to eliminate such errors. Combining this information with additional data to be developed during the planned research will lead to a description of an EFM system to minimize errors in transient flow measurement situations.
Displacements in Eccentric Annuli During Primary Cementing in Deviated Wells
Authors: Jakobson J. , Sterri N. , Saasen A. , Aas B. , Kjøsnes I. , Vigen A.
Published: December 2007

This paper presents an experimental study of the displacement process in a 60° deviated laboratory well with a 55 % eccentric annulus. The inner pipe was lying near the bottom of the simulated wellbore. In this geometry the displacing fluid have a tendency to flow in the upper, wide part of the annulus, and to bypass mud in the narrow part of the annulus. The results from the tests were applied to practical field operations.

The data presented show how fluid viscosities, degree of turbulence and buoyancy forces particularly affects the displacement process in the lower, narrow part of the annulus. When a displacing fluid with higher density than the displaced fluid was used, the simulated mud in the narrow part of the annulus floated up into the wide part and was transported away. This reduced the tendency of the simulated cement to bypass the fluid in the narrow part of the annulus. Significant improvements in the displacement efficiency were observed.
Artificial Lift Methods for Marginal Fields
Authors: Kahali K. , Rai R. , Mukerjie R. K.
Published: December 2007

Production from offshore fields has been dominating in the past and will continue to dominate in the future. It is expected that more than 50% of the production will come from the deeper, waters. Most of the new discoveries in the Indian offshore have been marginal in nature, where economics dictate selection and application of production systems. As a part of the development, many wells are being completed subsea. Due to the marginal nature of the fields, the self flow tram these wells has been minimal, necessitatinq application of artificial lift at the earliest and in many cases right from the begining. In the present study, an attempt has been made to evaluate the suitability of the available lift systems with special reference to its application in marginal fields of Indian Offshore. Also, some case histories of applications of different artificial lift modes have been reviewed which provide important parameters to evaluate their suitability and the field proven technology.
Long-Term Testing of Vertically Fractured Gas Condensate Wells
Authors: Søgnesand S.
Published: December 2007

This paper examines the effect of retrograde condensate blockage on long-term well performance of vertically fractured gas condensate wells. A method is presented to correct the effect of condensate blockage using the concept of time-dependent skin factor. Also documented is important differences in productivity loss due to condensate blockage for vertically-fractured and radial, unstimulated wells.

The effects of fluid properties and relative permeabilities are considered, as is the effect of production mode — i.e., constant-rate versus constant-sandface-pressure production. Results are based on numerical simulations using a fine-grid, vertical-fracture geometry model with a modified black-oil PVT formulation.

The stimulus for the work has been the historical performance of several North Sea condensate fields producing from chalk formations. Well performance history from these wells, which have been stimulated by large acid treatments, indicates no appreciable deterioration of well performance (i.e., skin) during the first ten years of depletion. Also, the author has not found any publications on productivity loss due to condensate blockage in vertically fractured wells, despite the common practice of stimulation in low-permeability gas condensate reservoirs.

The results show considerable differences in long-term productivity between stimulated and non-stimulated gas condensate wells. The argument is made that moderate-permeability wells, which otherwise would not require stimulation, may be prime candidates for stimulations to reduce or eliminate the effect of condensate blockage. Stimulation of such wells would be justified mainly on an analysis of the percentage of well pressure losses that are caused by reservoir and near-wellbore effects, relative to total pressure losses including flow through tubing.
Analysis of Buildup and Drawdown Tests With Variable Wellbore Storage and Skin
Authors: Soliman M. Y. , Hedayati S. , Daneshi T.
Published: December 2007

The partial differential equation describing the flow of fluid in a porous media was derived by combining the continuity equation (material balance), Darcy's equation of flow and the equation of state. The partial differential equation was linearized by neglecting high order gradient terms such as (∂2p/∂r2). The resulting partial differential equation is the well known parabolic diffusivity equation. This diffusivity equation which incorporates the effect of welibore storage and skin factor on the inner boundary condition has been solved1 and the solution is used to analyze the pressure drawdown. The pressure buildup testing theory was derived from the pressure drawdown theory described above.

By definition, a pressure buildup test consists of two parts; the drawdown (flow) and shut-in periods. Traditionally, the equations defining a buildup test were derived using the diffusivity equation utilizing the principle of superposition. Thus it was implicitly assumed that the equations governing fluid flow were linear and that constancy of inner boundary conditions prevail throughout the drawdown and shut-in periods. Although these conditions are usually met, certain conditions may exist that prevent application of superposition. For example, requirement of linear partial differential equation which is essential for the application of superposition, is not fulfilled when the turbulent condition prevails during drawdown period. During the shut-in period however, the fluid velocity inside the reservoir diminishes quickly and turbulent effect ceases to exist. This turbulent flow is known to occur in high permeability gas reservoirs producing at high rates.

The turbulent flow is usually accounted for by modifying the fluid flow equation for laminar flow by adding turbulent flow term.
An Expert Advisor Program for SSC and NACE MR-01-75
Authors: Craig B. D. , Thompson R. S.
Published: December 2007

Produced petroleum fluids containing hydrogen sulfide (H2S) gas are often referred to as "sour". Hydrogen sulfide gas in the presence of free water can cause certain metal alloys to crack which is referred to as Sulfide Stress Cracking (SSC). SSC of metals is a serious safety issue for the petroleum industry and is addressed by the NACE (National Association of Corrosion Engineers) MR-01-75 document1 which establishes requirements for metallic materials suitable for sour environments. Sour service materials selection is a complex problem often facing personnel not experts in this area.

Since SSC and the NACE MR-01-75 document are not easily understood by most petroleum engineers, an expert advisor computer program was developed to integrate expert comments, SSC fundamentals, key metallurgy concepts, and NACE MR-01-75 requirements.2 This program is termed an expert advisor rather man an expert system because it seeks to teach the knowledge rather than simply provide expert answers. A novice user is able to proceed through a structured tutorial to establish the necessary fundamentals on metallurgy, SSC technology, and NACE MR-01-75 requirements necessary for informed use of the NACE document. More experienced users can proceed directly to the expert system portions of the system for direct evaluation of an alloy specification. A general survey option is available within the expert system portion to evaluate NACE requirements in a general context without being limited to the specifics of a given alloy specification.

This software demonstrates that expert systems technology can be applied to SSC and NACE MR-01-75 to provide expert communication to users.
Compositional Reservoir Simulation: A New, Efficient, Fully Integrated Solution Technique for the Flow/Thermodynamic Equilibrium Equations
Authors: Guehria F. M. , Thompson L. G. , Reynolds A. C.
Published: December 2007

We present a novel highly efficient approach to the discretization and solution of the flow and thermodynamic equations describing multicomponent fluid flow in a porous medium. Comparisons with a standard fully-implicit compositional simulator which utilizes Newton's method indicates that typical execution times for our simulator are five to seven times faster than the fully-implicit model, and that these speeds are achieved with no degradation in accuracy, stability or robustness. In fact, our simulator does not experience convergence difficulties (oscillations) during phase transitions (crossing phase envelopes) that have been routinely observed in other simulators. The remarkable speed achieved by our simulator (with time step sizes controlled by accuracy requirements rather than stability requirements) arises from our radically novel approach to the linearization and solution of the discretized flow equations and thermodynamic equilibrium equations. An incremental gain in efficiency is also achieved by solving the minimum number of equations necessary for accurate flow description at each time step. For an Nc- component system, our model solves a maximum of Nc equations at each gridblock containing two phases (e.g., oil and gas) whereas a conventional fully-implicit simulator solves 2Nc equations (Nc flow mass balance equations and Nc thermodynamic equilibrium constraint equations). This reduction in equations is achieved by rigorously and explicitly incorporating the thermodynamic equilibrium equations in the component mass balance equations at the beginning of each time step. Moreover, the simulator is designed for flexibility, e.g., for describing thermodynamic equilibrium at any "point" in the reservoir where multiple phases coexist, the model uses a Generalized Equation of State1 (EOS) that degenerates to any of five widely used equations of state.
Air Quality Permitting of Onshore Oil and Gas Production Facilities in Santa Barbara County, California
Authors: Sheehan P. E.
Published: December 2007

This paper explains how to quantify the emission of air pollutants from a typical onshore oil and gas production facility in Santa Barbara County, and discusses common problems in the permitting process. The paper describes the sources of emissions, the calculation methods, and the data required to properly do the calculations. It outlines the trigger levels for Best Available Control Technology (BACT), Air Quality Impact Analysis (AQIA), and offsets.
The Evolution of Geothermal Drilling Fluid in the Imperial Valley
Authors: Zilch H. E. , Otto M. J. , Pye D. S.
Published: December 2007

The evolution of geothermal drilling muds used in the Imperial Valley, California began with the first generation Sepiolite muds in 1976. These muds had adequate rheology, but poor fluid loss control and were sensitive to contamination by brine or cement. The second generation muds, 1978 to 1980, utilized Sepiolite with increased amounts of bentonite and lignite to improve fluid loss control. Rheological properties of the second generation fluid were unacceptable and were extremely sensitive to contamination. The third generation muds, have exhibited excellent rheological stability, good filtration control, and are resistant to contamination.

The principal ingredients of the third generation geothermal drilling fluid are bentonite as a viscosifying agent, a low molecular weight copolymer for high temperature deflocculation and rheological stability, a sulfonated lignite and a modified vinyl copolymer for high temperature filtration control. Compared with the sepiolite and lignite based fluids, the new formulation performs better under extreme conditions, such as temperatures in excess of 500°F (260°C), contamination levels of 200,000 ppm CO2-2, soluble calcium over 7000 mg/l, and chlorides over 20,000 mg/l. Even at these high contamination levels, the current mud system maintains rheological stability as well as adequate filtration control.

After extensive laboratory testing of various high temperature fluids, the third generation system was selected as the most promising fluid to be used in California's geothermal drilling operations. Under actual field conditions, the fluid confirmed the performance shown in the laboratory tests, but much lower additive concentrations were required in field muds than in the laboratory tests.
Numerical Studies of Cold Water Injection into Vapor-Dominated Geothermal Systems
Authors: Lai C. H. , Bodvarsson G. S.
Published: December 2007

Recent reservoir pressure and steam flow rate declines at The Geysers geothermal field in California have attracted interest in studies of increased cold water injection into this system. In this paper, numerical studies of such injection into a fractured vapor-dominated reservoir are conducted using a two-dimensional radial, double-porosity model. The results obtained indicate that cold water injection into superheated (low-pressure) zones will greatly enhance the productivities of steam wells. Injection into two-phase zones with significant liquid reserves in the matrix blocks does not appear to aid in steam recovery until most of the original liquid reserves are depleted. Sensitivity studies are conducted over the range of fracture and matrix permeabilities applicable to the Geysers. The sensitivity of the grid size is also conducted, and shows very large grid effects. A fine vertical space discretization near the bottom of the reservoir is necessary to accurately predict the boiling of the injected water.
Reservoir Response to Production: Castle Rock Springs Area, East Geysers, California
Authors: Goyal K. P. , Box W. T.
Published: December 2007

Steam deliverability of the original 20 wells, supplying steam to PG&E Unit 13 power plant, has undergone annual exponential decline rates of 11.5%, 5%, 9%, 28.6% and 22% during 1980–81, 1983–84, 1985–86, 1987–88 and 1988–89 respectively. High decline rates after 1984 were influenced by the regional effects associated with the installation of new capacity in the adjoining areas totalling 383 MW (net) in 1983–84 and 347 MW (net) in 1985–86. Unit 13 production declined harmonically for the first 6.6 years, nearly exponentially for the next year and hyper-bolically to harmonically thereafter. The near exponential decline trend resulted from the combined effect of local and regional pressure drawdowns and an accelerated makeup well drilling program. Analysis of the decline rate versus generating capacity suggests that a sustainable 15% annual exponential decline rate (2 MW per month) is achievable if the capacity is held at about 170 MW (net) in the Unit 13–16 wellfield and 830 MW (net) in The East Geysers. This estimate excludes the positive effects of injection seen in late 1989 and 1990.
Process Enhancement in Horizontal Wells Through the Use of Vertical Drainage Channels and Hydrocarbon Additives
Authors: Nasr T. N. , Kimber K. D. , Vendrinsky D. A. , Jha K. N.
Published: December 2007

In a steam-assisted gravity drainage process, two horizontal wells, superposed 16.4 ft (5 m) apart, are placed near the bottom of the formation. Steam is generally circulated through the wells to establish hot communication paths between them and to initiate gravity drainage. However, this steam circulation phase delays oil production. Results of a research program to investigate two novel methods to eliminate steam circulation and enhance the recovery of bitumen or heavy oil through horizontal wells are described in this paper. In the first procedure, paired horizontal wells were linked transversely with vertical channels to improve liquid drainage, and in the second procedure, naphtha was used as a steam additive to accelerate oil drainage and to Increase ultimate oil recovery. The physical models used in this study were designed according to scaling techniques which insured that gravity drainage was the major mechanism of recovery. The scaling technique also ensured that field bitumen could be used in the model. Geometric similarity was maintained, and time was appropriately scaled.

Six experiments were conducted which indicated that more than 50% of the initial bitumen in place could be recovered in less than four years. Using vertical channels to enhance the drainage of fluids from the injection well to the production well improved oil recovery from paired horizontal wells. When one vertical channel was used for a 65.6 ft (20 m) portion of the horizontal wells, the occurrence of a maximum oil-steam ratio was observed 180 d before that of a baseline experiment and the final recovery increased from 52% to 64%. When two channels were used for a 65.6 ft (20 m) portion of the horizontal wells, the final recovery was lower than that for one channel (56% versus 64%) while the same early production was achieved. Hot fluids bypassed the region between the two horizontal wells, reducing recovery from that region.

The presence of naphtha in the steam further improved the rate of oil production and final recovery. When 5 wt% (0.05 kg/kg) naphtha in steam was used, the final recovery was 82% compared with 64% for a baseline experiment using steam-only injection with one vertical channel. When the naphtha concentration in steam was increased to 10 wt% (0.10 kg/kg), the final recovery was lower than that for the test with 5 wt% (0.05 kg/kg) naphtha (71% versus 82%). A high, non-condensible gas saturation in the steam chamber blanketed the heat transfer interface between the steam and bitumen, reducing heat transfer across the interface.
Oscillatory Injection-Production Schemes for Steamflooding Oil Reservoirs
Authors: Chu C.
Published: December 2007

This report embodies a simulation study on using oscillatory injection-production schemes for steamflooding oil reservoirs. The oscillation in injection being studied included ON-OFF alternation, HIGH-LOW alternation in steam quality and HIGH-LOW alternation in both steam injection rates and steam quality. ON-OFF alternation in production was assumed to be in phase, out of phase or partially in phase with the oscillation in injection. The effects of periods, amplitudes and timing of oscillation on steamflood performance were also studied.

The results showed that simple ON-OFF oscillation, in injection only, injecting steam at the rate of 600 BPD for 6 months, alternating with 6 months of non-injection, can increase the oil production by 6% over injecting steam at the rate of 300 BPD continuously. Furthermore, the oil recoveries at the ends of the first year and the second year are 5.5 and 20.7% of the oil-in-place, respectively, for the oscillating case, much greater than the 2.8 and 14.4%, respectively, obtained without oscillation.
Some Important Considerations in the Simulation of Naturally Fractured Reservoirs
Authors: McDonald A. E. , Beckner B. L. , Chan H. M. , Jones T. A. , Wooten S. O.
Published: December 2007

The effects of rock structural properties on porosity and permeability may be considered as generally well known, being particularly critical when modeling tight sands and limestones. Nevertheless, such effects have been slow to find their way into reservoir simulators. These effects are frequently even more important for fractured horizons where 10-20 porosity per cent changes, and/or several orders of magnitude change in permeability, can be observed under changing reservoir stress conditions. Rocks with weak tensile properties are particularly vulnerable to stress change. These include diatomite, chalks, and overpressured Gulf Coast shales.

Less well known is the dependence of relative permeability on stress. Moreover, the effects of relative permeability and capillary pressure in the fractures themselves need to be accounted for.

Production in naturally fractured reservoirs is limited by the exchange rates of oil and gas between matrix blocks and fractures. Naturally fractured simulators which use the conventional dual porosity formulation fail to resolve gradients in the matrix blocks unless some type of sub-gridding (subdomains) is used. This lack of resolution at the matrix/fracture interface leads to significant errors in production rates when modeling oil recovery from fractured reservoirs.
Treatment Design Changes Improve Production Results for the Codell Formation
Authors: Parker M. A. , Jacobs R. , Yeager R. R.
Published: December 2007

The Codell sandstone in the Denver-Julesburg Basin is a low permeability, clay-rich sandstone. It is bounded by the Ft. Hays limestone member of the Niobrara formation above and shales of the Carlile formation below. The Codell requires stimulation by hydraulic fracturing in order to produce at economic rates; however, some stimulation procedures are not effective.

Analysis of the less successful treatments indicated that inadequate fracture length and conductivity were common problems. Formation properties, gathered in situ, were used in a 3-D fracture design simulator to predict fracture growth in the Codell and bounding formations. Published laboratory data has proven that low proppant conductivities are associated with low proppant concentrations and imply that the use of high concentrations should improve conductivity. In addition, greater initial rates and sustained long-term Codell production support the use of high proppant concentration treatments.

This paper will present a history of treatments and changes which led to more effective stimulation of the Codell formation in the Denver-Julesburg Basin. Comparative production data will show the benefits of this improved treatment design.
Interpretation of In-Situ Pressure and Flow Measurements of the Salado Formation at the Waste Isolation Pilot Plant
Authors: Howarth S. M. , Peterson E. W. , Lagus P. L. , Lie K-H. , Finley S. J. , Nowak E. J.
Published: December 2007

This paper describes preliminary interpretation of in-situ pressure and flow measurements of the Salado Formation at the Waste Isolation Pilot Plant (WIPP). The WIPP facility is located 660 m underground in the Salado, a bedded salt deposit. Shut-in pressure tests were conducted prior to, and subsequent to, the mining of a circular drift in order to evaluate excavation effects on pore pressure, permeability, and host rock heterogeneity. Borehole deformation was measured during these tests and used to correct for changes in the test region volume due to salt creep effects.

Preliminary pre-excavation results indicate that the flow properties of this layered host rock are heterogeneous. Resulting pore pressures range from 1 to 14 MPa and permeabilities range from below measurable to about 1 nanodarcy. Normalized borehole diameter change rates were between -4 and 63 microstrains/day.

Shut-in pressures and borehole diameters in all test boreholes were affected by the excavation of Room Q coincident with the advances of the boring machine. Preliminary results from post-excavation test results show decreased pore pressures compared to pre-excavation values.
Modeling of Poroelastic Effects in Hydraulic Fracturing
Authors: Clifton R. J. , Wang J-J.
Published: December 2007

A computational model is presented which accounts for poroelastic effects, due to fluid migration in the reservoir, during hydraulic fracturing. For massive hydraulic fracturing in a high leakoff formation, the large fluid losses and long injection times cause significant changes in the in-situ stress and the pore pressure of the reservoir. The current model provides a new advanced capability for simulating the evolution of such fractures.

To model the poroelastic effects due to fluid injection, without temperature changes, the reservoir is considered to be a saturated, linear, poroelastic solid. The resulting three-dimensional poroelasticity problem is reduced to a pair of two-dimensional coupled surface-integral equations for the unknown crack opening and leakoff rates [Kurashige and Clifton, 1991]. By introducing commonly used leakoff relations, these equations are uncoupled to obtain an integral equation for crack opening in the poroelastic formation. The difference in pressure required for opening a crack in the poroelastic material versus a purely elastic material is due to the change in the in-situ stress (i.e., backstress) caused by the hydraulic fracturing treatment. These backstresses are evaluated by introducing approximations for the time histories of the crack openings and leakoff which appear in the integrals. These approximations allow the integrations with respect to time to be carried out explicitly in the back-stress calculations. Expressions to account for the poroelastic changes in in-situ stresses and pore pressures are presented. Implementation of this model in a three-dimensional hydraulic fracturing simulator is described. Example simulations are presented and discussed.
A Rapid Sequential Fracturing and Proppant Placement Method
Authors: Passamaneck R. S.
Published: December 2007

This paper describes a research project that was undertaken to develop an enhanced completion method. The criteria for the method was to have a procedure which was capable of perforating, fracturing, and propping in a very short period of time, i.e., on the order of a few seconds at most. A downhole energy generating device was developed which creates gas at high pressure for the Initial fracture. The control of this device is crucial to a successful completion. A means to store potential energy in the vicinity of the zone to be fractured was found in the form of a column of compressed sand-laddened foam. This foam provides from 90 to 95% of the total energy dissipated into the zone to be fractured. A computer code was developed to predict the pressure history of the material within the well bore during the procedure. A second computer code was developed which calculates the fracture volume and weight of sand injected into the fracture. Finally, a test was performed to check the operational procedures, reliability of the ignition sequence, and gas generation capability of the gas generating device.
Incentive Contract: A Contractor's Viewpoint
Authors: Geehan T. , Rospide J. P.
Published: December 2007

The use of incentive contracts in the drilling industry has become more common over the past few years. The introduction of performance related remuneration has developed for several reasons, the prime one being an effort to reduce overall drilling costs through increased efficiency. Another significant reason has been the operators desire to have their personnel concentrate on their core business which is finding and marketing oil.

This paper reviews the experience to-date and offers comment, from a drilling contractor’s viewpoint, on the types of incentive contracts presently in use. Discussion covers all phases from bidding to operation at the rig site. In particular certain work undertaken in France and Africa is discussed. The full range of incentive contract types are described, and the required change in attitude from the drilling crew is explained in order to allow successful completion. The need to maintain the correct approach in terms of safety and environmental awareness is also outlined..
A Multidisciplinary Approach to In-Situ Stress Determination and Its Application to Wellbore Stability Analysis
Authors: Ottesen S. , Kwakwa K. A.
Published: December 2007

Recent technical papers have demonstrated development flexibility, and the potential for increased ultimate hydrocarbon recovery resulting from the application of extended reach and horizontal drilling techniques. Serious mechanical borehole stability problems, principally borehole collapse and tensile fracturing, can be associated with the drilling of such wells. The threshold drilling fluid pressures for the onset of each mechanism depend on the earth stresses and the mechanical properties of the formations. Hence, there is the need for careful engineering assessments and planning prior to drilling these wells. In this paper the methods of approach used in determining the magnitudes of the principal in-situ stresses by collating geological, drilling, leak-off, logging, well test, mini-frac and laboratory test data are presented. The results formed the basis for a detailed assessment of the mechanical stability of a planned horizontal well in UKCS Block 9/13. This horizontal well was later successfully drilled from a semi-submersible drilling rig, utilising carefully tailored drilling fluid densities based on borehole stability analysis.
Abnormal Formation Pressures in Post-Eocene Formation, Potwar Basin, Pakistan
Authors: Kadri I. B.
Published: December 2007

The paper is based on experience gained during drilling in Potwar basin, on-shore Pakistan. The high cost of wells are primarily due to long drilling times resulting from extremely difficult drilling conditions, arising from abnormally high formation pressures. High pressure water inflows and loss circulations have led to premature abandonment of several wells on account of collapsed casing, bridging, caving, blowouts and cratering around the wells.

The post-Eocene Siwalik formations in the Potwar basin are notorious for abnormally high formation pressures and reversal of pressure regimes in the sedimentary sequence. Pressures close to geostatic have been encountered at shallow depths.

The aim of the paper is to take a close look at the mechanisms responsible for the generation of overpressure, identify problem areas, examine available options, keeping in view present drilling technology and equipment limitations, and finally recommend operational strategies to handle such situations.

Planning of wells, monitoring of drilling operations, selection of kick control procedures and wellbore integrity are considered to be critical factors for successful operations.
Integrated Driller's Cabin
Authors: McGill J.
Published: December 2007

A new generation driller's cabin has evolved due to the introduction of more advanced drilling equipment and controls. Remote control of rig floor and derrick equipment will lead to a safer moreefficient andmore acceptable working environment.

Integrating both the drillerand assistant driller (ex. derrickman)into one work station within a driller's cabin,enables moreefficient control and communication between the two most important persons directly involved with the drilling operation.
How a Computerized Drilling System has Improved Drilling Performance
Authors: Arnold M. S. , Schilhab L. , White D. B. , Dudleson W. J.
Published: December 2007

Recent advances in technology have given the drilling industry an opportunity to improve drilling performance. This new technology includes the application of innovative sensors, integrated computer systems, and advanced data processing software onboard the rig.

A complete system with all these facilities has been installed and operated by a drilling contractor on an offshore rig in the Middle East since mid-1989. The system has been used extensively by contractor and operator working together as a drilling team to increase safety and improve drilling performance.

An enhanced measurement of ROP gave drillers a faster indication of formation changes to avoid damage to PDC bits. With a new capability for interactive control of the monitoring system, contractor personnel had more credible input into the drilling process, which improved teamwork with operator personnel. Bit performance logs and well-to-well correlations were generated on the system's workstation to optimize bit selection.

As a result, drilling performance improved greatly over a series of wells in a field where the learning curve was thought to have been optimized. Resulting cost savings were substantial.
Metal Bearing Seal Technology Improves Drilling Efficiency of Rolling Cutter Bits in High-rpm North Sea Applications
Authors: Schmidt S. R. , Wittry A. E. , Burr B. H. , Kelly J. L.
Published: December 2007

The impact of the metal bearing seal on rolling cutter bit performance at high rotary speeds has been dramatic. In the high-cost drilling environment of the North Sea, the metal sealed bit has proven its ability to extend rolling cutter bearing life at high rotary speed and thereby provide significant reductions in drilling costs. This improvement is encouraging more widespread use of these bits with downhole motors and steerable systems.

An analysis of recent run data from the Norwegian sector of the North Sea shows metal sealed rolling cutter bits can be used for a much greater number of bit revolutions than their elastomer seal counterparts and, consequently, footage per bit has more than doubled without sacrificing rate of penetration. Cost savings of up to $100,000 per well have been documented.

This paper describes the design of the metal sealed bit and its performance in the Ekofisk and Eldfisk fields.
North Sea Field Application of an Environmentally Responsible Water-Base Shale Stabilizing System
Authors: Alford S. E.
Published: December 2007

Two exploratory wells were recently drilled in the North Sea which used a specially designed polymer drilling fluid to provide optimum shale and borehole stabilization. The first well was a deep Jurassic well in the Frigg and Balder area of the Norwegian North Sea; the second well was drilled in the Ekofisk area. (Figure 1.) FIGURE 1SHALE STABILITY MECHANISM

The mud for the reactive formation intervals was formulated to provide chemical stability for the reactive tertiary clays and claystones. Conventional fluid loss and rheology control polymers (polyanionic cellulose and xanthan gum, respectively) were used to achieve and maintain the required performance properties. Shale stability was obtained using a novel.additive composed of a polyvinyl alcohol polymer, potassium silicate, and potassium carbonate.

Shale stabilization is based on a unique new theoretical mechanism which was initially postulated in SPE 16687, "New Chemical Package Produces an Improved Shale Inhibitive Water-Based Drilling Fluid System," and presented at the 62th SPE Conference, Dallas, Texas, 1987 (Wingrave et al). Further details are included in this paper.

In the deeper intervals, high temperature polymer additives were used to maintain favorable rheological and filtration properties.

An injection system was used to inject prehydrated liquid polymer concentrate directly into the suction. This procedure was used to obtain optimum polymer efficiency and performance in the management of the drilling fluid system.

Drilling and drilling fluid performance data is presented for the 17.5", 12.25", and 8.5" hole sections. Mud weights from 10.0 to 16.0 ppg were required in the drilling program.

Drilling and fluid performance data from the first well (Frigg and Balder area), designated Well A, is compared with an earlier offset well in the same block, Well B, which was drilled with a conventional KCl/PHPA/Biopolymer/PAC polymer system.

Caliper data, borehole stability relative to exposure period, solids removal efficiency performance, wireline log quality, trouble-free casing and cementing operations, and minimal fluid-related hole problems while drilling - all provide supportive data indicative of superior chemical stabilization of the wellbore.

U.S. and Norway toxicity results support its use as an environmentally acceptable water base additive for offshore and onshore application.
Elements of Thermally Treating Oil-Base Mud Cuttings
Authors: Young G. A. , Growcock F. B. , Talbot K. J. , Lees J. , Worrell B.
Published: December 2007

This work shows that rotary retort distillation is a conceptually feasible alternative for removal of oil from cuttings produced while drilling with oil base mud. The work specifically examined the response and behavior of oil base mud drilled cuttings and associated fluids to heat in a tumbling bed. These test results established the temperature requirements necessary to clean oil base mud cuttings to various cleaning limits. Heat transfer coefficients have been calculated for the test apparatus. These heat transfer coefficients have been used to establish the size of a full scale unit necessary to process 15 metric tonne/hr of drilled cuttings. The recovered products, cuttings and oil have been evaluated for toxicity. The dried cuttings were evaluated with a metal leachate test to establish extraction procedure toxicity. The distillation products were chemically analyzed and the amount of noncondensable gas was estimated.

Finally a conceptual retort design is proposed for the offshore environment. Energy consumption and operating costs for a typical well are estimated.
New Oil-Base Mud Additive Reduces Oil Discharged on Cuttings
Authors: Friedheim J. E. , Shinnie J. R.
Published: December 2007

A new additive reduces the amount of oil retained on drill cuttings generated by drilling with an oil-base fluid. The oil retention on drill cuttings phenomenon and the approach used in dealing with it in the field are reviewed with particular emphasis on the use of high water content oil-base muds. Laboratory and field data using this new additive to decrease total cuttings oil retention are described.
Detection and Monitoring of the Slip-Stick Motion: Field Experiments
Authors: Dufeyte M-P. , Henneuse H.
Published: December 2007

By analysing simultaneous downhole and surface dynamic drilling measurements, it has been possible to characterize the drill string behaviour and, more precisely, the stick-slip motion.

Based on three thousand five hundred hours of real time field measurements, this paper presents the study of bit and drill string behaviour when the stick-slip phenomenon occurs.

Using correlations between downhole and surface recordings, it shows how, applied solely to surface drilling data such as torque and rotational speed, a simple mathematical calculation enables the detection of the stick-slip motion, estimation of its period, its sticking time and the maximum bit rotational speed.

It also demonstrates that it is possible to reduce and eliminate stick-slip by modifying certain drilling parameters such as weight on bit, rotational speed or mud characteristics. In addition, power swivel control can suppress the first mode but may also emphasize a higher mode of the stick-slip phenomenon.

Looking at the numerous hours of recordings which have been analysed, during 50 % of the time this phenomenon is seen to be permanently present while rotating.

As drill pipe fatigue and bit wear can be linked to the stick-slip motion, the possibility of controlling and limiting it by simple surface monitoring is a very attractive concept.
New Ultrasonic Caliper for MWD Operations
Authors: Orban J. J. , Dennison M. S. , Jorion B. M. , Mayes J. C.
Published: December 2007

An ultrasonic tool has been developed for MWD applications that simultaneously performs realtime bore-hole caliper measurements and realtime gas influx detection.

The caliper determines the ovalness of the hole with a high degree of accuracy and excellent vertical resolution. These measurements are transmitted to the surface and also used to compensate LWD measurements. Furthermore, with early and accurate real-time caliper measurements, bore-hole instability can be detected.

Real-time gas influx detection insures early and reliable gas kick detection and should provide a considerable improvement in drilling rig safety. The new tool is particularly useful for avoiding problems associated with shallow gas formation where response time for kick detection is critical.
Environmental Control Potential of Drilling Engineering: An Overview of Existing Technologies
Authors: Wojtanowicz A. K.
Published: December 2007

The overview paper examines environmental control techniques associated with borehole technology. The overview includes two aspects of environmental control: surface discharge of pollutants from the drilling process, and subsurface interzonal isolation resulting from well completion.

The definition and objectives of the environmental control technology for oilfield drilling operations are presented first. Its preventive function is derived from modem concepts of source separation and recycling in addition to the conventional remedial function of waste disposal.

The use of systems analysis to define the environmental constraints in the drilling process places environmental control technology as an integral part of modem mud engineering. The technology serves to control volume and toxicity of active mud systems. In well completions, environmental control comprises well cementing technologies to control the hydraulic integrity of annular seals.

Described is the technological mechanism of the mud system volume expansion resulting from inefficient cuttings removal. Special consideration is given to drilling fluid properties such as dispersivity and dewaterability; their physical nature and control measures are discussed. Also presented are examples of recent research efforts to develop new mud systems that have properties of low dispersivity and high dewaterability.

The discussion on drilling fluids toxicity control includes recent developments in toxicity measurements as well as toxicity reduction through the use of low-toxicity substitutes or remediation mechanisms. Examined are recent research efforts to develop a simple toxicity test which can be deployed at well sites. These efforts are discussed in view of the search for a correlation between the field tests and the conventional Mysid test Also presented are examples of recently developed substitutes for diesel oil, metal and salt-related toxicity. Further discussion covers remediation methods for oil-base mud cuttings, and the role of surface mechanisms in oil removal from solids.

Part of the overview focuses on the mechanisms related to the integrity of borehole annular seals and subsurface migration of pollutants. Specifically discussed are recent developments in the methodology of Mechanical Integrity Test using the Cement Bond Log and the neutron activation techniques. Also included is a short discussion of potential applications of recently developed techniques to design the annular cement seal integrity.